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path: root/Modules/arraymodule.c
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/* Array object implementation */

/* An array is a uniform list -- all items have the same type.
   The item type is restricted to simple C types like int or float */

#include "Python.h"

#ifdef STDC_HEADERS
#include <stddef.h>
#else /* !STDC_HEADERS */
#ifndef DONT_HAVE_SYS_TYPES_H
#include <sys/types.h>		/* For size_t */
#endif /* DONT_HAVE_SYS_TYPES_H */
#endif /* !STDC_HEADERS */

/* Shamelessy stolen from listobject.c */
static int
roundupsize(int n)
{
	unsigned int nbits = 0;
	unsigned int n2 = (unsigned int)n >> 5;

	/* Round up:
	 * If n <       256, to a multiple of        8.
	 * If n <      2048, to a multiple of       64.
	 * If n <     16384, to a multiple of      512.
	 * If n <    131072, to a multiple of     4096.
	 * If n <   1048576, to a multiple of    32768.
	 * If n <   8388608, to a multiple of   262144.
	 * If n <  67108864, to a multiple of  2097152.
	 * If n < 536870912, to a multiple of 16777216.
	 * ...
	 * If n < 2**(5+3*i), to a multiple of 2**(3*i).
	 *
	 * This over-allocates proportional to the list size, making room
	 * for additional growth.  The over-allocation is mild, but is
	 * enough to give linear-time amortized behavior over a long
	 * sequence of appends() in the presence of a poorly-performing
	 * system realloc() (which is a reality, e.g., across all flavors
	 * of Windows, with Win9x behavior being particularly bad -- and
	 * we've still got address space fragmentation problems on Win9x
	 * even with this scheme, although it requires much longer lists to
	 * provoke them than it used to).
	 */
	do {
		n2 >>= 3;
		nbits += 3;
	} while (n2);
	return ((n >> nbits) + 1) << nbits;
 }

#define NRESIZE(var, type, nitems)				\
do {								\
	size_t _new_size = roundupsize(nitems);			\
	if (_new_size <= ((~(size_t)0) / sizeof(type)))		\
		PyMem_RESIZE(var, type, _new_size);		\
	else							\
		var = NULL;					\
} while (0)
/* END SHAMELESSLY STOLEN CODE */

struct arrayobject; /* Forward */

/* All possible arraydescr values are defined in the vector "descriptors"
 * below.  That's defined later because the appropriate get and set
 * functions aren't visible yet.
 */
struct arraydescr {
	int typecode;
	int itemsize;
	PyObject * (*getitem)(struct arrayobject *, int);
	int (*setitem)(struct arrayobject *, int, PyObject *);
};

typedef struct arrayobject {
	PyObject_HEAD
	int ob_size;
	char *ob_item;
	struct arraydescr *ob_descr;
} arrayobject;

static PyTypeObject Arraytype;

#define array_Check(op) PyObject_TypeCheck(op, &Arraytype)
#define array_CheckExact(op) ((op)->ob_type == &Arraytype)

/****************************************************************************
Get and Set functions for each type.
A Get function takes an arrayobject* and an integer index, returning the
array value at that index wrapped in an appropriate PyObject*.
A Set function takes an arrayobject, integer index, and PyObject*; sets
the array value at that index to the raw C data extracted from the PyObject*,
and returns 0 if successful, else nonzero on failure (PyObject* not of an
appropriate type or value).
Note that the basic Get and Set functions do NOT check that the index is
in bounds; that's the responsibility of the caller.
****************************************************************************/

static PyObject *
c_getitem(arrayobject *ap, int i)
{
	return PyString_FromStringAndSize(&((char *)ap->ob_item)[i], 1);
}

static int
c_setitem(arrayobject *ap, int i, PyObject *v)
{
	char x;
	if (!PyArg_Parse(v, "c;array item must be char", &x))
		return -1;
	if (i >= 0)
		((char *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
b_getitem(arrayobject *ap, int i)
{
	long x = ((char *)ap->ob_item)[i];
	if (x >= 128)
		x -= 256;
	return PyInt_FromLong(x);
}

static int
b_setitem(arrayobject *ap, int i, PyObject *v)
{
	short x;
	/* PyArg_Parse's 'b' formatter is for an unsigned char, therefore
	   must use the next size up that is signed ('h') and manually do
	   the overflow checking */
	if (!PyArg_Parse(v, "h;array item must be integer", &x))
		return -1;
	else if (x < -128) {
		PyErr_SetString(PyExc_OverflowError,
			"signed char is less than minimum");
		return -1;
	}
	else if (x > 127) {
		PyErr_SetString(PyExc_OverflowError,
			"signed char is greater than maximum");
		return -1;
	}
	if (i >= 0)
		((char *)ap->ob_item)[i] = (char)x;
	return 0;
}

static PyObject *
BB_getitem(arrayobject *ap, int i)
{
	long x = ((unsigned char *)ap->ob_item)[i];
	return PyInt_FromLong(x);
}

static int
BB_setitem(arrayobject *ap, int i, PyObject *v)
{
	unsigned char x;
	/* 'B' == unsigned char, maps to PyArg_Parse's 'b' formatter */
	if (!PyArg_Parse(v, "b;array item must be integer", &x))
		return -1;
	if (i >= 0)
		((char *)ap->ob_item)[i] = x;
	return 0;
}

#ifdef Py_USING_UNICODE
static PyObject *
u_getitem(arrayobject *ap, int i)
{
	return PyUnicode_FromUnicode(&((Py_UNICODE *) ap->ob_item)[i], 1);
}

static int
u_setitem(arrayobject *ap, int i, PyObject *v)
{
	Py_UNICODE *p;
	int len;

	if (!PyArg_Parse(v, "u#;array item must be unicode character", &p, &len))
		return -1;
	if (len != 1) {
		PyErr_SetString(PyExc_TypeError, "array item must be unicode character");
		return -1;
	}
	if (i >= 0)
		((Py_UNICODE *)ap->ob_item)[i] = p[0];
	return 0;
}
#endif

static PyObject *
h_getitem(arrayobject *ap, int i)
{
	return PyInt_FromLong((long) ((short *)ap->ob_item)[i]);
}

static int
h_setitem(arrayobject *ap, int i, PyObject *v)
{
	short x;
	/* 'h' == signed short, maps to PyArg_Parse's 'h' formatter */
	if (!PyArg_Parse(v, "h;array item must be integer", &x))
		return -1;
	if (i >= 0)
		     ((short *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
HH_getitem(arrayobject *ap, int i)
{
	return PyInt_FromLong((long) ((unsigned short *)ap->ob_item)[i]);
}

static int
HH_setitem(arrayobject *ap, int i, PyObject *v)
{
	int x;
	/* PyArg_Parse's 'h' formatter is for a signed short, therefore
	   must use the next size up and manually do the overflow checking */
	if (!PyArg_Parse(v, "i;array item must be integer", &x))
		return -1;
	else if (x < 0) {
		PyErr_SetString(PyExc_OverflowError,
			"unsigned short is less than minimum");
		return -1;
	}
	else if (x > USHRT_MAX) {
		PyErr_SetString(PyExc_OverflowError,
			"unsigned short is greater than maximum");
		return -1;
	}
	if (i >= 0)
		((short *)ap->ob_item)[i] = (short)x;
	return 0;
}

static PyObject *
i_getitem(arrayobject *ap, int i)
{
	return PyInt_FromLong((long) ((int *)ap->ob_item)[i]);
}

static int
i_setitem(arrayobject *ap, int i, PyObject *v)
{
	int x;
	/* 'i' == signed int, maps to PyArg_Parse's 'i' formatter */
	if (!PyArg_Parse(v, "i;array item must be integer", &x))
		return -1;
	if (i >= 0)
		     ((int *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
II_getitem(arrayobject *ap, int i)
{
	return PyLong_FromUnsignedLong(
		(unsigned long) ((unsigned int *)ap->ob_item)[i]);
}

static int
II_setitem(arrayobject *ap, int i, PyObject *v)
{
	unsigned long x;
	if (PyLong_Check(v)) {
		x = PyLong_AsUnsignedLong(v);
		if (x == (unsigned long) -1 && PyErr_Occurred())
			return -1;
	}
	else {
		long y;
		if (!PyArg_Parse(v, "l;array item must be integer", &y))
			return -1;
		if (y < 0) {
			PyErr_SetString(PyExc_OverflowError,
				"unsigned int is less than minimum");
			return -1;
		}
		x = (unsigned long)y;

	}
	if (x > UINT_MAX) {
		PyErr_SetString(PyExc_OverflowError,
			"unsigned int is greater than maximum");
		return -1;
	}

	if (i >= 0)
		((unsigned int *)ap->ob_item)[i] = (unsigned int)x;
	return 0;
}

static PyObject *
l_getitem(arrayobject *ap, int i)
{
	return PyInt_FromLong(((long *)ap->ob_item)[i]);
}

static int
l_setitem(arrayobject *ap, int i, PyObject *v)
{
	long x;
	if (!PyArg_Parse(v, "l;array item must be integer", &x))
		return -1;
	if (i >= 0)
		     ((long *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
LL_getitem(arrayobject *ap, int i)
{
	return PyLong_FromUnsignedLong(((unsigned long *)ap->ob_item)[i]);
}

static int
LL_setitem(arrayobject *ap, int i, PyObject *v)
{
	unsigned long x;
	if (PyLong_Check(v)) {
		x = PyLong_AsUnsignedLong(v);
		if (x == (unsigned long) -1 && PyErr_Occurred())
			return -1;
	}
	else {
		long y;
		if (!PyArg_Parse(v, "l;array item must be integer", &y))
			return -1;
		if (y < 0) {
			PyErr_SetString(PyExc_OverflowError,
				"unsigned long is less than minimum");
			return -1;
		}
		x = (unsigned long)y;

	}
	if (x > ULONG_MAX) {
		PyErr_SetString(PyExc_OverflowError,
			"unsigned long is greater than maximum");
		return -1;
	}

	if (i >= 0)
		((unsigned long *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
f_getitem(arrayobject *ap, int i)
{
	return PyFloat_FromDouble((double) ((float *)ap->ob_item)[i]);
}

static int
f_setitem(arrayobject *ap, int i, PyObject *v)
{
	float x;
	if (!PyArg_Parse(v, "f;array item must be float", &x))
		return -1;
	if (i >= 0)
		     ((float *)ap->ob_item)[i] = x;
	return 0;
}

static PyObject *
d_getitem(arrayobject *ap, int i)
{
	return PyFloat_FromDouble(((double *)ap->ob_item)[i]);
}

static int
d_setitem(arrayobject *ap, int i, PyObject *v)
{
	double x;
	if (!PyArg_Parse(v, "d;array item must be float", &x))
		return -1;
	if (i >= 0)
		     ((double *)ap->ob_item)[i] = x;
	return 0;
}

/* Description of types */
static struct arraydescr descriptors[] = {
	{'c', sizeof(char), c_getitem, c_setitem},
	{'b', sizeof(char), b_getitem, b_setitem},
	{'B', sizeof(char), BB_getitem, BB_setitem},
#ifdef Py_USING_UNICODE
	{'u', sizeof(Py_UNICODE), u_getitem, u_setitem},
#endif
	{'h', sizeof(short), h_getitem, h_setitem},
	{'H', sizeof(short), HH_getitem, HH_setitem},
	{'i', sizeof(int), i_getitem, i_setitem},
	{'I', sizeof(int), II_getitem, II_setitem},
	{'l', sizeof(long), l_getitem, l_setitem},
	{'L', sizeof(long), LL_getitem, LL_setitem},
	{'f', sizeof(float), f_getitem, f_setitem},
	{'d', sizeof(double), d_getitem, d_setitem},
	{'\0', 0, 0, 0} /* Sentinel */
};

/****************************************************************************
Implementations of array object methods.
****************************************************************************/

static PyObject *
newarrayobject(PyTypeObject *type, int size, struct arraydescr *descr)
{
	arrayobject *op;
	size_t nbytes;

	if (size < 0) {
		PyErr_BadInternalCall();
		return NULL;
	}

	nbytes = size * descr->itemsize;
	/* Check for overflow */
	if (nbytes / descr->itemsize != (size_t)size) {
		return PyErr_NoMemory();
	}
	op = (arrayobject *) type->tp_alloc(type, 0);
	if (op == NULL) {
		return NULL;
	}
	op->ob_size = size;
	if (size <= 0) {
		op->ob_item = NULL;
	}
	else {
		op->ob_item = PyMem_NEW(char, nbytes);
		if (op->ob_item == NULL) {
			PyObject_Del(op);
			return PyErr_NoMemory();
		}
	}
	op->ob_descr = descr;
	return (PyObject *) op;
}

static PyObject *
getarrayitem(PyObject *op, int i)
{
	register arrayobject *ap;
	assert(array_Check(op));
	ap = (arrayobject *)op;
	assert(i>=0 && i<ap->ob_size);
	return (*ap->ob_descr->getitem)(ap, i);
}

static int
ins1(arrayobject *self, int where, PyObject *v)
{
	char *items;
	if (v == NULL) {
		PyErr_BadInternalCall();
		return -1;
	}
	if ((*self->ob_descr->setitem)(self, -1, v) < 0)
		return -1;
	items = self->ob_item;
	NRESIZE(items, char, (self->ob_size+1) * self->ob_descr->itemsize);
	if (items == NULL) {
		PyErr_NoMemory();
		return -1;
	}
	if (where < 0) {
		where += self->ob_size;
		if (where < 0)
			where = 0;
	}
	if (where > self->ob_size)
		where = self->ob_size;
	memmove(items + (where+1)*self->ob_descr->itemsize,
		items + where*self->ob_descr->itemsize,
		(self->ob_size-where)*self->ob_descr->itemsize);
	self->ob_item = items;
	self->ob_size++;
	return (*self->ob_descr->setitem)(self, where, v);
}

/* Methods */

static void
array_dealloc(arrayobject *op)
{
	if (op->ob_item != NULL)
		PyMem_DEL(op->ob_item);
	op->ob_type->tp_free((PyObject *)op);
}

static PyObject *
array_richcompare(PyObject *v, PyObject *w, int op)
{
	arrayobject *va, *wa;
	PyObject *vi = NULL;
	PyObject *wi = NULL;
	int i, k;
	PyObject *res;

	if (!array_Check(v) || !array_Check(w)) {
		Py_INCREF(Py_NotImplemented);
		return Py_NotImplemented;
	}

	va = (arrayobject *)v;
	wa = (arrayobject *)w;

	if (va->ob_size != wa->ob_size && (op == Py_EQ || op == Py_NE)) {
		/* Shortcut: if the lengths differ, the arrays differ */
		if (op == Py_EQ)
			res = Py_False;
		else
			res = Py_True;
		Py_INCREF(res);
		return res;
	}

	/* Search for the first index where items are different */
	k = 1;
	for (i = 0; i < va->ob_size && i < wa->ob_size; i++) {
		vi = getarrayitem(v, i);
		wi = getarrayitem(w, i);
		if (vi == NULL || wi == NULL) {
			Py_XDECREF(vi);
			Py_XDECREF(wi);
			return NULL;
		}
		k = PyObject_RichCompareBool(vi, wi, Py_EQ);
		if (k == 0)
			break; /* Keeping vi and wi alive! */
		Py_DECREF(vi);
		Py_DECREF(wi);
		if (k < 0)
			return NULL;
	}

	if (k) {
		/* No more items to compare -- compare sizes */
		int vs = va->ob_size;
		int ws = wa->ob_size;
		int cmp;
		switch (op) {
		case Py_LT: cmp = vs <  ws; break;
		case Py_LE: cmp = vs <= ws; break;
		case Py_EQ: cmp = vs == ws; break;
		case Py_NE: cmp = vs != ws; break;
		case Py_GT: cmp = vs >  ws; break;
		case Py_GE: cmp = vs >= ws; break;
		default: return NULL; /* cannot happen */
		}
		if (cmp)
			res = Py_True;
		else
			res = Py_False;
		Py_INCREF(res);
		return res;
	}

	/* We have an item that differs.  First, shortcuts for EQ/NE */
	if (op == Py_EQ) {
		Py_INCREF(Py_False);
		res = Py_False;
	}
	else if (op == Py_NE) {
		Py_INCREF(Py_True);
		res = Py_True;
	}
	else {
		/* Compare the final item again using the proper operator */
		res = PyObject_RichCompare(vi, wi, op);
	}
	Py_DECREF(vi);
	Py_DECREF(wi);
	return res;
}

static int
array_length(arrayobject *a)
{
	return a->ob_size;
}

static PyObject *
array_item(arrayobject *a, int i)
{
	if (i < 0 || i >= a->ob_size) {
		PyErr_SetString(PyExc_IndexError, "array index out of range");
		return NULL;
	}
	return getarrayitem((PyObject *)a, i);
}

static PyObject *
array_slice(arrayobject *a, int ilow, int ihigh)
{
	arrayobject *np;
	if (ilow < 0)
		ilow = 0;
	else if (ilow > a->ob_size)
		ilow = a->ob_size;
	if (ihigh < 0)
		ihigh = 0;
	if (ihigh < ilow)
		ihigh = ilow;
	else if (ihigh > a->ob_size)
		ihigh = a->ob_size;
	np = (arrayobject *) newarrayobject(&Arraytype, ihigh - ilow, a->ob_descr);
	if (np == NULL)
		return NULL;
	memcpy(np->ob_item, a->ob_item + ilow * a->ob_descr->itemsize,
	       (ihigh-ilow) * a->ob_descr->itemsize);
	return (PyObject *)np;
}

static PyObject *
array_concat(arrayobject *a, PyObject *bb)
{
	int size;
	arrayobject *np;
	if (!array_Check(bb)) {
		PyErr_Format(PyExc_TypeError,
		     "can only append array (not \"%.200s\") to array",
			     bb->ob_type->tp_name);
		return NULL;
	}
#define b ((arrayobject *)bb)
	if (a->ob_descr != b->ob_descr) {
		PyErr_BadArgument();
		return NULL;
	}
	size = a->ob_size + b->ob_size;
	np = (arrayobject *) newarrayobject(&Arraytype, size, a->ob_descr);
	if (np == NULL) {
		return NULL;
	}
	memcpy(np->ob_item, a->ob_item, a->ob_size*a->ob_descr->itemsize);
	memcpy(np->ob_item + a->ob_size*a->ob_descr->itemsize,
	       b->ob_item, b->ob_size*b->ob_descr->itemsize);
	return (PyObject *)np;
#undef b
}

static PyObject *
array_repeat(arrayobject *a, int n)
{
	int i;
	int size;
	arrayobject *np;
	char *p;
	int nbytes;
	if (n < 0)
		n = 0;
	size = a->ob_size * n;
	np = (arrayobject *) newarrayobject(&Arraytype, size, a->ob_descr);
	if (np == NULL)
		return NULL;
	p = np->ob_item;
	nbytes = a->ob_size * a->ob_descr->itemsize;
	for (i = 0; i < n; i++) {
		memcpy(p, a->ob_item, nbytes);
		p += nbytes;
	}
	return (PyObject *) np;
}

static int
array_ass_slice(arrayobject *a, int ilow, int ihigh, PyObject *v)
{
	char *item;
	int n; /* Size of replacement array */
	int d; /* Change in size */
#define b ((arrayobject *)v)
	if (v == NULL)
		n = 0;
	else if (array_Check(v)) {
		n = b->ob_size;
		if (a == b) {
			/* Special case "a[i:j] = a" -- copy b first */
			int ret;
			v = array_slice(b, 0, n);
			ret = array_ass_slice(a, ilow, ihigh, v);
			Py_DECREF(v);
			return ret;
		}
		if (b->ob_descr != a->ob_descr) {
			PyErr_BadArgument();
			return -1;
		}
	}
	else {
		PyErr_Format(PyExc_TypeError,
	     "can only assign array (not \"%.200s\") to array slice",
			     v->ob_type->tp_name);
		return -1;
	}
	if (ilow < 0)
		ilow = 0;
	else if (ilow > a->ob_size)
		ilow = a->ob_size;
	if (ihigh < 0)
		ihigh = 0;
	if (ihigh < ilow)
		ihigh = ilow;
	else if (ihigh > a->ob_size)
		ihigh = a->ob_size;
	item = a->ob_item;
	d = n - (ihigh-ilow);
	if (d < 0) { /* Delete -d items */
		memmove(item + (ihigh+d)*a->ob_descr->itemsize,
			item + ihigh*a->ob_descr->itemsize,
			(a->ob_size-ihigh)*a->ob_descr->itemsize);
		a->ob_size += d;
		PyMem_RESIZE(item, char, a->ob_size*a->ob_descr->itemsize);
						/* Can't fail */
		a->ob_item = item;
	}
	else if (d > 0) { /* Insert d items */
		PyMem_RESIZE(item, char,
			     (a->ob_size + d)*a->ob_descr->itemsize);
		if (item == NULL) {
			PyErr_NoMemory();
			return -1;
		}
		memmove(item + (ihigh+d)*a->ob_descr->itemsize,
			item + ihigh*a->ob_descr->itemsize,
			(a->ob_size-ihigh)*a->ob_descr->itemsize);
		a->ob_item = item;
		a->ob_size += d;
	}
	if (n > 0)
		memcpy(item + ilow*a->ob_descr->itemsize, b->ob_item,
		       n*b->ob_descr->itemsize);
	return 0;
#undef b
}

static int
array_ass_item(arrayobject *a, int i, PyObject *v)
{
	if (i < 0 || i >= a->ob_size) {
		PyErr_SetString(PyExc_IndexError,
			         "array assignment index out of range");
		return -1;
	}
	if (v == NULL)
		return array_ass_slice(a, i, i+1, v);
	return (*a->ob_descr->setitem)(a, i, v);
}

static int
setarrayitem(PyObject *a, int i, PyObject *v)
{
	assert(array_Check(a));
	return array_ass_item((arrayobject *)a, i, v);
}

static int
array_do_extend(arrayobject *self, PyObject *bb)
{
	int size;

	if (!array_Check(bb)) {
		PyErr_Format(PyExc_TypeError,
			"can only extend array with array (not \"%.200s\")",
			bb->ob_type->tp_name);
		return -1;
	}
#define b ((arrayobject *)bb)
	if (self->ob_descr != b->ob_descr) {
		PyErr_SetString(PyExc_TypeError,
			     "can only extend with array of same kind");
		return -1;
	}
	size = self->ob_size + b->ob_size;
        PyMem_RESIZE(self->ob_item, char, size*self->ob_descr->itemsize);
        if (self->ob_item == NULL) {
                PyObject_Del(self);
                PyErr_NoMemory();
		return -1;
        }
	memcpy(self->ob_item + self->ob_size*self->ob_descr->itemsize,
               b->ob_item, b->ob_size*b->ob_descr->itemsize);
        self->ob_size = size;

	return 0;
#undef b
}

static PyObject *
array_inplace_concat(arrayobject *self, PyObject *bb)
{
	if (array_do_extend(self, bb) == -1)
		return NULL;
	Py_INCREF(self);
	return (PyObject *)self;
}

static PyObject *
array_inplace_repeat(arrayobject *self, int n)
{
	char *items, *p;
	int size, i;

	if (self->ob_size > 0) {
		if (n < 0)
			n = 0;
		items = self->ob_item;
		size = self->ob_size * self->ob_descr->itemsize;
		if (n == 0) {
			PyMem_FREE(items);
			self->ob_item = NULL;
			self->ob_size = 0;
		}
		else {
			PyMem_Resize(items, char, n * size);
			if (items == NULL)
				return PyErr_NoMemory();
			p = items;
			for (i = 1; i < n; i++) {
				p += size;
				memcpy(p, items, size);
			}
			self->ob_item = items;
			self->ob_size *= n;
		}
	}
	Py_INCREF(self);
	return (PyObject *)self;
}


static PyObject *
ins(arrayobject *self, int where, PyObject *v)
{
	if (ins1(self, where, v) != 0)
		return NULL;
	Py_INCREF(Py_None);
	return Py_None;
}

static PyObject *
array_count(arrayobject *self, PyObject *v)
{
	int count = 0;
	int i;

	for (i = 0; i < self->ob_size; i++) {
		PyObject *selfi = getarrayitem((PyObject *)self, i);
		int cmp = PyObject_RichCompareBool(selfi, v, Py_EQ);
		Py_DECREF(selfi);
		if (cmp > 0)
			count++;
		else if (cmp < 0)
			return NULL;
	}
	return PyInt_FromLong((long)count);
}

PyDoc_STRVAR(count_doc,
"count(x)\n\
\n\
Return number of occurences of x in the array.");

static PyObject *
array_index(arrayobject *self, PyObject *v)
{
	int i;

	for (i = 0; i < self->ob_size; i++) {
		PyObject *selfi = getarrayitem((PyObject *)self, i);
		int cmp = PyObject_RichCompareBool(selfi, v, Py_EQ);
		Py_DECREF(selfi);
		if (cmp > 0) {
			return PyInt_FromLong((long)i);
		}
		else if (cmp < 0)
			return NULL;
	}
	PyErr_SetString(PyExc_ValueError, "array.index(x): x not in list");
	return NULL;
}

PyDoc_STRVAR(index_doc,
"index(x)\n\
\n\
Return index of first occurence of x in the array.");

static int
array_contains(arrayobject *self, PyObject *v)
{
	int i, cmp;

	for (i = 0, cmp = 0 ; cmp == 0 && i < self->ob_size; i++) {
		PyObject *selfi = getarrayitem((PyObject *)self, i);
		cmp = PyObject_RichCompareBool(selfi, v, Py_EQ);
		Py_DECREF(selfi);
	}
	return cmp;
}

static PyObject *
array_remove(arrayobject *self, PyObject *v)
{
	int i;

	for (i = 0; i < self->ob_size; i++) {
		PyObject *selfi = getarrayitem((PyObject *)self,i);
		int cmp = PyObject_RichCompareBool(selfi, v, Py_EQ);
		Py_DECREF(selfi);
		if (cmp > 0) {
			if (array_ass_slice(self, i, i+1,
					   (PyObject *)NULL) != 0)
				return NULL;
			Py_INCREF(Py_None);
			return Py_None;
		}
		else if (cmp < 0)
			return NULL;
	}
	PyErr_SetString(PyExc_ValueError, "array.remove(x): x not in list");
	return NULL;
}

PyDoc_STRVAR(remove_doc,
"remove(x)\n\
\n\
Remove the first occurence of x in the array.");

static PyObject *
array_pop(arrayobject *self, PyObject *args)
{
	int i = -1;
	PyObject *v;
	if (!PyArg_ParseTuple(args, "|i:pop", &i))
		return NULL;
	if (self->ob_size == 0) {
		/* Special-case most common failure cause */
		PyErr_SetString(PyExc_IndexError, "pop from empty array");
		return NULL;
	}
	if (i < 0)
		i += self->ob_size;
	if (i < 0 || i >= self->ob_size) {
		PyErr_SetString(PyExc_IndexError, "pop index out of range");
		return NULL;
	}
	v = getarrayitem((PyObject *)self,i);
	if (array_ass_slice(self, i, i+1, (PyObject *)NULL) != 0) {
		Py_DECREF(v);
		return NULL;
	}
	return v;
}

PyDoc_STRVAR(pop_doc,
"pop([i])\n\
\n\
Return the i-th element and delete it from the array. i defaults to -1.");

static PyObject *
array_extend(arrayobject *self, PyObject *bb)
{
	if (array_do_extend(self, bb) == -1)
		return NULL;
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(extend_doc,
"extend(array)\n\
\n\
 Append array items to the end of the array.");

static PyObject *
array_insert(arrayobject *self, PyObject *args)
{
	int i;
	PyObject *v;
        if (!PyArg_ParseTuple(args, "iO:insert", &i, &v))
		return NULL;
	return ins(self, i, v);
}

PyDoc_STRVAR(insert_doc,
"insert(i,x)\n\
\n\
Insert a new item x into the array before position i.");


static PyObject *
array_buffer_info(arrayobject *self, PyObject *unused)
{
	PyObject* retval = NULL;
	retval = PyTuple_New(2);
	if (!retval)
		return NULL;

	PyTuple_SET_ITEM(retval, 0, PyLong_FromVoidPtr(self->ob_item));
	PyTuple_SET_ITEM(retval, 1, PyInt_FromLong((long)(self->ob_size)));

	return retval;
}

PyDoc_STRVAR(buffer_info_doc,
"buffer_info() -> (address, length)\n\
\n\
Return a tuple (address, length) giving the current memory address and\n\
the length in items of the buffer used to hold array's contents\n\
The length should be multiplied by the itemsize attribute to calculate\n\
the buffer length in bytes.");


static PyObject *
array_append(arrayobject *self, PyObject *v)
{
	return ins(self, (int) self->ob_size, v);
}

PyDoc_STRVAR(append_doc,
"append(x)\n\
\n\
Append new value x to the end of the array.");


static PyObject *
array_byteswap(arrayobject *self, PyObject *unused)
{
	char *p;
	int i;

	switch (self->ob_descr->itemsize) {
	case 1:
		break;
	case 2:
		for (p = self->ob_item, i = self->ob_size; --i >= 0; p += 2) {
			char p0 = p[0];
			p[0] = p[1];
			p[1] = p0;
		}
		break;
	case 4:
		for (p = self->ob_item, i = self->ob_size; --i >= 0; p += 4) {
			char p0 = p[0];
			char p1 = p[1];
			p[0] = p[3];
			p[1] = p[2];
			p[2] = p1;
			p[3] = p0;
		}
		break;
	case 8:
		for (p = self->ob_item, i = self->ob_size; --i >= 0; p += 8) {
			char p0 = p[0];
			char p1 = p[1];
			char p2 = p[2];
			char p3 = p[3];
			p[0] = p[7];
			p[1] = p[6];
			p[2] = p[5];
			p[3] = p[4];
			p[4] = p3;
			p[5] = p2;
			p[6] = p1;
			p[7] = p0;
		}
		break;
	default:
		PyErr_SetString(PyExc_RuntimeError,
			   "don't know how to byteswap this array type");
		return NULL;
	}
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(byteswap_doc,
"byteswap()\n\
\n\
Byteswap all items of the array.  If the items in the array are not 1, 2,\n\
4, or 8 bytes in size, RuntimeError is raised.");

static PyObject *
array_reverse(arrayobject *self, PyObject *unused)
{
	register int itemsize = self->ob_descr->itemsize;
	register char *p, *q;
	/* little buffer to hold items while swapping */
	char tmp[256];	/* 8 is probably enough -- but why skimp */
	assert(itemsize <= sizeof(tmp));

	if (self->ob_size > 1) {
		for (p = self->ob_item,
		     q = self->ob_item + (self->ob_size - 1)*itemsize;
		     p < q;
		     p += itemsize, q -= itemsize) {
			/* memory areas guaranteed disjoint, so memcpy
			 * is safe (& memmove may be slower).
			 */
			memcpy(tmp, p, itemsize);
			memcpy(p, q, itemsize);
			memcpy(q, tmp, itemsize);
		}
	}

	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(reverse_doc,
"reverse()\n\
\n\
Reverse the order of the items in the array.");

static PyObject *
array_fromfile(arrayobject *self, PyObject *args)
{
	PyObject *f;
	int n;
	FILE *fp;
        if (!PyArg_ParseTuple(args, "Oi:fromfile", &f, &n))
		return NULL;
	fp = PyFile_AsFile(f);
	if (fp == NULL) {
		PyErr_SetString(PyExc_TypeError, "arg1 must be open file");
		return NULL;
	}
	if (n > 0) {
		char *item = self->ob_item;
		int itemsize = self->ob_descr->itemsize;
		size_t nread;
		int newlength;
		size_t newbytes;
		/* Be careful here about overflow */
		if ((newlength = self->ob_size + n) <= 0 ||
		    (newbytes = newlength * itemsize) / itemsize !=
		    (size_t)newlength)
			goto nomem;
		PyMem_RESIZE(item, char, newbytes);
		if (item == NULL) {
		  nomem:
			PyErr_NoMemory();
			return NULL;
		}
		self->ob_item = item;
		self->ob_size += n;
		nread = fread(item + (self->ob_size - n) * itemsize,
			      itemsize, n, fp);
		if (nread < (size_t)n) {
			self->ob_size -= (n - nread);
			PyMem_RESIZE(item, char, self->ob_size*itemsize);
			self->ob_item = item;
			PyErr_SetString(PyExc_EOFError,
				         "not enough items in file");
			return NULL;
		}
	}
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(fromfile_doc,
"fromfile(f, n)\n\
\n\
Read n objects from the file object f and append them to the end of the\n\
array.  Also called as read.");


static PyObject *
array_tofile(arrayobject *self, PyObject *f)
{
	FILE *fp;

	fp = PyFile_AsFile(f);
	if (fp == NULL) {
		PyErr_SetString(PyExc_TypeError, "arg must be open file");
		return NULL;
	}
	if (self->ob_size > 0) {
		if (fwrite(self->ob_item, self->ob_descr->itemsize,
			   self->ob_size, fp) != (size_t)self->ob_size) {
			PyErr_SetFromErrno(PyExc_IOError);
			clearerr(fp);
			return NULL;
		}
	}
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(tofile_doc,
"tofile(f)\n\
\n\
Write all items (as machine values) to the file object f.  Also called as\n\
write.");


static PyObject *
array_fromlist(arrayobject *self, PyObject *list)
{
	int n;
	int itemsize = self->ob_descr->itemsize;

	if (!PyList_Check(list)) {
		PyErr_SetString(PyExc_TypeError, "arg must be list");
		return NULL;
	}
	n = PyList_Size(list);
	if (n > 0) {
		char *item = self->ob_item;
		int i;
		PyMem_RESIZE(item, char, (self->ob_size + n) * itemsize);
		if (item == NULL) {
			PyErr_NoMemory();
			return NULL;
		}
		self->ob_item = item;
		self->ob_size += n;
		for (i = 0; i < n; i++) {
			PyObject *v = PyList_GetItem(list, i);
			if ((*self->ob_descr->setitem)(self,
					self->ob_size - n + i, v) != 0) {
				self->ob_size -= n;
				PyMem_RESIZE(item, char,
					          self->ob_size * itemsize);
				self->ob_item = item;
				return NULL;
			}
		}
	}
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(fromlist_doc,
"fromlist(list)\n\
\n\
Append items to array from list.");


static PyObject *
array_tolist(arrayobject *self, PyObject *unused)
{
	PyObject *list = PyList_New(self->ob_size);
	int i;

	if (list == NULL)
		return NULL;
	for (i = 0; i < self->ob_size; i++) {
		PyObject *v = getarrayitem((PyObject *)self, i);
		if (v == NULL) {
			Py_DECREF(list);
			return NULL;
		}
		PyList_SetItem(list, i, v);
	}
	return list;
}

PyDoc_STRVAR(tolist_doc,
"tolist() -> list\n\
\n\
Convert array to an ordinary list with the same items.");


static PyObject *
array_fromstring(arrayobject *self, PyObject *args)
{
	char *str;
	int n;
	int itemsize = self->ob_descr->itemsize;
        if (!PyArg_ParseTuple(args, "s#:fromstring", &str, &n))
		return NULL;
	if (n % itemsize != 0) {
		PyErr_SetString(PyExc_ValueError,
			   "string length not a multiple of item size");
		return NULL;
	}
	n = n / itemsize;
	if (n > 0) {
		char *item = self->ob_item;
		PyMem_RESIZE(item, char, (self->ob_size + n) * itemsize);
		if (item == NULL) {
			PyErr_NoMemory();
			return NULL;
		}
		self->ob_item = item;
		self->ob_size += n;
		memcpy(item + (self->ob_size - n) * itemsize,
		       str, itemsize*n);
	}
	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(fromstring_doc,
"fromstring(string)\n\
\n\
Appends items from the string, interpreting it as an array of machine\n\
values,as if it had been read from a file using the fromfile() method).");


static PyObject *
array_tostring(arrayobject *self, PyObject *unused)
{
	return PyString_FromStringAndSize(self->ob_item,
				    self->ob_size * self->ob_descr->itemsize);
}

PyDoc_STRVAR(tostring_doc,
"tostring() -> string\n\
\n\
Convert the array to an array of machine values and return the string\n\
representation.");



#ifdef Py_USING_UNICODE
static PyObject *
array_fromunicode(arrayobject *self, PyObject *args)
{
	Py_UNICODE *ustr;
	int n;

        if (!PyArg_ParseTuple(args, "u#:fromunicode", &ustr, &n))
		return NULL;
	if (self->ob_descr->typecode != 'u') {
		PyErr_SetString(PyExc_ValueError,
			"fromunicode() may only be called on "
			"type 'u' arrays");
		return NULL;
	}
	if (n > 0) {
		Py_UNICODE *item = (Py_UNICODE *) self->ob_item;
		PyMem_RESIZE(item, Py_UNICODE, self->ob_size + n);
		if (item == NULL) {
			PyErr_NoMemory();
			return NULL;
		}
		self->ob_item = (char *) item;
		self->ob_size += n;
		memcpy(item + self->ob_size - n,
		       ustr, n * sizeof(Py_UNICODE));
	}

	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(fromunicode_doc,
"fromunicode(ustr)\n\
\n\
Extends this array with data from the unicode string ustr.\n\
The array must be a type 'u' array; otherwise a ValueError\n\
is raised.  Use array.fromstring(ustr.decode(...)) to\n\
append Unicode data to an array of some other type.");


static PyObject *
array_tounicode(arrayobject *self, PyObject *unused)
{
	if (self->ob_descr->typecode != 'u') {
		PyErr_SetString(PyExc_ValueError,
			"tounicode() may only be called on type 'u' arrays");
		return NULL;
	}
	return PyUnicode_FromUnicode((Py_UNICODE *) self->ob_item, self->ob_size);
}

PyDoc_STRVAR(tounicode_doc,
"tounicode() -> unicode\n\
\n\
Convert the array to a unicode string.  The array must be\n\
a type 'u' array; otherwise a ValueError is raised.  Use\n\
array.tostring().decode() to obtain a unicode string from\n\
an array of some other type.");

#endif /* Py_USING_UNICODE */


static PyObject *
array_get_typecode(arrayobject *a, void *closure)
{
	char tc = a->ob_descr->typecode;
	return PyString_FromStringAndSize(&tc, 1);
}

static PyObject *
array_get_itemsize(arrayobject *a, void *closure)
{
	return PyInt_FromLong((long)a->ob_descr->itemsize);
}

static PyGetSetDef array_getsets [] = {
	{"typecode", (getter) array_get_typecode, NULL,
	 "the typecode character used to create the array"},
	{"itemsize", (getter) array_get_itemsize, NULL,
	 "the size, in bytes, of one array item"},
	{NULL}
};

PyMethodDef array_methods[] = {
	{"append",	(PyCFunction)array_append,	METH_O,
	 append_doc},
	{"buffer_info", (PyCFunction)array_buffer_info, METH_NOARGS,
	 buffer_info_doc},
	{"byteswap",	(PyCFunction)array_byteswap,	METH_NOARGS,
	 byteswap_doc},
	{"count",	(PyCFunction)array_count,	METH_O,
	 count_doc},
	{"extend",      (PyCFunction)array_extend,	METH_O,
	 extend_doc},
	{"fromfile",	(PyCFunction)array_fromfile,	METH_VARARGS,
	 fromfile_doc},
	{"fromlist",	(PyCFunction)array_fromlist,	METH_O,
	 fromlist_doc},
	{"fromstring",	(PyCFunction)array_fromstring,	METH_VARARGS,
	 fromstring_doc},
#ifdef Py_USING_UNICODE
	{"fromunicode",	(PyCFunction)array_fromunicode,	METH_VARARGS,
	 fromunicode_doc},
#endif
	{"index",	(PyCFunction)array_index,	METH_O,
	 index_doc},
	{"insert",	(PyCFunction)array_insert,	METH_VARARGS,
	 insert_doc},
	{"pop",		(PyCFunction)array_pop,		METH_VARARGS,
	 pop_doc},
	{"read",	(PyCFunction)array_fromfile,	METH_VARARGS,
	 fromfile_doc},
	{"remove",	(PyCFunction)array_remove,	METH_O,
	 remove_doc},
	{"reverse",	(PyCFunction)array_reverse,	METH_NOARGS,
	 reverse_doc},
/*	{"sort",	(PyCFunction)array_sort,	METH_VARARGS,
	sort_doc},*/
	{"tofile",	(PyCFunction)array_tofile,	METH_O,
	 tofile_doc},
	{"tolist",	(PyCFunction)array_tolist,	METH_NOARGS,
	 tolist_doc},
	{"tostring",	(PyCFunction)array_tostring,	METH_NOARGS,
	 tostring_doc},
#ifdef Py_USING_UNICODE
	{"tounicode",   (PyCFunction)array_tounicode,	METH_NOARGS,
	 tounicode_doc},
#endif
	{"write",	(PyCFunction)array_tofile,	METH_O,
	 tofile_doc},
	{NULL,		NULL}		/* sentinel */
};

static PyObject *
array_repr(arrayobject *a)
{
	char buf[256], typecode;
	PyObject *s, *t, *v = NULL;
	int len;

	len = a->ob_size;
	typecode = a->ob_descr->typecode;
	if (len == 0) {
		PyOS_snprintf(buf, sizeof(buf), "array('%c')", typecode);
		return PyString_FromString(buf);
	}
		
	if (typecode == 'c')
		v = array_tostring(a, NULL);
#ifdef Py_USING_UNICODE
	else if (typecode == 'u')
		v = array_tounicode(a, NULL);
#endif
	else
		v = array_tolist(a, NULL);
	t = PyObject_Repr(v);
	Py_XDECREF(v);

	PyOS_snprintf(buf, sizeof(buf), "array('%c', ", typecode);
	s = PyString_FromString(buf);
	PyString_ConcatAndDel(&s, t);
	PyString_ConcatAndDel(&s, PyString_FromString(")"));
	return s;
}

static PyObject*
array_subscr(arrayobject* self, PyObject* item)
{
	if (PyInt_Check(item)) {
		long i = PyInt_AS_LONG(item);
		if (i < 0)
			i += self->ob_size;
		return array_item(self, i);
	}
	else if (PyLong_Check(item)) {
		long i = PyLong_AsLong(item);
		if (i == -1 && PyErr_Occurred())
			return NULL;
		if (i < 0)
			i += self->ob_size;
		return array_item(self, i);
	}
	else if (PySlice_Check(item)) {
		int start, stop, step, slicelength, cur, i;
		PyObject* result;
		arrayobject* ar;
		int itemsize = self->ob_descr->itemsize;

		if (PySlice_GetIndicesEx((PySliceObject*)item, self->ob_size,
				 &start, &stop, &step, &slicelength) < 0) {
			return NULL;
		}

		if (slicelength <= 0) {
			return newarrayobject(&Arraytype, 0, self->ob_descr);
		}
		else {
			result = newarrayobject(&Arraytype, slicelength, self->ob_descr);
			if (!result) return NULL;

			ar = (arrayobject*)result;

			for (cur = start, i = 0; i < slicelength; 
			     cur += step, i++) {
				memcpy(ar->ob_item + i*itemsize,
				       self->ob_item + cur*itemsize,
				       itemsize);
			}
			
			return result;
		}		
	}
	else {
		PyErr_SetString(PyExc_TypeError, 
				"list indices must be integers");
		return NULL;
	}
}

static int
array_ass_subscr(arrayobject* self, PyObject* item, PyObject* value)
{
	if (PyInt_Check(item)) {
		long i = PyInt_AS_LONG(item);
		if (i < 0)
			i += self->ob_size;
		return array_ass_item(self, i, value);
	}
	else if (PyLong_Check(item)) {
		long i = PyLong_AsLong(item);
		if (i == -1 && PyErr_Occurred())
			return -1;
		if (i < 0)
			i += self->ob_size;
		return array_ass_item(self, i, value);
	}
	else if (PySlice_Check(item)) {
		int start, stop, step, slicelength;
		int itemsize = self->ob_descr->itemsize;

		if (PySlice_GetIndicesEx((PySliceObject*)item, self->ob_size,
				 &start, &stop, &step, &slicelength) < 0) {
			return -1;
		}

		/* treat A[slice(a,b)] = v _exactly_ like A[a:b] = v */
		if (step == 1 && ((PySliceObject*)item)->step == Py_None)
			return array_ass_slice(self, start, stop, value);

		if (value == NULL) {
			/* delete slice */
			int cur, i, extra;
			
			if (slicelength <= 0)
				return 0;

			if (step < 0) {
				stop = start + 1;
				start = stop + step*(slicelength - 1) - 1;
				step = -step;
			}

			for (cur = start, i = 0; i < slicelength - 1;
			     cur += step, i++) {
				memmove(self->ob_item + (cur - i)*itemsize,
					self->ob_item + (cur + 1)*itemsize,
					(step - 1) * itemsize);
			}
			extra = self->ob_size - (cur + 1);
			if (extra > 0) {
				memmove(self->ob_item + (cur - i)*itemsize,
					self->ob_item + (cur + 1)*itemsize,
					extra*itemsize);
			}

			self->ob_size -= slicelength;
			self->ob_item = PyMem_REALLOC(self->ob_item, itemsize*self->ob_size);


			return 0;
		}
		else {
			/* assign slice */
			int cur, i;
			arrayobject* av;

			if (!array_Check(value)) {
				PyErr_Format(PyExc_TypeError,
			     "must assign array (not \"%.200s\") to slice",
					     value->ob_type->tp_name);
				return -1;
			}

			av = (arrayobject*)value;

			if (av->ob_size != slicelength) {
				PyErr_Format(PyExc_ValueError,
            "attempt to assign array of size %d to extended slice of size %d",
					     av->ob_size, slicelength);
				return -1;
			}

			if (!slicelength)
				return 0;

			/* protect against a[::-1] = a */
			if (self == av) { 
				value = array_slice(av, 0, av->ob_size);
				av = (arrayobject*)value;
			} 
			else {
				Py_INCREF(value);
			}

			for (cur = start, i = 0; i < slicelength; 
			     cur += step, i++) {
				memcpy(self->ob_item + cur*itemsize,
				       av->ob_item + i*itemsize,
				       itemsize);
			}

			Py_DECREF(value);
			
			return 0;
		}
	} 
	else {
		PyErr_SetString(PyExc_TypeError, 
				"list indices must be integers");
		return -1;
	}
}

static PyMappingMethods array_as_mapping = {
	(inquiry)array_length,
	(binaryfunc)array_subscr,
	(objobjargproc)array_ass_subscr
};

static int
array_buffer_getreadbuf(arrayobject *self, int index, const void **ptr)
{
	if ( index != 0 ) {
		PyErr_SetString(PyExc_SystemError,
				"Accessing non-existent array segment");
		return -1;
	}
	*ptr = (void *)self->ob_item;
	return self->ob_size*self->ob_descr->itemsize;
}

static int
array_buffer_getwritebuf(arrayobject *self, int index, const void **ptr)
{
	if ( index != 0 ) {
		PyErr_SetString(PyExc_SystemError,
				"Accessing non-existent array segment");
		return -1;
	}
	*ptr = (void *)self->ob_item;
	return self->ob_size*self->ob_descr->itemsize;
}

static int
array_buffer_getsegcount(arrayobject *self, int *lenp)
{
	if ( lenp )
		*lenp = self->ob_size*self->ob_descr->itemsize;
	return 1;
}

static PySequenceMethods array_as_sequence = {
	(inquiry)array_length,		        /*sq_length*/
	(binaryfunc)array_concat,               /*sq_concat*/
	(intargfunc)array_repeat,		/*sq_repeat*/
	(intargfunc)array_item,		        /*sq_item*/
	(intintargfunc)array_slice,		/*sq_slice*/
	(intobjargproc)array_ass_item,		/*sq_ass_item*/
	(intintobjargproc)array_ass_slice,	/*sq_ass_slice*/
	(objobjproc)array_contains,		/*sq_contains*/
	(binaryfunc)array_inplace_concat,	/*sq_inplace_concat*/
	(intargfunc)array_inplace_repeat	/*sq_inplace_repeat*/
};

static PyBufferProcs array_as_buffer = {
	(getreadbufferproc)array_buffer_getreadbuf,
	(getwritebufferproc)array_buffer_getwritebuf,
	(getsegcountproc)array_buffer_getsegcount,
};

static PyObject *
array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	char c;
	PyObject *initial = NULL;
	struct arraydescr *descr;

	if (kwds != NULL) {
		int i = PyObject_Length(kwds);
		if (i < 0)
			return NULL;
		else if (i > 0) {
			PyErr_SetString(PyExc_TypeError,
			    "array.array constructor takes "
			    "no keyword arguments");
			return NULL;
		}
	}

	if (!PyArg_ParseTuple(args, "c|O:array", &c, &initial))
		return NULL;

	if (!(initial == NULL || PyList_Check(initial)
	      || PyString_Check(initial) || PyTuple_Check(initial)
	      || (c == 'u' && PyUnicode_Check(initial)))) {
		PyErr_SetString(PyExc_TypeError,
		    "array initializer must be list or string");
		return NULL;
	}
	for (descr = descriptors; descr->typecode != '\0'; descr++) {
		if (descr->typecode == c) {
			PyObject *a;
			int len;

			if (initial == NULL || !(PyList_Check(initial) 
				|| PyTuple_Check(initial)))
				len = 0;
			else
				len = PySequence_Size(initial);

			a = newarrayobject(type, len, descr);
			if (a == NULL)
				return NULL;

			if (len > 0) {
				int i;
				for (i = 0; i < len; i++) {
					PyObject *v =
					        PySequence_GetItem(initial, i);
					if (setarrayitem(a, i, v) != 0) {
						Py_DECREF(a);
						return NULL;
					}
				}
			}
			if (initial != NULL && PyString_Check(initial)) {
				PyObject *t_initial = Py_BuildValue("(O)",
								    initial);
				PyObject *v =
					array_fromstring((arrayobject *)a,
							 t_initial);
				Py_DECREF(t_initial);
				if (v == NULL) {
					Py_DECREF(a);
					return NULL;
				}
				Py_DECREF(v);
#ifdef Py_USING_UNICODE
			} else if (initial != NULL && PyUnicode_Check(initial))  {
				int n = PyUnicode_GET_DATA_SIZE(initial);
				if (n > 0) {
					arrayobject *self = (arrayobject *)a;
					char *item = self->ob_item;
					item = PyMem_Realloc(item, n);
					if (item == NULL) {
						PyErr_NoMemory();
						Py_DECREF(a);
						return NULL;
					}
					self->ob_item = item;
					self->ob_size = n / sizeof(Py_UNICODE);
					memcpy(item, PyUnicode_AS_DATA(initial), n);
				}
#endif
			}
			return a;
		}
	}
	PyErr_SetString(PyExc_ValueError,
		"bad typecode (must be c, b, B, u, h, H, i, I, l, L, f or d)");
	return NULL;
}


PyDoc_STRVAR(module_doc,
"This module defines an object type which can efficiently represent\n\
an array of basic values: characters, integers, floating point\n\
numbers.  Arrays are sequence types and behave very much like lists,\n\
except that the type of objects stored in them is constrained.  The\n\
type is specified at object creation time by using a type code, which\n\
is a single character.  The following type codes are defined:\n\
\n\
    Type code   C Type             Minimum size in bytes \n\
    'c'         character          1 \n\
    'b'         signed integer     1 \n\
    'B'         unsigned integer   1 \n\
    'u'         Unicode character  2 \n\
    'h'         signed integer     2 \n\
    'H'         unsigned integer   2 \n\
    'i'         signed integer     2 \n\
    'I'         unsigned integer   2 \n\
    'l'         signed integer     4 \n\
    'L'         unsigned integer   4 \n\
    'f'         floating point     4 \n\
    'd'         floating point     8 \n\
\n\
The constructor is:\n\
\n\
array(typecode [, initializer]) -- create a new array\n\
");

PyDoc_STRVAR(arraytype_doc,
"array(typecode [, initializer]) -> array\n\
\n\
Return a new array whose items are restricted by typecode, and\n\
initialized from the optional initializer value, which must be a list\n\
or a string.\n\
\n\
Arrays represent basic values and behave very much like lists, except\n\
the type of objects stored in them is constrained.\n\
\n\
Methods:\n\
\n\
append() -- append a new item to the end of the array\n\
buffer_info() -- return information giving the current memory info\n\
byteswap() -- byteswap all the items of the array\n\
count() -- return number of occurences of an object\n\
extend() -- extend array by appending array elements\n\
fromfile() -- read items from a file object\n\
fromlist() -- append items from the list\n\
fromstring() -- append items from the string\n\
index() -- return index of first occurence of an object\n\
insert() -- insert a new item into the array at a provided position\n\
pop() -- remove and return item (default last)\n\
read() -- DEPRECATED, use fromfile()\n\
remove() -- remove first occurence of an object\n\
reverse() -- reverse the order of the items in the array\n\
tofile() -- write all items to a file object\n\
tolist() -- return the array converted to an ordinary list\n\
tostring() -- return the array converted to a string\n\
write() -- DEPRECATED, use tofile()\n\
\n\
Attributes:\n\
\n\
typecode -- the typecode character used to create the array\n\
itemsize -- the length in bytes of one array item\n\
");

static PyObject *array_iter(arrayobject *ao);

static PyTypeObject Arraytype = {
	PyObject_HEAD_INIT(NULL)
	0,
	"array.array",
	sizeof(arrayobject),
	0,
	(destructor)array_dealloc,		/* tp_dealloc */
	0,					/* tp_print */
	0,					/* tp_getattr */
	0,					/* tp_setattr */
	0,					/* tp_compare */
	(reprfunc)array_repr,			/* tp_repr */
	0,					/* tp_as _number*/
	&array_as_sequence,			/* tp_as _sequence*/
	&array_as_mapping,			/* tp_as _mapping*/
	0, 					/* tp_hash */
	0,					/* tp_call */
	0,					/* tp_str */
	PyObject_GenericGetAttr,		/* tp_getattro */
	0,					/* tp_setattro */
	&array_as_buffer,			/* tp_as_buffer*/
	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /* tp_flags */
	arraytype_doc,				/* tp_doc */
 	0,					/* tp_traverse */
	0,					/* tp_clear */
	array_richcompare,			/* tp_richcompare */
	0,					/* tp_weaklistoffset */
	(getiterfunc)array_iter,		/* tp_iter */
	0,					/* tp_iternext */
	array_methods,				/* tp_methods */
	0,					/* tp_members */
	array_getsets,				/* tp_getset */
	0,					/* tp_base */
	0,					/* tp_dict */
	0,					/* tp_descr_get */
	0,					/* tp_descr_set */
	0,					/* tp_dictoffset */
	0,					/* tp_init */
	PyType_GenericAlloc,			/* tp_alloc */
	array_new,				/* tp_new */
	PyObject_Del,				/* tp_free */
};


/*********************** Array Iterator **************************/

typedef struct {
	PyObject_HEAD
	long			index;
	arrayobject		*ao;
	PyObject		* (*getitem)(struct arrayobject *, int);
} arrayiterobject;

static PyTypeObject PyArrayIter_Type;

#define PyArrayIter_Check(op) PyObject_TypeCheck(op, &PyArrayIter_Type)

static PyObject *
array_iter(arrayobject *ao)
{
	arrayiterobject *it;

	if (!array_Check(ao)) {
		PyErr_BadInternalCall();
		return NULL;
	}

	it = PyObject_GC_New(arrayiterobject, &PyArrayIter_Type);
	if (it == NULL)
		return NULL;

	Py_INCREF(ao);
	it->ao = ao;
	it->index = 0;
	it->getitem = ao->ob_descr->getitem;
	PyObject_GC_Track(it);
	return (PyObject *)it;
}

static PyObject *
arrayiter_next(arrayiterobject *it)
{
	assert(PyArrayIter_Check(it));
	if (it->index < it->ao->ob_size)
		return (*it->getitem)(it->ao, it->index++);
	return NULL;
}

static void
arrayiter_dealloc(arrayiterobject *it)
{
	PyObject_GC_UnTrack(it);
	Py_XDECREF(it->ao);
	PyObject_GC_Del(it);
}

static int
arrayiter_traverse(arrayiterobject *it, visitproc visit, void *arg)
{
	if (it->ao != NULL)
		return visit((PyObject *)(it->ao), arg);
	return 0;
}

static PyTypeObject PyArrayIter_Type = {
	PyObject_HEAD_INIT(NULL)
	0,                                      /* ob_size */
	"arrayiterator",                        /* tp_name */
	sizeof(arrayiterobject),                /* tp_basicsize */
	0,                                      /* tp_itemsize */
	/* methods */
	(destructor)arrayiter_dealloc,		/* tp_dealloc */
	0,                                      /* tp_print */
	0,                                      /* tp_getattr */
	0,                                      /* tp_setattr */
	0,                                      /* tp_compare */
	0,                                      /* tp_repr */
	0,                                      /* tp_as_number */
	0,                                      /* tp_as_sequence */
	0,                                      /* tp_as_mapping */
	0,                                      /* tp_hash */
	0,                                      /* tp_call */
	0,                                      /* tp_str */
	PyObject_GenericGetAttr,                /* tp_getattro */
	0,                                      /* tp_setattro */
	0,                                      /* tp_as_buffer */
	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
	0,                                      /* tp_doc */
	(traverseproc)arrayiter_traverse,	/* tp_traverse */
	0,					/* tp_clear */
	0,                                      /* tp_richcompare */
	0,                                      /* tp_weaklistoffset */
	PyObject_SelfIter,			/* tp_iter */
	(iternextfunc)arrayiter_next,		/* tp_iternext */
	0,					/* tp_methods */
};


/*********************** Install Module **************************/

/* No functions in array module. */
static PyMethodDef a_methods[] = {
    {NULL, NULL, 0, NULL}        /* Sentinel */
};


PyMODINIT_FUNC
initarray(void)
{
	PyObject *m;

	Arraytype.ob_type = &PyType_Type;
	PyArrayIter_Type.ob_type = &PyType_Type;
	m = Py_InitModule3("array", a_methods, module_doc);

        Py_INCREF((PyObject *)&Arraytype);
	PyModule_AddObject(m, "ArrayType", (PyObject *)&Arraytype);
        Py_INCREF((PyObject *)&Arraytype);
	PyModule_AddObject(m, "array", (PyObject *)&Arraytype);
	/* No need to check the error here, the caller will do that */
}
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/*
 * tclIO.c --
 *
 *	This file provides the generic portions (those that are the same on
 *	all platforms and for all channel types) of Tcl's IO facilities.
 *
 * Copyright (c) 1998-2000 Ajuba Solutions
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclIO.c,v 1.156 2008/12/18 16:52:53 ferrieux Exp $
 */

#include "tclInt.h"
#include "tclIO.h"
#include <assert.h>

/*
 * All static variables used in this file are collected into a single instance
 * of the following structure. For multi-threaded implementations, there is
 * one instance of this structure for each thread.
 *
 * Notice that different structures with the same name appear in other files.
 * The structure defined below is used in this file only.
 */

typedef struct ThreadSpecificData {
    NextChannelHandler *nestedHandlerPtr;
				/* This variable holds the list of nested
				 * ChannelHandlerEventProc invocations. */
    ChannelState *firstCSPtr;	/* List of all channels currently open,
				 * indexed by ChannelState, as only one
				 * ChannelState exists per set of stacked
				 * channels. */
    Tcl_Channel stdinChannel;	/* Static variable for the stdin channel. */
    int stdinInitialized;
    Tcl_Channel stdoutChannel;	/* Static variable for the stdout channel. */
    int stdoutInitialized;
    Tcl_Channel stderrChannel;	/* Static variable for the stderr channel. */
    int stderrInitialized;
    Tcl_Encoding binaryEncoding;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * Static functions in this file:
 */

static ChannelBuffer *	AllocChannelBuffer(int length);
static void		ChannelTimerProc(ClientData clientData);
static int		CheckChannelErrors(ChannelState *statePtr,
			    int direction);
static int		CheckFlush(Channel *chanPtr, ChannelBuffer *bufPtr,
			    int newlineFlag);
static int		CheckForDeadChannel(Tcl_Interp *interp,
			    ChannelState *statePtr);
static void		CheckForStdChannelsBeingClosed(Tcl_Channel chan);
static void		CleanupChannelHandlers(Tcl_Interp *interp,
			    Channel *chanPtr);
static int		CloseChannel(Tcl_Interp *interp, Channel *chanPtr,
			    int errorCode);
static void		CommonGetsCleanup(Channel *chanPtr);
static int		CopyAndTranslateBuffer(ChannelState *statePtr,
			    char *result, int space);
static int		CopyBuffer(Channel *chanPtr, char *result, int space);
static int		CopyData(CopyState *csPtr, int mask);
static void		CopyEventProc(ClientData clientData, int mask);
static void		CreateScriptRecord(Tcl_Interp *interp,
			    Channel *chanPtr, int mask, Tcl_Obj *scriptPtr);
static void		DeleteChannelTable(ClientData clientData,
			    Tcl_Interp *interp);
static void		DeleteScriptRecord(Tcl_Interp *interp,
			    Channel *chanPtr, int mask);
static int		DetachChannel(Tcl_Interp *interp, Tcl_Channel chan);
static void		DiscardInputQueued(ChannelState *statePtr,
			    int discardSavedBuffers);
static void		DiscardOutputQueued(ChannelState *chanPtr);
static int		DoRead(Channel *chanPtr, char *srcPtr, int slen);
static int		DoWrite(Channel *chanPtr, const char *src, int srcLen);
static int		DoReadChars(Channel *chan, Tcl_Obj *objPtr, int toRead,
			    int appendFlag);
static int		DoWriteChars(Channel *chan, const char *src, int len);
static int		FilterInputBytes(Channel *chanPtr,
			    GetsState *statePtr);
static int		FlushChannel(Tcl_Interp *interp, Channel *chanPtr,
			    int calledFromAsyncFlush);
static int		TclGetsObjBinary(Tcl_Channel chan, Tcl_Obj *objPtr);
static void		FreeBinaryEncoding(ClientData clientData);
static Tcl_HashTable *	GetChannelTable(Tcl_Interp *interp);
static int		GetInput(Channel *chanPtr);
static int		HaveVersion(const Tcl_ChannelType *typePtr,
			    Tcl_ChannelTypeVersion minimumVersion);
static void		PeekAhead(Channel *chanPtr, char **dstEndPtr,
			    GetsState *gsPtr);
static int		ReadBytes(ChannelState *statePtr, Tcl_Obj *objPtr,
			    int charsLeft, int *offsetPtr);
static int		ReadChars(ChannelState *statePtr, Tcl_Obj *objPtr,
			    int charsLeft, int *offsetPtr, int *factorPtr);
static void		RecycleBuffer(ChannelState *statePtr,
			    ChannelBuffer *bufPtr, int mustDiscard);
static int		StackSetBlockMode(Channel *chanPtr, int mode);
static int		SetBlockMode(Tcl_Interp *interp, Channel *chanPtr,
			    int mode);
static void		StopCopy(CopyState *csPtr);
static int		TranslateInputEOL(ChannelState *statePtr, char *dst,
			    const char *src, int *dstLenPtr, int *srcLenPtr);
static int		TranslateOutputEOL(ChannelState *statePtr, char *dst,
			    const char *src, int *dstLenPtr, int *srcLenPtr);
static void		UpdateInterest(Channel *chanPtr);
static int		WriteBytes(Channel *chanPtr, const char *src,
			    int srcLen);
static int		WriteChars(Channel *chanPtr, const char *src,
			    int srcLen);
static Tcl_Obj *	FixLevelCode(Tcl_Obj *msg);
static void		SpliceChannel(Tcl_Channel chan);
static void		CutChannel(Tcl_Channel chan);

/*
 * Simplifying helper macros. All may use their argument(s) multiple times.
 * The ANSI C "prototypes" for the macros are listed below, together with a
 * short description of what the macro does.
 *
 * --------------------------------------------------------------------------
 * int BytesLeft(ChannelBuffer *bufPtr)
 *
 *	Returns the number of bytes of data remaining in the buffer.
 *
 * int SpaceLeft(ChannelBuffer *bufPtr)
 *
 *	Returns the number of bytes of space remaining at the end of the
 *	buffer.
 *
 * int IsBufferReady(ChannelBuffer *bufPtr)
 *
 *	Returns whether a buffer has bytes available within it.
 *
 * int IsBufferEmpty(ChannelBuffer *bufPtr)
 *
 *	Returns whether a buffer is entirely empty. Note that this is not the
 *	inverse of the above operation; trying to merge the two seems to lead
 *	to occasional crashes...
 *
 * int IsBufferFull(ChannelBuffer *bufPtr)
 *
 *	Returns whether more data can be added to a buffer.
 *
 * int IsBufferOverflowing(ChannelBuffer *bufPtr)
 *
 *	Returns whether a buffer has more data in it than it should.
 *
 * char *InsertPoint(ChannelBuffer *bufPtr)
 *
 *	Returns a pointer to where characters should be added to the buffer.
 *
 * char *RemovePoint(ChannelBuffer *bufPtr)
 *
 *	Returns a pointer to where characters should be removed from the
 *	buffer.
 * --------------------------------------------------------------------------
 */

#define BytesLeft(bufPtr)	((bufPtr)->nextAdded - (bufPtr)->nextRemoved)

#define SpaceLeft(bufPtr)	((bufPtr)->bufLength - (bufPtr)->nextAdded)

#define IsBufferReady(bufPtr)	((bufPtr)->nextAdded > (bufPtr)->nextRemoved)

#define IsBufferEmpty(bufPtr)	((bufPtr)->nextAdded == (bufPtr)->nextRemoved)

#define IsBufferFull(bufPtr)	((bufPtr)->nextAdded >= (bufPtr)->bufLength)

#define IsBufferOverflowing(bufPtr) ((bufPtr)->nextAdded>(bufPtr)->bufLength)

#define InsertPoint(bufPtr)	((bufPtr)->buf + (bufPtr)->nextAdded)

#define RemovePoint(bufPtr)	((bufPtr)->buf + (bufPtr)->nextRemoved)

/*
 * For working with channel state flag bits.
 */

#define SetFlag(statePtr, flag)		((statePtr)->flags |= (flag))
#define ResetFlag(statePtr, flag)	((statePtr)->flags &= ~(flag))
#define GotFlag(statePtr, flag)		((statePtr)->flags & (flag))

/*
 * Macro for testing whether a string (in optionName, length len) matches a
 * value (prefix matching rules). Arguments are the minimum length to match
 * and the value to match against. (Can't use Tcl_GetIndexFromObj as this is
 * used in a situation where no objects are available.)
 */

#define HaveOpt(minLength, nameString) \
	((len > (minLength)) && (optionName[1] == (nameString)[1]) \
		&& (strncmp(optionName, (nameString), len) == 0))

/*
 * The ChannelObjType type.  We actually store the ChannelState structure
 * as that lives longest and we want to return the bottomChanPtr when
 * requested (consistent with Tcl_GetChannel).  The setFromAny and
 * updateString can be NULL as they should not be called.
 */

static void		DupChannelIntRep(Tcl_Obj *objPtr, Tcl_Obj *copyPtr);
static int		SetChannelFromAny(Tcl_Interp *interp,
			    Tcl_Obj *objPtr);
static void		UpdateStringOfChannel(Tcl_Obj *objPtr);
static void		FreeChannelIntRep(Tcl_Obj *objPtr);

static const Tcl_ObjType tclChannelType = {
    "channel",			/* name for this type */
    FreeChannelIntRep,		/* freeIntRepProc */
    DupChannelIntRep,		/* dupIntRepProc */
    NULL,			/* updateStringProc UpdateStringOfChannel */
    NULL			/* setFromAnyProc SetChannelFromAny */
};

#define GET_CHANNELSTATE(objPtr) \
    ((ChannelState *) (objPtr)->internalRep.otherValuePtr)
#define SET_CHANNELSTATE(objPtr, storePtr) \
    ((objPtr)->internalRep.otherValuePtr = (void *) (storePtr))
#define GET_CHANNELINTERP(objPtr) \
    ((Interp *) (objPtr)->internalRep.twoPtrValue.ptr2)
#define SET_CHANNELINTERP(objPtr, storePtr) \
    ((objPtr)->internalRep.twoPtrValue.ptr2 = (void *) (storePtr))

#define BUSY_STATE(st,fl) \
     ((((st)->csPtrR) && ((fl) & TCL_READABLE)) || \
      (((st)->csPtrW) && ((fl) & TCL_WRITABLE)))

#define MAX_CHANNEL_BUFFER_SIZE (1024*1024)

/*
 *---------------------------------------------------------------------------
 *
 * ChanClose, ChanRead, ChanSeek, ChanThreadAction, ChanWatch, ChanWrite --
 *
 *	Simplify the access to selected channel driver "methods" that are used
 *	in multiple places in a stereotypical fashion. These are just thin
 *	wrappers around the driver functions.
 *
 *---------------------------------------------------------------------------
 */

static inline int
ChanClose(
    Channel *chanPtr,
    Tcl_Interp *interp)
{
    if (chanPtr->typePtr->closeProc != TCL_CLOSE2PROC) {
	return chanPtr->typePtr->closeProc(chanPtr->instanceData, interp);
    } else {
	return chanPtr->typePtr->close2Proc(chanPtr->instanceData, interp, 0);
    }
}

static inline int
ChanRead(
    Channel *chanPtr,
    char *dst,
    int dstSize,
    int *errnoPtr)
{
    return chanPtr->typePtr->inputProc(chanPtr->instanceData, dst, dstSize,
	    errnoPtr);
}

static inline Tcl_WideInt
ChanSeek(
    Channel *chanPtr,
    Tcl_WideInt offset,
    int mode,
    int *errnoPtr)
{
    /*
     * Note that we prefer the wideSeekProc if that field is available in the
     * type and non-NULL.
     */

    if (HaveVersion(chanPtr->typePtr, TCL_CHANNEL_VERSION_3) &&
	    chanPtr->typePtr->wideSeekProc != NULL) {
	return chanPtr->typePtr->wideSeekProc(chanPtr->instanceData,
		offset, mode, errnoPtr);
    }

    if (offset<Tcl_LongAsWide(LONG_MIN) || offset>Tcl_LongAsWide(LONG_MAX)) {
	*errnoPtr = EOVERFLOW;
	return Tcl_LongAsWide(-1);
    }

    return Tcl_LongAsWide(chanPtr->typePtr->seekProc(chanPtr->instanceData,
	    Tcl_WideAsLong(offset), mode, errnoPtr));
}

static inline void
ChanThreadAction(
    Channel *chanPtr,
    int action)
{
    Tcl_DriverThreadActionProc *threadActionProc =
	    Tcl_ChannelThreadActionProc(chanPtr->typePtr);

    if (threadActionProc != NULL) {
	threadActionProc(chanPtr->instanceData, action);
    }
}

static inline void
ChanWatch(
    Channel *chanPtr,
    int mask)
{
    chanPtr->typePtr->watchProc(chanPtr->instanceData, mask);
}

static inline int
ChanWrite(
    Channel *chanPtr,
    const char *src,
    int srcLen,
    int *errnoPtr)
{
    return chanPtr->typePtr->outputProc(chanPtr->instanceData, src, srcLen,
	    errnoPtr);
}

/*
 *---------------------------------------------------------------------------
 *
 * TclInitIOSubsystem --
 *
 *	Initialize all resources used by this subsystem on a per-process
 *	basis.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Depends on the memory subsystems.
 *
 *---------------------------------------------------------------------------
 */

void
TclInitIOSubsystem(void)
{
    /*
     * By fetching thread local storage we take care of allocating it for each
     * thread.
     */

    (void) TCL_TSD_INIT(&dataKey);
}

/*
 *-------------------------------------------------------------------------
 *
 * TclFinalizeIOSubsystem --
 *
 *	Releases all resources used by this subsystem on a per-process basis.
 *	Closes all extant channels that have not already been closed because
 *	they were not owned by any interp.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Depends on encoding and memory subsystems.
 *
 *-------------------------------------------------------------------------
 */

	/* ARGSUSED */
void
TclFinalizeIOSubsystem(void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel *chanPtr = NULL;	/* Iterates over open channels. */
    ChannelState *statePtr;	/* State of channel stack */
    int active = 1;		/* Flag == 1 while there's still work to do */

    /*
     * Walk all channel state structures known to this thread and close
     * corresponding channels.
     */

    while (active) {
	/*
	 * Iterate through the open channel list, and find the first channel
	 * that isn't dead. We start from the head of the list each time,
	 * because the close action on one channel can close others.
	 */

	active = 0;
	for (statePtr = tsdPtr->firstCSPtr;
		statePtr != NULL;
		statePtr = statePtr->nextCSPtr) {
	    chanPtr = statePtr->topChanPtr;
	    if (!GotFlag(statePtr, CHANNEL_INCLOSE | CHANNEL_CLOSED |
		    CHANNEL_DEAD)) {
		active = 1;
		break;
	    }
	}

	/*
	 * We've found a live channel. Close it.
	 */

	if (active) {
	    /*
	     * Set the channel back into blocking mode to ensure that we wait
	     * for all data to flush out.
	     */

	    (void) Tcl_SetChannelOption(NULL, (Tcl_Channel) chanPtr,
		    "-blocking", "on");

	    if ((chanPtr == (Channel *) tsdPtr->stdinChannel) ||
		    (chanPtr == (Channel *) tsdPtr->stdoutChannel) ||
		    (chanPtr == (Channel *) tsdPtr->stderrChannel)) {
		/*
		 * Decrement the refcount which was earlier artificially
		 * bumped up to keep the channel from being closed.
		 */

		statePtr->refCount--;
	    }

	    if (statePtr->refCount <= 0) {
		/*
		 * Close it only if the refcount indicates that the channel is
		 * not referenced from any interpreter. If it is, that
		 * interpreter will close the channel when it gets destroyed.
		 */

		(void) Tcl_Close(NULL, (Tcl_Channel) chanPtr);
	    } else {
		/*
		 * The refcount is greater than zero, so flush the channel.
		 */

		Tcl_Flush((Tcl_Channel) chanPtr);

		/*
		 * Call the device driver to actually close the underlying
		 * device for this channel.
		 */

		(void) ChanClose(chanPtr, NULL);

		/*
		 * Finally, we clean up the fields in the channel data
		 * structure since all of them have been deleted already. We
		 * mark the channel with CHANNEL_DEAD to prevent any further
		 * IO operations on it.
		 */

		chanPtr->instanceData = NULL;
		SetFlag(statePtr, CHANNEL_DEAD);
	    }
	}
    }

    TclpFinalizeSockets();
    TclpFinalizePipes();
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetStdChannel --
 *
 *	This function is used to change the channels that are used for
 *	stdin/stdout/stderr in new interpreters.
 *
 * Results:
 *	None
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetStdChannel(
    Tcl_Channel channel,
    int type)			/* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    switch (type) {
    case TCL_STDIN:
	tsdPtr->stdinInitialized = 1;
	tsdPtr->stdinChannel = channel;
	break;
    case TCL_STDOUT:
	tsdPtr->stdoutInitialized = 1;
	tsdPtr->stdoutChannel = channel;
	break;
    case TCL_STDERR:
	tsdPtr->stderrInitialized = 1;
	tsdPtr->stderrChannel = channel;
	break;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetStdChannel --
 *
 *	Returns the specified standard channel.
 *
 * Results:
 *	Returns the specified standard channel, or NULL.
 *
 * Side effects:
 *	May cause the creation of a standard channel and the underlying file.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetStdChannel(
    int type)			/* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR. */
{
    Tcl_Channel channel = NULL;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * If the channels were not created yet, create them now and store them in
     * the static variables.
     */

    switch (type) {
    case TCL_STDIN:
	if (!tsdPtr->stdinInitialized) {
	    tsdPtr->stdinChannel = TclpGetDefaultStdChannel(TCL_STDIN);
	    tsdPtr->stdinInitialized = 1;

	    /*
	     * Artificially bump the refcount to ensure that the channel is
	     * only closed on exit.
	     *
	     * NOTE: Must only do this if stdinChannel is not NULL. It can be
	     * NULL in situations where Tcl is unable to connect to the
	     * standard input.
	     */

	    if (tsdPtr->stdinChannel != NULL) {
		Tcl_RegisterChannel(NULL, tsdPtr->stdinChannel);
	    }
	}
	channel = tsdPtr->stdinChannel;
	break;
    case TCL_STDOUT:
	if (!tsdPtr->stdoutInitialized) {
	    tsdPtr->stdoutChannel = TclpGetDefaultStdChannel(TCL_STDOUT);
	    tsdPtr->stdoutInitialized = 1;
	    if (tsdPtr->stdoutChannel != NULL) {
		Tcl_RegisterChannel(NULL, tsdPtr->stdoutChannel);
	    }
	}
	channel = tsdPtr->stdoutChannel;
	break;
    case TCL_STDERR:
	if (!tsdPtr->stderrInitialized) {
	    tsdPtr->stderrChannel = TclpGetDefaultStdChannel(TCL_STDERR);
	    tsdPtr->stderrInitialized = 1;
	    if (tsdPtr->stderrChannel != NULL) {
		Tcl_RegisterChannel(NULL, tsdPtr->stderrChannel);
	    }
	}
	channel = tsdPtr->stderrChannel;
	break;
    }
    return channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateCloseHandler
 *
 *	Creates a close callback which will be called when the channel is
 *	closed.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Causes the callback to be called in the future when the channel will
 *	be closed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateCloseHandler(
    Tcl_Channel chan,		/* The channel for which to create the close
				 * callback. */
    Tcl_CloseProc *proc,	/* The callback routine to call when the
				 * channel will be closed. */
    ClientData clientData)	/* Arbitrary data to pass to the close
				 * callback. */
{
    ChannelState *statePtr;
    CloseCallback *cbPtr;

    statePtr = ((Channel *) chan)->state;

    cbPtr = (CloseCallback *) ckalloc(sizeof(CloseCallback));
    cbPtr->proc = proc;
    cbPtr->clientData = clientData;

    cbPtr->nextPtr = statePtr->closeCbPtr;
    statePtr->closeCbPtr = cbPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteCloseHandler --
 *
 *	Removes a callback that would have been called on closing the channel.
 *	If there is no matching callback then this function has no effect.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The callback will not be called in the future when the channel is
 *	eventually closed.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteCloseHandler(
    Tcl_Channel chan,		/* The channel for which to cancel the close
				 * callback. */
    Tcl_CloseProc *proc,	/* The procedure for the callback to
				 * remove. */
    ClientData clientData)	/* The callback data for the callback to
				 * remove. */
{
    ChannelState *statePtr;
    CloseCallback *cbPtr, *cbPrevPtr;

    statePtr = ((Channel *) chan)->state;
    for (cbPtr = statePtr->closeCbPtr, cbPrevPtr = NULL;
	    cbPtr != NULL; cbPtr = cbPtr->nextPtr) {
	if ((cbPtr->proc == proc) && (cbPtr->clientData == clientData)) {
	    if (cbPrevPtr == NULL) {
		statePtr->closeCbPtr = cbPtr->nextPtr;
	    }
	    ckfree((char *) cbPtr);
	    break;
	} else {
	    cbPrevPtr = cbPtr;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * GetChannelTable --
 *
 *	Gets and potentially initializes the channel table for an interpreter.
 *	If it is initializing the table it also inserts channels for stdin,
 *	stdout and stderr if the interpreter is trusted.
 *
 * Results:
 *	A pointer to the hash table created, for use by the caller.
 *
 * Side effects:
 *	Initializes the channel table for an interpreter. May create channels
 *	for stdin, stdout and stderr.
 *
 *----------------------------------------------------------------------
 */

static Tcl_HashTable *
GetChannelTable(
    Tcl_Interp *interp)
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_Channel stdinChan, stdoutChan, stderrChan;

    hTblPtr = Tcl_GetAssocData(interp, "tclIO", NULL);
    if (hTblPtr == NULL) {
	hTblPtr = (Tcl_HashTable *) ckalloc(sizeof(Tcl_HashTable));
	Tcl_InitHashTable(hTblPtr, TCL_STRING_KEYS);
	Tcl_SetAssocData(interp, "tclIO",
		(Tcl_InterpDeleteProc *) DeleteChannelTable, hTblPtr);

	/*
	 * If the interpreter is trusted (not "safe"), insert channels for
	 * stdin, stdout and stderr (possibly creating them in the process).
	 */

	if (Tcl_IsSafe(interp) == 0) {
	    stdinChan = Tcl_GetStdChannel(TCL_STDIN);
	    if (stdinChan != NULL) {
		Tcl_RegisterChannel(interp, stdinChan);
	    }
	    stdoutChan = Tcl_GetStdChannel(TCL_STDOUT);
	    if (stdoutChan != NULL) {
		Tcl_RegisterChannel(interp, stdoutChan);
	    }
	    stderrChan = Tcl_GetStdChannel(TCL_STDERR);
	    if (stderrChan != NULL) {
		Tcl_RegisterChannel(interp, stderrChan);
	    }
	}
    }
    return hTblPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteChannelTable --
 *
 *	Deletes the channel table for an interpreter, closing any open
 *	channels whose refcount reaches zero. This procedure is invoked when
 *	an interpreter is deleted, via the AssocData cleanup mechanism.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Deletes the hash table of channels. May close channels. May flush
 *	output on closed channels. Removes any channeEvent handlers that were
 *	registered in this interpreter.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteChannelTable(
    ClientData clientData,	/* The per-interpreter data structure. */
    Tcl_Interp *interp)		/* The interpreter being deleted. */
{
    Tcl_HashTable *hTblPtr;	/* The hash table. */
    Tcl_HashSearch hSearch;	/* Search variable. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Channel *chanPtr;		/* Channel being deleted. */
    ChannelState *statePtr;	/* State of Channel being deleted. */
    EventScriptRecord *sPtr, *prevPtr, *nextPtr;
				/* Variables to loop over all channel events
				 * registered, to delete the ones that refer
				 * to the interpreter being deleted. */

    /*
     * Delete all the registered channels - this will close channels whose
     * refcount reaches zero.
     */

    hTblPtr = clientData;
    for (hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch); hPtr != NULL;
	    hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch)) {
	chanPtr = Tcl_GetHashValue(hPtr);
	statePtr = chanPtr->state;

	/*
	 * Remove any fileevents registered in this interpreter.
	 */

	for (sPtr = statePtr->scriptRecordPtr, prevPtr = NULL;
		sPtr != NULL; sPtr = nextPtr) {
	    nextPtr = sPtr->nextPtr;
	    if (sPtr->interp == interp) {
		if (prevPtr == NULL) {
		    statePtr->scriptRecordPtr = nextPtr;
		} else {
		    prevPtr->nextPtr = nextPtr;
		}

		Tcl_DeleteChannelHandler((Tcl_Channel) chanPtr,
			TclChannelEventScriptInvoker, sPtr);

		TclDecrRefCount(sPtr->scriptPtr);
		ckfree((char *) sPtr);
	    } else {
		prevPtr = sPtr;
	    }
	}

	/*
	 * Cannot call Tcl_UnregisterChannel because that procedure calls
	 * Tcl_GetAssocData to get the channel table, which might already be
	 * inaccessible from the interpreter structure. Instead, we emulate
	 * the behavior of Tcl_UnregisterChannel directly here.
	 */

	Tcl_DeleteHashEntry(hPtr);
	SetFlag(statePtr, CHANNEL_TAINTED);
	statePtr->refCount--;
	if (statePtr->refCount <= 0) {
	    if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
		(void) Tcl_Close(interp, (Tcl_Channel) chanPtr);
	    }
	}

    }
    Tcl_DeleteHashTable(hTblPtr);
    ckfree((char *) hTblPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * CheckForStdChannelsBeingClosed --
 *
 *	Perform special handling for standard channels being closed. When
 *	given a standard channel, if the refcount is now 1, it means that the
 *	last reference to the standard channel is being explicitly closed. Now
 *	bump the refcount artificially down to 0, to ensure the normal
 *	handling of channels being closed will occur. Also reset the static
 *	pointer to the channel to NULL, to avoid dangling references.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Manipulates the refcount on standard channels. May smash the global
 *	static pointer to a standard channel.
 *
 *----------------------------------------------------------------------
 */

static void
CheckForStdChannelsBeingClosed(
    Tcl_Channel chan)
{
    ChannelState *statePtr = ((Channel *) chan)->state;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if ((chan == tsdPtr->stdinChannel) && tsdPtr->stdinInitialized) {
	if (statePtr->refCount < 2) {
	    statePtr->refCount = 0;
	    tsdPtr->stdinChannel = NULL;
	    return;
	}
    } else if ((chan == tsdPtr->stdoutChannel) && tsdPtr->stdoutInitialized) {
	if (statePtr->refCount < 2) {
	    statePtr->refCount = 0;
	    tsdPtr->stdoutChannel = NULL;
	    return;
	}
    } else if ((chan == tsdPtr->stderrChannel) && tsdPtr->stderrInitialized) {
	if (statePtr->refCount < 2) {
	    statePtr->refCount = 0;
	    tsdPtr->stderrChannel = NULL;
	    return;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_IsStandardChannel --
 *
 *	Test if the given channel is a standard channel. No attempt is made to
 *	check if the channel or the standard channels are initialized or
 *	otherwise valid.
 *
 * Results:
 *	Returns 1 if true, 0 if false.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_IsStandardChannel(
    Tcl_Channel chan)		/* Channel to check. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if ((chan == tsdPtr->stdinChannel)
	    || (chan == tsdPtr->stdoutChannel)
	    || (chan == tsdPtr->stderrChannel)) {
	return 1;
    } else {
	return 0;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_RegisterChannel --
 *
 *	Adds an already-open channel to the channel table of an interpreter.
 *	If the interpreter passed as argument is NULL, it only increments the
 *	channel refCount.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May increment the reference count of a channel.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_RegisterChannel(
    Tcl_Interp *interp,		/* Interpreter in which to add the channel. */
    Tcl_Channel chan)		/* The channel to add to this interpreter
				 * channel table. */
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    int isNew;			/* Is the hash entry new or does it exist? */
    Channel *chanPtr;		/* The actual channel. */
    ChannelState *statePtr;	/* State of the actual channel. */

    /*
     * Always (un)register bottom-most channel in the stack. This makes
     * management of the channel list easier because no manipulation is
     * necessary during (un)stack operation.
     */

    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    statePtr = chanPtr->state;

    if (statePtr->channelName == NULL) {
	Tcl_Panic("Tcl_RegisterChannel: channel without name");
    }
    if (interp != NULL) {
	hTblPtr = GetChannelTable(interp);
	hPtr = Tcl_CreateHashEntry(hTblPtr, statePtr->channelName, &isNew);
	if (!isNew) {
	    if (chan == Tcl_GetHashValue(hPtr)) {
		return;
	    }

	    Tcl_Panic("Tcl_RegisterChannel: duplicate channel names");
	}
	Tcl_SetHashValue(hPtr, chanPtr);
    }
    statePtr->refCount++;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnregisterChannel --
 *
 *	Deletes the hash entry for a channel associated with an interpreter.
 *	If the interpreter given as argument is NULL, it only decrements the
 *	reference count. (This all happens in the Tcl_DetachChannel helper
 *	function).
 *
 *	Finally, if the reference count of the channel drops to zero, it is
 *	deleted.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Calls Tcl_DetachChannel which deletes the hash entry for a channel
 *	associated with an interpreter.
 *
 *	May delete the channel, which can have a variety of consequences,
 *	especially if we are forced to close the channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UnregisterChannel(
    Tcl_Interp *interp,		/* Interpreter in which channel is defined. */
    Tcl_Channel chan)		/* Channel to delete. */
{
    ChannelState *statePtr;	/* State of the real channel. */

    statePtr = ((Channel *) chan)->state->bottomChanPtr->state;

    if (GotFlag(statePtr, CHANNEL_INCLOSE)) {
	if (interp != NULL) {
	    Tcl_AppendResult(interp, "Illegal recursive call to close "
		    "through close-handler of channel", NULL);
	}
	return TCL_ERROR;
    }

    if (DetachChannel(interp, chan) != TCL_OK) {
	return TCL_OK;
    }

    statePtr = ((Channel *) chan)->state->bottomChanPtr->state;

    /*
     * Perform special handling for standard channels being closed. If the
     * refCount is now 1 it means that the last reference to the standard
     * channel is being explicitly closed, so bump the refCount down
     * artificially to 0. This will ensure that the channel is actually
     * closed, below. Also set the static pointer to NULL for the channel.
     */

    CheckForStdChannelsBeingClosed(chan);

    /*
     * If the refCount reached zero, close the actual channel.
     */

    if (statePtr->refCount <= 0) {
	/*
	 * Ensure that if there is another buffer, it gets flushed whether or
	 * not we are doing a background flush.
	 */

	if ((statePtr->curOutPtr != NULL) &&
		IsBufferReady(statePtr->curOutPtr)) {
	    SetFlag(statePtr, BUFFER_READY);
	}
	Tcl_Preserve(statePtr);
	if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    /*
	     * We don't want to re-enter Tcl_Close().
	     */

	    if (!GotFlag(statePtr, CHANNEL_CLOSED)) {
		if (Tcl_Close(interp, chan) != TCL_OK) {
		    SetFlag(statePtr, CHANNEL_CLOSED);
		    Tcl_Release(statePtr);
		    return TCL_ERROR;
		}
	    }
	}
	SetFlag(statePtr, CHANNEL_CLOSED);
	Tcl_Release(statePtr);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DetachChannel --
 *
 *	Deletes the hash entry for a channel associated with an interpreter.
 *	If the interpreter given as argument is NULL, it only decrements the
 *	reference count. Even if the ref count drops to zero, the channel is
 *	NOT closed or cleaned up. This allows a channel to be detached from an
 *	interpreter and left in the same state it was in when it was
 *	originally returned by 'Tcl_OpenFileChannel', for example.
 *
 *	This function cannot be used on the standard channels, and will return
 *	TCL_ERROR if that is attempted.
 *
 *	This function should only be necessary for special purposes in which
 *	you need to generate a pristine channel from one that has already been
 *	used. All ordinary purposes will almost always want to use
 *	Tcl_UnregisterChannel instead.
 *
 *	Provided the channel is not attached to any other interpreter, it can
 *	then be closed with Tcl_Close, rather than with Tcl_UnregisterChannel.
 *
 * Results:
 *	A standard Tcl result. If the channel is not currently registered with
 *	the given interpreter, TCL_ERROR is returned, otherwise TCL_OK.
 *	However no error messages are left in the interp's result.
 *
 * Side effects:
 *	Deletes the hash entry for a channel associated with an interpreter.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DetachChannel(
    Tcl_Interp *interp,		/* Interpreter in which channel is defined. */
    Tcl_Channel chan)		/* Channel to delete. */
{
    if (Tcl_IsStandardChannel(chan)) {
	return TCL_ERROR;
    }

    return DetachChannel(interp, chan);
}

/*
 *----------------------------------------------------------------------
 *
 * DetachChannel --
 *
 *	Deletes the hash entry for a channel associated with an interpreter.
 *	If the interpreter given as argument is NULL, it only decrements the
 *	reference count. Even if the ref count drops to zero, the channel is
 *	NOT closed or cleaned up. This allows a channel to be detached from an
 *	interpreter and left in the same state it was in when it was
 *	originally returned by 'Tcl_OpenFileChannel', for example.
 *
 * Results:
 *	A standard Tcl result. If the channel is not currently registered with
 *	the given interpreter, TCL_ERROR is returned, otherwise TCL_OK.
 *	However no error messages are left in the interp's result.
 *
 * Side effects:
 *	Deletes the hash entry for a channel associated with an interpreter.
 *
 *----------------------------------------------------------------------
 */

static int
DetachChannel(
    Tcl_Interp *interp,		/* Interpreter in which channel is defined. */
    Tcl_Channel chan)		/* Channel to delete. */
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of the real channel. */

    /*
     * Always (un)register bottom-most channel in the stack. This makes
     * management of the channel list easier because no manipulation is
     * necessary during (un)stack operation.
     */

    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    statePtr = chanPtr->state;

    if (interp != NULL) {
	hTblPtr = Tcl_GetAssocData(interp, "tclIO", NULL);
	if (hTblPtr == NULL) {
	    return TCL_ERROR;
	}
	hPtr = Tcl_FindHashEntry(hTblPtr, statePtr->channelName);
	if (hPtr == NULL) {
	    return TCL_ERROR;
	}
	if ((Channel *) Tcl_GetHashValue(hPtr) != chanPtr) {
	    return TCL_ERROR;
	}
	Tcl_DeleteHashEntry(hPtr);
	SetFlag(statePtr, CHANNEL_TAINTED);

	/*
	 * Remove channel handlers that refer to this interpreter, so that
	 * they will not be present if the actual close is delayed and more
	 * events happen on the channel. This may occur if the channel is
	 * shared between several interpreters, or if the channel has async
	 * flushing active.
	 */

	CleanupChannelHandlers(interp, chanPtr);
    }

    statePtr->refCount--;

    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_GetChannel --
 *
 *	Finds an existing Tcl_Channel structure by name in a given
 *	interpreter. This function is public because it is used by
 *	channel-type-specific functions.
 *
 * Results:
 *	A Tcl_Channel or NULL on failure. If failed, interp's result object
 *	contains an error message. *modePtr is filled with the modes in which
 *	the channel was opened.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetChannel(
    Tcl_Interp *interp,		/* Interpreter in which to find or create the
				 * channel. */
    const char *chanName,	/* The name of the channel. */
    int *modePtr)		/* Where to store the mode in which the
				 * channel was opened? Will contain an ORed
				 * combination of TCL_READABLE and
				 * TCL_WRITABLE, if non-NULL. */
{
    Channel *chanPtr;		/* The actual channel. */
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    const char *name;		/* Translated name. */

    /*
     * Substitute "stdin", etc. Note that even though we immediately find the
     * channel using Tcl_GetStdChannel, we still need to look it up in the
     * specified interpreter to ensure that it is present in the channel
     * table. Otherwise, safe interpreters would always have access to the
     * standard channels.
     */

    name = chanName;
    if ((chanName[0] == 's') && (chanName[1] == 't')) {
	chanPtr = NULL;
	if (strcmp(chanName, "stdin") == 0) {
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDIN);
	} else if (strcmp(chanName, "stdout") == 0) {
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDOUT);
	} else if (strcmp(chanName, "stderr") == 0) {
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDERR);
	}
	if (chanPtr != NULL) {
	    name = chanPtr->state->channelName;
	}
    }

    hTblPtr = GetChannelTable(interp);
    hPtr = Tcl_FindHashEntry(hTblPtr, name);
    if (hPtr == NULL) {
	Tcl_AppendResult(interp, "can not find channel named \"", chanName,
		"\"", NULL);
	Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "CHANNEL", chanName, NULL);
	return NULL;
    }

    /*
     * Always return bottom-most channel in the stack. This one lives the
     * longest - other channels may go away unnoticed. The other APIs
     * compensate where necessary to retrieve the topmost channel again.
     */

    chanPtr = Tcl_GetHashValue(hPtr);
    chanPtr = chanPtr->state->bottomChanPtr;
    if (modePtr != NULL) {
	*modePtr = chanPtr->state->flags & (TCL_READABLE|TCL_WRITABLE);
    }

    return (Tcl_Channel) chanPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclGetChannelFromObj --
 *
 *	Finds an existing Tcl_Channel structure by name in a given
 *	interpreter. This function is public because it is used by
 *	channel-type-specific functions.
 *
 * Results:
 *	A Tcl_Channel or NULL on failure. If failed, interp's result object
 *	contains an error message. *modePtr is filled with the modes in which
 *	the channel was opened.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TclGetChannelFromObj(
    Tcl_Interp *interp,		/* Interpreter in which to find or create the
				 * channel. */
    Tcl_Obj *objPtr,
    Tcl_Channel *channelPtr,
    int *modePtr,		/* Where to store the mode in which the
				 * channel was opened? Will contain an ORed
				 * combination of TCL_READABLE and
				 * TCL_WRITABLE, if non-NULL. */
    int flags)
{
    ChannelState *statePtr;

    if (SetChannelFromAny(interp, objPtr) != TCL_OK) {
	return TCL_ERROR;
    }

    statePtr = GET_CHANNELSTATE(objPtr);
    *channelPtr = (Tcl_Channel) statePtr->bottomChanPtr;

    if (modePtr != NULL) {
	*modePtr = statePtr->flags & (TCL_READABLE|TCL_WRITABLE);
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateChannel --
 *
 *	Creates a new entry in the hash table for a Tcl_Channel record.
 *
 * Results:
 *	Returns the new Tcl_Channel.
 *
 * Side effects:
 *	Creates a new Tcl_Channel instance and inserts it into the hash table.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_CreateChannel(
    const Tcl_ChannelType *typePtr, /* The channel type record. */
    const char *chanName,	/* Name of channel to record. */
    ClientData instanceData,	/* Instance specific data. */
    int mask)			/* TCL_READABLE & TCL_WRITABLE to indicate if
				 * the channel is readable, writable. */
{
    Channel *chanPtr;		/* The channel structure newly created. */
    ChannelState *statePtr;	/* The stack-level independent state info for
				 * the channel. */
    const char *name;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * With the change of the Tcl_ChannelType structure to use a version in
     * 8.3.2+, we have to make sure that our assumption that the structure
     * remains a binary compatible size is true.
     *
     * If this assertion fails on some system, then it can be removed only if
     * the user recompiles code with older channel drivers in the new system
     * as well.
     */

    assert(sizeof(Tcl_ChannelTypeVersion)==sizeof(Tcl_DriverBlockModeProc *));

    /*
     * JH: We could subsequently memset these to 0 to avoid the numerous
     * assignments to 0/NULL below.
     */

    chanPtr = (Channel *) ckalloc(sizeof(Channel));
    statePtr = (ChannelState *) ckalloc(sizeof(ChannelState));
    chanPtr->state = statePtr;

    chanPtr->instanceData = instanceData;
    chanPtr->typePtr = typePtr;

    /*
     * Set all the bits that are part of the stack-independent state
     * information for the channel.
     */

    if (chanName != NULL) {
	char *tmp = ckalloc((unsigned) (strlen(chanName) + 1));

	statePtr->channelName = tmp;
	strcpy(tmp, chanName);
    } else {
	Tcl_Panic("Tcl_CreateChannel: NULL channel name");
    }

    statePtr->flags = mask;

    /*
     * Set the channel to system default encoding.
     *
     * Note the strange bit of protection taking place here. If the system
     * encoding name is reported back as "binary", something weird is
     * happening. Tcl provides no "binary" encoding, so someone else has
     * provided one. We ignore it so as not to interfere with the "magic"
     * interpretation that Tcl_Channels give to the "-encoding binary" option.
     */

    statePtr->encoding = NULL;
    name = Tcl_GetEncodingName(NULL);
    if (strcmp(name, "binary") != 0) {
	statePtr->encoding = Tcl_GetEncoding(NULL, name);
    }
    statePtr->inputEncodingState  = NULL;
    statePtr->inputEncodingFlags  = TCL_ENCODING_START;
    statePtr->outputEncodingState = NULL;
    statePtr->outputEncodingFlags = TCL_ENCODING_START;

    /*
     * Set the channel up initially in AUTO input translation mode to accept
     * "\n", "\r" and "\r\n". Output translation mode is set to a platform
     * specific default value. The eofChar is set to 0 for both input and
     * output, so that Tcl does not look for an in-file EOF indicator (e.g.
     * ^Z) and does not append an EOF indicator to files.
     */

    statePtr->inputTranslation	= TCL_TRANSLATE_AUTO;
    statePtr->outputTranslation	= TCL_PLATFORM_TRANSLATION;
    statePtr->inEofChar		= 0;
    statePtr->outEofChar	= 0;

    statePtr->unreportedError	= 0;
    statePtr->refCount		= 0;
    statePtr->closeCbPtr	= NULL;
    statePtr->curOutPtr		= NULL;
    statePtr->outQueueHead	= NULL;
    statePtr->outQueueTail	= NULL;
    statePtr->saveInBufPtr	= NULL;
    statePtr->inQueueHead	= NULL;
    statePtr->inQueueTail	= NULL;
    statePtr->chPtr		= NULL;
    statePtr->interestMask	= 0;
    statePtr->scriptRecordPtr	= NULL;
    statePtr->bufSize		= CHANNELBUFFER_DEFAULT_SIZE;
    statePtr->timer		= NULL;
    statePtr->csPtrR		= NULL;
    statePtr->csPtrW		= NULL;

    statePtr->outputStage	= NULL;
    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
	statePtr->outputStage = ckalloc((unsigned) statePtr->bufSize + 2);
    }

    /*
     * As we are creating the channel, it is obviously the top for now.
     */

    statePtr->topChanPtr	= chanPtr;
    statePtr->bottomChanPtr	= chanPtr;
    chanPtr->downChanPtr	= NULL;
    chanPtr->upChanPtr		= NULL;
    chanPtr->inQueueHead	= NULL;
    chanPtr->inQueueTail	= NULL;

    /*
     * TIP #219, Tcl Channel Reflection API
     */

    statePtr->chanMsg		= NULL;
    statePtr->unreportedMsg	= NULL;

    /*
     * Link the channel into the list of all channels; create an on-exit
     * handler if there is not one already, to close off all the channels in
     * the list on exit.
     *
     * JH: Could call Tcl_SpliceChannel, but need to avoid NULL check.
     *
     * TIP #218.
     * AK: Just initialize the field to NULL before invoking Tcl_SpliceChannel
     *	   We need Tcl_SpliceChannel, for the threadAction calls. There is no
     *	   real reason to duplicate all of this.
     * NOTE: All drivers using thread actions now have to perform their TSD
     *	     manipulation only in their thread action proc. Doing it when
     *	     creating their instance structures will collide with the thread
     *	     action activity and lead to damaged lists.
     */

    statePtr->nextCSPtr = NULL;
    SpliceChannel((Tcl_Channel) chanPtr);

    /*
     * Install this channel in the first empty standard channel slot, if the
     * channel was previously closed explicitly.
     */

    if ((tsdPtr->stdinChannel == NULL) && (tsdPtr->stdinInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDIN);
	Tcl_RegisterChannel(NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stdoutChannel == NULL) &&
	    (tsdPtr->stdoutInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDOUT);
	Tcl_RegisterChannel(NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stderrChannel == NULL) &&
	    (tsdPtr->stderrInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDERR);
	Tcl_RegisterChannel(NULL, (Tcl_Channel) chanPtr);
    }
    return (Tcl_Channel) chanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_StackChannel --
 *
 *	Replaces an entry in the hash table for a Tcl_Channel record. The
 *	replacement is a new channel with same name, it supercedes the
 *	replaced channel. Input and output of the superceded channel is now
 *	going through the newly created channel and allows the arbitrary
 *	filtering/manipulation of the dataflow.
 *
 *	Andreas Kupries <a.kupries@westend.com>, 12/13/1998 "Trf-Patch for
 *	filtering channels"
 *
 * Results:
 *	Returns the new Tcl_Channel, which actually contains the saved
 *	information about prevChan.
 *
 * Side effects:
 *	A new channel structure is allocated and linked below the existing
 *	channel. The channel operations and client data of the existing
 *	channel are copied down to the newly created channel, and the current
 *	channel has its operations replaced by the new typePtr.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_StackChannel(
    Tcl_Interp *interp,		/* The interpreter we are working in */
    const Tcl_ChannelType *typePtr,
				/* The channel type record for the new
				 * channel. */
    ClientData instanceData,	/* Instance specific data for the new
				 * channel. */
    int mask,			/* TCL_READABLE & TCL_WRITABLE to indicate if
				 * the channel is readable, writable. */
    Tcl_Channel prevChan)	/* The channel structure to replace */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel *chanPtr, *prevChanPtr;
    ChannelState *statePtr;

    /*
     * Find the given channel (prevChan) in the list of all channels. If we do
     * not find it, then it was never registered correctly.
     *
     * This operation should occur at the top of a channel stack.
     */

    statePtr = (ChannelState *) tsdPtr->firstCSPtr;
    prevChanPtr = ((Channel *) prevChan)->state->topChanPtr;

    while ((statePtr != NULL) && (statePtr->topChanPtr != prevChanPtr)) {
	statePtr = statePtr->nextCSPtr;
    }

    if (statePtr == NULL) {
	if (interp) {
	    Tcl_AppendResult(interp, "couldn't find state for channel \"",
		    Tcl_GetChannelName(prevChan), "\"", NULL);
	}
	return NULL;
    }

    /*
     * Here we check if the given "mask" matches the "flags" of the already
     * existing channel.
     *
     *	  | - | R | W | RW |
     *	--+---+---+---+----+	<=>  0 != (chan->mask & prevChan->mask)
     *	- |   |   |   |    |
     *	R |   | + |   | +  |	The superceding channel is allowed to restrict
     *	W |   |   | + | +  |	the capabilities of the superceded one!
     *	RW|   | + | + | +  |
     *	--+---+---+---+----+
     */

    if ((mask & (statePtr->flags & (TCL_READABLE | TCL_WRITABLE))) == 0) {
	if (interp) {
	    Tcl_AppendResult(interp,
		    "reading and writing both disallowed for channel \"",
		    Tcl_GetChannelName(prevChan), "\"", NULL);
	}
	return NULL;
    }

    /*
     * Flush the buffers. This ensures that any data still in them at this
     * time is not handled by the new transformation. Restrict this to
     * writable channels. Take care to hide a possible bg-copy in progress
     * from Tcl_Flush and the CheckForChannelErrors inside.
     */

    if ((mask & TCL_WRITABLE) != 0) {
	CopyState *csPtrR = statePtr->csPtrR;
	CopyState *csPtrW = statePtr->csPtrW;

	statePtr->csPtrR = NULL;
	statePtr->csPtrW = NULL;

	if (Tcl_Flush((Tcl_Channel) prevChanPtr) != TCL_OK) {
	    statePtr->csPtrR = csPtrR;
	    statePtr->csPtrW = csPtrW;
	    if (interp) {
		Tcl_AppendResult(interp, "could not flush channel \"",
			Tcl_GetChannelName(prevChan), "\"", NULL);
	    }
	    return NULL;
	}

	statePtr->csPtrR = csPtrR;
	statePtr->csPtrW = csPtrW;
    }

    /*
     * Discard any input in the buffers. They are not yet read by the user of
     * the channel, so they have to go through the new transformation before
     * reading. As the buffers contain the untransformed form their contents
     * are not only useless but actually distorts our view of the system.
     *
     * To preserve the information without having to read them again and to
     * avoid problems with the location in the channel (seeking might be
     * impossible) we move the buffers from the common state structure into
     * the channel itself. We use the buffers in the channel below the new
     * transformation to hold the data. In the future this allows us to write
     * transformations which pre-read data and push the unused part back when
     * they are going away.
     */

    if (((mask & TCL_READABLE) != 0) && (statePtr->inQueueHead != NULL)) {
	/*
	 * Remark: It is possible that the channel buffers contain data from
	 * some earlier push-backs.
	 */

	statePtr->inQueueTail->nextPtr = prevChanPtr->inQueueHead;
	prevChanPtr->inQueueHead = statePtr->inQueueHead;

	if (prevChanPtr->inQueueTail == NULL) {
	    prevChanPtr->inQueueTail = statePtr->inQueueTail;
	}

	statePtr->inQueueHead = NULL;
	statePtr->inQueueTail = NULL;
    }

    chanPtr = (Channel *) ckalloc(sizeof(Channel));

    /*
     * Save some of the current state into the new structure, reinitialize the
     * parts which will stay with the transformation.
     *
     * Remarks:
     */

    chanPtr->state		= statePtr;
    chanPtr->instanceData	= instanceData;
    chanPtr->typePtr		= typePtr;
    chanPtr->downChanPtr	= prevChanPtr;
    chanPtr->upChanPtr		= NULL;
    chanPtr->inQueueHead	= NULL;
    chanPtr->inQueueTail	= NULL;

    /*
     * Place new block at the head of a possibly existing list of previously
     * stacked channels.
     */

    prevChanPtr->upChanPtr	= chanPtr;
    statePtr->topChanPtr	= chanPtr;

    /*
     * TIP #218, Channel Thread Actions.
     *
     * We call the thread actions for the new channel directly. We _cannot_
     * use SpliceChannel, because the (thread-)global list of all channels
     * always contains the _ChannelState_ for a stack of channels, not the
     * individual channels. And SpliceChannel would not only call the thread
     * actions, but also add the shared ChannelState to this list a second
     * time, mangling it.
     */

    ChanThreadAction(chanPtr, TCL_CHANNEL_THREAD_INSERT);

    return (Tcl_Channel) chanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnstackChannel --
 *
 *	Unstacks an entry in the hash table for a Tcl_Channel record. This is
 *	the reverse to 'Tcl_StackChannel'.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	If TCL_ERROR is returned, the posix error code will be set with
 *	Tcl_SetErrno. May leave a message in interp result as well.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_UnstackChannel(
    Tcl_Interp *interp,		/* The interpreter we are working in */
    Tcl_Channel chan)		/* The channel to unstack */
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
    int result = 0;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (chanPtr->downChanPtr != NULL) {
	/*
	 * Instead of manipulating the per-thread / per-interp list/hashtable
	 * of registered channels we wind down the state of the transformation,
	 * and then restore the state of underlying channel into the old
	 * structure.
	 */

	Channel *downChanPtr = chanPtr->downChanPtr;

	/*
	 * Flush the buffers. This ensures that any data still in them at this
	 * time _is_ handled by the transformation we are unstacking right
	 * now. Restrict this to writable channels. Take care to hide a
	 * possible bg-copy in progress from Tcl_Flush and the
	 * CheckForChannelErrors inside.
	 */

	if (GotFlag(statePtr, TCL_WRITABLE)) {
	    CopyState *csPtrR = statePtr->csPtrR;
	    CopyState *csPtrW = statePtr->csPtrW;

	    statePtr->csPtrR = NULL;
	    statePtr->csPtrW = NULL;

	    if (Tcl_Flush((Tcl_Channel) chanPtr) != TCL_OK) {
		statePtr->csPtrR = csPtrR;
		statePtr->csPtrW = csPtrW;

		/*
		 * TIP #219, Tcl Channel Reflection API.
		 * Move error messages put by the driver into the chan/ip
		 * bypass area into the regular interpreter result. Fall back
		 * to the regular message if nothing was found in the
		 * bypasses.
		 */

		if (!TclChanCaughtErrorBypass(interp, chan) && interp) {
		    Tcl_AppendResult(interp, "could not flush channel \"",
			    Tcl_GetChannelName((Tcl_Channel) chanPtr), "\"",
			    NULL);
		}
		return TCL_ERROR;
	    }

	    statePtr->csPtrR  = csPtrR;
	    statePtr->csPtrW = csPtrW;
	}

	/*
	 * Anything in the input queue and the push-back buffers of the
	 * transformation going away is transformed data, but not yet read. As
	 * unstacking means that the caller does not want to see transformed
	 * data any more we have to discard these bytes. To avoid writing an
	 * analogue to 'DiscardInputQueued' we move the information in the
	 * push back buffers to the input queue and then call
	 * 'DiscardInputQueued' on that.
	 */

	if (GotFlag(statePtr, TCL_READABLE) &&
		((statePtr->inQueueHead != NULL) ||
		(chanPtr->inQueueHead != NULL))) {
	    if ((statePtr->inQueueHead != NULL) &&
		    (chanPtr->inQueueHead != NULL)) {
		statePtr->inQueueTail->nextPtr = chanPtr->inQueueHead;
		statePtr->inQueueTail = chanPtr->inQueueTail;
		statePtr->inQueueHead = statePtr->inQueueTail;
	    } else if (chanPtr->inQueueHead != NULL) {
		statePtr->inQueueHead = chanPtr->inQueueHead;
		statePtr->inQueueTail = chanPtr->inQueueTail;
	    }

	    chanPtr->inQueueHead = NULL;
	    chanPtr->inQueueTail = NULL;

	    DiscardInputQueued(statePtr, 0);
	}

	/*
	 * TIP #218, Channel Thread Actions.
	 *
	 * We call the thread actions for the new channel directly. We
	 * _cannot_ use CutChannel, because the (thread-)global list of all
	 * channels always contains the _ChannelState_ for a stack of
	 * channels, not the individual channels. And SpliceChannel would not
	 * only call the thread actions, but also remove the shared
	 * ChannelState from this list despite there being more channels for
	 * the state which are still active.
	 */

	ChanThreadAction(chanPtr, TCL_CHANNEL_THREAD_REMOVE);

	statePtr->topChanPtr = downChanPtr;
	downChanPtr->upChanPtr = NULL;

	/*
	 * Leave this link intact for closeproc
	 *  chanPtr->downChanPtr = NULL;
	 */

	/*
	 * Close and free the channel driver state.
	 */

	result = ChanClose(chanPtr, interp);
	chanPtr->typePtr = NULL;

	/*
	 * AK: Tcl_NotifyChannel may hold a reference to this block of memory
	 */

	Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
	UpdateInterest(downChanPtr);

	if (result != 0) {
	    Tcl_SetErrno(result);

	    /*
	     * TIP #219, Tcl Channel Reflection API.
	     * Move error messages put by the driver into the chan/ip bypass
	     * area into the regular interpreter result.
	     */

	    TclChanCaughtErrorBypass(interp, chan);
	    return TCL_ERROR;
	}
    } else {
	/*
	 * This channel does not cover another one. Simply do a close, if
	 * necessary.
	 */

	if (statePtr->refCount <= 0) {
	    if (Tcl_Close(interp, chan) != TCL_OK) {
		/*
		 * TIP #219, Tcl Channel Reflection API.
		 * "TclChanCaughtErrorBypass" is not required here, it was
		 * done already by "Tcl_Close".
		 */

		return TCL_ERROR;
	    }
	}

	/*
	 * TIP #218, Channel Thread Actions.
	 * Not required in this branch, this is done by Tcl_Close. If
	 * Tcl_Close is not called then the ChannelState is still active in
	 * the thread and no action has to be taken either.
	 */
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetStackedChannel --
 *
 *	Determines whether the specified channel is stacked upon another.
 *
 * Results:
 *	NULL if the channel is not stacked upon another one, or a reference to
 *	the channel it is stacked upon. This reference can be used in queries,
 *	but modification is not allowed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetStackedChannel(
    Tcl_Channel chan)
{
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */

    return (Tcl_Channel) chanPtr->downChanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetTopChannel --
 *
 *	Returns the top channel of a channel stack.
 *
 * Results:
 *	NULL if the channel is not stacked upon another one, or a reference to
 *	the channel it is stacked upon. This reference can be used in queries,
 *	but modification is not allowed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetTopChannel(
    Tcl_Channel chan)
{
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */

    return (Tcl_Channel) chanPtr->state->topChanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelInstanceData --
 *
 *	Returns the client data associated with a channel.
 *
 * Results:
 *	The client data.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_GetChannelInstanceData(
    Tcl_Channel chan)		/* Channel for which to return client data. */
{
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */

    return chanPtr->instanceData;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelThread --
 *
 *	Given a channel structure, returns the thread managing it. TIP #10
 *
 * Results:
 *	Returns the id of the thread managing the channel.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_ThreadId
Tcl_GetChannelThread(
    Tcl_Channel chan)		/* The channel to return the managing thread
				 * for. */
{
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */

    return chanPtr->state->managingThread;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelType --
 *
 *	Given a channel structure, returns the channel type structure.
 *
 * Results:
 *	Returns a pointer to the channel type structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

const Tcl_ChannelType *
Tcl_GetChannelType(
    Tcl_Channel chan)		/* The channel to return type for. */
{
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */

    return chanPtr->typePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelMode --
 *
 *	Computes a mask indicating whether the channel is open for reading and
 *	writing.
 *
 * Results:
 *	An OR-ed combination of TCL_READABLE and TCL_WRITABLE.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelMode(
    Tcl_Channel chan)		/* The channel for which the mode is being
				 * computed. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of actual channel. */

    return (statePtr->flags & (TCL_READABLE | TCL_WRITABLE));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelName --
 *
 *	Returns the string identifying the channel name.
 *
 * Results:
 *	The string containing the channel name. This memory is owned by the
 *	generic layer and should not be modified by the caller.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

const char *
Tcl_GetChannelName(
    Tcl_Channel chan)		/* The channel for which to return the name. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of actual channel. */

    return statePtr->channelName;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelHandle --
 *
 *	Returns an OS handle associated with a channel.
 *
 * Results:
 *	Returns TCL_OK and places the handle in handlePtr, or returns
 *	TCL_ERROR on failure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelHandle(
    Tcl_Channel chan,		/* The channel to get file from. */
    int direction,		/* TCL_WRITABLE or TCL_READABLE. */
    ClientData *handlePtr)	/* Where to store handle */
{
    Channel *chanPtr;		/* The actual channel. */
    ClientData handle;
    int result;

    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    result = chanPtr->typePtr->getHandleProc(chanPtr->instanceData, direction,
	    &handle);
    if (handlePtr) {
	*handlePtr = handle;
    }
    return result;
}

/*
 *---------------------------------------------------------------------------
 *
 * AllocChannelBuffer --
 *
 *	A channel buffer has BUFFER_PADDING bytes extra at beginning to hold
 *	any bytes of a native-encoding character that got split by the end of
 *	the previous buffer and need to be moved to the beginning of the next
 *	buffer to make a contiguous string so it can be converted to UTF-8.
 *
 *	A channel buffer has BUFFER_PADDING bytes extra at the end to hold any
 *	bytes of a native-encoding character (generated from a UTF-8
 *	character) that overflow past the end of the buffer and need to be
 *	moved to the next buffer.
 *
 * Results:
 *	A newly allocated channel buffer.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static ChannelBuffer *
AllocChannelBuffer(
    int length)			/* Desired length of channel buffer. */
{
    ChannelBuffer *bufPtr;
    int n;

    n = length + CHANNELBUFFER_HEADER_SIZE + BUFFER_PADDING + BUFFER_PADDING;
    bufPtr = (ChannelBuffer *) ckalloc((unsigned) n);
    bufPtr->nextAdded	= BUFFER_PADDING;
    bufPtr->nextRemoved	= BUFFER_PADDING;
    bufPtr->bufLength	= length + BUFFER_PADDING;
    bufPtr->nextPtr	= NULL;
    return bufPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * RecycleBuffer --
 *
 *	Helper function to recycle input and output buffers. Ensures that two
 *	input buffers are saved (one in the input queue and another in the
 *	saveInBufPtr field) and that curOutPtr is set to a buffer. Only if
 *	these conditions are met is the buffer freed to the OS.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May free a buffer to the OS.
 *
 *----------------------------------------------------------------------
 */

static void
RecycleBuffer(
    ChannelState *statePtr,	/* ChannelState in which to recycle buffers. */
    ChannelBuffer *bufPtr,	/* The buffer to recycle. */
    int mustDiscard)		/* If nonzero, free the buffer to the OS,
				 * always. */
{
    /*
     * Do we have to free the buffer to the OS?
     */

    if (mustDiscard) {
	ckfree((char *) bufPtr);
	return;
    }

    /*
     * Only save buffers which are at least as big as the requested buffersize
     * for the channel. This is to honor dynamic changes of the buffersize
     * made by the user.
     */

    if ((bufPtr->bufLength - BUFFER_PADDING) < statePtr->bufSize) {
	ckfree((char *) bufPtr);
	return;
    }

    /*
     * Only save buffers for the input queue if the channel is readable.
     */

    if (GotFlag(statePtr, TCL_READABLE)) {
	if (statePtr->inQueueHead == NULL) {
	    statePtr->inQueueHead = bufPtr;
	    statePtr->inQueueTail = bufPtr;
	    goto keepBuffer;
	}
	if (statePtr->saveInBufPtr == NULL) {
	    statePtr->saveInBufPtr = bufPtr;
	    goto keepBuffer;
	}
    }

    /*
     * Only save buffers for the output queue if the channel is writable.
     */

    if (GotFlag(statePtr, TCL_WRITABLE)) {
	if (statePtr->curOutPtr == NULL) {
	    statePtr->curOutPtr = bufPtr;
	    goto keepBuffer;
	}
    }

    /*
     * If we reached this code we return the buffer to the OS.
     */

    ckfree((char *) bufPtr);
    return;

  keepBuffer:
    bufPtr->nextRemoved = BUFFER_PADDING;
    bufPtr->nextAdded = BUFFER_PADDING;
    bufPtr->nextPtr = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * DiscardOutputQueued --
 *
 *	Discards all output queued in the output queue of a channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Recycles buffers.
 *
 *----------------------------------------------------------------------
 */

static void
DiscardOutputQueued(
    ChannelState *statePtr)	/* ChannelState for which to discard output. */
{
    ChannelBuffer *bufPtr;

    while (statePtr->outQueueHead != NULL) {
	bufPtr = statePtr->outQueueHead;
	statePtr->outQueueHead = bufPtr->nextPtr;
	RecycleBuffer(statePtr, bufPtr, 0);
    }
    statePtr->outQueueHead = NULL;
    statePtr->outQueueTail = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CheckForDeadChannel --
 *
 *	This function checks is a given channel is Dead (a channel that has
 *	been closed but not yet deallocated.)
 *
 * Results:
 *	True (1) if channel is Dead, False (0) if channel is Ok
 *
 * Side effects:
 *	None
 *
 *----------------------------------------------------------------------
 */

static int
CheckForDeadChannel(
    Tcl_Interp *interp,		/* For error reporting (can be NULL) */
    ChannelState *statePtr)	/* The channel state to check. */
{
    if (!GotFlag(statePtr, CHANNEL_DEAD)) {
	return 0;
    }

    Tcl_SetErrno(EINVAL);
    if (interp) {
	Tcl_AppendResult(interp, "unable to access channel: invalid channel",
		NULL);
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * FlushChannel --
 *
 *	This function flushes as much of the queued output as is possible
 *	now. If calledFromAsyncFlush is nonzero, it is being called in an
 *	event handler to flush channel output asynchronously.
 *
 * Results:
 *	0 if successful, else the error code that was returned by the channel
 *	type operation. May leave a message in the interp result.
 *
 * Side effects:
 *	May produce output on a channel. May block indefinitely if the channel
 *	is synchronous. May schedule an async flush on the channel. May
 *	recycle memory for buffers in the output queue.
 *
 *----------------------------------------------------------------------
 */

static int
FlushChannel(
    Tcl_Interp *interp,		/* For error reporting during close. */
    Channel *chanPtr,		/* The channel to flush on. */
    int calledFromAsyncFlush)	/* If nonzero then we are being called from an
				 * asynchronous flush callback. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State of the channel stack. */
    ChannelBuffer *bufPtr;	/* Iterates over buffered output queue. */
    int toWrite;		/* Amount of output data in current buffer
				 * available to be written. */
    int written;		/* Amount of output data actually written in
				 * current round. */
    int errorCode = 0;		/* Stores POSIX error codes from channel
				 * driver operations. */
    int wroteSome = 0;		/* Set to one if any data was written to the
				 * driver. */

    /*
     * Prevent writing on a dead channel -- a channel that has been closed but
     * not yet deallocated. This can occur if the exit handler for the channel
     * deallocation runs before all channels are deregistered in all
     * interpreters.
     */

    if (CheckForDeadChannel(interp, statePtr)) {
	return -1;
    }

    /*
     * Loop over the queued buffers and attempt to flush as much as possible
     * of the queued output to the channel.
     */

    while (1) {
	/*
	 * If the queue is empty and there is a ready current buffer, OR if
	 * the current buffer is full, then move the current buffer to the
	 * queue.
	 */

	if (((statePtr->curOutPtr != NULL) &&
		IsBufferFull(statePtr->curOutPtr))
		|| (GotFlag(statePtr, BUFFER_READY) &&
			(statePtr->outQueueHead == NULL))) {
	    ResetFlag(statePtr, BUFFER_READY);
	    statePtr->curOutPtr->nextPtr = NULL;
	    if (statePtr->outQueueHead == NULL) {
		statePtr->outQueueHead = statePtr->curOutPtr;
	    } else {
		statePtr->outQueueTail->nextPtr = statePtr->curOutPtr;
	    }
	    statePtr->outQueueTail = statePtr->curOutPtr;
	    statePtr->curOutPtr = NULL;
	}
	bufPtr = statePtr->outQueueHead;

	/*
	 * If we are not being called from an async flush and an async flush
	 * is active, we just return without producing any output.
	 */

	if (!calledFromAsyncFlush && GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    return 0;
	}

	/*
	 * If the output queue is still empty, break out of the while loop.
	 */

	if (bufPtr == NULL) {
	    break;		/* Out of the "while (1)". */
	}

	/*
	 * Produce the output on the channel.
	 */

	toWrite = BytesLeft(bufPtr);
	written = ChanWrite(chanPtr, RemovePoint(bufPtr),toWrite, &errorCode);

	/*
	 * If the write failed completely attempt to start the asynchronous
	 * flush mechanism and break out of this loop - do not attempt to
	 * write any more output at this time.
	 */

	if (written < 0) {
	    /*
	     * If the last attempt to write was interrupted, simply retry.
	     */

	    if (errorCode == EINTR) {
		errorCode = 0;
		continue;
	    }

	    /*
	     * If the channel is non-blocking and we would have blocked, start
	     * a background flushing handler and break out of the loop.
	     */

	    if ((errorCode == EWOULDBLOCK) || (errorCode == EAGAIN)) {
		/*
		 * This used to check for CHANNEL_NONBLOCKING, and panic if
		 * the channel was blocking. However, it appears that setting
		 * stdin to -blocking 0 has some effect on the stdout when
		 * it's a tty channel (dup'ed underneath)
		 */

		if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
		    SetFlag(statePtr, BG_FLUSH_SCHEDULED);
		    UpdateInterest(chanPtr);
		}
		errorCode = 0;
		break;
	    }

	    /*
	     * Decide whether to report the error upwards or defer it.
	     */

	    if (calledFromAsyncFlush) {
		/*
		 * TIP #219, Tcl Channel Reflection API.
		 * When defering the error copy a message from the bypass into
		 * the unreported area. Or discard it if the new error is to be
		 * ignored in favor of an earlier defered error.
		 */

		Tcl_Obj *msg = statePtr->chanMsg;

		if (statePtr->unreportedError == 0) {
		    statePtr->unreportedError = errorCode;
		    statePtr->unreportedMsg = msg;
		    if (msg != NULL) {
			Tcl_IncrRefCount(msg);
		    }
		} else {
		    /*
		     * An old unreported error is kept, and this error thrown
		     * away.
		     */

		    statePtr->chanMsg = NULL;
		    if (msg != NULL) {
			TclDecrRefCount(msg);
		    }
		}
	    } else {
		/*
		 * TIP #219, Tcl Channel Reflection API.
		 * Move error messages put by the driver into the chan bypass
		 * area into the regular interpreter result. Fall back to the
		 * regular message if nothing was found in the bypasses.
		 */

		Tcl_SetErrno(errorCode);
		if (interp != NULL && !TclChanCaughtErrorBypass(interp,
			(Tcl_Channel) chanPtr)) {
		    Tcl_SetObjResult(interp,
			    Tcl_NewStringObj(Tcl_PosixError(interp), -1));
		}

		/*
		 * An unreportable bypassed message is kept, for the caller of
		 * Tcl_Seek, Tcl_Write, etc.
		 */
	    }

	    /*
	     * When we get an error we throw away all the output currently
	     * queued.
	     */

	    DiscardOutputQueued(statePtr);
	    continue;
	} else {
	    wroteSome = 1;
	}

	bufPtr->nextRemoved += written;

	/*
	 * If this buffer is now empty, recycle it.
	 */

	if (IsBufferEmpty(bufPtr)) {
	    statePtr->outQueueHead = bufPtr->nextPtr;
	    if (statePtr->outQueueHead == NULL) {
		statePtr->outQueueTail = NULL;
	    }
	    RecycleBuffer(statePtr, bufPtr, 0);
	}
    }	/* Closes "while (1)". */

    /*
     * If we wrote some data while flushing in the background, we are done.
     * We can't finish the background flush until we run out of data and the
     * channel becomes writable again. This ensures that all of the pending
     * data has been flushed at the system level.
     */

    if (GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	if (wroteSome) {
	    return errorCode;
	} else if (statePtr->outQueueHead == NULL) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	    ChanWatch(chanPtr, statePtr->interestMask);
	}
    }

    /*
     * If the channel is flagged as closed, delete it when the refCount drops
     * to zero, the output queue is empty and there is no output in the
     * current output buffer.
     */

    if (GotFlag(statePtr, CHANNEL_CLOSED) && (statePtr->refCount <= 0) &&
	    (statePtr->outQueueHead == NULL) &&
	    ((statePtr->curOutPtr == NULL) ||
	    IsBufferEmpty(statePtr->curOutPtr))) {
	return CloseChannel(interp, chanPtr, errorCode);
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * CloseChannel --
 *
 *	Utility procedure to close a channel and free associated resources.
 *
 *	If the channel was stacked, then the it will copy the necessary
 *	elements of the NEXT channel into the TOP channel, in essence
 *	unstacking the channel. The NEXT channel will then be freed.
 *
 *	If the channel was not stacked, then we will free all the bits for the
 *	TOP channel, including the data structure itself.
 *
 * Results:
 *	Error code from an unreported error or the driver close operation.
 *
 * Side effects:
 *	May close the actual channel, may free memory, may change the value of
 *	errno.
 *
 *----------------------------------------------------------------------
 */

static int
CloseChannel(
    Tcl_Interp *interp,		/* For error reporting. */
    Channel *chanPtr,		/* The channel to close. */
    int errorCode)		/* Status of operation so far. */
{
    int result = 0;		/* Of calling driver close operation. */
    ChannelState *statePtr;	/* State of the channel stack. */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (chanPtr == NULL) {
	return result;
    }
    statePtr = chanPtr->state;

    /*
     * No more input can be consumed so discard any leftover input.
     */

    DiscardInputQueued(statePtr, 1);

    /*
     * Discard a leftover buffer in the current output buffer field.
     */

    if (statePtr->curOutPtr != NULL) {
	ckfree((char *) statePtr->curOutPtr);
	statePtr->curOutPtr = NULL;
    }

    /*
     * The caller guarantees that there are no more buffers queued for output.
     */

    if (statePtr->outQueueHead != NULL) {
	Tcl_Panic("TclFlush, closed channel: queued output left");
    }

    /*
     * If the EOF character is set in the channel, append that to the output
     * device.
     */

    if ((statePtr->outEofChar != 0) && GotFlag(statePtr, TCL_WRITABLE)) {
	int dummy;
	char c = (char) statePtr->outEofChar;

	(void) ChanWrite(chanPtr, &c, 1, &dummy);
    }

    /*
     * TIP #219, Tcl Channel Reflection API.
     * Move a leftover error message in the channel bypass into the
     * interpreter bypass. Just clear it if there is no interpreter.
     */

    if (statePtr->chanMsg != NULL) {
	if (interp != NULL) {
	    Tcl_SetChannelErrorInterp(interp,statePtr->chanMsg);
	}
	TclDecrRefCount(statePtr->chanMsg);
	statePtr->chanMsg = NULL;
    }

    /*
     * Remove this channel from of the list of all channels.
     */

    CutChannel((Tcl_Channel) chanPtr);

    /*
     * Close and free the channel driver state.
     * This may leave a TIP #219 error message in the interp.
     */

    result = ChanClose(chanPtr, interp);

    /*
     * Some resources can be cleared only if the bottom channel in a stack is
     * closed. All the other channels in the stack are not allowed to remove.
     */

    if (chanPtr == statePtr->bottomChanPtr) {
	if (statePtr->channelName != NULL) {
	    ckfree((char *) statePtr->channelName);
	    statePtr->channelName = NULL;
	}

	Tcl_FreeEncoding(statePtr->encoding);
	if (statePtr->outputStage != NULL) {
	    ckfree((char *) statePtr->outputStage);
	    statePtr->outputStage = NULL;
	}
    }

    /*
     * If we are being called synchronously, report either any latent error on
     * the channel or the current error.
     */

    if (statePtr->unreportedError != 0) {
	errorCode = statePtr->unreportedError;

	/*
	 * TIP #219, Tcl Channel Reflection API.
	 * Move an error message found in the unreported area into the regular
	 * bypass (interp). This kills any message in the channel bypass area.
	 */

	if (statePtr->chanMsg != NULL) {
	    TclDecrRefCount(statePtr->chanMsg);
	    statePtr->chanMsg = NULL;
	}
	if (interp) {
	    Tcl_SetChannelErrorInterp(interp,statePtr->unreportedMsg);
	}
    }
    if (errorCode == 0) {
	errorCode = result;
	if (errorCode != 0) {
	    Tcl_SetErrno(errorCode);
	}
    }

    /*
     * Cancel any outstanding timer.
     */

    Tcl_DeleteTimerHandler(statePtr->timer);

    /*
     * Mark the channel as deleted by clearing the type structure.
     */

    if (chanPtr->downChanPtr != NULL) {
	Channel *downChanPtr = chanPtr->downChanPtr;

	statePtr->nextCSPtr = tsdPtr->firstCSPtr;
	tsdPtr->firstCSPtr = statePtr;

	statePtr->topChanPtr = downChanPtr;
	downChanPtr->upChanPtr = NULL;
	chanPtr->typePtr = NULL;

	Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
	return Tcl_Close(interp, (Tcl_Channel) downChanPtr);
    }

    /*
     * There is only the TOP Channel, so we free the remaining pointers we
     * have and then ourselves. Since this is the last of the channels in the
     * stack, make sure to free the ChannelState structure associated with it.
     * We use Tcl_EventuallyFree to allow for any last references.
     */

    chanPtr->typePtr = NULL;

    Tcl_EventuallyFree(statePtr, TCL_DYNAMIC);
    Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);

    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CutChannel --
 * CutChannel --
 *
 *	Removes a channel from the (thread-)global list of all channels (in
 *	that thread). This is actually the statePtr for the stack of channel.
 *
 * Results:
 *	Nothing.
 *
 * Side effects:
 *	Resets the field 'nextCSPtr' of the specified channel state to NULL.
 *
 * NOTE:
 *	The channel to cut out of the list must not be referenced in any
 *	interpreter. This is something this procedure cannot check (despite
 *	the refcount) because the caller usually wants fiddle with the channel
 *	(like transfering it to a different thread) and thus keeps the
 *	refcount artifically high to prevent its destruction.
 *
 *----------------------------------------------------------------------
 */

static void
CutChannel(
    Tcl_Channel chan)		/* The channel being removed. Must not be
				 * referenced in any interpreter. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelState *prevCSPtr;	/* Preceding channel state in list of all
				 * states - used to splice a channel out of
				 * the list on close. */
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of the channel stack. */

    /*
     * Remove this channel from of the list of all channels (in the current
     * thread).
     */

    if (tsdPtr->firstCSPtr && (statePtr == tsdPtr->firstCSPtr)) {
	tsdPtr->firstCSPtr = statePtr->nextCSPtr;
    } else {
	for (prevCSPtr = tsdPtr->firstCSPtr;
		prevCSPtr && (prevCSPtr->nextCSPtr != statePtr);
		prevCSPtr = prevCSPtr->nextCSPtr) {
	    /* Empty loop body. */
	}
	if (prevCSPtr == NULL) {
	    Tcl_Panic("FlushChannel: damaged channel list");
	}
	prevCSPtr->nextCSPtr = statePtr->nextCSPtr;
    }

    statePtr->nextCSPtr = NULL;

    /*
     * TIP #218, Channel Thread Actions
     */

    ChanThreadAction((Channel *) chan, TCL_CHANNEL_THREAD_REMOVE);
}

void
Tcl_CutChannel(
    Tcl_Channel chan)		/* The channel being added. Must not be
				 * referenced in any interpreter. */
{
    Channel *chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelState *prevCSPtr;	/* Preceding channel state in list of all
				 * states - used to splice a channel out of
				 * the list on close. */
    ChannelState *statePtr = chanPtr->state;
				/* State of the channel stack. */

    /*
     * Remove this channel from of the list of all channels (in the current
     * thread).
     */

    if (tsdPtr->firstCSPtr && (statePtr == tsdPtr->firstCSPtr)) {
	tsdPtr->firstCSPtr = statePtr->nextCSPtr;
    } else {
	for (prevCSPtr = tsdPtr->firstCSPtr;
		prevCSPtr && (prevCSPtr->nextCSPtr != statePtr);
		prevCSPtr = prevCSPtr->nextCSPtr) {
	    /* Empty loop body. */
	}
	if (prevCSPtr == NULL) {
	    Tcl_Panic("FlushChannel: damaged channel list");
	}
	prevCSPtr->nextCSPtr = statePtr->nextCSPtr;
    }

    statePtr->nextCSPtr = NULL;

    /*
     * TIP #218, Channel Thread Actions
     * For all transformations and the base channel.
     */

    for (; chanPtr != NULL ; chanPtr = chanPtr->upChanPtr) {
	ChanThreadAction(chanPtr, TCL_CHANNEL_THREAD_REMOVE);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SpliceChannel --
 * SpliceChannel --
 *
 *	Adds a channel to the (thread-)global list of all channels (in that
 *	thread). Expects that the field 'nextChanPtr' in the channel is set to
 *	NULL.
 *
 * Results:
 *	Nothing.
 *
 * Side effects:
 *	Nothing.
 *
 * NOTE:
 *	The channel to splice into the list must not be referenced in any
 *	interpreter. This is something this procedure cannot check (despite
 *	the refcount) because the caller usually wants figgle with the channel
 *	(like transfering it to a different thread) and thus keeps the
 *	refcount artifically high to prevent its destruction.
 *
 *----------------------------------------------------------------------
 */

static void
SpliceChannel(
    Tcl_Channel chan)		/* The channel being added. Must not be
				 * referenced in any interpreter. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelState *statePtr = ((Channel *) chan)->state;

    if (statePtr->nextCSPtr != NULL) {
	Tcl_Panic("SpliceChannel: trying to add channel used in different list");
    }

    statePtr->nextCSPtr = tsdPtr->firstCSPtr;
    tsdPtr->firstCSPtr = statePtr;

    /*
     * TIP #10. Mark the current thread as the new one managing this channel.
     *		Note: 'Tcl_GetCurrentThread' returns sensible values even for
     *		a non-threaded core.
     */

    statePtr->managingThread = Tcl_GetCurrentThread();

    /*
     * TIP #218, Channel Thread Actions
     */

    ChanThreadAction((Channel *) chan, TCL_CHANNEL_THREAD_INSERT);
}

void
Tcl_SpliceChannel(
    Tcl_Channel chan)		/* The channel being added. Must not be
				 * referenced in any interpreter. */
{
    Channel *chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelState *statePtr = chanPtr->state;

    if (statePtr->nextCSPtr != NULL) {
	Tcl_Panic("SpliceChannel: trying to add channel used in different list");
    }

    statePtr->nextCSPtr = tsdPtr->firstCSPtr;
    tsdPtr->firstCSPtr = statePtr;

    /*
     * TIP #10. Mark the current thread as the new one managing this channel.
     *		Note: 'Tcl_GetCurrentThread' returns sensible values even for
     *		a non-threaded core.
     */

    statePtr->managingThread = Tcl_GetCurrentThread();

    /*
     * TIP #218, Channel Thread Actions
     * For all transformations and the base channel.
     */

    for (; chanPtr != NULL ; chanPtr = chanPtr->upChanPtr) {
	ChanThreadAction(chanPtr, TCL_CHANNEL_THREAD_INSERT);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Close --
 *
 *	Closes a channel.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Closes the channel if this is the last reference.
 *
 * NOTE:
 *	Tcl_Close removes the channel as far as the user is concerned.
 *	However, it may continue to exist for a while longer if it has a
 *	background flush scheduled. The device itself is eventually closed and
 *	the channel record removed, in CloseChannel, above.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
int
Tcl_Close(
    Tcl_Interp *interp,		/* Interpreter for errors. */
    Tcl_Channel chan)		/* The channel being closed. Must not be
				 * referenced in any interpreter. */
{
    CloseCallback *cbPtr;	/* Iterate over close callbacks for this
				 * channel. */
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of real IO channel. */
    int result;			/* Of calling FlushChannel. */
    int flushcode;

    if (chan == NULL) {
	return TCL_OK;
    }

    /*
     * Perform special handling for standard channels being closed. If the
     * refCount is now 1 it means that the last reference to the standard
     * channel is being explicitly closed, so bump the refCount down
     * artificially to 0. This will ensure that the channel is actually
     * closed, below. Also set the static pointer to NULL for the channel.
     */

    CheckForStdChannelsBeingClosed(chan);

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;
    chanPtr = statePtr->topChanPtr;

    if (statePtr->refCount > 0) {
	Tcl_Panic("called Tcl_Close on channel with refCount > 0");
    }

    if (GotFlag(statePtr, CHANNEL_INCLOSE)) {
	if (interp) {
	    Tcl_AppendResult(interp, "Illegal recursive call to close "
		    "through close-handler of channel", NULL);
	}
	return TCL_ERROR;
    }
    SetFlag(statePtr, CHANNEL_INCLOSE);

    /*
     * When the channel has an escape sequence driven encoding such as
     * iso2022, the terminated escape sequence must write to the buffer.
     */

    if ((statePtr->encoding != NULL) && (statePtr->curOutPtr != NULL)
	    && (CheckChannelErrors(statePtr, TCL_WRITABLE) == 0)) {
	statePtr->outputEncodingFlags |= TCL_ENCODING_END;
	WriteChars(chanPtr, "", 0);

	/*
	 * TIP #219, Tcl Channel Reflection API.
	 * Move an error message found in the channel bypass into the
	 * interpreter bypass. Just clear it if there is no interpreter.
	 */

	if (statePtr->chanMsg != NULL) {
	    if (interp != NULL) {
		Tcl_SetChannelErrorInterp(interp,statePtr->chanMsg);
	    }
	    TclDecrRefCount(statePtr->chanMsg);
	    statePtr->chanMsg = NULL;
	}
    }

    Tcl_ClearChannelHandlers(chan);

    /*
     * Invoke the registered close callbacks and delete their records.
     */

    while (statePtr->closeCbPtr != NULL) {
	cbPtr = statePtr->closeCbPtr;
	statePtr->closeCbPtr = cbPtr->nextPtr;
	cbPtr->proc(cbPtr->clientData);
	ckfree((char *) cbPtr);
    }

    ResetFlag(statePtr, CHANNEL_INCLOSE);

    /*
     * Ensure that the last output buffer will be flushed.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    /*
     * If this channel supports it, close the read side, since we don't need
     * it anymore and this will help avoid deadlocks on some channel types.
     */

    if (chanPtr->typePtr->closeProc == TCL_CLOSE2PROC) {
	result = chanPtr->typePtr->close2Proc(chanPtr->instanceData, interp,
		TCL_CLOSE_READ);
    } else {
	result = 0;
    }

    /*
     * The call to FlushChannel will flush any queued output and invoke the
     * close function of the channel driver, or it will set up the channel to
     * be flushed and closed asynchronously.
     */

    SetFlag(statePtr, CHANNEL_CLOSED);

    flushcode = FlushChannel(interp, chanPtr, 0);

    /*
     * TIP #219.
     * Capture error messages put by the driver into the bypass area and put
     * them into the regular interpreter result.
     *
     * Notes: Due to the assertion of CHANNEL_CLOSED in the flags
     * FlushChannel() has called CloseChannel() and thus freed all the channel
     * structures. We must not try to access "chan" anymore, hence the NULL
     * argument in the call below. The only place which may still contain a
     * message is the interpreter itself, and "CloseChannel" made sure to lift
     * any channel message it generated into it.
     */

    if (TclChanCaughtErrorBypass(interp, NULL)) {
	result = EINVAL;
    }

    if ((flushcode != 0) || (result != 0)) {
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CloseEx --
 *
 *	Half closes a channel.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Closes one direction of the channel.
 *
 * NOTE:
 *	Tcl_CloseEx closes the specified direction of the channel as far as
 *	the user is concerned. The channel keeps existing however. You cannot
 *	calls this function to close the last possible direction of the
 *	channel. Use Tcl_Close for that.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
int
Tcl_CloseEx(
    Tcl_Interp *interp,		/* Interpreter for errors. */
    Tcl_Channel chan,		/* The channel being closed. May still be used by some interpreter */
    int flags)                  /* Flags telling us which side to close. */
{
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of real IO channel. */
    int result;			/* Of calling FlushChannel. */

    if (chan == NULL) {
	return TCL_OK;
    }

    /* TODO: assert flags validity ? */

    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;

    /*
     * Does the channel support half-close anyway ? Error if not.
     */

    if (!chanPtr->typePtr->close2Proc) {
	Tcl_AppendResult (interp, "Half-close of channels not supported by ",
			  chanPtr->typePtr->typeName, "s", NULL);
	return TCL_ERROR;
    }

    /*
     * Is the channel unstacked ? If not we fail.
     */

    if (chanPtr != statePtr->topChanPtr) {
	Tcl_AppendResult (interp,
			  "Half-close not applicable to stack of transformations",
			  NULL);
	return TCL_ERROR;
    }
    
    /*
     * Check direction against channel mode. It is an error if we try to close
     * a direction not supported by the channel (already closed, or never
     * opened for that direction).
     */

    if (!(statePtr->flags & (TCL_READABLE | TCL_WRITABLE) & flags)) {
	const char *msg;
	if (flags & TCL_CLOSE_READ) {
	    msg = "read";
	} else {
	    msg = "write";
	}
	Tcl_AppendResult (interp, "Half-close of ", msg,
			      "-side not possible, side not opened or already closed",
			      NULL);
	return TCL_ERROR;
    }

    /*
     * A user may try to call half-close from within a channel close
     * handler. That won't do.
     */

    if (statePtr->flags & CHANNEL_INCLOSE) {
	if (interp) {
	    Tcl_AppendResult(interp, "Illegal recursive call to close "
		    "through close-handler of channel", NULL);
	}
	return TCL_ERROR;
    }

	/*
	 * Flush any data if [close w]
	 */

	if (flags & TCL_CLOSE_WRITE) {  
		if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
			SetFlag(statePtr, BUFFER_READY);
		}
		/*
		 * Ignoring the outcome of the flush (like EPIPE), since we don't want
		 * to disrupt the close path with such errors
		 */
		FlushChannel(NULL, chanPtr, 0);
	}

    /*
     * Finally do what is asked of us.
     */

    result = chanPtr->typePtr->close2Proc(chanPtr->instanceData, interp,
					  flags);

    /*
     * TIP #219.
     * Capture error messages put by the driver into the bypass area and put
     * them into the regular interpreter result.
     */

    if (TclChanCaughtErrorBypass(interp, chan)) {
	result = EINVAL;
    }

    if (result != 0) {
	return TCL_ERROR;
    }

    /*
     * Remove the closed side from the channel mode/flags.
     */

    statePtr->flags &= ~(flags & (TCL_READABLE | TCL_WRITABLE));

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ClearChannelHandlers --
 *
 *	Removes all channel handlers and event scripts from the channel,
 *	cancels all background copies involving the channel and any interest
 *	in events.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	See above. Deallocates memory.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ClearChannelHandlers(
    Tcl_Channel channel)
{
    ChannelHandler *chPtr, *chNext;	/* Iterate over channel handlers. */
    EventScriptRecord *ePtr, *eNextPtr;	/* Iterate over eventscript records. */
    Channel *chanPtr;			/* The real IO channel. */
    ChannelState *statePtr;		/* State of real IO channel. */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    NextChannelHandler *nhPtr;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) channel;
    statePtr = chanPtr->state;
    chanPtr = statePtr->topChanPtr;

    /*
     * Cancel any outstanding timer.
     */

    Tcl_DeleteTimerHandler(statePtr->timer);

    /*
     * Remove any references to channel handlers for this channel that may be
     * about to be invoked.
     */

    for (nhPtr = tsdPtr->nestedHandlerPtr; nhPtr != NULL;
	    nhPtr = nhPtr->nestedHandlerPtr) {
	if (nhPtr->nextHandlerPtr &&
		(nhPtr->nextHandlerPtr->chanPtr == chanPtr)) {
	    nhPtr->nextHandlerPtr = NULL;
	}
    }

    /*
     * Remove all the channel handler records attached to the channel itself.
     */

    for (chPtr = statePtr->chPtr; chPtr != NULL; chPtr = chNext) {
	chNext = chPtr->nextPtr;
	ckfree((char *) chPtr);
    }
    statePtr->chPtr = NULL;

    /*
     * Cancel any pending copy operation.
     */

    StopCopy(statePtr->csPtrR);
    StopCopy(statePtr->csPtrW);

    /*
     * Must set the interest mask now to 0, otherwise infinite loops
     * will occur if Tcl_DoOneEvent is called before the channel is
     * finally deleted in FlushChannel. This can happen if the channel
     * has a background flush active.
     */

    statePtr->interestMask = 0;

    /*
     * Remove any EventScript records for this channel.
     */

    for (ePtr = statePtr->scriptRecordPtr; ePtr != NULL; ePtr = eNextPtr) {
	eNextPtr = ePtr->nextPtr;
	TclDecrRefCount(ePtr->scriptPtr);
	ckfree((char *) ePtr);
    }
    statePtr->scriptRecordPtr = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Write --
 *
 *	Puts a sequence of bytes into an output buffer, may queue the buffer
 *	for output if it gets full, and also remembers whether the current
 *	buffer is ready e.g. if it contains a newline and we are in line
 *	buffering mode. Compensates stacking, i.e. will redirect the data from
 *	the specified channel to the topmost channel in a stack.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Write(
    Tcl_Channel chan,		/* The channel to buffer output for. */
    const char *src,		/* Data to queue in output buffer. */
    int srcLen)			/* Length of data in bytes, or < 0 for
				 * strlen(). */
{
    /*
     * Always use the topmost channel of the stack
     */

    Channel *chanPtr;
    ChannelState *statePtr;	/* State info for channel */

    statePtr = ((Channel *) chan)->state;
    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    if (srcLen < 0) {
	srcLen = strlen(src);
    }
    return DoWrite(chanPtr, src, srcLen);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_WriteRaw --
 *
 *	Puts a sequence of bytes into an output buffer, may queue the buffer
 *	for output if it gets full, and also remembers whether the current
 *	buffer is ready e.g. if it contains a newline and we are in line
 *	buffering mode. Writes directly to the driver of the channel, does not
 *	compensate for stacking.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WriteRaw(
    Tcl_Channel chan,		/* The channel to buffer output for. */
    const char *src,		/* Data to queue in output buffer. */
    int srcLen)			/* Length of data in bytes, or < 0 for
				 * strlen(). */
{
    Channel *chanPtr = ((Channel *) chan);
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int errorCode, written;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE | CHANNEL_RAW_MODE) != 0) {
	return -1;
    }

    if (srcLen < 0) {
	srcLen = strlen(src);
    }

    /*
     * Go immediately to the driver, do all the error handling by ourselves.
     * The code was stolen from 'FlushChannel'.
     */

    written = ChanWrite(chanPtr, src, srcLen, &errorCode);
    if (written < 0) {
	Tcl_SetErrno(errorCode);
    }

    return written;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_WriteChars --
 *
 *	Takes a sequence of UTF-8 characters and converts them for output
 *	using the channel's current encoding, may queue the buffer for output
 *	if it gets full, and also remembers whether the current buffer is
 *	ready e.g. if it contains a newline and we are in line buffering
 *	mode. Compensates stacking, i.e. will redirect the data from the
 *	specified channel to the topmost channel in a stack.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WriteChars(
    Tcl_Channel chan,		/* The channel to buffer output for. */
    const char *src,		/* UTF-8 characters to queue in output
				 * buffer. */
    int len)			/* Length of string in bytes, or < 0 for
				 * strlen(). */
{
    ChannelState *statePtr;	/* State info for channel */

    statePtr = ((Channel *) chan)->state;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    return DoWriteChars((Channel *) chan, src, len);
}

/*
 *---------------------------------------------------------------------------
 *
 * DoWriteChars --
 *
 *	Takes a sequence of UTF-8 characters and converts them for output
 *	using the channel's current encoding, may queue the buffer for output
 *	if it gets full, and also remembers whether the current buffer is
 *	ready e.g. if it contains a newline and we are in line buffering mode.
 *	Compensates stacking, i.e. will redirect the data from the specified
 *	channel to the topmost channel in a stack.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

static int
DoWriteChars(
    Channel *chanPtr,		/* The channel to buffer output for. */
    const char *src,		/* UTF-8 characters to queue in output
				 * buffer. */
    int len)			/* Length of string in bytes, or < 0 for
				 * strlen(). */
{
    /*
     * Always use the topmost channel of the stack
     */

    ChannelState *statePtr;	/* State info for channel */

    statePtr = chanPtr->state;
    chanPtr = statePtr->topChanPtr;

    if (len < 0) {
	len = strlen(src);
    }
    if (statePtr->encoding == NULL) {
	/*
	 * Inefficient way to convert UTF-8 to byte-array, but the code
	 * parallels the way it is done for objects.
	 * Special case for 1-byte (used by eg [puts] for the \n) could
	 * be extended to more efficient translation of the src string.
	 */

	int result;

	if ((len == 1) && (UCHAR(*src) < 0xC0)) {
	    result = WriteBytes(chanPtr, src, len);
	} else {
	    Tcl_Obj *objPtr = Tcl_NewStringObj(src, len);

	    src = (char *) Tcl_GetByteArrayFromObj(objPtr, &len);
	    result = WriteBytes(chanPtr, src, len);
	    TclDecrRefCount(objPtr);
	}
	return result;
    }
    return WriteChars(chanPtr, src, len);
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_WriteObj --
 *
 *	Takes the Tcl object and queues its contents for output. If the
 *	encoding of the channel is NULL, takes the byte-array representation
 *	of the object and queues those bytes for output. Otherwise, takes the
 *	characters in the UTF-8 (string) representation of the object and
 *	converts them for output using the channel's current encoding. May
 *	flush internal buffers to output if one becomes full or is ready for
 *	some other reason, e.g. if it contains a newline and the channel is in
 *	line buffering mode.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno() will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WriteObj(
    Tcl_Channel chan,		/* The channel to buffer output for. */
    Tcl_Obj *objPtr)		/* The object to write. */
{
    /*
     * Always use the topmost channel of the stack
     */

    Channel *chanPtr;
    ChannelState *statePtr;	/* State info for channel */
    char *src;
    int srcLen;

    statePtr = ((Channel *) chan)->state;
    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }
    if (statePtr->encoding == NULL) {
	src = (char *) Tcl_GetByteArrayFromObj(objPtr, &srcLen);
	return WriteBytes(chanPtr, src, srcLen);
    } else {
	src = TclGetStringFromObj(objPtr, &srcLen);
	return WriteChars(chanPtr, src, srcLen);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * WriteBytes --
 *
 *	Write a sequence of bytes into an output buffer, may queue the buffer
 *	for output if it gets full, and also remembers whether the current
 *	buffer is ready e.g. if it contains a newline and we are in line
 *	buffering mode.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

static int
WriteBytes(
    Channel *chanPtr,		/* The channel to buffer output for. */
    const char *src,		/* Bytes to write. */
    int srcLen)			/* Number of bytes to write. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    char *dst;
    int dstMax, sawLF, savedLF, total, dstLen, toWrite, translate;

    total = 0;
    sawLF = 0;
    savedLF = 0;
    translate = GotFlag(statePtr, CHANNEL_LINEBUFFERED)
	    || (statePtr->outputTranslation != TCL_TRANSLATE_LF);

    /*
     * Loop over all bytes in src, storing them in output buffer with proper
     * EOL translation.
     */

    while (srcLen + savedLF > 0) {
	bufPtr = statePtr->curOutPtr;
	if (bufPtr == NULL) {
	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
	    statePtr->curOutPtr = bufPtr;
	}
	dst = InsertPoint(bufPtr);
	dstMax = SpaceLeft(bufPtr);
	dstLen = dstMax;

	toWrite = dstLen;
	if (toWrite > srcLen) {
	    toWrite = srcLen;
	}

	if (translate) {
	    if (savedLF) {
		/*
		 * A '\n' was left over from last call to TranslateOutputEOL()
		 * and we need to store it in this buffer. If the channel is
		 * line-based, we will need to flush it.
		 */

		*dst++ = '\n';
		dstLen--;
		sawLF++;
	    }
	    if (TranslateOutputEOL(statePtr, dst, src, &dstLen, &toWrite)) {
		sawLF++;
	    }
	    dstLen += savedLF;
	    savedLF = 0;
	    if (dstLen > dstMax) {
		savedLF = 1;
		dstLen = dstMax;
	    }
	} else {
	    memcpy(dst, src, toWrite);
	    dstLen = toWrite;
	}

	bufPtr->nextAdded += dstLen;
	if (CheckFlush(chanPtr, bufPtr, sawLF) != 0) {
	    return -1;
	}
	total += dstLen;
	src += toWrite;
	srcLen -= toWrite;
	sawLF = 0;
    }
    return total;
}

/*
 *----------------------------------------------------------------------
 *
 * WriteChars --
 *
 *	Convert UTF-8 bytes to the channel's external encoding and write the
 *	produced bytes into an output buffer, may queue the buffer for output
 *	if it gets full, and also remembers whether the current buffer is
 *	ready e.g. if it contains a newline and we are in line buffering mode.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

static int
WriteChars(
    Channel *chanPtr,		/* The channel to buffer output for. */
    const char *src,		/* UTF-8 string to write. */
    int srcLen)			/* Length of UTF-8 string in bytes. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    char *dst, *stage;
    int saved, savedLF, sawLF, total, dstLen, stageMax, dstWrote;
    int stageLen, toWrite, stageRead, endEncoding, result;
    int consumedSomething, translate;
    Tcl_Encoding encoding;
    char safe[BUFFER_PADDING];

    total = 0;
    sawLF = 0;
    savedLF = 0;
    saved = 0;
    encoding = statePtr->encoding;

    /*
     * Write the terminated escape sequence even if srcLen is 0.
     */

    endEncoding = ((statePtr->outputEncodingFlags & TCL_ENCODING_END) != 0);

    translate = GotFlag(statePtr, CHANNEL_LINEBUFFERED)
	    || (statePtr->outputTranslation != TCL_TRANSLATE_LF);

    /*
     * Loop over all UTF-8 characters in src, storing them in staging buffer
     * with proper EOL translation.
     */

    consumedSomething = 1;
    while (consumedSomething && (srcLen + savedLF + endEncoding > 0)) {
	consumedSomething = 0;
	stage = statePtr->outputStage;
	stageMax = statePtr->bufSize;
	stageLen = stageMax;

	toWrite = stageLen;
	if (toWrite > srcLen) {
	    toWrite = srcLen;
	}

	if (translate) {
	    if (savedLF) {
		/*
		 * A '\n' was left over from last call to TranslateOutputEOL()
		 * and we need to store it in the staging buffer. If the
		 * channel is line-based, we will need to flush the output
		 * buffer (after translating the staging buffer).
		 */

		*stage++ = '\n';
		stageLen--;
		sawLF++;
	    }
	    if (TranslateOutputEOL(statePtr, stage, src, &stageLen,
		    &toWrite)) {
		sawLF++;
	    }

	    stage -= savedLF;
	    stageLen += savedLF;
	    savedLF = 0;

	    if (stageLen > stageMax) {
		savedLF = 1;
		stageLen = stageMax;
	    }
	} else {
	    memcpy(stage, src, toWrite);
	    stageLen = toWrite;
	}
	src += toWrite;
	srcLen -= toWrite;

	/*
	 * Loop over all UTF-8 characters in staging buffer, converting them
	 * to external encoding, storing them in output buffer.
	 */

	while (stageLen + saved + endEncoding > 0) {
	    bufPtr = statePtr->curOutPtr;
	    if (bufPtr == NULL) {
		bufPtr = AllocChannelBuffer(statePtr->bufSize);
		statePtr->curOutPtr = bufPtr;
	    }
	    dst = InsertPoint(bufPtr);
	    dstLen = SpaceLeft(bufPtr);

	    if (saved != 0) {
		/*
		 * Here's some translated bytes left over from the last buffer
		 * that we need to stick at the beginning of this buffer.
		 */

		memcpy(dst, safe, (size_t) saved);
		bufPtr->nextAdded += saved;
		dst += saved;
		dstLen -= saved;
		saved = 0;
	    }

	    result = Tcl_UtfToExternal(NULL, encoding, stage, stageLen,
		    statePtr->outputEncodingFlags,
		    &statePtr->outputEncodingState, dst,
		    dstLen + BUFFER_PADDING, &stageRead, &dstWrote, NULL);

	    /*
	     * Fix for SF #506297, reported by Martin Forssen
	     * <ruric@users.sourceforge.net>.
	     *
	     * The encoding chosen in the script exposing the bug writes out
	     * three intro characters when TCL_ENCODING_START is set, but does
	     * not consume any input as TCL_ENCODING_END is cleared. As some
	     * output was generated the enclosing loop calls UtfToExternal
	     * again, again with START set. Three more characters in the out
	     * and still no use of input ... To break this infinite loop we
	     * remove TCL_ENCODING_START from the set of flags after the first
	     * call (no condition is required, the later calls remove an unset
	     * flag, which is a no-op). This causes the subsequent calls to
	     * UtfToExternal to consume and convert the actual input.
	     */

	    statePtr->outputEncodingFlags &= ~TCL_ENCODING_START;

	    /*
	     * The following code must be executed only when result is not 0.
	     */

	    if ((result != 0) && (stageRead + dstWrote == 0)) {
		/*
		 * We have an incomplete UTF-8 character at the end of the
		 * staging buffer. It will get moved to the beginning of the
		 * staging buffer followed by more bytes from src.
		 */

		src -= stageLen;
		srcLen += stageLen;
		stageLen = 0;
		savedLF = 0;
		break;
	    }
	    bufPtr->nextAdded += dstWrote;
	    if (IsBufferOverflowing(bufPtr)) {
		/*
		 * When translating from UTF-8 to external encoding, we
		 * allowed the translation to produce a character that crossed
		 * the end of the output buffer, so that we would get a
		 * completely full buffer before flushing it. The extra bytes
		 * will be moved to the beginning of the next buffer.
		 */

		saved = -SpaceLeft(bufPtr);
		memcpy(safe, dst + dstLen, (size_t) saved);
		bufPtr->nextAdded = bufPtr->bufLength;
	    }
	    if (CheckFlush(chanPtr, bufPtr, sawLF) != 0) {
		return -1;
	    }

	    total += dstWrote;
	    stage += stageRead;
	    stageLen -= stageRead;
	    sawLF = 0;

	    consumedSomething = 1;

	    /*
	     * If all translated characters are written to the buffer,
	     * endEncoding is set to 0 because the escape sequence may be
	     * output.
	     */

	    if ((stageLen + saved == 0) && (result == 0)) {
		endEncoding = 0;
	    }
	}
    }

    /*
     * If nothing was written and it happened because there was no progress in
     * the UTF conversion, we throw an error.
     */

    if (!consumedSomething && (total == 0)) {
	Tcl_SetErrno(EINVAL);
	return -1;
    }
    return total;
}

/*
 *---------------------------------------------------------------------------
 *
 * TranslateOutputEOL --
 *
 *	Helper function for WriteBytes() and WriteChars(). Converts the '\n'
 *	characters in the source buffer into the appropriate EOL form
 *	specified by the output translation mode.
 *
 *	EOL translation stops either when the source buffer is empty or the
 *	output buffer is full.
 *
 *	When converting to CRLF mode and there is only 1 byte left in the
 *	output buffer, this routine stores the '\r' in the last byte and then
 *	stores the '\n' in the byte just past the end of the buffer. The
 *	caller is responsible for passing in a buffer that is large enough to
 *	hold the extra byte.
 *
 * Results:
 *	The return value is 1 if a '\n' was translated from the source buffer,
 *	or 0 otherwise -- this can be used by the caller to decide to flush a
 *	line-based channel even though the channel buffer is not full.
 *
 *	*dstLenPtr is filled with how many bytes of the output buffer were
 *	used. As mentioned above, this can be one more that the output
 *	buffer's specified length if a CRLF was stored.
 *
 *	*srcLenPtr is filled with how many bytes of the source buffer were
 *	consumed.
 *
 * Side effects:
 *	It may be obvious, but bears mentioning that when converting in CRLF
 *	mode (which requires two bytes of storage in the output buffer), the
 *	number of bytes consumed from the source buffer will be less than the
 *	number of bytes stored in the output buffer.
 *
 *---------------------------------------------------------------------------
 */

static int
TranslateOutputEOL(
    ChannelState *statePtr,	/* Channel being read, for translation and
				 * buffering modes. */
    char *dst,			/* Output buffer filled with UTF-8 chars by
				 * applying appropriate EOL translation to
				 * source characters. */
    const char *src,		/* Source UTF-8 characters. */
    int *dstLenPtr,		/* On entry, the maximum length of output
				 * buffer in bytes. On exit, the number of
				 * bytes actually used in output buffer. */
    int *srcLenPtr)		/* On entry, the length of source buffer. On
				 * exit, the number of bytes read from the
				 * source buffer. */
{
    char *dstEnd;
    int srcLen, newlineFound;

    newlineFound = 0;
    srcLen = *srcLenPtr;

    switch (statePtr->outputTranslation) {
    case TCL_TRANSLATE_LF:
	for (dstEnd = dst + srcLen; dst < dstEnd; ) {
	    if (*src == '\n') {
		newlineFound = 1;
	    }
	    *dst++ = *src++;
	}
	*dstLenPtr = srcLen;
	break;
    case TCL_TRANSLATE_CR:
	for (dstEnd = dst + srcLen; dst < dstEnd;) {
	    if (*src == '\n') {
		*dst++ = '\r';
		newlineFound = 1;
		src++;
	    } else {
		*dst++ = *src++;
	    }
	}
	*dstLenPtr = srcLen;
	break;
    case TCL_TRANSLATE_CRLF: {
	/*
	 * Since this causes the number of bytes to grow, we start off trying
	 * to put 'srcLen' bytes into the output buffer, but allow it to store
	 * more bytes, as long as there's still source bytes and room in the
	 * output buffer.
	 */

	char *dstStart, *dstMax;
	const char *srcStart;

	dstStart = dst;
	dstMax = dst + *dstLenPtr;

	srcStart = src;

	if (srcLen < *dstLenPtr) {
	    dstEnd = dst + srcLen;
	} else {
	    dstEnd = dst + *dstLenPtr;
	}
	while (dst < dstEnd) {
	    if (*src == '\n') {
		if (dstEnd < dstMax) {
		    dstEnd++;
		}
		*dst++ = '\r';
		newlineFound = 1;
	    }
	    *dst++ = *src++;
	}
	*srcLenPtr = src - srcStart;
	*dstLenPtr = dst - dstStart;
	break;
    }
    default:
	break;
    }
    return newlineFound;
}

/*
 *---------------------------------------------------------------------------
 *
 * CheckFlush --
 *
 *	Helper function for WriteBytes() and WriteChars(). If the channel
 *	buffer is ready to be flushed, flush it.
 *
 * Results:
 *	The return value is -1 if there was a problem flushing the channel
 *	buffer, or 0 otherwise.
 *
 * Side effects:
 *	The buffer will be recycled if it is flushed.
 *
 *---------------------------------------------------------------------------
 */

static int
CheckFlush(
    Channel *chanPtr,		/* Channel being read, for buffering mode. */
    ChannelBuffer *bufPtr,	/* Channel buffer to possibly flush. */
    int newlineFlag)		/* Non-zero if a the channel buffer contains a
				 * newline. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    /*
     * The current buffer is ready for output:
     * 1. if it is full.
     * 2. if it contains a newline and this channel is line-buffered.
     * 3. if it contains any output and this channel is unbuffered.
     */

    if (!GotFlag(statePtr, BUFFER_READY)) {
	if (IsBufferFull(bufPtr)) {
	    SetFlag(statePtr, BUFFER_READY);
	} else if (GotFlag(statePtr, CHANNEL_LINEBUFFERED)) {
	    if (newlineFlag != 0) {
		SetFlag(statePtr, BUFFER_READY);
	    }
	} else if (GotFlag(statePtr, CHANNEL_UNBUFFERED)) {
	    SetFlag(statePtr, BUFFER_READY);
	}
    }
    if (GotFlag(statePtr, BUFFER_READY)) {
	if (FlushChannel(NULL, chanPtr, 0) != 0) {
	    return -1;
	}
    }
    return 0;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_Gets --
 *
 *	Reads a complete line of input from the channel into a Tcl_DString.
 *
 * Results:
 *	Length of line read (in characters) or -1 if error, EOF, or blocked.
 *	If -1, use Tcl_GetErrno() to retrieve the POSIX error code for the
 *	error or condition that occurred.
 *
 * Side effects:
 *	May flush output on the channel. May cause input to be consumed from
 *	the channel.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_Gets(
    Tcl_Channel chan,		/* Channel from which to read. */
    Tcl_DString *lineRead)	/* The line read will be appended to this
				 * DString as UTF-8 characters. The caller
				 * must have initialized it and is responsible
				 * for managing the storage. */
{
    Tcl_Obj *objPtr;
    int charsStored, length;
    char *string;

    TclNewObj(objPtr);
    charsStored = Tcl_GetsObj(chan, objPtr);
    if (charsStored > 0) {
	string = TclGetStringFromObj(objPtr, &length);
	Tcl_DStringAppend(lineRead, string, length);
    }
    TclDecrRefCount(objPtr);
    return charsStored;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_GetsObj --
 *
 *	Accumulate input from the input channel until end-of-line or
 *	end-of-file has been seen. Bytes read from the input channel are
 *	converted to UTF-8 using the encoding specified by the channel.
 *
 * Results:
 *	Number of characters accumulated in the object or -1 if error,
 *	blocked, or EOF. If -1, use Tcl_GetErrno() to retrieve the POSIX error
 *	code for the error or condition that occurred.
 *
 * Side effects:
 *	Consumes input from the channel.
 *
 *	On reading EOF, leave channel pointing at EOF char. On reading EOL,
 *	leave channel pointing after EOL, but don't return EOL in dst buffer.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_GetsObj(
    Tcl_Channel chan,		/* Channel from which to read. */
    Tcl_Obj *objPtr)		/* The line read will be appended to this
				 * object as UTF-8 characters. */
{
    GetsState gs;
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    int inEofChar, skip, copiedTotal, oldLength, oldFlags, oldRemoved;
    Tcl_Encoding encoding;
    char *dst, *dstEnd, *eol, *eof;
    Tcl_EncodingState oldState;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	copiedTotal = -1;
	goto done;
    }

    /*
     * A binary version of Tcl_GetsObj. This could also handle encodings that
     * are ascii-7 pure (iso8859, utf-8, ...) with a final encoding conversion
     * done on objPtr.
     */

    if ((statePtr->encoding == NULL)
	    && ((statePtr->inputTranslation == TCL_TRANSLATE_LF)
		    || (statePtr->inputTranslation == TCL_TRANSLATE_CR))) {
	return TclGetsObjBinary(chan, objPtr);
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    bufPtr = statePtr->inQueueHead;
    encoding = statePtr->encoding;

    /*
     * Preserved so we can restore the channel's state in case we don't find a
     * newline in the available input.
     */

    TclGetStringFromObj(objPtr, &oldLength);
    oldFlags = statePtr->inputEncodingFlags;
    oldState = statePtr->inputEncodingState;
    oldRemoved = BUFFER_PADDING;
    if (bufPtr != NULL) {
	oldRemoved = bufPtr->nextRemoved;
    }

    /*
     * If there is no encoding, use "iso8859-1" -- Tcl_GetsObj() doesn't
     * produce ByteArray objects.
     */

    if (encoding == NULL) {
	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

	if (tsdPtr->binaryEncoding == NULL) {
	    tsdPtr->binaryEncoding = Tcl_GetEncoding(NULL, "iso8859-1");
	    Tcl_CreateThreadExitHandler(FreeBinaryEncoding, NULL);
	}
	encoding = tsdPtr->binaryEncoding;
	if (encoding == NULL) {
	    Tcl_Panic("attempted gets on binary channel where no iso8859-1 encoding available");
	}
    }

    /*
     * Object used by FilterInputBytes to keep track of how much data has been
     * consumed from the channel buffers.
     */

    gs.objPtr		= objPtr;
    gs.dstPtr		= &dst;
    gs.encoding		= encoding;
    gs.bufPtr		= bufPtr;
    gs.state		= oldState;
    gs.rawRead		= 0;
    gs.bytesWrote	= 0;
    gs.charsWrote	= 0;
    gs.totalChars	= 0;

    dst = objPtr->bytes + oldLength;
    dstEnd = dst;

    skip = 0;
    eof = NULL;
    inEofChar = statePtr->inEofChar;

    while (1) {
	if (dst >= dstEnd) {
	    if (FilterInputBytes(chanPtr, &gs) != 0) {
		goto restore;
	    }
	    dstEnd = dst + gs.bytesWrote;
	}

	/*
	 * Remember if EOF char is seen, then look for EOL anyhow, because the
	 * EOL might be before the EOF char.
	 */

	if (inEofChar != '\0') {
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == inEofChar) {
		    dstEnd = eol;
		    eof = eol;
		    break;
		}
	    }
	}

	/*
	 * On EOL, leave current file position pointing after the EOL, but
	 * don't store the EOL in the output string.
	 */

	switch (statePtr->inputTranslation) {
	case TCL_TRANSLATE_LF:
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == '\n') {
		    skip = 1;
		    goto gotEOL;
		}
	    }
	    break;
	case TCL_TRANSLATE_CR:
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == '\r') {
		    skip = 1;
		    goto gotEOL;
		}
	    }
	    break;
	case TCL_TRANSLATE_CRLF:
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == '\r') {
		    eol++;

		    /*
		     * If a CR is at the end of the buffer, then check for a
		     * LF at the begining of the next buffer, unless EOF char
		     * was found already.
		     */

		    if (eol >= dstEnd) {
			int offset;

			if (eol != eof) {
			    offset = eol - objPtr->bytes;
			    dst = dstEnd;
			    if (FilterInputBytes(chanPtr, &gs) != 0) {
				goto restore;
			    }
			    dstEnd = dst + gs.bytesWrote;
			    eol = objPtr->bytes + offset;
			}
			if (eol >= dstEnd) {
			    skip = 0;
			    goto gotEOL;
			}
		    }
		    if (*eol == '\n') {
			eol--;
			skip = 2;
			goto gotEOL;
		    }
		}
	    }
	    break;
	case TCL_TRANSLATE_AUTO:
	    eol = dst;
	    skip = 1;
	    if (GotFlag(statePtr, INPUT_SAW_CR)) {
		ResetFlag(statePtr, INPUT_SAW_CR);
		if ((eol < dstEnd) && (*eol == '\n')) {
		    /*
		     * Skip the raw bytes that make up the '\n'.
		     */

		    char tmp[1 + TCL_UTF_MAX];
		    int rawRead;

		    bufPtr = gs.bufPtr;
		    Tcl_ExternalToUtf(NULL, gs.encoding, RemovePoint(bufPtr),
			    gs.rawRead, statePtr->inputEncodingFlags,
			    &gs.state, tmp, 1 + TCL_UTF_MAX, &rawRead, NULL,
			    NULL);
		    bufPtr->nextRemoved += rawRead;
		    gs.rawRead -= rawRead;
		    gs.bytesWrote--;
		    gs.charsWrote--;
		    memmove(dst, dst + 1, (size_t) (dstEnd - dst));
		    dstEnd--;
		}
	    }
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == '\r') {
		    eol++;
		    if (eol == dstEnd) {
			/*
			 * If buffer ended on \r, peek ahead to see if a \n is
			 * available, unless EOF char was found already.
			 */

			if (eol != eof) {
			    int offset;

			    offset = eol - objPtr->bytes;
			    dst = dstEnd;
			    PeekAhead(chanPtr, &dstEnd, &gs);
			    eol = objPtr->bytes + offset;
			}

			if (eol >= dstEnd) {
			    eol--;
			    SetFlag(statePtr, INPUT_SAW_CR);
			    goto gotEOL;
			}
		    }
		    if (*eol == '\n') {
			skip++;
		    }
		    eol--;
		    goto gotEOL;
		} else if (*eol == '\n') {
		    goto gotEOL;
		}
	    }
	}
	if (eof != NULL) {
	    /*
	     * EOF character was seen. On EOF, leave current file position
	     * pointing at the EOF character, but don't store the EOF
	     * character in the output string.
	     */

	    dstEnd = eof;
	    SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	}
	if (GotFlag(statePtr, CHANNEL_EOF)) {
	    skip = 0;
	    eol = dstEnd;
	    if (eol == objPtr->bytes + oldLength) {
		/*
		 * If we didn't append any bytes before encountering EOF,
		 * caller needs to see -1.
		 */

		Tcl_SetObjLength(objPtr, oldLength);
		CommonGetsCleanup(chanPtr);
		copiedTotal = -1;
		goto done;
	    }
	    goto gotEOL;
	}
	dst = dstEnd;
    }

    /*
     * Found EOL or EOF, but the output buffer may now contain too many UTF-8
     * characters. We need to know how many raw bytes correspond to the number
     * of UTF-8 characters we want, plus how many raw bytes correspond to the
     * character(s) making up EOL (if any), so we can remove the correct
     * number of bytes from the channel buffer.
     */

  gotEOL:
    bufPtr = gs.bufPtr;
    if (bufPtr == NULL) {
	Tcl_Panic("Tcl_GetsObj: gotEOL reached with bufPtr==NULL");
    }
    statePtr->inputEncodingState = gs.state;
    Tcl_ExternalToUtf(NULL, gs.encoding, RemovePoint(bufPtr), gs.rawRead,
	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState, dst,
	    eol - dst + skip + TCL_UTF_MAX, &gs.rawRead, NULL,
	    &gs.charsWrote);
    bufPtr->nextRemoved += gs.rawRead;

    /*
     * Recycle all the emptied buffers.
     */

    Tcl_SetObjLength(objPtr, eol - objPtr->bytes);
    CommonGetsCleanup(chanPtr);
    ResetFlag(statePtr, CHANNEL_BLOCKED);
    copiedTotal = gs.totalChars + gs.charsWrote - skip;
    goto done;

    /*
     * Couldn't get a complete line. This only happens if we get a error
     * reading from the channel or we are non-blocking and there wasn't an EOL
     * or EOF in the data available.
     */

  restore:
    bufPtr = statePtr->inQueueHead;
    if (bufPtr == NULL) {
	Tcl_Panic("Tcl_GetsObj: restore reached with bufPtr==NULL");
    }
    bufPtr->nextRemoved = oldRemoved;

    for (bufPtr = bufPtr->nextPtr; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
	bufPtr->nextRemoved = BUFFER_PADDING;
    }
    CommonGetsCleanup(chanPtr);

    statePtr->inputEncodingState = oldState;
    statePtr->inputEncodingFlags = oldFlags;
    Tcl_SetObjLength(objPtr, oldLength);

    /*
     * We didn't get a complete line so we need to indicate to UpdateInterest
     * that the gets blocked. It will wait for more data instead of firing a
     * timer, avoiding a busy wait. This is where we are assuming that the
     * next operation is a gets. No more file events will be delivered on this
     * channel until new data arrives or some operation is performed on the
     * channel (e.g. gets, read, fconfigure) that changes the blocking state.
     * Note that this means a file event will not be delivered even though a
     * read would be able to consume the buffered data.
     */

    SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
    copiedTotal = -1;

    /*
     * Update the notifier state so we don't block while there is still data
     * in the buffers.
     */

  done:
    UpdateInterest(chanPtr);
    return copiedTotal;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclGetsObjBinary --
 *
 *	A variation of Tcl_GetsObj that works directly on the buffers until
 *	end-of-line or end-of-file has been seen. Bytes read from the input
 *	channel return as a ByteArray obj.
 *
 * Results:
 *	Number of characters accumulated in the object or -1 if error,
 *	blocked, or EOF. If -1, use Tcl_GetErrno() to retrieve the POSIX error
 *	code for the error or condition that occurred.
 *
 * Side effects:
 *	Consumes input from the channel.
 *
 *	On reading EOF, leave channel pointing at EOF char. On reading EOL,
 *	leave channel pointing after EOL, but don't return EOL in dst buffer.
 *
 *---------------------------------------------------------------------------
 */

static int
TclGetsObjBinary(
    Tcl_Channel chan,		/* Channel from which to read. */
    Tcl_Obj *objPtr)		/* The line read will be appended to this
				 * object as UTF-8 characters. */
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    int inEofChar, skip, copiedTotal, oldLength, oldFlags, oldRemoved;
    int rawLen, byteLen, eolChar;
    unsigned char *dst, *dstEnd, *eol, *eof, *byteArray;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    bufPtr = statePtr->inQueueHead;

    /*
     * Preserved so we can restore the channel's state in case we don't find a
     * newline in the available input.
     */

    byteArray = Tcl_GetByteArrayFromObj(objPtr, &byteLen);
    oldFlags = statePtr->inputEncodingFlags;
    oldRemoved = BUFFER_PADDING;
    oldLength = byteLen;
    if (bufPtr != NULL) {
	oldRemoved = bufPtr->nextRemoved;
    }

    rawLen = 0;
    skip = 0;
    eof = NULL;
    inEofChar = statePtr->inEofChar;

    /*
     * Only handle TCL_TRANSLATE_LF and TCL_TRANSLATE_CR.
     */

    eolChar = (statePtr->inputTranslation == TCL_TRANSLATE_LF) ? '\n' : '\r';

    while (1) {
	/*
	 * Subtract the number of bytes that were removed from channel
	 * buffer during last call.
	 */

	if (bufPtr != NULL) {
	    bufPtr->nextRemoved += rawLen;
	    if (!IsBufferReady(bufPtr)) {
		bufPtr = bufPtr->nextPtr;
	    }
	}

	if ((bufPtr == NULL) || (bufPtr->nextAdded == BUFFER_PADDING)) {
	    /*
	     * All channel buffers were exhausted and the caller still
	     * hasn't seen EOL. Need to read more bytes from the channel
	     * device. Side effect is to allocate another channel buffer.
	     */

	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		    goto restore;
		}
		ResetFlag(statePtr, CHANNEL_BLOCKED);
	    }
	    if (GetInput(chanPtr) != 0) {
		goto restore;
	    }
	    bufPtr = statePtr->inQueueTail;
	}

	dst = (unsigned char *) RemovePoint(bufPtr);
	dstEnd = dst + BytesLeft(bufPtr);

	/*
	 * Remember if EOF char is seen, then look for EOL anyhow, because the
	 * EOL might be before the EOF char.
	 * XXX - in the binary case, consider coincident search for eol/eof.
	 */

	if (inEofChar != '\0') {
	    for (eol = dst; eol < dstEnd; eol++) {
		if (*eol == inEofChar) {
		    dstEnd = eol;
		    eof = eol;
		    break;
		}
	    }
	}

	/*
	 * On EOL, leave current file position pointing after the EOL, but
	 * don't store the EOL in the output string.
	 */

	for (eol = dst; eol < dstEnd; eol++) {
	    if (*eol == eolChar) {
		skip = 1;
		goto gotEOL;
	    }
	}
	if (eof != NULL) {
	    /*
	     * EOF character was seen. On EOF, leave current file position
	     * pointing at the EOF character, but don't store the EOF
	     * character in the output string.
	     */

	    SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	}
	if (GotFlag(statePtr, CHANNEL_EOF)) {
	    skip = 0;
	    eol = dstEnd;
	    if ((dst == dstEnd) && (byteLen == oldLength)) {
		/*
		 * If we didn't append any bytes before encountering EOF,
		 * caller needs to see -1.
		 */

		byteArray = Tcl_SetByteArrayLength(objPtr, oldLength);
		CommonGetsCleanup(chanPtr);
		copiedTotal = -1;
		goto done;
	    }
	    goto gotEOL;
	}

	/*
	 * Copy bytes from the channel buffer to the ByteArray.
	 * This may realloc space, so keep track of result.
	 */

	rawLen = dstEnd - dst;
	byteArray = Tcl_SetByteArrayLength(objPtr, byteLen + rawLen);
	memcpy(byteArray + byteLen, dst, (size_t) rawLen);
	byteLen += rawLen;
    }

    /*
     * Found EOL or EOF, but the output buffer may now contain too many bytes.
     * We need to know how many bytes correspond to the number we want, so we
     * can remove the correct number of bytes from the channel buffer.
     */

  gotEOL:
    if (bufPtr == NULL) {
	Tcl_Panic("TclGetsObjBinary: gotEOL reached with bufPtr==NULL");
    }

    rawLen = eol - dst;
    byteArray = Tcl_SetByteArrayLength(objPtr, byteLen + rawLen);
    memcpy(byteArray + byteLen, dst, (size_t) rawLen);
    byteLen += rawLen;
    bufPtr->nextRemoved += rawLen + skip;

    /*
     * Convert the buffer if there was an encoding.
     * XXX - unimplemented.
     */

    if (statePtr->encoding != NULL) {
    }

    /*
     * Recycle all the emptied buffers.
     */

    CommonGetsCleanup(chanPtr);
    ResetFlag(statePtr, CHANNEL_BLOCKED);
    copiedTotal = byteLen;
    goto done;

    /*
     * Couldn't get a complete line. This only happens if we get a error
     * reading from the channel or we are non-blocking and there wasn't an EOL
     * or EOF in the data available.
     */

  restore:
    bufPtr = statePtr->inQueueHead;
    if (bufPtr == NULL) {
	Tcl_Panic("TclGetsObjBinary: restore reached with bufPtr==NULL");
    }
    bufPtr->nextRemoved = oldRemoved;

    for (bufPtr = bufPtr->nextPtr; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
	bufPtr->nextRemoved = BUFFER_PADDING;
    }
    CommonGetsCleanup(chanPtr);

    statePtr->inputEncodingFlags = oldFlags;
    byteArray = Tcl_SetByteArrayLength(objPtr, oldLength);

    /*
     * We didn't get a complete line so we need to indicate to UpdateInterest
     * that the gets blocked. It will wait for more data instead of firing a
     * timer, avoiding a busy wait. This is where we are assuming that the
     * next operation is a gets. No more file events will be delivered on this
     * channel until new data arrives or some operation is performed on the
     * channel (e.g. gets, read, fconfigure) that changes the blocking state.
     * Note that this means a file event will not be delivered even though a
     * read would be able to consume the buffered data.
     */

    SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
    copiedTotal = -1;

    /*
     * Update the notifier state so we don't block while there is still data
     * in the buffers.
     */

  done:
    UpdateInterest(chanPtr);
    return copiedTotal;
}

/*
 *---------------------------------------------------------------------------
 *
 * FreeBinaryEncoding --
 *
 *	Frees any "iso8859-1" Tcl_Encoding created by [gets] on a binary
 *	channel in a thread as part of that thread's finalization.
 *
 * Results:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static void
FreeBinaryEncoding(
    ClientData dummy)	/* Not used */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tsdPtr->binaryEncoding != NULL) {
	Tcl_FreeEncoding(tsdPtr->binaryEncoding);
	tsdPtr->binaryEncoding = NULL;
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * FilterInputBytes --
 *
 *	Helper function for Tcl_GetsObj. Produces UTF-8 characters from raw
 *	bytes read from the channel.
 *
 *	Consumes available bytes from channel buffers. When channel buffers
 *	are exhausted, reads more bytes from channel device into a new channel
 *	buffer. It is the caller's responsibility to free the channel buffers
 *	that have been exhausted.
 *
 * Results:
 *	The return value is -1 if there was an error reading from the channel,
 *	0 otherwise.
 *
 * Side effects:
 *	Status object keeps track of how much data from channel buffers has
 *	been consumed and where UTF-8 bytes should be stored.
 *
 *---------------------------------------------------------------------------
 */

static int
FilterInputBytes(
    Channel *chanPtr,		/* Channel to read. */
    GetsState *gsPtr)		/* Current state of gets operation. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    char *raw, *rawStart, *dst;
    int offset, toRead, dstNeeded, spaceLeft, result, rawLen, length;
    Tcl_Obj *objPtr;
#define ENCODING_LINESIZE 20	/* Lower bound on how many bytes to convert at
				 * a time. Since we don't know a priori how
				 * many bytes of storage this many source
				 * bytes will use, we actually need at least
				 * ENCODING_LINESIZE * TCL_MAX_UTF bytes of
				 * room. */

    objPtr = gsPtr->objPtr;

    /*
     * Subtract the number of bytes that were removed from channel buffer
     * during last call.
     */

    bufPtr = gsPtr->bufPtr;
    if (bufPtr != NULL) {
	bufPtr->nextRemoved += gsPtr->rawRead;
	if (!IsBufferReady(bufPtr)) {
	    bufPtr = bufPtr->nextPtr;
	}
    }
    gsPtr->totalChars += gsPtr->charsWrote;

    if ((bufPtr == NULL) || (bufPtr->nextAdded == BUFFER_PADDING)) {
	/*
	 * All channel buffers were exhausted and the caller still hasn't seen
	 * EOL. Need to read more bytes from the channel device. Side effect
	 * is to allocate another channel buffer.
	 */

    read:
	if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		gsPtr->charsWrote = 0;
		gsPtr->rawRead = 0;
		return -1;
	    }
	    ResetFlag(statePtr, CHANNEL_BLOCKED);
	}
	if (GetInput(chanPtr) != 0) {
	    gsPtr->charsWrote = 0;
	    gsPtr->rawRead = 0;
	    return -1;
	}
	bufPtr = statePtr->inQueueTail;
	gsPtr->bufPtr = bufPtr;
    }

    /*
     * Convert some of the bytes from the channel buffer to UTF-8. Space in
     * objPtr's string rep is used to hold the UTF-8 characters. Grow the
     * string rep if we need more space.
     */

    rawStart = RemovePoint(bufPtr);
    raw = rawStart;
    rawLen = BytesLeft(bufPtr);

    dst = *gsPtr->dstPtr;
    offset = dst - objPtr->bytes;
    toRead = ENCODING_LINESIZE;
    if (toRead > rawLen) {
	toRead = rawLen;
    }
    dstNeeded = toRead * TCL_UTF_MAX + 1;
    spaceLeft = objPtr->length - offset - TCL_UTF_MAX - 1;
    if (dstNeeded > spaceLeft) {
	length = offset * 2;
	if (offset < dstNeeded) {
	    length = offset + dstNeeded;
	}
	length += TCL_UTF_MAX + 1;
	Tcl_SetObjLength(objPtr, length);
	spaceLeft = length - offset;
	dst = objPtr->bytes + offset;
	*gsPtr->dstPtr = dst;
    }
    gsPtr->state = statePtr->inputEncodingState;
    result = Tcl_ExternalToUtf(NULL, gsPtr->encoding, raw, rawLen,
	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
	    dst, spaceLeft, &gsPtr->rawRead, &gsPtr->bytesWrote,
	    &gsPtr->charsWrote);

    /*
     * Make sure that if we go through 'gets', that we reset the
     * TCL_ENCODING_START flag still. [Bug #523988]
     */

    statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;

    if (result == TCL_CONVERT_MULTIBYTE) {
	/*
	 * The last few bytes in this channel buffer were the start of a
	 * multibyte sequence. If this buffer was full, then move them to the
	 * next buffer so the bytes will be contiguous.
	 */

	ChannelBuffer *nextPtr;
	int extra;

	nextPtr = bufPtr->nextPtr;
	if (!IsBufferFull(bufPtr)) {
	    if (gsPtr->rawRead > 0) {
		/*
		 * Some raw bytes were converted to UTF-8. Fall through,
		 * returning those UTF-8 characters because a EOL might be
		 * present in them.
		 */
	    } else if (GotFlag(statePtr, CHANNEL_EOF)) {
		/*
		 * There was a partial character followed by EOF on the
		 * device. Fall through, returning that nothing was found.
		 */

		bufPtr->nextRemoved = bufPtr->nextAdded;
	    } else {
		/*
		 * There are no more cached raw bytes left. See if we can get
		 * some more.
		 */

		goto read;
	    }
	} else {
	    if (nextPtr == NULL) {
		nextPtr = AllocChannelBuffer(statePtr->bufSize);
		bufPtr->nextPtr = nextPtr;
		statePtr->inQueueTail = nextPtr;
	    }
	    extra = rawLen - gsPtr->rawRead;
	    memcpy(nextPtr->buf + (BUFFER_PADDING - extra),
		    raw + gsPtr->rawRead, (size_t) extra);
	    nextPtr->nextRemoved -= extra;
	    bufPtr->nextAdded -= extra;
	}
    }

    gsPtr->bufPtr = bufPtr;
    return 0;
}

/*
 *---------------------------------------------------------------------------
 *
 * PeekAhead --
 *
 *	Helper function used by Tcl_GetsObj(). Called when we've seen a \r at
 *	the end of the UTF-8 string and want to look ahead one character to
 *	see if it is a \n.
 *
 * Results:
 *	*gsPtr->dstPtr is filled with a pointer to the start of the range of
 *	UTF-8 characters that were found by peeking and *dstEndPtr is filled
 *	with a pointer to the bytes just after the end of the range.
 *
 * Side effects:
 *	If no more raw bytes were available in one of the channel buffers,
 *	tries to perform a non-blocking read to get more bytes from the
 *	channel device.
 *
 *---------------------------------------------------------------------------
 */

static void
PeekAhead(
    Channel *chanPtr,		/* The channel to read. */
    char **dstEndPtr,		/* Filled with pointer to end of new range of
				 * UTF-8 characters. */
    GetsState *gsPtr)		/* Current state of gets operation. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    Tcl_DriverBlockModeProc *blockModeProc;
    int bytesLeft;

    bufPtr = gsPtr->bufPtr;

    /*
     * If there's any more raw input that's still buffered, we'll peek into
     * that. Otherwise, only get more data from the channel driver if it looks
     * like there might actually be more data. The assumption is that if the
     * channel buffer is filled right up to the end, then there might be more
     * data to read.
     */

    blockModeProc = NULL;
    if (bufPtr->nextPtr == NULL) {
	bytesLeft = BytesLeft(bufPtr) - gsPtr->rawRead;
	if (bytesLeft == 0) {
	    if (!IsBufferFull(bufPtr)) {
		/*
		 * Don't peek ahead if last read was short read.
		 */

		goto cleanup;
	    }
	    if (!GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		blockModeProc = Tcl_ChannelBlockModeProc(chanPtr->typePtr);
		if (blockModeProc == NULL) {
		    /*
		     * Don't peek ahead if cannot set non-blocking mode.
		     */

		    goto cleanup;
		}
		StackSetBlockMode(chanPtr, TCL_MODE_NONBLOCKING);
	    }
	}
    }
    if (FilterInputBytes(chanPtr, gsPtr) == 0) {
	*dstEndPtr = *gsPtr->dstPtr + gsPtr->bytesWrote;
    }
    if (blockModeProc != NULL) {
	StackSetBlockMode(chanPtr, TCL_MODE_BLOCKING);
    }
    return;

  cleanup:
    bufPtr->nextRemoved += gsPtr->rawRead;
    gsPtr->rawRead = 0;
    gsPtr->totalChars += gsPtr->charsWrote;
    gsPtr->bytesWrote = 0;
    gsPtr->charsWrote = 0;
}

/*
 *---------------------------------------------------------------------------
 *
 * CommonGetsCleanup --
 *
 *	Helper function for Tcl_GetsObj() to restore the channel after a
 *	"gets" operation.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Encoding may be freed.
 *
 *---------------------------------------------------------------------------
 */

static void
CommonGetsCleanup(
    Channel *chanPtr)
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr, *nextPtr;

    bufPtr = statePtr->inQueueHead;
    for ( ; bufPtr != NULL; bufPtr = nextPtr) {
	nextPtr = bufPtr->nextPtr;
	if (IsBufferReady(bufPtr)) {
	    break;
	}
	RecycleBuffer(statePtr, bufPtr, 0);
    }
    statePtr->inQueueHead = bufPtr;
    if (bufPtr == NULL) {
	statePtr->inQueueTail = NULL;
    } else {
	/*
	 * If any multi-byte characters were split across channel buffer
	 * boundaries, the split-up bytes were moved to the next channel
	 * buffer by FilterInputBytes(). Move the bytes back to their original
	 * buffer because the caller could change the channel's encoding which
	 * could change the interpretation of whether those bytes really made
	 * up multi-byte characters after all.
	 */

	nextPtr = bufPtr->nextPtr;
	for ( ; nextPtr != NULL; nextPtr = bufPtr->nextPtr) {
	    int extra;

	    extra = SpaceLeft(bufPtr);
	    if (extra > 0) {
		memcpy(InsertPoint(bufPtr),
			nextPtr->buf + (BUFFER_PADDING - extra),
			(size_t) extra);
		bufPtr->nextAdded += extra;
		nextPtr->nextRemoved = BUFFER_PADDING;
	    }
	    bufPtr = nextPtr;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Read --
 *
 *	Reads a given number of bytes from a channel. EOL and EOF translation
 *	is done on the bytes being read, so the number of bytes consumed from
 *	the channel may not be equal to the number of bytes stored in the
 *	destination buffer.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of bytes read, or -1 on error. Use Tcl_GetErrno() to
 *	retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Read(
    Tcl_Channel chan,		/* The channel from which to read. */
    char *dst,			/* Where to store input read. */
    int bytesToRead)		/* Maximum number of bytes to read. */
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	return -1;
    }

    return DoRead(chanPtr, dst, bytesToRead);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ReadRaw --
 *
 *	Reads a given number of bytes from a channel. EOL and EOF translation
 *	is done on the bytes being read, so the number of bytes consumed from
 *	the channel may not be equal to the number of bytes stored in the
 *	destination buffer.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of bytes read, or -1 on error. Use Tcl_GetErrno() to
 *	retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ReadRaw(
    Tcl_Channel chan,		/* The channel from which to read. */
    char *bufPtr,		/* Where to store input read. */
    int bytesToRead)		/* Maximum number of bytes to read. */
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int nread, result, copied, copiedNow;

    /*
     * The check below does too much because it will reject a call to this
     * function with a channel which is part of an 'fcopy'. But we have to
     * allow this here or else the chaining in the transformation drivers will
     * fail with 'file busy' error instead of retrieving and transforming the
     * data to copy.
     *
     * We let the check procedure now believe that there is no fcopy in
     * progress. A better solution than this might be an additional flag
     * argument to switch off specific checks.
     */

    if (CheckChannelErrors(statePtr, TCL_READABLE | CHANNEL_RAW_MODE) != 0) {
	return -1;
    }

    /*
     * Check for information in the push-back buffers. If there is some, use
     * it. Go to the driver only if there is none (anymore) and the caller
     * requests more bytes.
     */

    for (copied = 0; copied < bytesToRead; copied += copiedNow) {
	copiedNow = CopyBuffer(chanPtr, bufPtr + copied,
		bytesToRead - copied);
	if (copiedNow == 0) {
	    if (GotFlag(statePtr, CHANNEL_EOF)) {
		goto done;
	    }
	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		    goto done;
		}
		ResetFlag(statePtr, CHANNEL_BLOCKED);
	    }

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
	    /*
	     * [Bug 943274]. Better emulation of non-blocking channels for
	     * channels without BlockModeProc, by keeping track of true
	     * fileevents generated by the OS == Data waiting and reading if
	     * and only if we are sure to have data.
	     */

	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
		    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
		    !GotFlag(statePtr, CHANNEL_HAS_MORE_DATA)) {
		/*
		 * We bypass the driver; it would block as no data is
		 * available.
		 */

		nread = -1;
		result = EWOULDBLOCK;
	    } else
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
	    {
		/*
		 * Now go to the driver to get as much as is possible to fill
		 * the remaining request. Do all the error handling by
		 * ourselves. The code was stolen from 'GetInput' and slightly
		 * adapted (different return value here).
		 *
		 * The case of 'bytesToRead == 0' at this point cannot happen.
		 */

		nread = ChanRead(chanPtr, bufPtr + copied,
			bytesToRead - copied, &result);
	    }

	    if (nread > 0) {
		/*
		 * If we get a short read, signal up that we may be BLOCKED.
		 * We should avoid calling the driver because on some
		 * platforms we will block in the low level reading code even
		 * though the channel is set into nonblocking mode.
		 */

		if (nread < (bytesToRead - copied)) {
		    SetFlag(statePtr, CHANNEL_BLOCKED);
		}

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
		if (nread <= (bytesToRead - copied)) {
		    /*
		     * [Bug 943274] We have read the available data, clear
		     * flag.
		     */

		    ResetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
		}
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
	    } else if (nread == 0) {
		SetFlag(statePtr, CHANNEL_EOF);
		statePtr->inputEncodingFlags |= TCL_ENCODING_END;

	    } else if (nread < 0) {
		if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
		    if (copied > 0) {
			/*
			 * Information that was copied earlier has precedence
			 * over EAGAIN/WOULDBLOCK handling.
			 */

			return copied;
		    }

		    SetFlag(statePtr, CHANNEL_BLOCKED);
		    result = EAGAIN;
		}

		Tcl_SetErrno(result);
		return -1;
	    }

	    return copied + nread;
	}
    }

  done:
    return copied;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_ReadChars --
 *
 *	Reads from the channel until the requested number of characters have
 *	been seen, EOF is seen, or the channel would block. EOL and EOF
 *	translation is done. If reading binary data, the raw bytes are wrapped
 *	in a Tcl byte array object. Otherwise, the raw bytes are converted to
 *	UTF-8 using the channel's current encoding and stored in a Tcl string
 *	object.
 *
 * Results:
 *	The number of characters read, or -1 on error. Use Tcl_GetErrno() to
 *	retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_ReadChars(
    Tcl_Channel chan,		/* The channel to read. */
    Tcl_Obj *objPtr,		/* Input data is stored in this object. */
    int toRead,			/* Maximum number of characters to store, or
				 * -1 to read all available data (up to EOF or
				 * when channel blocks). */
    int appendFlag)		/* If non-zero, data read from the channel
				 * will be appended to the object. Otherwise,
				 * the data will replace the existing contents
				 * of the object. */
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	/*
	 * Update the notifier state so we don't block while there is still
	 * data in the buffers.
	 */

	UpdateInterest(chanPtr);
	return -1;
    }

    return DoReadChars(chanPtr, objPtr, toRead, appendFlag);
}
/*
 *---------------------------------------------------------------------------
 *
 * DoReadChars --
 *
 *	Reads from the channel until the requested number of characters have
 *	been seen, EOF is seen, or the channel would block. EOL and EOF
 *	translation is done. If reading binary data, the raw bytes are wrapped
 *	in a Tcl byte array object. Otherwise, the raw bytes are converted to
 *	UTF-8 using the channel's current encoding and stored in a Tcl string
 *	object.
 *
 * Results:
 *	The number of characters read, or -1 on error. Use Tcl_GetErrno() to
 *	retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *---------------------------------------------------------------------------
 */

static int
DoReadChars(
    Channel *chanPtr,		/* The channel to read. */
    Tcl_Obj *objPtr,		/* Input data is stored in this object. */
    int toRead,			/* Maximum number of characters to store, or
				 * -1 to read all available data (up to EOF or
				 * when channel blocks). */
    int appendFlag)		/* If non-zero, data read from the channel
				 * will be appended to the object. Otherwise,
				 * the data will replace the existing contents
				 * of the object. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *bufPtr;
    int offset, factor, copied, copiedNow, result;
    Tcl_Encoding encoding;
#define UTF_EXPANSION_FACTOR	1024

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;
    encoding = statePtr->encoding;
    factor = UTF_EXPANSION_FACTOR;

    if (appendFlag == 0) {
	if (encoding == NULL) {
	    Tcl_SetByteArrayLength(objPtr, 0);
	} else {
	    Tcl_SetObjLength(objPtr, 0);

	    /*
	     * We're going to access objPtr->bytes directly, so we must ensure
	     * that this is actually a string object (otherwise it might have
	     * been pure Unicode).
	     */

	    TclGetString(objPtr);
	}
	offset = 0;
    } else {
	if (encoding == NULL) {
	    Tcl_GetByteArrayFromObj(objPtr, &offset);
	} else {
	    TclGetStringFromObj(objPtr, &offset);
	}
    }

    for (copied = 0; (unsigned) toRead > 0; ) {
	copiedNow = -1;
	if (statePtr->inQueueHead != NULL) {
	    if (encoding == NULL) {
		copiedNow = ReadBytes(statePtr, objPtr, toRead, &offset);
	    } else {
		copiedNow = ReadChars(statePtr, objPtr, toRead, &offset,
			&factor);
	    }

	    /*
	     * If the current buffer is empty recycle it.
	     */

	    bufPtr = statePtr->inQueueHead;
	    if (IsBufferEmpty(bufPtr)) {
		ChannelBuffer *nextPtr = bufPtr->nextPtr;

		RecycleBuffer(statePtr, bufPtr, 0);
		statePtr->inQueueHead = nextPtr;
		if (nextPtr == NULL) {
		    statePtr->inQueueTail = NULL;
		}
	    }
	}

	if (copiedNow < 0) {
	    if (GotFlag(statePtr, CHANNEL_EOF)) {
		break;
	    }
	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		    break;
		}
		ResetFlag(statePtr, CHANNEL_BLOCKED);
	    }
	    result = GetInput(chanPtr);
	    if (result != 0) {
		if (result == EAGAIN) {
		    break;
		}
		copied = -1;
		goto done;
	    }
	} else {
	    copied += copiedNow;
	    toRead -= copiedNow;
	}
    }

    ResetFlag(statePtr, CHANNEL_BLOCKED);
    if (encoding == NULL) {
	Tcl_SetByteArrayLength(objPtr, offset);
    } else {
	Tcl_SetObjLength(objPtr, offset);
    }

    /*
     * Update the notifier state so we don't block while there is still data
     * in the buffers.
     */

  done:
    UpdateInterest(chanPtr);
    return copied;
}

/*
 *---------------------------------------------------------------------------
 *
 * ReadBytes --
 *
 *	Reads from the channel until the requested number of bytes have been
 *	seen, EOF is seen, or the channel would block. Bytes from the channel
 *	are stored in objPtr as a ByteArray object. EOL and EOF translation
 *	are done.
 *
 *	'bytesToRead' can safely be a very large number because space is only
 *	allocated to hold data read from the channel as needed.
 *
 * Results:
 *	The return value is the number of bytes appended to the object and
 *	*offsetPtr is filled with the total number of bytes in the object
 *	(greater than the return value if there were already bytes in the
 *	object).
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
ReadBytes(
    ChannelState *statePtr,	/* State of the channel to read. */
    Tcl_Obj *objPtr,		/* Input data is appended to this ByteArray
				 * object. Its length is how much space has
				 * been allocated to hold data, not how many
				 * bytes of data have been stored in the
				 * object. */
    int bytesToRead,		/* Maximum number of bytes to store, or < 0 to
				 * get all available bytes. Bytes are obtained
				 * from the first buffer in the queue - even
				 * if this number is larger than the number of
				 * bytes available in the first buffer, only
				 * the bytes from the first buffer are
				 * returned. */
    int *offsetPtr)		/* On input, contains how many bytes of objPtr
				 * have been used to hold data. On output,
				 * filled with how many bytes are now being
				 * used. */
{
    int toRead, srcLen, offset, length, srcRead, dstWrote;
    ChannelBuffer *bufPtr;
    char *src, *dst;

    offset = *offsetPtr;

    bufPtr = statePtr->inQueueHead;
    src = RemovePoint(bufPtr);
    srcLen = BytesLeft(bufPtr);

    toRead = bytesToRead;
    if ((unsigned) toRead > (unsigned) srcLen) {
	toRead = srcLen;
    }

    dst = (char *) Tcl_GetByteArrayFromObj(objPtr, &length);
    if (toRead > length - offset - 1) {
	/*
	 * Double the existing size of the object or make enough room to hold
	 * all the characters we may get from the source buffer, whichever is
	 * larger.
	 */

	length = offset * 2;
	if (offset < toRead) {
	    length = offset + toRead + 1;
	}
	dst = (char *) Tcl_SetByteArrayLength(objPtr, length);
    }
    dst += offset;

    if (GotFlag(statePtr, INPUT_NEED_NL)) {
	ResetFlag(statePtr, INPUT_NEED_NL);
	if ((srcLen == 0) || (*src != '\n')) {
	    *dst = '\r';
	    *offsetPtr += 1;
	    return 1;
	}
	*dst++ = '\n';
	src++;
	srcLen--;
	toRead--;
    }

    srcRead = srcLen;
    dstWrote = toRead;
    if (TranslateInputEOL(statePtr, dst, src, &dstWrote, &srcRead) != 0) {
	if (dstWrote == 0) {
	    return -1;
	}
    }
    bufPtr->nextRemoved += srcRead;
    *offsetPtr += dstWrote;
    return dstWrote;
}

/*
 *---------------------------------------------------------------------------
 *
 * ReadChars --
 *
 *	Reads from the channel until the requested number of UTF-8 characters
 *	have been seen, EOF is seen, or the channel would block. Raw bytes
 *	from the channel are converted to UTF-8 and stored in objPtr. EOL and
 *	EOF translation is done.
 *
 *	'charsToRead' can safely be a very large number because space is only
 *	allocated to hold data read from the channel as needed.
 *
 * Results:
 *	The return value is the number of characters appended to the object,
 *	*offsetPtr is filled with the number of bytes that were appended, and
 *	*factorPtr is filled with the expansion factor used to guess how many
 *	bytes of UTF-8 to allocate to hold N source bytes.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
ReadChars(
    ChannelState *statePtr,	/* State of channel to read. */
    Tcl_Obj *objPtr,		/* Input data is appended to this object.
				 * objPtr->length is how much space has been
				 * allocated to hold data, not how many bytes
				 * of data have been stored in the object. */
    int charsToRead,		/* Maximum number of characters to store, or
				 * -1 to get all available characters.
				 * Characters are obtained from the first
				 * buffer in the queue -- even if this number
				 * is larger than the number of characters
				 * available in the first buffer, only the
				 * characters from the first buffer are
				 * returned. */
    int *offsetPtr,		/* On input, contains how many bytes of objPtr
				 * have been used to hold data. On output,
				 * filled with how many bytes are now being
				 * used. */
    int *factorPtr)		/* On input, contains a guess of how many
				 * bytes need to be allocated to hold the
				 * result of converting N source bytes to
				 * UTF-8. On output, contains another guess
				 * based on the data seen so far. */
{
    int toRead, factor, offset, spaceLeft, length, srcLen, dstNeeded;
    int srcRead, dstWrote, numChars, dstRead;
    ChannelBuffer *bufPtr;
    char *src, *dst;
    Tcl_EncodingState oldState;
    int encEndFlagSuppressed = 0;

    factor = *factorPtr;
    offset = *offsetPtr;

    bufPtr = statePtr->inQueueHead;
    src = RemovePoint(bufPtr);
    srcLen = BytesLeft(bufPtr);

    toRead = charsToRead;
    if ((unsigned) toRead > (unsigned) srcLen) {
	toRead = srcLen;
    }

    /*
     * 'factor' is how much we guess that the bytes in the source buffer will
     * expand when converted to UTF-8 chars. This guess comes from analyzing
     * how many characters were produced by the previous pass.
     */

    dstNeeded = toRead * factor / UTF_EXPANSION_FACTOR;
    spaceLeft = objPtr->length - offset - TCL_UTF_MAX - 1;

    if (dstNeeded > spaceLeft) {
	/*
	 * Double the existing size of the object or make enough room to hold
	 * all the characters we want from the source buffer, whichever is
	 * larger.
	 */

	length = offset * 2;
	if (offset < dstNeeded) {
	    length = offset + dstNeeded;
	}
	spaceLeft = length - offset;
	length += TCL_UTF_MAX + 1;
	Tcl_SetObjLength(objPtr, length);
    }
    if (toRead == srcLen) {
	/*
	 * Want to convert the whole buffer in one pass. If we have enough
	 * space, convert it using all available space in object rather than
	 * using the factor.
	 */

	dstNeeded = spaceLeft;
    }
    dst = objPtr->bytes + offset;

    /*
     * [Bug 1462248]: The cause of the crash reported in this bug is this:
     *
     * - ReadChars, called with a single buffer, with a incomplete
     *	 multi-byte character at the end (only the first byte of it).
     * - Encoding translation fails, asks for more data
     * - Data is read, and eof is reached, TCL_ENCODING_END (TEE) is set.
     * - ReadChar is called again, converts the first buffer, but due to TEE
     *	 it does not check for incomplete multi-byte data, and the character
     *	 just after the end of the first buffer is a valid completion of the
     *	 multi-byte header in the actual buffer. The conversion reads more
     *	 characters from the buffer then present. This causes nextRemoved to
     *	 overshoot nextAdded and the next reads compute a negative srcLen,
     *	 cause further translations to fail, causing copying of data into the
     *	 next buffer using bad arguments, causing the mecpy for to eventually
     *	 fail.
     *
     * In the end it is a memory access bug spiraling out of control if the
     * conditions are _just so_. And ultimate cause is that TEE is given to a
     * conversion where it should not. TEE signals that this is the last
     * buffer. Except in our case it is not.
     *
     * My solution is to suppress TEE if the first buffer is not the last. We
     * will eventually need it given that EOF has been reached, but not right
     * now. This is what the new flag "endEncSuppressFlag" is for.
     *
     * The bug in 'Tcl_Utf2UtfProc' where it read from memory behind the
     * actual buffer has been fixed as well, and fixes the problem with the
     * crash too, but this would still allow the generic layer to
     * accidentially break a multi-byte sequence if the conditions are just
     * right, because again the ExternalToUtf would be successful where it
     * should not.
     */

    if ((statePtr->inputEncodingFlags & TCL_ENCODING_END) &&
	    (bufPtr->nextPtr != NULL)) {
	/*
	 * TEE is set for a buffer which is not the last. Squash it for now,
	 * and restore it later, before yielding control to our caller.
	 */

	statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
	encEndFlagSuppressed = 1;
    }

    oldState = statePtr->inputEncodingState;
    if (GotFlag(statePtr, INPUT_NEED_NL)) {
	/*
	 * We want a '\n' because the last character we saw was '\r'.
	 */

	ResetFlag(statePtr, INPUT_NEED_NL);
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, TCL_UTF_MAX + 1, &srcRead, &dstWrote, &numChars);
	if ((dstWrote > 0) && (*dst == '\n')) {
	    /*
	     * The next char was a '\n'. Consume it and produce a '\n'.
	     */

	    bufPtr->nextRemoved += srcRead;
	} else {
	    /*
	     * The next char was not a '\n'. Produce a '\r'.
	     */

	    *dst = '\r';
	}
	statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
	*offsetPtr += 1;

	if (encEndFlagSuppressed) {
	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	}
	return 1;
    }

    Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState, dst,
	    dstNeeded + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);

    if (encEndFlagSuppressed) {
	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
    }

    if (srcRead == 0) {
	/*
	 * Not enough bytes in src buffer to make a complete char. Copy the
	 * bytes to the next buffer to make a new contiguous string, then tell
	 * the caller to fill the buffer with more bytes.
	 */

	ChannelBuffer *nextPtr;

	nextPtr = bufPtr->nextPtr;
	if (nextPtr == NULL) {
	    if (srcLen > 0) {
		/*
		 * There isn't enough data in the buffers to complete the next
		 * character, so we need to wait for more data before the next
		 * file event can be delivered. [Bug 478856]
		 *
		 * The exception to this is if the input buffer was completely
		 * empty before we tried to convert its contents. Nothing in,
		 * nothing out, and no incomplete character data. The
		 * conversion before the current one was complete.
		 */

		SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
	    }
	    return -1;
	}

	/*
	 * Space is made at the beginning of the buffer to copy the previous
	 * unused bytes there. Check first if the buffer we are using actually
	 * has enough space at its beginning for the data we are copying.
	 * Because if not we will write over the buffer management
	 * information, especially the 'nextPtr'.
	 *
	 * Note that the BUFFER_PADDING (See AllocChannelBuffer) is used to
	 * prevent exactly this situation. I.e. it should never happen.
	 * Therefore it is ok to panic should it happen despite the
	 * precautions.
	 */

	if (nextPtr->nextRemoved - srcLen < 0) {
	    Tcl_Panic("Buffer Underflow, BUFFER_PADDING not enough");
	}

	nextPtr->nextRemoved -= srcLen;
	memcpy(RemovePoint(nextPtr), src, (size_t) srcLen);
	RecycleBuffer(statePtr, bufPtr, 0);
	statePtr->inQueueHead = nextPtr;
	return ReadChars(statePtr, objPtr, charsToRead, offsetPtr, factorPtr);
    }

    dstRead = dstWrote;
    if (TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead) != 0) {
	/*
	 * Hit EOF char. How many bytes of src correspond to where the EOF was
	 * located in dst? Run the conversion again with an output buffer just
	 * big enough to hold the data so we can get the correct value for
	 * srcRead.
	 */

	if (dstWrote == 0) {
	    return -1;
	}
	statePtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, dstRead + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
    }

    /*
     * The number of characters that we got may be less than the number that
     * we started with because "\r\n" sequences may have been turned into just
     * '\n' in dst.
     */

    numChars -= dstRead - dstWrote;

    if ((unsigned) numChars > (unsigned) toRead) {
	/*
	 * Got too many chars.
	 */

	const char *eof = Tcl_UtfAtIndex(dst, toRead);

	statePtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, eof - dst + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
	dstRead = dstWrote;
	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
	numChars -= (dstRead - dstWrote);
    }
    statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;

    bufPtr->nextRemoved += srcRead;
    if (dstWrote > srcRead + 1) {
	*factorPtr = dstWrote * UTF_EXPANSION_FACTOR / srcRead;
    }
    *offsetPtr += dstWrote;
    return numChars;
}

/*
 *---------------------------------------------------------------------------
 *
 * TranslateInputEOL --
 *
 *	Perform input EOL and EOF translation on the source buffer, leaving
 *	the translated result in the destination buffer.
 *
 * Results:
 *	The return value is 1 if the EOF character was found when copying
 *	bytes to the destination buffer, 0 otherwise.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
TranslateInputEOL(
    ChannelState *statePtr,	/* Channel being read, for EOL translation and
				 * EOF character. */
    char *dstStart,		/* Output buffer filled with chars by applying
				 * appropriate EOL translation to source
				 * characters. */
    const char *srcStart,	/* Source characters. */
    int *dstLenPtr,		/* On entry, the maximum length of output
				 * buffer in bytes; must be <= *srcLenPtr. On
				 * exit, the number of bytes actually used in
				 * output buffer. */
    int *srcLenPtr)		/* On entry, the length of source buffer. On
				 * exit, the number of bytes read from the
				 * source buffer. */
{
    int dstLen, srcLen, inEofChar;
    const char *eof;

    dstLen = *dstLenPtr;

    eof = NULL;
    inEofChar = statePtr->inEofChar;
    if (inEofChar != '\0') {
	/*
	 * Find EOF in translated buffer then compress out the EOL. The source
	 * buffer may be much longer than the destination buffer - we only
	 * want to return EOF if the EOF has been copied to the destination
	 * buffer.
	 */

	const char *src, *srcMax = srcStart + *srcLenPtr;

	for (src = srcStart; src < srcMax; src++) {
	    if (*src == inEofChar) {
		eof = src;
		srcLen = src - srcStart;
		if (srcLen < dstLen) {
		    dstLen = srcLen;
		}
		*srcLenPtr = srcLen;
		break;
	    }
	}
    }
    switch (statePtr->inputTranslation) {
    case TCL_TRANSLATE_LF:
	if (dstStart != srcStart) {
	    memcpy(dstStart, srcStart, (size_t) dstLen);
	}
	srcLen = dstLen;
	break;
    case TCL_TRANSLATE_CR: {
	char *dst, *dstEnd;

	if (dstStart != srcStart) {
	    memcpy(dstStart, srcStart, (size_t) dstLen);
	}
	dstEnd = dstStart + dstLen;
	for (dst = dstStart; dst < dstEnd; dst++) {
	    if (*dst == '\r') {
		*dst = '\n';
	    }
	}
	srcLen = dstLen;
	break;
    }
    case TCL_TRANSLATE_CRLF: {
	char *dst;
	const char *src, *srcEnd, *srcMax;

	dst = dstStart;
	src = srcStart;
	srcEnd = srcStart + dstLen;
	srcMax = srcStart + *srcLenPtr;

	for ( ; src < srcEnd; ) {
	    if (*src == '\r') {
		src++;
		if (src >= srcMax) {
		    SetFlag(statePtr, INPUT_NEED_NL);
		} else if (*src == '\n') {
		    *dst++ = *src++;
		} else {
		    *dst++ = '\r';
		}
	    } else {
		*dst++ = *src++;
	    }
	}
	srcLen = src - srcStart;
	dstLen = dst - dstStart;
	break;
    }
    case TCL_TRANSLATE_AUTO: {
	char *dst;
	const char *src, *srcEnd, *srcMax;

	dst = dstStart;
	src = srcStart;
	srcEnd = srcStart + dstLen;
	srcMax = srcStart + *srcLenPtr;

	if (GotFlag(statePtr, INPUT_SAW_CR) && (src < srcMax)) {
	    if (*src == '\n') {
		src++;
	    }
	    ResetFlag(statePtr, INPUT_SAW_CR);
	}
	for ( ; src < srcEnd; ) {
	    if (*src == '\r') {
		src++;
		if (src >= srcMax) {
		    SetFlag(statePtr, INPUT_SAW_CR);
		} else if (*src == '\n') {
		    if (srcEnd < srcMax) {
			srcEnd++;
		    }
		    src++;
		}
		*dst++ = '\n';
	    } else {
		*dst++ = *src++;
	    }
	}
	srcLen = src - srcStart;
	dstLen = dst - dstStart;
	break;
    }
    default:
	return 0;
    }
    *dstLenPtr = dstLen;

    if ((eof != NULL) && (srcStart + srcLen >= eof)) {
	/*
	 * EOF character was seen in EOL translated range. Leave current file
	 * position pointing at the EOF character, but don't store the EOF
	 * character in the output string.
	 */

	SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	ResetFlag(statePtr, INPUT_SAW_CR | INPUT_NEED_NL);
	return 1;
    }

    *srcLenPtr = srcLen;
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Ungets --
 *
 *	Causes the supplied string to be added to the input queue of the
 *	channel, at either the head or tail of the queue.
 *
 * Results:
 *	The number of bytes stored in the channel, or -1 on error.
 *
 * Side effects:
 *	Adds input to the input queue of a channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Ungets(
    Tcl_Channel chan,		/* The channel for which to add the input. */
    const char *str,		/* The input itself. */
    int len,			/* The length of the input. */
    int atEnd)			/* If non-zero, add at end of queue; otherwise
				 * add at head of queue. */
{
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of actual channel. */
    ChannelBuffer *bufPtr;	/* Buffer to contain the data. */
    int flags;

    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * CheckChannelErrors clears too many flag bits in this one case.
     */

    flags = statePtr->flags;
    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	len = -1;
	goto done;
    }
    statePtr->flags = flags;

    /*
     * If we have encountered a sticky EOF, just punt without storing (sticky
     * EOF is set if we have seen the input eofChar, to prevent reading beyond
     * the eofChar). Otherwise, clear the EOF flags, and clear the BLOCKED
     * bit. We want to discover these conditions anew in each operation.
     */

    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
	goto done;
    }
    ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_EOF);

    bufPtr = AllocChannelBuffer(len);
    memcpy(InsertPoint(bufPtr), str, (size_t) len);
    bufPtr->nextAdded += len;

    if (statePtr->inQueueHead == NULL) {
	bufPtr->nextPtr = NULL;
	statePtr->inQueueHead = bufPtr;
	statePtr->inQueueTail = bufPtr;
    } else if (atEnd) {
	bufPtr->nextPtr = NULL;
	statePtr->inQueueTail->nextPtr = bufPtr;
	statePtr->inQueueTail = bufPtr;
    } else {
	bufPtr->nextPtr = statePtr->inQueueHead;
	statePtr->inQueueHead = bufPtr;
    }

    /*
     * Update the notifier state so we don't block while there is still data
     * in the buffers.
     */

  done:
    UpdateInterest(chanPtr);
    return len;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Flush --
 *
 *	Flushes output data on a channel.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	May flush output queued on this channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Flush(
    Tcl_Channel chan)		/* The Channel to flush. */
{
    int result;			/* Of calling FlushChannel. */
    Channel *chanPtr = (Channel *) chan;
				/* The actual channel. */
    ChannelState *statePtr = chanPtr->state;
				/* State of actual channel. */

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    /*
     * Force current output buffer to be output also.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    result = FlushChannel(NULL, chanPtr, 0);
    if (result != 0) {
	return TCL_ERROR;
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DiscardInputQueued --
 *
 *	Discards any input read from the channel but not yet consumed by Tcl
 *	reading commands.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May discard input from the channel. If discardLastBuffer is zero,
 *	leaves one buffer in place for back-filling.
 *
 *----------------------------------------------------------------------
 */

static void
DiscardInputQueued(
    ChannelState *statePtr,	/* Channel on which to discard the queued
				 * input. */
    int discardSavedBuffers)	/* If non-zero, discard all buffers including
				 * last one. */
{
    ChannelBuffer *bufPtr, *nxtPtr;
				/* Loop variables. */

    bufPtr = statePtr->inQueueHead;
    statePtr->inQueueHead = NULL;
    statePtr->inQueueTail = NULL;
    for (; bufPtr != NULL; bufPtr = nxtPtr) {
	nxtPtr = bufPtr->nextPtr;
	RecycleBuffer(statePtr, bufPtr, discardSavedBuffers);
    }

    /*
     * If discardSavedBuffers is nonzero, must also discard any previously
     * saved buffer in the saveInBufPtr field.
     */

    if (discardSavedBuffers && statePtr->saveInBufPtr != NULL) {
	ckfree((char *) statePtr->saveInBufPtr);
	statePtr->saveInBufPtr = NULL;
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * GetInput --
 *
 *	Reads input data from a device into a channel buffer.
 *
 * Results:
 *	The return value is the Posix error code if an error occurred while
 *	reading from the file, or 0 otherwise.
 *
 * Side effects:
 *	Reads from the underlying device.
 *
 *---------------------------------------------------------------------------
 */

static int
GetInput(
    Channel *chanPtr)		/* Channel to read input from. */
{
    int toRead;			/* How much to read? */
    int result;			/* Of calling driver. */
    int nread;			/* How much was read from channel? */
    ChannelBuffer *bufPtr;	/* New buffer to add to input queue. */
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    /*
     * Prevent reading from a dead channel -- a channel that has been closed
     * but not yet deallocated, which can happen if the exit handler for
     * channel cleanup has run but the channel is still registered in some
     * interpreter.
     */

    if (CheckForDeadChannel(NULL, statePtr)) {
	return EINVAL;
    }

    /*
     * First check for more buffers in the pushback area of the topmost
     * channel in the stack and use them. They can be the result of a
     * transformation which went away without reading all the information
     * placed in the area when it was stacked.
     *
     * Two possibilities for the state: No buffers in it, or a single empty
     * buffer. In the latter case we can recycle it now.
     */

    if (chanPtr->inQueueHead != NULL) {
	if (statePtr->inQueueHead != NULL) {
	    RecycleBuffer(statePtr, statePtr->inQueueHead, 0);
	    statePtr->inQueueHead = NULL;
	}

	statePtr->inQueueHead = chanPtr->inQueueHead;
	statePtr->inQueueTail = chanPtr->inQueueTail;
	chanPtr->inQueueHead = NULL;
	chanPtr->inQueueTail = NULL;
	return 0;
    }

    /*
     * Nothing in the pushback area, fall back to the usual handling (driver,
     * etc.)
     */

    /*
     * See if we can fill an existing buffer. If we can, read only as much as
     * will fit in it. Otherwise allocate a new buffer, add it to the input
     * queue and attempt to fill it to the max.
     */

    bufPtr = statePtr->inQueueTail;
    if ((bufPtr != NULL) && !IsBufferFull(bufPtr)) {
	toRead = SpaceLeft(bufPtr);
    } else {
	bufPtr = statePtr->saveInBufPtr;
	statePtr->saveInBufPtr = NULL;

	/*
	 * Check the actual buffersize against the requested buffersize.
	 * Buffers which are smaller than requested are squashed. This is done
	 * to honor dynamic changes of the buffersize made by the user.
	 */

	if ((bufPtr != NULL)
		&& (bufPtr->bufLength - BUFFER_PADDING < statePtr->bufSize)) {
	    ckfree((char *) bufPtr);
	    bufPtr = NULL;
	}

	if (bufPtr == NULL) {
	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
	}
	bufPtr->nextPtr = NULL;

	/*
	 * SF #427196: Use the actual size of the buffer to determine the
	 * number of bytes to read from the channel and not the size for new
	 * buffers. They can be different if the buffersize was changed
	 * between reads.
	 *
	 * Note: This affects performance negatively if the buffersize was
	 * extended but this small buffer is reused for all subsequent reads.
	 * The system never uses buffers with the requested bigger size in
	 * that case. An adjunct patch could try and delete all unused buffers
	 * it encounters and which are smaller than the formally requested
	 * buffersize.
	 */

	toRead = SpaceLeft(bufPtr);

	if (statePtr->inQueueTail == NULL) {
	    statePtr->inQueueHead = bufPtr;
	} else {
	    statePtr->inQueueTail->nextPtr = bufPtr;
	}
	statePtr->inQueueTail = bufPtr;
    }

    /*
     * If EOF is set, we should avoid calling the driver because on some
     * platforms it is impossible to read from a device after EOF.
     */

    if (GotFlag(statePtr, CHANNEL_EOF)) {
	return 0;
    }

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
    /*
     * [SF Tcl Bug 943274]. Better emulation of non-blocking channels for
     * channels without BlockModeProc, by keeping track of true fileevents
     * generated by the OS == Data waiting and reading if and only if we are
     * sure to have data.
     */

    if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
	    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
	    !GotFlag(statePtr, CHANNEL_HAS_MORE_DATA)) {
	/*
	 * Bypass the driver, it would block, as no data is available
	 */

	nread = -1;
	result = EWOULDBLOCK;
    } else
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
    {
	nread = ChanRead(chanPtr, InsertPoint(bufPtr), toRead, &result);
    }

    if (nread > 0) {
	bufPtr->nextAdded += nread;

	/*
	 * If we get a short read, signal up that we may be BLOCKED. We should
	 * avoid calling the driver because on some platforms we will block in
	 * the low level reading code even though the channel is set into
	 * nonblocking mode.
	 */

	if (nread < toRead) {
	    SetFlag(statePtr, CHANNEL_BLOCKED);
	}

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
	if (nread <= toRead) {
	    /*
	     * [SF Tcl Bug 943274] We have read the available data, clear
	     * flag.
	     */

	    ResetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
	}
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
    } else if (nread == 0) {
	SetFlag(statePtr, CHANNEL_EOF);
	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
    } else if (nread < 0) {
	if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
	    SetFlag(statePtr, CHANNEL_BLOCKED);
	    result = EAGAIN;
	}
	Tcl_SetErrno(result);
	return result;
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Seek --
 *
 *	Implements seeking on Tcl Channels. This is a public function so that
 *	other C facilities may be implemented on top of it.
 *
 * Results:
 *	The new access point or -1 on error. If error, use Tcl_GetErrno() to
 *	retrieve the POSIX error code for the error that occurred.
 *
 * Side effects:
 *	May flush output on the channel. May discard queued input.
 *
 *----------------------------------------------------------------------
 */

Tcl_WideInt
Tcl_Seek(
    Tcl_Channel chan,		/* The channel on which to seek. */
    Tcl_WideInt offset,		/* Offset to seek to. */
    int mode)			/* Relative to which location to seek? */
{
    Channel *chanPtr = (Channel *) chan;
				/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int inputBuffered, outputBuffered;
				/* # bytes held in buffers. */
    int result;			/* Of device driver operations. */
    Tcl_WideInt curPos;		/* Position on the device. */
    int wasAsync;		/* Was the channel nonblocking before the seek
				 * operation? If so, must restore to
				 * non-blocking mode after the seek. */

    if (CheckChannelErrors(statePtr, TCL_WRITABLE | TCL_READABLE) != 0) {
	return Tcl_LongAsWide(-1);
    }

    /*
     * Disallow seek on dead channels - channels that have been closed but not
     * yet been deallocated. Such channels can be found if the exit handler
     * for channel cleanup has run but the channel is still registered in an
     * interpreter.
     */

    if (CheckForDeadChannel(NULL, statePtr)) {
	return Tcl_LongAsWide(-1);
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * Disallow seek on channels whose type does not have a seek procedure
     * defined. This means that the channel does not support seeking.
     */

    if (chanPtr->typePtr->seekProc == NULL) {
	Tcl_SetErrno(EINVAL);
	return Tcl_LongAsWide(-1);
    }

    /*
     * Compute how much input and output is buffered. If both input and output
     * is buffered, cannot compute the current position.
     */

    inputBuffered = Tcl_InputBuffered(chan);
    outputBuffered = Tcl_OutputBuffered(chan);

    if ((inputBuffered != 0) && (outputBuffered != 0)) {
	Tcl_SetErrno(EFAULT);
	return Tcl_LongAsWide(-1);
    }

    /*
     * If we are seeking relative to the current position, compute the
     * corrected offset taking into account the amount of unread input.
     */

    if (mode == SEEK_CUR) {
	offset -= inputBuffered;
    }

    /*
     * Discard any queued input - this input should not be read after the
     * seek.
     */

    DiscardInputQueued(statePtr, 0);

    /*
     * Reset EOF and BLOCKED flags. We invalidate them by moving the access
     * point. Also clear CR related flags.
     */

    ResetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF | CHANNEL_BLOCKED |
	    INPUT_SAW_CR);

    /*
     * If the channel is in asynchronous output mode, switch it back to
     * synchronous mode and cancel any async flush that may be scheduled.
     * After the flush, the channel will be put back into asynchronous output
     * mode.
     */

    wasAsync = 0;
    if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
	wasAsync = 1;
	result = StackSetBlockMode(chanPtr, TCL_MODE_BLOCKING);
	if (result != 0) {
	    return Tcl_LongAsWide(-1);
	}
	ResetFlag(statePtr, CHANNEL_NONBLOCKING);
	if (GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	}
    }

    /*
     * If there is data buffered in statePtr->curOutPtr then mark the channel
     * as ready to flush before invoking FlushChannel.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    /*
     * If the flush fails we cannot recover the original position. In that
     * case the seek is not attempted because we do not know where the access
     * position is - instead we return the error. FlushChannel has already
     * called Tcl_SetErrno() to report the error upwards. If the flush
     * succeeds we do the seek also.
     */

    if (FlushChannel(NULL, chanPtr, 0) != 0) {
	curPos = -1;
    } else {
	/*
	 * Now seek to the new position in the channel as requested by the
	 * caller.
	 */

	curPos = ChanSeek(chanPtr, offset, mode, &result);
	if (curPos == Tcl_LongAsWide(-1)) {
	    Tcl_SetErrno(result);
	}
    }

    /*
     * Restore to nonblocking mode if that was the previous behavior.
     *
     * NOTE: Even if there was an async flush active we do not restore it now
     * because we already flushed all the queued output, above.
     */

    if (wasAsync) {
	SetFlag(statePtr, CHANNEL_NONBLOCKING);
	result = StackSetBlockMode(chanPtr, TCL_MODE_NONBLOCKING);
	if (result != 0) {
	    return Tcl_LongAsWide(-1);
	}
    }

    return curPos;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Tell --
 *
 *	Returns the position of the next character to be read/written on this
 *	channel.
 *
 * Results:
 *	A nonnegative integer on success, -1 on failure. If failed, use
 *	Tcl_GetErrno() to retrieve the POSIX error code for the error that
 *	occurred.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_WideInt
Tcl_Tell(
    Tcl_Channel chan)		/* The channel to return pos for. */
{
    Channel *chanPtr = (Channel *) chan;
				/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int inputBuffered, outputBuffered;
				/* # bytes held in buffers. */
    int result;			/* Of calling device driver. */
    Tcl_WideInt curPos;		/* Position on device. */

    if (CheckChannelErrors(statePtr, TCL_WRITABLE | TCL_READABLE) != 0) {
	return Tcl_LongAsWide(-1);
    }

    /*
     * Disallow tell on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still registered
     * in an interpreter.
     */

    if (CheckForDeadChannel(NULL, statePtr)) {
	return Tcl_LongAsWide(-1);
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * Disallow tell on channels whose type does not have a seek procedure
     * defined. This means that the channel does not support seeking.
     */

    if (chanPtr->typePtr->seekProc == NULL) {
	Tcl_SetErrno(EINVAL);
	return Tcl_LongAsWide(-1);
    }

    /*
     * Compute how much input and output is buffered. If both input and output
     * is buffered, cannot compute the current position.
     */

    inputBuffered = Tcl_InputBuffered(chan);
    outputBuffered = Tcl_OutputBuffered(chan);

    if ((inputBuffered != 0) && (outputBuffered != 0)) {
	Tcl_SetErrno(EFAULT);
	return Tcl_LongAsWide(-1);
    }

    /*
     * Get the current position in the device and compute the position where
     * the next character will be read or written. Note that we prefer the
     * wideSeekProc if that is available and non-NULL...
     */

    curPos = ChanSeek(chanPtr, Tcl_LongAsWide(0), SEEK_CUR, &result);
    if (curPos == Tcl_LongAsWide(-1)) {
	Tcl_SetErrno(result);
	return Tcl_LongAsWide(-1);
    }
    if (inputBuffered != 0) {
	return curPos - inputBuffered;
    }
    return curPos + outputBuffered;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_SeekOld, Tcl_TellOld --
 *
 *	Backward-compatability versions of the seek/tell interface that do not
 *	support 64-bit offsets. This interface is not documented or expected
 *	to be supported indefinitely.
 *
 * Results:
 *	As for Tcl_Seek and Tcl_Tell respectively, except truncated to
 *	whatever value will fit in an 'int'.
 *
 * Side effects:
 *	As for Tcl_Seek and Tcl_Tell respectively.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_SeekOld(
    Tcl_Channel chan,		/* The channel on which to seek. */
    int offset,			/* Offset to seek to. */
    int mode)			/* Relative to which location to seek? */
{
    Tcl_WideInt wOffset, wResult;

    wOffset = Tcl_LongAsWide((long) offset);
    wResult = Tcl_Seek(chan, wOffset, mode);
    return (int) Tcl_WideAsLong(wResult);
}

int
Tcl_TellOld(
    Tcl_Channel chan)		/* The channel to return pos for. */
{
    Tcl_WideInt wResult = Tcl_Tell(chan);

    return (int) Tcl_WideAsLong(wResult);
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_TruncateChannel --
 *
 *	Truncate a channel to the given length.
 *
 * Results:
 *	TCL_OK on success, TCL_ERROR if the operation failed (e.g. is not
 *	supported by the type of channel, or the underlying OS operation
 *	failed in some way).
 *
 * Side effects:
 *	Seeks the channel to the current location. Sets errno on OS error.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_TruncateChannel(
    Tcl_Channel chan,		/* Channel to truncate. */
    Tcl_WideInt length)		/* Length to truncate it to. */
{
    Channel *chanPtr = (Channel *) chan;
    Tcl_DriverTruncateProc *truncateProc =
	    Tcl_ChannelTruncateProc(chanPtr->typePtr);
    int result;

    if (truncateProc == NULL) {
	/*
	 * Feature not supported and it's not emulatable. Pretend it's
	 * returned an EINVAL, a very generic error!
	 */

	Tcl_SetErrno(EINVAL);
	return TCL_ERROR;
    }

    if (!GotFlag(chanPtr->state, TCL_WRITABLE)) {
	/*
	 * We require that the file was opened of writing. Do that check now
	 * so that we only flush if we think we're going to succeed.
	 */

	Tcl_SetErrno(EINVAL);
	return TCL_ERROR;
    }

    /*
     * Seek first to force a total flush of all pending buffers and ditch any
     * pre-read input data.
     */

    if (Tcl_Seek(chan, (Tcl_WideInt) 0, SEEK_CUR) == Tcl_LongAsWide(-1)) {
	return TCL_ERROR;
    }

    /*
     * We're all flushed to disk now and we also don't have any unfortunate
     * input baggage around either; can truncate with impunity.
     */

    result = truncateProc(chanPtr->instanceData, length);
    if (result != 0) {
	Tcl_SetErrno(result);
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * CheckChannelErrors --
 *
 *	See if the channel is in an ready state and can perform the desired
 *	operation.
 *
 * Results:
 *	The return value is 0 if the channel is OK, otherwise the return value
 *	is -1 and errno is set to indicate the error.
 *
 * Side effects:
 *	May clear the EOF and/or BLOCKED bits if reading from channel.
 *
 *---------------------------------------------------------------------------
 */

static int
CheckChannelErrors(
    ChannelState *statePtr,	/* Channel to check. */
    int flags)			/* Test if channel supports desired operation:
				 * TCL_READABLE, TCL_WRITABLE. Also indicates
				 * Raw read or write for special close
				 * processing */
{
    int direction = flags & (TCL_READABLE|TCL_WRITABLE);

    /*
     * Check for unreported error.
     */

    if (statePtr->unreportedError != 0) {
	Tcl_SetErrno(statePtr->unreportedError);
	statePtr->unreportedError = 0;

	/*
	 * TIP #219, Tcl Channel Reflection API.
	 * Move a defered error message back into the channel bypass.
	 */

	if (statePtr->chanMsg != NULL) {
	    TclDecrRefCount(statePtr->chanMsg);
	}
	statePtr->chanMsg = statePtr->unreportedMsg;
	statePtr->unreportedMsg = NULL;
	return -1;
    }

    /*
     * Only the raw read and write operations are allowed during close in
     * order to drain data from stacked channels.
     */

    if (GotFlag(statePtr, CHANNEL_CLOSED) && !(flags & CHANNEL_RAW_MODE)) {
	Tcl_SetErrno(EACCES);
	return -1;
    }

    /*
     * Fail if the channel is not opened for desired operation.
     */

    if ((statePtr->flags & direction) == 0) {
	Tcl_SetErrno(EACCES);
	return -1;
    }

    /*
     * Fail if the channel is in the middle of a background copy.
     *
     * Don't do this tests for raw channels here or else the chaining in the
     * transformation drivers will fail with 'file busy' error instead of
     * retrieving and transforming the data to copy.
     */

    if (BUSY_STATE(statePtr,flags) && ((flags & CHANNEL_RAW_MODE) == 0)) {
	Tcl_SetErrno(EBUSY);
	return -1;
    }

    if (direction == TCL_READABLE) {
	/*
	 * If we have not encountered a sticky EOF, clear the EOF bit (sticky
	 * EOF is set if we have seen the input eofChar, to prevent reading
	 * beyond the eofChar). Also, always clear the BLOCKED bit. We want to
	 * discover these conditions anew in each operation.
	 */

	if (!GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
	    ResetFlag(statePtr, CHANNEL_EOF);
	}
	ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);
    }

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Eof --
 *
 *	Returns 1 if the channel is at EOF, 0 otherwise.
 *
 * Results:
 *	1 or 0, always.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_Eof(
    Tcl_Channel chan)		/* Does this channel have EOF? */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */

    return (GotFlag(statePtr, CHANNEL_STICKY_EOF) ||
	    (GotFlag(statePtr, CHANNEL_EOF) &&
	    (Tcl_InputBuffered(chan) == 0))) ? 1 : 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InputBlocked --
 *
 *	Returns 1 if input is blocked on this channel, 0 otherwise.
 *
 * Results:
 *	0 or 1, always.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_InputBlocked(
    Tcl_Channel chan)		/* Is this channel blocked? */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */

    return GotFlag(statePtr, CHANNEL_BLOCKED) ? 1 : 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InputBuffered --
 *
 *	Returns the number of bytes of input currently buffered in the common
 *	internal buffer of a channel.
 *
 * Results:
 *	The number of input bytes buffered, or zero if the channel is not open
 *	for reading.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_InputBuffered(
    Tcl_Channel chan)		/* The channel to query. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */
    ChannelBuffer *bufPtr;
    int bytesBuffered;

    for (bytesBuffered = 0, bufPtr = statePtr->inQueueHead; bufPtr != NULL;
	    bufPtr = bufPtr->nextPtr) {
	bytesBuffered += BytesLeft(bufPtr);
    }

    /*
     * Don't forget the bytes in the topmost pushback area.
     */

    for (bufPtr = statePtr->topChanPtr->inQueueHead; bufPtr != NULL;
	    bufPtr = bufPtr->nextPtr) {
	bytesBuffered += BytesLeft(bufPtr);
    }

    return bytesBuffered;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_OutputBuffered --
 *
 *    Returns the number of bytes of output currently buffered in the common
 *    internal buffer of a channel.
 *
 * Results:
 *    The number of output bytes buffered, or zero if the channel is not open
 *    for writing.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_OutputBuffered(
    Tcl_Channel chan)		/* The channel to query. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */
    ChannelBuffer *bufPtr;
    int bytesBuffered;

    for (bytesBuffered = 0, bufPtr = statePtr->outQueueHead; bufPtr != NULL;
	    bufPtr = bufPtr->nextPtr) {
	bytesBuffered += BytesLeft(bufPtr);
    }
    if (statePtr->curOutPtr != NULL) {
	register ChannelBuffer *curOutPtr = statePtr->curOutPtr;

	if (IsBufferReady(curOutPtr)) {
	    bytesBuffered += BytesLeft(curOutPtr);
	}
    }

    return bytesBuffered;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelBuffered --
 *
 *	Returns the number of bytes of input currently buffered in the
 *	internal buffer (push back area) of a channel.
 *
 * Results:
 *	The number of input bytes buffered, or zero if the channel is not open
 *	for reading.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ChannelBuffered(
    Tcl_Channel chan)		/* The channel to query. */
{
    Channel *chanPtr = (Channel *) chan;
				/* Real channel structure. */
    ChannelBuffer *bufPtr;
    int bytesBuffered = 0;

    for (bufPtr = chanPtr->inQueueHead; bufPtr != NULL;
	    bufPtr = bufPtr->nextPtr) {
	bytesBuffered += BytesLeft(bufPtr);
    }

    return bytesBuffered;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetChannelBufferSize --
 *
 *	Sets the size of buffers to allocate to store input or output in the
 *	channel. The size must be between 1 byte and 1 MByte.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets the size of buffers subsequently allocated for this channel.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetChannelBufferSize(
    Tcl_Channel chan,		/* The channel whose buffer size to set. */
    int sz)			/* The size to set. */
{
    ChannelState *statePtr;	/* State of real channel structure. */

    /*
     * Clip the buffer size to force it into the [1,1M] range
     */

    if (sz < 1) {
	sz = 1;
    } else if (sz > MAX_CHANNEL_BUFFER_SIZE) {
	sz = MAX_CHANNEL_BUFFER_SIZE;
    }

    statePtr = ((Channel *) chan)->state;
    statePtr->bufSize = sz;

    if (statePtr->outputStage != NULL) {
	ckfree((char *) statePtr->outputStage);
	statePtr->outputStage = NULL;
    }
    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
	statePtr->outputStage = ckalloc((unsigned) statePtr->bufSize + 2);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelBufferSize --
 *
 *	Retrieves the size of buffers to allocate for this channel.
 *
 * Results:
 *	The size.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelBufferSize(
    Tcl_Channel chan)		/* The channel for which to find the buffer
				 * size. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */

    return statePtr->bufSize;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_BadChannelOption --
 *
 *	This procedure generates a "bad option" error message in an (optional)
 *	interpreter. It is used by channel drivers when a invalid Set/Get
 *	option is requested. Its purpose is to concatenate the generic options
 *	list to the specific ones and factorize the generic options error
 *	message string.
 *
 * Results:
 *	TCL_ERROR.
 *
 * Side effects:

 *	An error message is generated in interp's result object to indicate
 *	that a command was invoked with the a bad option. The message has the
 *	form:
 *		bad option "blah": should be one of
 *		<...generic options...>+<...specific options...>
 *	"blah" is the optionName argument and "<specific options>" is a space
 *	separated list of specific option words. The function takes good care
 *	of inserting minus signs before each option, commas after, and an "or"
 *	before the last option.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_BadChannelOption(
    Tcl_Interp *interp,		/* Current interpreter (can be NULL).*/
    const char *optionName,	/* 'bad option' name */
    const char *optionList)	/* Specific options list to append to the
				 * standard generic options. Can be NULL for
				 * generic options only. */
{
    if (interp != NULL) {
	const char *genericopt =
		"blocking buffering buffersize encoding eofchar translation";
	const char **argv;
	int argc, i;
	Tcl_DString ds;

	Tcl_DStringInit(&ds);
	Tcl_DStringAppend(&ds, genericopt, -1);
	if (optionList && (*optionList)) {
	    Tcl_DStringAppend(&ds, " ", 1);
	    Tcl_DStringAppend(&ds, optionList, -1);
	}
	if (Tcl_SplitList(interp, Tcl_DStringValue(&ds),
		&argc, &argv) != TCL_OK) {
	    Tcl_Panic("malformed option list in channel driver");
	}
	Tcl_ResetResult(interp);
	Tcl_AppendResult(interp, "bad option \"", optionName,
		"\": should be one of ", NULL);
	argc--;
	for (i = 0; i < argc; i++) {
	    Tcl_AppendResult(interp, "-", argv[i], ", ", NULL);
	}
	Tcl_AppendResult(interp, "or -", argv[i], NULL);
	Tcl_DStringFree(&ds);
	ckfree((char *) argv);
    }
    Tcl_SetErrno(EINVAL);
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelOption --
 *
 *	Gets a mode associated with an IO channel. If the optionName arg is
 *	non NULL, retrieves the value of that option. If the optionName arg is
 *	NULL, retrieves a list of alternating option names and values for the
 *	given channel.
 *
 * Results:
 *	A standard Tcl result. Also sets the supplied DString to the string
 *	value of the option(s) returned.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelOption(
    Tcl_Interp *interp,		/* For error reporting - can be NULL. */
    Tcl_Channel chan,		/* Channel on which to get option. */
    const char *optionName,	/* Option to get. */
    Tcl_DString *dsPtr)		/* Where to store value(s). */
{
    size_t len;			/* Length of optionName string. */
    char optionVal[128];	/* Buffer for sprintf. */
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int flags;

    /*
     * Disallow options on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still registered
     * in an interpreter.
     */

    if (CheckForDeadChannel(interp, statePtr)) {
	return TCL_ERROR;
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * If we are in the middle of a background copy, use the saved flags.
     */

    if (statePtr->csPtrR) {
	flags = statePtr->csPtrR->readFlags;
    } else if (statePtr->csPtrW) {
	flags = statePtr->csPtrW->writeFlags;
    } else {
	flags = statePtr->flags;
    }

    /*
     * If the optionName is NULL it means that we want a list of all options
     * and values.
     */

    if (optionName == NULL) {
	len = 0;
    } else {
	len = strlen(optionName);
    }

    if (len == 0 || HaveOpt(2, "-blocking")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-blocking");
	}
	Tcl_DStringAppendElement(dsPtr,
		(flags & CHANNEL_NONBLOCKING) ? "0" : "1");
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if (len == 0 || HaveOpt(7, "-buffering")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-buffering");
	}
	if (flags & CHANNEL_LINEBUFFERED) {
	    Tcl_DStringAppendElement(dsPtr, "line");
	} else if (flags & CHANNEL_UNBUFFERED) {
	    Tcl_DStringAppendElement(dsPtr, "none");
	} else {
	    Tcl_DStringAppendElement(dsPtr, "full");
	}
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if (len == 0 || HaveOpt(7, "-buffersize")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-buffersize");
	}
	TclFormatInt(optionVal, statePtr->bufSize);
	Tcl_DStringAppendElement(dsPtr, optionVal);
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if (len == 0 || HaveOpt(2, "-encoding")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-encoding");
	}
	if (statePtr->encoding == NULL) {
	    Tcl_DStringAppendElement(dsPtr, "binary");
	} else {
	    Tcl_DStringAppendElement(dsPtr,
		    Tcl_GetEncodingName(statePtr->encoding));
	}
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if (len == 0 || HaveOpt(2, "-eofchar")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-eofchar");
	}
	if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
		(TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
	    Tcl_DStringStartSublist(dsPtr);
	}
	if (flags & TCL_READABLE) {
	    if (statePtr->inEofChar == 0) {
		Tcl_DStringAppendElement(dsPtr, "");
	    } else {
		char buf[4];

		sprintf(buf, "%c", statePtr->inEofChar);
		Tcl_DStringAppendElement(dsPtr, buf);
	    }
	}
	if (flags & TCL_WRITABLE) {
	    if (statePtr->outEofChar == 0) {
		Tcl_DStringAppendElement(dsPtr, "");
	    } else {
		char buf[4];

		sprintf(buf, "%c", statePtr->outEofChar);
		Tcl_DStringAppendElement(dsPtr, buf);
	    }
	}
	if (!(flags & (TCL_READABLE|TCL_WRITABLE))) {
	    /*
	     * Not readable or writable (e.g. server socket)
	     */

	    Tcl_DStringAppendElement(dsPtr, "");
	}
	if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
		(TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
	    Tcl_DStringEndSublist(dsPtr);
	}
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if (len == 0 || HaveOpt(1, "-translation")) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-translation");
	}
	if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
		(TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
	    Tcl_DStringStartSublist(dsPtr);
	}
	if (flags & TCL_READABLE) {
	    if (statePtr->inputTranslation == TCL_TRANSLATE_AUTO) {
		Tcl_DStringAppendElement(dsPtr, "auto");
	    } else if (statePtr->inputTranslation == TCL_TRANSLATE_CR) {
		Tcl_DStringAppendElement(dsPtr, "cr");
	    } else if (statePtr->inputTranslation == TCL_TRANSLATE_CRLF) {
		Tcl_DStringAppendElement(dsPtr, "crlf");
	    } else {
		Tcl_DStringAppendElement(dsPtr, "lf");
	    }
	}
	if (flags & TCL_WRITABLE) {
	    if (statePtr->outputTranslation == TCL_TRANSLATE_AUTO) {
		Tcl_DStringAppendElement(dsPtr, "auto");
	    } else if (statePtr->outputTranslation == TCL_TRANSLATE_CR) {
		Tcl_DStringAppendElement(dsPtr, "cr");
	    } else if (statePtr->outputTranslation == TCL_TRANSLATE_CRLF) {
		Tcl_DStringAppendElement(dsPtr, "crlf");
	    } else {
		Tcl_DStringAppendElement(dsPtr, "lf");
	    }
	}
	if (!(flags & (TCL_READABLE|TCL_WRITABLE))) {
	    /*
	     * Not readable or writable (e.g. server socket)
	     */

	    Tcl_DStringAppendElement(dsPtr, "auto");
	}
	if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
		(TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
	    Tcl_DStringEndSublist(dsPtr);
	}
	if (len > 0) {
	    return TCL_OK;
	}
    }

    if (chanPtr->typePtr->getOptionProc != NULL) {
	/*
	 * Let the driver specific handle additional options and result code
	 * and message.
	 */

	return chanPtr->typePtr->getOptionProc(chanPtr->instanceData, interp,
		optionName, dsPtr);
    } else {
	/*
	 * No driver specific options case.
	 */

	if (len == 0) {
	    return TCL_OK;
	}
	return Tcl_BadChannelOption(interp, optionName, NULL);
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_SetChannelOption --
 *
 *	Sets an option on a channel.
 *
 * Results:
 *	A standard Tcl result. On error, sets interp's result object if
 *	interp is not NULL.
 *
 * Side effects:
 *	May modify an option on a device.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_SetChannelOption(
    Tcl_Interp *interp,		/* For error reporting - can be NULL. */
    Tcl_Channel chan,		/* Channel on which to set mode. */
    const char *optionName,	/* Which option to set? */
    const char *newValue)	/* New value for option. */
{
    Channel *chanPtr = (Channel *) chan;
				/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    size_t len;			/* Length of optionName string. */
    int argc;
    const char **argv;

    /*
     * If the channel is in the middle of a background copy, fail.
     */

    if (statePtr->csPtrR || statePtr->csPtrW) {
	if (interp) {
	    Tcl_AppendResult(interp, "unable to set channel options: "
		    "background copy in progress", NULL);
	}
	return TCL_ERROR;
    }

    /*
     * Disallow options on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still registered
     * in an interpreter.
     */

    if (CheckForDeadChannel(NULL, statePtr)) {
	return TCL_ERROR;
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    len = strlen(optionName);

    if (HaveOpt(2, "-blocking")) {
	int newMode;

	if (Tcl_GetBoolean(interp, newValue, &newMode) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	if (newMode) {
	    newMode = TCL_MODE_BLOCKING;
	} else {
	    newMode = TCL_MODE_NONBLOCKING;
	}
	return SetBlockMode(interp, chanPtr, newMode);
    } else if (HaveOpt(7, "-buffering")) {
	len = strlen(newValue);
	if ((newValue[0] == 'f') && (strncmp(newValue, "full", len) == 0)) {
	    ResetFlag(statePtr, CHANNEL_UNBUFFERED | CHANNEL_LINEBUFFERED);
	} else if ((newValue[0] == 'l') &&
		(strncmp(newValue, "line", len) == 0)) {
	    ResetFlag(statePtr, CHANNEL_UNBUFFERED);
	    SetFlag(statePtr, CHANNEL_LINEBUFFERED);
	} else if ((newValue[0] == 'n') &&
		(strncmp(newValue, "none", len) == 0)) {
	    ResetFlag(statePtr, CHANNEL_LINEBUFFERED);
	    SetFlag(statePtr, CHANNEL_UNBUFFERED);
	} else {
	    if (interp) {
		Tcl_AppendResult(interp, "bad value for -buffering: "
			"must be one of full, line, or none", NULL);
		return TCL_ERROR;
	    }
	}
	return TCL_OK;
    } else if (HaveOpt(7, "-buffersize")) {
	int newBufferSize;

	if (Tcl_GetInt(interp, newValue, &newBufferSize) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	Tcl_SetChannelBufferSize(chan, newBufferSize);
    } else if (HaveOpt(2, "-encoding")) {
	Tcl_Encoding encoding;

	if ((newValue[0] == '\0') || (strcmp(newValue, "binary") == 0)) {
	    encoding = NULL;
	} else {
	    encoding = Tcl_GetEncoding(interp, newValue);
	    if (encoding == NULL) {
		return TCL_ERROR;
	    }
	}

	/*
	 * When the channel has an escape sequence driven encoding such as
	 * iso2022, the terminated escape sequence must write to the buffer.
	 */

	if ((statePtr->encoding != NULL) && (statePtr->curOutPtr != NULL)
		&& (CheckChannelErrors(statePtr, TCL_WRITABLE) == 0)) {
	    statePtr->outputEncodingFlags |= TCL_ENCODING_END;
	    WriteChars(chanPtr, "", 0);
	}
	Tcl_FreeEncoding(statePtr->encoding);
	statePtr->encoding = encoding;
	statePtr->inputEncodingState = NULL;
	statePtr->inputEncodingFlags = TCL_ENCODING_START;
	statePtr->outputEncodingState = NULL;
	statePtr->outputEncodingFlags = TCL_ENCODING_START;
	ResetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
	UpdateInterest(chanPtr);
    } else if (HaveOpt(2, "-eofchar")) {
	if (Tcl_SplitList(interp, newValue, &argc, &argv) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	if (argc == 0) {
	    statePtr->inEofChar = 0;
	    statePtr->outEofChar = 0;
	} else if (argc == 1 || argc == 2) {
	    int outIndex = (argc - 1);
	    int inValue = (int) argv[0][0];
	    int outValue = (int) argv[outIndex][0];

	    if (inValue & 0x80 || outValue & 0x80) {
		if (interp) {
		    Tcl_AppendResult(interp, "bad value for -eofchar: ",
			    "must be non-NUL ASCII character", NULL);
		}
		ckfree((char *) argv);
		return TCL_ERROR;
	    }
	    if (GotFlag(statePtr, TCL_READABLE)) {
		statePtr->inEofChar = inValue;
	    }
	    if (GotFlag(statePtr, TCL_WRITABLE)) {
		statePtr->outEofChar = outValue;
	    }
	} else {
	    if (interp) {
		Tcl_AppendResult(interp,
			"bad value for -eofchar: should be a list of zero,"
			" one, or two elements", NULL);
	    }
	    ckfree((char *) argv);
	    return TCL_ERROR;
	}
	if (argv != NULL) {
	    ckfree((char *) argv);
	}

	/*
	 * [Bug 930851] Reset EOF and BLOCKED flags. Changing the character
	 * which signals eof can transform a current eof condition into a 'go
	 * ahead'. Ditto for blocked.
	 */

	ResetFlag(statePtr, CHANNEL_EOF|CHANNEL_STICKY_EOF|CHANNEL_BLOCKED);
	return TCL_OK;
    } else if (HaveOpt(1, "-translation")) {
	const char *readMode, *writeMode;

	if (Tcl_SplitList(interp, newValue, &argc, &argv) == TCL_ERROR) {
	    return TCL_ERROR;
	}

	if (argc == 1) {
	    readMode = GotFlag(statePtr, TCL_READABLE) ? argv[0] : NULL;
	    writeMode = GotFlag(statePtr, TCL_WRITABLE) ? argv[0] : NULL;
	} else if (argc == 2) {
	    readMode = GotFlag(statePtr, TCL_READABLE) ? argv[0] : NULL;
	    writeMode = GotFlag(statePtr, TCL_WRITABLE) ? argv[1] : NULL;
	} else {
	    if (interp) {
		Tcl_AppendResult(interp,
			"bad value for -translation: must be a one or two"
			" element list", NULL);
	    }
	    ckfree((char *) argv);
	    return TCL_ERROR;
	}

	if (readMode) {
	    TclEolTranslation translation;

	    if (*readMode == '\0') {
		translation = statePtr->inputTranslation;
	    } else if (strcmp(readMode, "auto") == 0) {
		translation = TCL_TRANSLATE_AUTO;
	    } else if (strcmp(readMode, "binary") == 0) {
		translation = TCL_TRANSLATE_LF;
		statePtr->inEofChar = 0;
		Tcl_FreeEncoding(statePtr->encoding);
		statePtr->encoding = NULL;
	    } else if (strcmp(readMode, "lf") == 0) {
		translation = TCL_TRANSLATE_LF;
	    } else if (strcmp(readMode, "cr") == 0) {
		translation = TCL_TRANSLATE_CR;
	    } else if (strcmp(readMode, "crlf") == 0) {
		translation = TCL_TRANSLATE_CRLF;
	    } else if (strcmp(readMode, "platform") == 0) {
		translation = TCL_PLATFORM_TRANSLATION;
	    } else {
		if (interp) {
		    Tcl_AppendResult(interp,
			    "bad value for -translation: "
			    "must be one of auto, binary, cr, lf, crlf,"
			    " or platform", NULL);
		}
		ckfree((char *) argv);
		return TCL_ERROR;
	    }

	    /*
	     * Reset the EOL flags since we need to look at any buffered data
	     * to see if the new translation mode allows us to complete the
	     * line.
	     */

	    if (translation != statePtr->inputTranslation) {
		statePtr->inputTranslation = translation;
		ResetFlag(statePtr, INPUT_SAW_CR | CHANNEL_NEED_MORE_DATA);
		UpdateInterest(chanPtr);
	    }
	}
	if (writeMode) {
	    if (*writeMode == '\0') {
		/* Do nothing. */
	    } else if (strcmp(writeMode, "auto") == 0) {
		/*
		 * This is a hack to get TCP sockets to produce output in CRLF
		 * mode if they are being set into AUTO mode. A better
		 * solution for achieving this effect will be coded later.
		 */

		if (strcmp(Tcl_ChannelName(chanPtr->typePtr), "tcp") == 0) {
		    statePtr->outputTranslation = TCL_TRANSLATE_CRLF;
		} else {
		    statePtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
		}
	    } else if (strcmp(writeMode, "binary") == 0) {
		statePtr->outEofChar = 0;
		statePtr->outputTranslation = TCL_TRANSLATE_LF;
		Tcl_FreeEncoding(statePtr->encoding);
		statePtr->encoding = NULL;
	    } else if (strcmp(writeMode, "lf") == 0) {
		statePtr->outputTranslation = TCL_TRANSLATE_LF;
	    } else if (strcmp(writeMode, "cr") == 0) {
		statePtr->outputTranslation = TCL_TRANSLATE_CR;
	    } else if (strcmp(writeMode, "crlf") == 0) {
		statePtr->outputTranslation = TCL_TRANSLATE_CRLF;
	    } else if (strcmp(writeMode, "platform") == 0) {
		statePtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
	    } else {
		if (interp) {
		    Tcl_AppendResult(interp,
			    "bad value for -translation: "
			    "must be one of auto, binary, cr, lf, crlf,"
			    " or platform", NULL);
		}
		ckfree((char *) argv);
		return TCL_ERROR;
	    }
	}
	ckfree((char *) argv);
	return TCL_OK;
    } else if (chanPtr->typePtr->setOptionProc != NULL) {
	return chanPtr->typePtr->setOptionProc(chanPtr->instanceData, interp,
		optionName, newValue);
    } else {
	return Tcl_BadChannelOption(interp, optionName, NULL);
    }

    /*
     * If bufsize changes, need to get rid of old utility buffer.
     */

    if (statePtr->saveInBufPtr != NULL) {
	RecycleBuffer(statePtr, statePtr->saveInBufPtr, 1);
	statePtr->saveInBufPtr = NULL;
    }
    if ((statePtr->inQueueHead != NULL)
	    && (statePtr->inQueueHead->nextPtr == NULL)
	    && IsBufferEmpty(statePtr->inQueueHead)) {
	RecycleBuffer(statePtr, statePtr->inQueueHead, 1);
	statePtr->inQueueHead = NULL;
	statePtr->inQueueTail = NULL;
    }

    /*
     * If encoding or bufsize changes, need to update output staging buffer.
     */

    if (statePtr->outputStage != NULL) {
	ckfree(statePtr->outputStage);
	statePtr->outputStage = NULL;
    }
    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
	statePtr->outputStage = ckalloc((unsigned) (statePtr->bufSize + 2));
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * CleanupChannelHandlers --
 *
 *	Removes channel handlers that refer to the supplied interpreter, so
 *	that if the actual channel is not closed now, these handlers will not
 *	run on subsequent events on the channel. This would be erroneous,
 *	because the interpreter no longer has a reference to this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes channel handlers.
 *
 *----------------------------------------------------------------------
 */

static void
CleanupChannelHandlers(
    Tcl_Interp *interp,
    Channel *chanPtr)
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    EventScriptRecord *sPtr, *prevPtr, *nextPtr;

    /*
     * Remove fileevent records on this channel that refer to the given
     * interpreter.
     */

    for (sPtr = statePtr->scriptRecordPtr, prevPtr = NULL;
	    sPtr != NULL; sPtr = nextPtr) {
	nextPtr = sPtr->nextPtr;
	if (sPtr->interp == interp) {
	    if (prevPtr == NULL) {
		statePtr->scriptRecordPtr = nextPtr;
	    } else {
		prevPtr->nextPtr = nextPtr;
	    }

	    Tcl_DeleteChannelHandler((Tcl_Channel) chanPtr,
		    TclChannelEventScriptInvoker, sPtr);

	    TclDecrRefCount(sPtr->scriptPtr);
	    ckfree((char *) sPtr);
	} else {
	    prevPtr = sPtr;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_NotifyChannel --
 *
 *	This procedure is called by a channel driver when a driver detects an
 *	event on a channel. This procedure is responsible for actually
 *	handling the event by invoking any channel handler callbacks.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Whatever the channel handler callback procedure does.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_NotifyChannel(
    Tcl_Channel channel,	/* Channel that detected an event. */
    int mask)			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which events were detected. */
{
    Channel *chanPtr = (Channel *) channel;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelHandler *chPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    NextChannelHandler nh;
    Channel *upChanPtr;
    const Tcl_ChannelType *upTypePtr;

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
    /*
     * [SF Tcl Bug 943274] For a non-blocking channel without blockmodeproc we
     * keep track of actual input coming from the OS so that we can do a
     * credible imitation of non-blocking behaviour.
     */

    if ((mask & TCL_READABLE) &&
	    GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
	    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
	    !GotFlag(statePtr, CHANNEL_TIMER_FEV)) {
	SetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
    }
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */

    /*
     * In contrast to the other API functions this procedure walks towards the
     * top of a stack and not down from it.
     *
     * The channel calling this procedure is the one who generated the event,
     * and thus does not take part in handling it. IOW, its HandlerProc is not
     * called, instead we begin with the channel above it.
     *
     * This behaviour also allows the transformation channels to generate
     * their own events and pass them upward.
     */

    while (mask && (chanPtr->upChanPtr != NULL)) {
	Tcl_DriverHandlerProc *upHandlerProc;

	upChanPtr = chanPtr->upChanPtr;
	upTypePtr = upChanPtr->typePtr;
	upHandlerProc = Tcl_ChannelHandlerProc(upTypePtr);
	if (upHandlerProc != NULL) {
	    mask = upHandlerProc(upChanPtr->instanceData, mask);
	}

	/*
	 * ELSE: Ignore transformations which are unable to handle the event
	 * coming from below. Assume that they don't change the mask and pass
	 * it on.
	 */

	chanPtr = upChanPtr;
    }

    channel = (Tcl_Channel) chanPtr;

    /*
     * Here we have either reached the top of the stack or the mask is empty.
     * We break out of the procedure if it is the latter.
     */

    if (!mask) {
	return;
    }

    /*
     * We are now above the topmost channel in a stack and have events left.
     * Now call the channel handlers as usual.
     *
     * Preserve the channel struct in case the script closes it.
     */

    Tcl_Preserve(channel);
    Tcl_Preserve(statePtr);

    /*
     * If we are flushing in the background, be sure to call FlushChannel for
     * writable events. Note that we have to discard the writable event so we
     * don't call any write handlers before the flush is complete.
     */

    if (GotFlag(statePtr, BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
	FlushChannel(NULL, chanPtr, 1);
	mask &= ~TCL_WRITABLE;
    }

    /*
     * Add this invocation to the list of recursive invocations of
     * ChannelHandlerEventProc.
     */

    nh.nextHandlerPtr = NULL;
    nh.nestedHandlerPtr = tsdPtr->nestedHandlerPtr;
    tsdPtr->nestedHandlerPtr = &nh;

    for (chPtr = statePtr->chPtr; chPtr != NULL; ) {
	/*
	 * If this channel handler is interested in any of the events that
	 * have occurred on the channel, invoke its procedure.
	 */

	if ((chPtr->mask & mask) != 0) {
	    nh.nextHandlerPtr = chPtr->nextPtr;
	    chPtr->proc(chPtr->clientData, mask);
	    chPtr = nh.nextHandlerPtr;
	} else {
	    chPtr = chPtr->nextPtr;
	}
    }

    /*
     * Update the notifier interest, since it may have changed after invoking
     * event handlers. Skip that if the channel was deleted in the call to the
     * channel handler.
     */

    if (chanPtr->typePtr != NULL) {
	UpdateInterest(chanPtr);
    }

    Tcl_Release(statePtr);
    Tcl_Release(channel);

    tsdPtr->nestedHandlerPtr = nh.nestedHandlerPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateInterest --
 *
 *	Arrange for the notifier to call us back at appropriate times based on
 *	the current state of the channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May schedule a timer or driver handler.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateInterest(
    Channel *chanPtr)		/* Channel to update. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int mask = statePtr->interestMask;

    /*
     * If there are flushed buffers waiting to be written, then we need to
     * watch for the channel to become writable.
     */

    if (GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	mask |= TCL_WRITABLE;
    }

    /*
     * If there is data in the input queue, and we aren't waiting for more
     * data, then we need to schedule a timer so we don't block in the
     * notifier. Also, cancel the read interest so we don't get duplicate
     * events.
     */

    if (mask & TCL_READABLE) {
	if (!GotFlag(statePtr, CHANNEL_NEED_MORE_DATA)
		&& (statePtr->inQueueHead != NULL)
		&& IsBufferReady(statePtr->inQueueHead)) {
	    mask &= ~TCL_READABLE;

	    /*
	     * Andreas Kupries, April 11, 2003
	     *
	     * Some operating systems (Solaris 2.6 and higher (but not Solaris
	     * 2.5, go figure)) generate READABLE and EXCEPTION events when
	     * select()'ing [*] on a plain file, even if EOF was not yet
	     * reached. This is a problem in the following situation:
	     *
	     * - An extension asks to get both READABLE and EXCEPTION events.
	     * - It reads data into a buffer smaller than the buffer used by
	     *	 Tcl itself.
	     * - It does not process all events in the event queue, but only
	     *	 one, at least in some situations.
	     *
	     * In that case we can get into a situation where
	     *
	     * - Tcl drops READABLE here, because it has data in its own
	     *	 buffers waiting to be read by the extension.
	     * - A READABLE event is syntesized via timer.
	     * - The OS still reports the EXCEPTION condition on the file.
	     * - And the extension gets the EXCPTION event first, and handles
	     *	 this as EOF.
	     *
	     * End result ==> Premature end of reading from a file.
	     *
	     * The concrete example is 'Expect', and its [expect] command
	     * (and at the C-level, deep in the bowels of Expect,
	     * 'exp_get_next_event'. See marker 'SunOS' for commentary in
	     * that function too).
	     *
	     * [*] As the Tcl notifier does. See also for marker 'SunOS' in
	     * file 'exp_event.c' of Expect.
	     *
	     * Our solution here is to drop the interest in the EXCEPTION
	     * events too. This compiles on all platforms, and also passes the
	     * testsuite on all of them.
	     */

	    mask &= ~TCL_EXCEPTION;

	    if (!statePtr->timer) {
		statePtr->timer = Tcl_CreateTimerHandler(0, ChannelTimerProc,
			chanPtr);
	    }
	}
    }
    ChanWatch(chanPtr, mask);
}

/*
 *----------------------------------------------------------------------
 *
 * ChannelTimerProc --
 *
 *	Timer handler scheduled by UpdateInterest to monitor the channel
 *	buffers until they are empty.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May invoke channel handlers.
 *
 *----------------------------------------------------------------------
 */

static void
ChannelTimerProc(
    ClientData clientData)
{
    Channel *chanPtr = clientData;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    if (!GotFlag(statePtr, CHANNEL_NEED_MORE_DATA)
	    && (statePtr->interestMask & TCL_READABLE)
	    && (statePtr->inQueueHead != NULL)
	    && IsBufferReady(statePtr->inQueueHead)) {
	/*
	 * Restart the timer in case a channel handler reenters the event loop
	 * before UpdateInterest gets called by Tcl_NotifyChannel.
	 */

	statePtr->timer = Tcl_CreateTimerHandler(0, ChannelTimerProc,chanPtr);

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
	/*
	 * Set the TIMER flag to notify the higher levels that the driver
	 * might have no data for us. We do this only if we are in
	 * non-blocking mode and the driver has no BlockModeProc because only
	 * then we really don't know if the driver will block or not. A
	 * similar test is done in "PeekAhead".
	 */

	if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
		(Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL)) {
	    SetFlag(statePtr, CHANNEL_TIMER_FEV);
	}
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */

	Tcl_Preserve(statePtr);
	Tcl_NotifyChannel((Tcl_Channel)chanPtr, TCL_READABLE);

#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
	ResetFlag(statePtr, CHANNEL_TIMER_FEV);
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */

	Tcl_Release(statePtr);
    } else {
	statePtr->timer = NULL;
	UpdateInterest(chanPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateChannelHandler --
 *
 *	Arrange for a given procedure to be invoked whenever the channel
 *	indicated by the chanPtr arg becomes readable or writable.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	From now on, whenever the I/O channel given by chanPtr becomes ready
 *	in the way indicated by mask, proc will be invoked. See the manual
 *	entry for details on the calling sequence to proc. If there is already
 *	an event handler for chan, proc and clientData, then the mask will be
 *	updated.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateChannelHandler(
    Tcl_Channel chan,		/* The channel to create the handler for. */
    int mask,			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, and TCL_EXCEPTION: indicates
				 * conditions under which proc should be
				 * called. Use 0 to disable a registered
				 * handler. */
    Tcl_ChannelProc *proc,	/* Procedure to call for each selected
				 * event. */
    ClientData clientData)	/* Arbitrary data to pass to proc. */
{
    ChannelHandler *chPtr;
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    /*
     * Check whether this channel handler is not already registered. If it is
     * not, create a new record, else reuse existing record (smash current
     * values).
     */

    for (chPtr = statePtr->chPtr; chPtr != NULL; chPtr = chPtr->nextPtr) {
	if ((chPtr->chanPtr == chanPtr) && (chPtr->proc == proc) &&
		(chPtr->clientData == clientData)) {
	    break;
	}
    }
    if (chPtr == NULL) {
	chPtr = (ChannelHandler *) ckalloc(sizeof(ChannelHandler));
	chPtr->mask = 0;
	chPtr->proc = proc;
	chPtr->clientData = clientData;
	chPtr->chanPtr = chanPtr;
	chPtr->nextPtr = statePtr->chPtr;
	statePtr->chPtr = chPtr;
    }

    /*
     * The remainder of the initialization below is done regardless of whether
     * or not this is a new record or a modification of an old one.
     */

    chPtr->mask = mask;

    /*
     * Recompute the interest mask for the channel - this call may actually be
     * disabling an existing handler.
     */

    statePtr->interestMask = 0;
    for (chPtr = statePtr->chPtr; chPtr != NULL; chPtr = chPtr->nextPtr) {
	statePtr->interestMask |= chPtr->mask;
    }

    UpdateInterest(statePtr->topChanPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteChannelHandler --
 *
 *	Cancel a previously arranged callback arrangement for an IO channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered for this chan, proc and
 *	clientData, it is removed and the callback will no longer be called
 *	when the channel becomes ready for IO.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteChannelHandler(
    Tcl_Channel chan,		/* The channel for which to remove the
				 * callback. */
    Tcl_ChannelProc *proc,	/* The procedure in the callback to delete. */
    ClientData clientData)	/* The client data in the callback to
				 * delete. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelHandler *chPtr, *prevChPtr;
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    NextChannelHandler *nhPtr;

    /*
     * Find the entry and the previous one in the list.
     */

    for (prevChPtr = NULL, chPtr = statePtr->chPtr; chPtr != NULL;
	    chPtr = chPtr->nextPtr) {
	if ((chPtr->chanPtr == chanPtr) && (chPtr->clientData == clientData)
		&& (chPtr->proc == proc)) {
	    break;
	}
	prevChPtr = chPtr;
    }

    /*
     * If not found, return without doing anything.
     */

    if (chPtr == NULL) {
	return;
    }

    /*
     * If ChannelHandlerEventProc is about to process this handler, tell it to
     * process the next one instead - we are going to delete *this* one.
     */

    for (nhPtr = tsdPtr->nestedHandlerPtr; nhPtr != NULL;
	    nhPtr = nhPtr->nestedHandlerPtr) {
	if (nhPtr->nextHandlerPtr == chPtr) {
	    nhPtr->nextHandlerPtr = chPtr->nextPtr;
	}
    }

    /*
     * Splice it out of the list of channel handlers.
     */

    if (prevChPtr == NULL) {
	statePtr->chPtr = chPtr->nextPtr;
    } else {
	prevChPtr->nextPtr = chPtr->nextPtr;
    }
    ckfree((char *) chPtr);

    /*
     * Recompute the interest list for the channel, so that infinite loops
     * will not result if Tcl_DeleteChannelHandler is called inside an event.
     */

    statePtr->interestMask = 0;
    for (chPtr = statePtr->chPtr; chPtr != NULL; chPtr = chPtr->nextPtr) {
	statePtr->interestMask |= chPtr->mask;
    }

    UpdateInterest(statePtr->topChanPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteScriptRecord --
 *
 *	Delete a script record for this combination of channel, interp and
 *	mask.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Deletes a script record and cancels a channel event handler.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteScriptRecord(
    Tcl_Interp *interp,		/* Interpreter in which script was to be
				 * executed. */
    Channel *chanPtr,		/* The channel for which to delete the script
				 * record (if any). */
    int mask)			/* Events in mask must exactly match mask of
				 * script to delete. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    EventScriptRecord *esPtr, *prevEsPtr;

    for (esPtr = statePtr->scriptRecordPtr, prevEsPtr = NULL; esPtr != NULL;
	    prevEsPtr = esPtr, esPtr = esPtr->nextPtr) {
	if ((esPtr->interp == interp) && (esPtr->mask == mask)) {
	    if (esPtr == statePtr->scriptRecordPtr) {
		statePtr->scriptRecordPtr = esPtr->nextPtr;
	    } else {
		prevEsPtr->nextPtr = esPtr->nextPtr;
	    }

	    Tcl_DeleteChannelHandler((Tcl_Channel) chanPtr,
		    TclChannelEventScriptInvoker, esPtr);

	    TclDecrRefCount(esPtr->scriptPtr);
	    ckfree((char *) esPtr);

	    break;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * CreateScriptRecord --
 *
 *	Creates a record to store a script to be executed when a specific
 *	event fires on a specific channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Causes the script to be stored for later execution.
 *
 *----------------------------------------------------------------------
 */

static void
CreateScriptRecord(
    Tcl_Interp *interp,		/* Interpreter in which to execute the stored
				 * script. */
    Channel *chanPtr,		/* Channel for which script is to be stored */
    int mask,			/* Set of events for which script will be
				 * invoked. */
    Tcl_Obj *scriptPtr)		/* Pointer to script object. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    EventScriptRecord *esPtr;

    for (esPtr=statePtr->scriptRecordPtr; esPtr!=NULL; esPtr=esPtr->nextPtr) {
	if ((esPtr->interp == interp) && (esPtr->mask == mask)) {
	    TclDecrRefCount(esPtr->scriptPtr);
	    esPtr->scriptPtr = NULL;
	    break;
	}
    }
    if (esPtr == NULL) {
	esPtr = (EventScriptRecord *) ckalloc(sizeof(EventScriptRecord));
	Tcl_CreateChannelHandler((Tcl_Channel) chanPtr, mask,
		TclChannelEventScriptInvoker, esPtr);
	esPtr->nextPtr = statePtr->scriptRecordPtr;
	statePtr->scriptRecordPtr = esPtr;
    }
    esPtr->chanPtr = chanPtr;
    esPtr->interp = interp;
    esPtr->mask = mask;
    Tcl_IncrRefCount(scriptPtr);
    esPtr->scriptPtr = scriptPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclChannelEventScriptInvoker --
 *
 *	Invokes a script scheduled by "fileevent" for when the channel becomes
 *	ready for IO. This function is invoked by the channel handler which
 *	was created by the Tcl "fileevent" command.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Whatever the script does.
 *
 *----------------------------------------------------------------------
 */

void
TclChannelEventScriptInvoker(
    ClientData clientData,	/* The script+interp record. */
    int mask)			/* Not used. */
{
    Tcl_Interp *interp;		/* Interpreter in which to eval the script. */
    Channel *chanPtr;		/* The channel for which this handler is
				 * registered. */
    EventScriptRecord *esPtr;	/* The event script + interpreter to eval it
				 * in. */
    int result;			/* Result of call to eval script. */

    esPtr = clientData;
    chanPtr = esPtr->chanPtr;
    mask = esPtr->mask;
    interp = esPtr->interp;

    /*
     * We must preserve the interpreter so we can report errors on it later.
     * Note that we do not need to preserve the channel because that is done
     * by Tcl_NotifyChannel before calling channel handlers.
     */

    Tcl_Preserve(interp);
    result = Tcl_EvalObjEx(interp, esPtr->scriptPtr, TCL_EVAL_GLOBAL);

    /*
     * On error, cause a background error and remove the channel handler and
     * the script record.
     *
     * NOTE: Must delete channel handler before causing the background error
     * because the background error may want to reinstall the handler.
     */

    if (result != TCL_OK) {
	if (chanPtr->typePtr != NULL) {
	    DeleteScriptRecord(interp, chanPtr, mask);
	}
	Tcl_BackgroundException(interp, result);
    }
    Tcl_Release(interp);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FileEventObjCmd --
 *
 *	This procedure implements the "fileevent" Tcl command. See the user
 *	documentation for details on what it does. This command is based on
 *	the Tk command "fileevent" which in turn is based on work contributed
 *	by Mark Diekhans.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	May create a channel handler for the specified channel.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
int
Tcl_FileEventObjCmd(
    ClientData clientData,	/* Not used. */
    Tcl_Interp *interp,		/* Interpreter in which the channel for which
				 * to create the handler is found. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    Channel *chanPtr;		/* The channel to create the handler for. */
    ChannelState *statePtr;	/* State info for channel */
    Tcl_Channel chan;		/* The opaque type for the channel. */
    char *chanName;
    int modeIndex;		/* Index of mode argument. */
    int mask;
    static const char *const modeOptions[] = {"readable", "writable", NULL};
    static int maskArray[] = {TCL_READABLE, TCL_WRITABLE};

    if ((objc != 3) && (objc != 4)) {
	Tcl_WrongNumArgs(interp, 1, objv, "channelId event ?script?");
	return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[2], modeOptions, "event name", 0,
	    &modeIndex) != TCL_OK) {
	return TCL_ERROR;
    }
    mask = maskArray[modeIndex];

    chanName = TclGetString(objv[1]);
    chan = Tcl_GetChannel(interp, chanName, NULL);
    if (chan == NULL) {
	return TCL_ERROR;
    }
    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;
    if ((statePtr->flags & mask) == 0) {
	Tcl_AppendResult(interp, "channel is not ",
		(mask == TCL_READABLE) ? "readable" : "writable", NULL);
	return TCL_ERROR;
    }

    /*
     * If we are supposed to return the script, do so.
     */

    if (objc == 3) {
	EventScriptRecord *esPtr;

	for (esPtr = statePtr->scriptRecordPtr; esPtr != NULL;
		esPtr = esPtr->nextPtr) {
	    if ((esPtr->interp == interp) && (esPtr->mask == mask)) {
		Tcl_SetObjResult(interp, esPtr->scriptPtr);
		break;
	    }
	}
	return TCL_OK;
    }

    /*
     * If we are supposed to delete a stored script, do so.
     */

    if (*(TclGetString(objv[3])) == '\0') {
	DeleteScriptRecord(interp, chanPtr, mask);
	return TCL_OK;
    }

    /*
     * Make the script record that will link between the event and the script
     * to invoke. This also creates a channel event handler which will
     * evaluate the script in the supplied interpreter.
     */

    CreateScriptRecord(interp, chanPtr, mask, objv[3]);

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclCopyChannel --
 *
 *	This routine copies data from one channel to another, either
 *	synchronously or asynchronously. If a command script is supplied, the
 *	operation runs in the background. The script is invoked when the copy
 *	completes. Otherwise the function waits until the copy is completed
 *	before returning.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	May schedule a background copy operation that causes both channels to
 *	be marked busy.
 *
 *----------------------------------------------------------------------
 */

int
TclCopyChannel(
    Tcl_Interp *interp,		/* Current interpreter. */
    Tcl_Channel inChan,		/* Channel to read from. */
    Tcl_Channel outChan,	/* Channel to write to. */
    int toRead,			/* Amount of data to copy, or -1 for all. */
    Tcl_Obj *cmdPtr)		/* Pointer to script to execute or NULL. */
{
    Channel *inPtr = (Channel *) inChan;
    Channel *outPtr = (Channel *) outChan;
    ChannelState *inStatePtr, *outStatePtr;
    int readFlags, writeFlags;
    CopyState *csPtr;
    int nonBlocking = (cmdPtr) ? CHANNEL_NONBLOCKING : 0;

    inStatePtr = inPtr->state;
    outStatePtr = outPtr->state;

    if (BUSY_STATE(inStatePtr,TCL_READABLE)) {
	if (interp) {
	    Tcl_AppendResult(interp, "channel \"",
		    Tcl_GetChannelName(inChan), "\" is busy", NULL);
	}
	return TCL_ERROR;
    }
    if (BUSY_STATE(outStatePtr,TCL_WRITABLE)) {
	if (interp) {
	    Tcl_AppendResult(interp, "channel \"",
		    Tcl_GetChannelName(outChan), "\" is busy", NULL);
	}
	return TCL_ERROR;
    }

    readFlags = inStatePtr->flags;
    writeFlags = outStatePtr->flags;

    /*
     * Set up the blocking mode appropriately. Background copies need
     * non-blocking channels. Foreground copies need blocking channels. If
     * there is an error, restore the old blocking mode.
     */

    if (nonBlocking != (readFlags & CHANNEL_NONBLOCKING)) {
	if (SetBlockMode(interp, inPtr, nonBlocking ?
		TCL_MODE_NONBLOCKING : TCL_MODE_BLOCKING) != TCL_OK) {
	    return TCL_ERROR;
	}
    }
    if ((inPtr!=outPtr) && (nonBlocking!=(writeFlags&CHANNEL_NONBLOCKING)) &&
	    (SetBlockMode(NULL, outPtr, nonBlocking ?
		    TCL_MODE_NONBLOCKING : TCL_MODE_BLOCKING) != TCL_OK) &&
	    (nonBlocking != (readFlags & CHANNEL_NONBLOCKING))) {
	SetBlockMode(NULL, inPtr, (readFlags & CHANNEL_NONBLOCKING)
		? TCL_MODE_NONBLOCKING : TCL_MODE_BLOCKING);
	return TCL_ERROR;
    }

    /*
     * Make sure the output side is unbuffered.
     */

    outStatePtr->flags = (outStatePtr->flags & ~CHANNEL_LINEBUFFERED)
	    | CHANNEL_UNBUFFERED;

    /*
     * Allocate a new CopyState to maintain info about the current copy in
     * progress. This structure will be deallocated when the copy is
     * completed.
     */

    csPtr = (CopyState *) ckalloc(sizeof(CopyState) + inStatePtr->bufSize);
    csPtr->bufSize = inStatePtr->bufSize;
    csPtr->readPtr = inPtr;
    csPtr->writePtr = outPtr;
    csPtr->readFlags = readFlags;
    csPtr->writeFlags = writeFlags;
    csPtr->toRead = toRead;
    csPtr->total = 0;
    csPtr->interp = interp;
    if (cmdPtr) {
	Tcl_IncrRefCount(cmdPtr);
    }
    csPtr->cmdPtr = cmdPtr;

    inStatePtr->csPtrR  = csPtr;
    outStatePtr->csPtrW = csPtr;

    /*
     * Start copying data between the channels.
     */

    return CopyData(csPtr, 0);
}

/*
 *----------------------------------------------------------------------
 *
 * CopyData --
 *
 *	This function implements the lowest level of the copying mechanism for
 *	TclCopyChannel.
 *
 * Results:
 *	Returns TCL_OK on success, else TCL_ERROR.
 *
 * Side effects:
 *	Moves data between channels, may create channel handlers.
 *
 *----------------------------------------------------------------------
 */

static int
CopyData(
    CopyState *csPtr,		/* State of copy operation. */
    int mask)			/* Current channel event flags. */
{
    Tcl_Interp *interp;
    Tcl_Obj *cmdPtr, *errObj = NULL, *bufObj = NULL, *msg = NULL;
    Tcl_Channel inChan, outChan;
    ChannelState *inStatePtr, *outStatePtr;
    int result = TCL_OK, size, total, sizeb;
    char *buffer;
    int inBinary, outBinary, sameEncoding;
				/* Encoding control */
    int underflow;		/* Input underflow */

    inChan	= (Tcl_Channel) csPtr->readPtr;
    outChan	= (Tcl_Channel) csPtr->writePtr;
    inStatePtr	= csPtr->readPtr->state;
    outStatePtr	= csPtr->writePtr->state;
    interp	= csPtr->interp;
    cmdPtr	= csPtr->cmdPtr;

    /*
     * Copy the data the slow way, using the translation mechanism.
     *
     * Note: We have make sure that we use the topmost channel in a stack for
     * the copying. The caller uses Tcl_GetChannel to access it, and thus gets
     * the bottom of the stack.
     */

    inBinary = (inStatePtr->encoding == NULL);
    outBinary = (outStatePtr->encoding == NULL);
    sameEncoding = (inStatePtr->encoding == outStatePtr->encoding);

    if (!(inBinary || sameEncoding)) {
	TclNewObj(bufObj);
	Tcl_IncrRefCount(bufObj);
    }

    while (csPtr->toRead != 0) {
	/*
	 * Check for unreported background errors.
	 */

	Tcl_GetChannelError(inChan, &msg);
	if ((inStatePtr->unreportedError != 0) || (msg != NULL)) {
	    Tcl_SetErrno(inStatePtr->unreportedError);
	    inStatePtr->unreportedError = 0;
	    goto readError;
	}
	Tcl_GetChannelError(outChan, &msg);
	if ((outStatePtr->unreportedError != 0) || (msg != NULL)) {
	    Tcl_SetErrno(outStatePtr->unreportedError);
	    outStatePtr->unreportedError = 0;
	    goto writeError;
	}

	if (cmdPtr && (mask == 0)) {
	    /*
	     * In async mode, we skip reading synchronously and fake an
	     * underflow instead to prime the readable fileevent.
	     */

	    size = 0;
	    underflow = 1;
	} else {
	    /*
	     * Read up to bufSize bytes.
	     */

	    if ((csPtr->toRead == -1) || (csPtr->toRead > csPtr->bufSize)) {
		sizeb = csPtr->bufSize;
	    } else {
		sizeb = csPtr->toRead;
	    }

	    if (inBinary || sameEncoding) {
		size = DoRead(inStatePtr->topChanPtr, csPtr->buffer, sizeb);
	    } else {
		size = DoReadChars(inStatePtr->topChanPtr, bufObj, sizeb,
				   0 /* No append */);
	    }
	    underflow = (size >= 0) && (size < sizeb);	/* Input underflow */
	}

	if (size < 0) {
	readError:
	    if (interp) {
		TclNewObj(errObj);
		Tcl_AppendStringsToObj(errObj, "error reading \"",
			Tcl_GetChannelName(inChan), "\": ", NULL);
		if (msg != NULL) {
		    Tcl_AppendObjToObj(errObj, msg);
		} else {
		    Tcl_AppendStringsToObj(errObj, Tcl_PosixError(interp),
			    NULL);
		}
	    }
	    if (msg != NULL) {
		Tcl_DecrRefCount(msg);
	    }
	    break;
	} else if (underflow) {
	    /*
	     * We had an underflow on the read side. If we are at EOF, and not
	     * in the synchronous part of an asynchronous fcopy, then the
	     * copying is done, otherwise set up a channel handler to detect
	     * when the channel becomes readable again.
	     */

	    if ((size == 0) && Tcl_Eof(inChan) && !(cmdPtr && (mask == 0))) {
		break;
	    }
	    if (((!Tcl_Eof(inChan)) || (cmdPtr && (mask == 0))) &&
		!(mask & TCL_READABLE)) {
		if (mask & TCL_WRITABLE) {
		    Tcl_DeleteChannelHandler(outChan, CopyEventProc, csPtr);
		}
		Tcl_CreateChannelHandler(inChan, TCL_READABLE, CopyEventProc,
			csPtr);
	    }
	    if (size == 0) {
		if (bufObj != NULL) {
		    TclDecrRefCount(bufObj);
		    bufObj = NULL;
		}
		return TCL_OK;
	    }
	}

	/*
	 * Now write the buffer out.
	 */

	if (inBinary || sameEncoding) {
	    buffer = csPtr->buffer;
	    sizeb = size;
	} else {
	    buffer = TclGetStringFromObj(bufObj, &sizeb);
	}

	if (outBinary || sameEncoding) {
	    sizeb = DoWrite(outStatePtr->topChanPtr, buffer, sizeb);
	} else {
	    sizeb = DoWriteChars(outStatePtr->topChanPtr, buffer, sizeb);
	}

	if (inBinary || sameEncoding) {
	    /*
	     * Both read and write counted bytes.
	     */

	    size = sizeb;
	} /* else: Read counted characters, write counted bytes, i.e.
	   * size != sizeb */

	if (sizeb < 0) {
	writeError:
	    if (interp) {
		TclNewObj(errObj);
		Tcl_AppendStringsToObj(errObj, "error writing \"",
			Tcl_GetChannelName(outChan), "\": ", NULL);
		if (msg != NULL) {
		    Tcl_AppendObjToObj(errObj, msg);
		} else {
		    Tcl_AppendStringsToObj(errObj, Tcl_PosixError(interp),
			    NULL);
		}
	    }
	    if (msg != NULL) {
		Tcl_DecrRefCount(msg);
	    }
	    break;
	}

	/*
	 * Update the current byte count. Do it now so the count is valid
	 * before a return or break takes us out of the loop. The invariant at
	 * the top of the loop should be that csPtr->toRead holds the number
	 * of bytes left to copy.
	 */

	if (csPtr->toRead != -1) {
	    csPtr->toRead -= size;
	}
	csPtr->total += size;

	/*
	 * Break loop if EOF && (size>0)
	 */

	if (Tcl_Eof(inChan)) {
	    break;
	}

	/*
	 * Check to see if the write is happening in the background. If so,
	 * stop copying and wait for the channel to become writable again.
	 * After input underflow we already installed a readable handler
	 * therefore we don't need a writable handler.
	 */

	if (!underflow && GotFlag(outStatePtr, BG_FLUSH_SCHEDULED)) {
	    if (!(mask & TCL_WRITABLE)) {
		if (mask & TCL_READABLE) {
		    Tcl_DeleteChannelHandler(inChan, CopyEventProc, csPtr);
		}
		Tcl_CreateChannelHandler(outChan, TCL_WRITABLE,
			CopyEventProc, csPtr);
	    }
	    if (bufObj != NULL) {
		TclDecrRefCount(bufObj);
		bufObj = NULL;
	    }
	    return TCL_OK;
	}

	/*
	 * For background copies, we only do one buffer per invocation so we
	 * don't starve the rest of the system.
	 */

	if (cmdPtr && (csPtr->toRead != 0)) {
	    /*
	     * The first time we enter this code, there won't be a channel
	     * handler established yet, so do it here.
	     */

	    if (mask == 0) {
		Tcl_CreateChannelHandler(outChan, TCL_WRITABLE, CopyEventProc,
			csPtr);
	    }
	    if (bufObj != NULL) {
		TclDecrRefCount(bufObj);
		bufObj = NULL;
	    }
	    return TCL_OK;
	}
    } /* while */

    if (bufObj != NULL) {
	TclDecrRefCount(bufObj);
	bufObj = NULL;
    }

    /*
     * Make the callback or return the number of bytes transferred. The local
     * total is used because StopCopy frees csPtr.
     */

    total = csPtr->total;
    if (cmdPtr && interp) {
	int code;

	/*
	 * Get a private copy of the command so we can mutate it by adding
	 * arguments. Note that StopCopy frees our saved reference to the
	 * original command obj.
	 */

	cmdPtr = Tcl_DuplicateObj(cmdPtr);
	Tcl_IncrRefCount(cmdPtr);
	StopCopy(csPtr);
	Tcl_Preserve(interp);

	Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewIntObj(total));
	if (errObj) {
	    Tcl_ListObjAppendElement(interp, cmdPtr, errObj);
	}
	code = Tcl_EvalObjEx(interp, cmdPtr, TCL_EVAL_GLOBAL);
	if (code != TCL_OK) {
	    Tcl_BackgroundException(interp, code);
	    result = TCL_ERROR;
	}
	TclDecrRefCount(cmdPtr);
	Tcl_Release(interp);
    } else {
	StopCopy(csPtr);
	if (interp) {
	    if (errObj) {
		Tcl_SetObjResult(interp, errObj);
		result = TCL_ERROR;
	    } else {
		Tcl_ResetResult(interp);
		Tcl_SetObjResult(interp, Tcl_NewIntObj(total));
	    }
	}
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * DoRead --
 *
 *	Reads a given number of bytes from a channel.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of characters read, or -1 on error. Use Tcl_GetErrno() to
 *	retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *----------------------------------------------------------------------
 */

static int
DoRead(
    Channel *chanPtr,		/* The channel from which to read. */
    char *bufPtr,		/* Where to store input read. */
    int toRead)			/* Maximum number of bytes to read. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    int copied;			/* How many characters were copied into the
				 * result string? */
    int copiedNow;		/* How many characters were copied from the
				 * current input buffer? */
    int result;			/* Of calling GetInput. */

    /*
     * If we have not encountered a sticky EOF, clear the EOF bit. Either way
     * clear the BLOCKED bit. We want to discover these anew during each
     * operation.
     */

    if (!GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
	ResetFlag(statePtr, CHANNEL_EOF);
    }
    ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);

    for (copied = 0; copied < toRead; copied += copiedNow) {
	copiedNow = CopyAndTranslateBuffer(statePtr, bufPtr + copied,
		toRead - copied);
	if (copiedNow == 0) {
	    if (GotFlag(statePtr, CHANNEL_EOF)) {
		goto done;
	    }
	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
		    goto done;
		}
		ResetFlag(statePtr, CHANNEL_BLOCKED);
	    }
	    result = GetInput(chanPtr);
	    if (result != 0) {
		if (result != EAGAIN) {
		    copied = -1;
		}
		goto done;
	    }
	}
    }

    ResetFlag(statePtr, CHANNEL_BLOCKED);

    /*
     * Update the notifier state so we don't block while there is still data
     * in the buffers.
     */

  done:
    UpdateInterest(chanPtr);
    return copied;
}

/*
 *----------------------------------------------------------------------
 *
 * CopyAndTranslateBuffer --
 *
 *	Copy at most one buffer of input to the result space, doing eol
 *	translations according to mode in effect currently.
 *
 * Results:
 *	Number of bytes stored in the result buffer (as opposed to the number
 *	of bytes read from the channel). May return zero if no input is
 *	available to be translated.
 *
 * Side effects:
 *	Consumes buffered input. May deallocate one buffer.
 *
 *----------------------------------------------------------------------
 */

static int
CopyAndTranslateBuffer(
    ChannelState *statePtr,	/* Channel state from which to read input. */
    char *result,		/* Where to store the copied input. */
    int space)			/* How many bytes are available in result to
				 * store the copied input? */
{
    ChannelBuffer *bufPtr;	/* The buffer from which to copy bytes. */
    int bytesInBuffer;		/* How many bytes are available to be copied
				 * in the current input buffer? */
    int copied;			/* How many characters were already copied
				 * into the destination space? */
    int i;			/* Iterates over the copied input looking for
				 * the input eofChar. */

    /*
     * If there is no input at all, return zero. The invariant is that either
     * there is no buffer in the queue, or if the first buffer is empty, it is
     * also the last buffer (and thus there is no input in the queue). Note
     * also that if the buffer is empty, we leave it in the queue.
     */

    if (statePtr->inQueueHead == NULL) {
	return 0;
    }
    bufPtr = statePtr->inQueueHead;
    bytesInBuffer = BytesLeft(bufPtr);

    copied = 0;
    switch (statePtr->inputTranslation) {
    case TCL_TRANSLATE_LF:
	if (bytesInBuffer == 0) {
	    return 0;
	}

	/*
	 * Copy the current chunk into the result buffer.
	 */

	if (bytesInBuffer < space) {
	    space = bytesInBuffer;
	}
	memcpy(result, RemovePoint(bufPtr), (size_t) space);
	bufPtr->nextRemoved += space;
	copied = space;
	break;
    case TCL_TRANSLATE_CR: {
	char *end;

	if (bytesInBuffer == 0) {
	    return 0;
	}

	/*
	 * Copy the current chunk into the result buffer, then replace all \r
	 * with \n.
	 */

	if (bytesInBuffer < space) {
	    space = bytesInBuffer;
	}
	memcpy(result, RemovePoint(bufPtr), (size_t) space);
	bufPtr->nextRemoved += space;
	copied = space;

	for (end = result + copied; result < end; result++) {
	    if (*result == '\r') {
		*result = '\n';
	    }
	}
	break;
    }
    case TCL_TRANSLATE_CRLF: {
	char *src, *end, *dst;
	int curByte;

	/*
	 * If there is a held-back "\r" at EOF, produce it now.
	 */

	if (bytesInBuffer == 0) {
	    if ((statePtr->flags & (INPUT_SAW_CR | CHANNEL_EOF)) ==
		    (INPUT_SAW_CR | CHANNEL_EOF)) {
		result[0] = '\r';
		ResetFlag(statePtr, INPUT_SAW_CR);
		return 1;
	    }
	    return 0;
	}

	/*
	 * Copy the current chunk and replace "\r\n" with "\n" (but not
	 * standalone "\r"!).
	 */

	if (bytesInBuffer < space) {
	    space = bytesInBuffer;
	}
	memcpy(result, RemovePoint(bufPtr), (size_t) space);
	bufPtr->nextRemoved += space;
	copied = space;

	end = result + copied;
	dst = result;
	for (src = result; src < end; src++) {
	    curByte = *src;
	    if (curByte == '\n') {
		ResetFlag(statePtr, INPUT_SAW_CR);
	    } else if (GotFlag(statePtr, INPUT_SAW_CR)) {
		ResetFlag(statePtr, INPUT_SAW_CR);
		*dst = '\r';
		dst++;
	    }
	    if (curByte == '\r') {
		SetFlag(statePtr, INPUT_SAW_CR);
	    } else {
		*dst = (char) curByte;
		dst++;
	    }
	}
	copied = dst - result;
	break;
    }
    case TCL_TRANSLATE_AUTO: {
	char *src, *end, *dst;
	int curByte;

	if (bytesInBuffer == 0) {
	    return 0;
	}

	/*
	 * Loop over the current buffer, converting "\r" and "\r\n" to "\n".
	 */

	if (bytesInBuffer < space) {
	    space = bytesInBuffer;
	}
	memcpy(result, RemovePoint(bufPtr), (size_t) space);
	bufPtr->nextRemoved += space;
	copied = space;

	end = result + copied;
	dst = result;
	for (src = result; src < end; src++) {
	    curByte = *src;
	    if (curByte == '\r') {
		SetFlag(statePtr, INPUT_SAW_CR);
		*dst = '\n';
		dst++;
	    } else {
		if ((curByte != '\n') || !GotFlag(statePtr, INPUT_SAW_CR)) {
		    *dst = (char) curByte;
		    dst++;
		}
		ResetFlag(statePtr, INPUT_SAW_CR);
	    }
	}
	copied = dst - result;
	break;
    }
    default:
	Tcl_Panic("unknown eol translation mode");
    }

    /*
     * If an in-stream EOF character is set for this channel, check that the
     * input we copied so far does not contain the EOF char. If it does, copy
     * only up to and excluding that character.
     */

    if (statePtr->inEofChar != 0) {
	for (i = 0; i < copied; i++) {
	    if (result[i] == (char) statePtr->inEofChar) {
		/*
		 * Set sticky EOF so that no further input is presented to the
		 * caller.
		 */

		SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
		statePtr->inputEncodingFlags |= TCL_ENCODING_END;
		copied = i;
		break;
	    }
	}
    }

    /*
     * If the current buffer is empty recycle it.
     */

    if (IsBufferEmpty(bufPtr)) {
	statePtr->inQueueHead = bufPtr->nextPtr;
	if (statePtr->inQueueHead == NULL) {
	    statePtr->inQueueTail = NULL;
	}
	RecycleBuffer(statePtr, bufPtr, 0);
    }

    /*
     * Return the number of characters copied into the result buffer. This may
     * be different from the number of bytes consumed, because of EOL
     * translations.
     */

    return copied;
}

/*
 *----------------------------------------------------------------------
 *
 * CopyBuffer --
 *
 *	Copy at most one buffer of input to the result space.
 *
 * Results:
 *	Number of bytes stored in the result buffer. May return zero if no
 *	input is available.
 *
 * Side effects:
 *	Consumes buffered input. May deallocate one buffer.
 *
 *----------------------------------------------------------------------
 */

static int
CopyBuffer(
    Channel *chanPtr,		/* Channel from which to read input. */
    char *result,		/* Where to store the copied input. */
    int space)			/* How many bytes are available in result to
				 * store the copied input? */
{
    ChannelBuffer *bufPtr;	/* The buffer from which to copy bytes. */
    int bytesInBuffer;		/* How many bytes are available to be copied
				 * in the current input buffer? */
    int copied;			/* How many characters were already copied
				 * into the destination space? */

    /*
     * If there is no input at all, return zero. The invariant is that either
     * there is no buffer in the queue, or if the first buffer is empty, it is
     * also the last buffer (and thus there is no input in the queue). Note
     * also that if the buffer is empty, we don't leave it in the queue, but
     * recycle it.
     */

    if (chanPtr->inQueueHead == NULL) {
	return 0;
    }
    bufPtr = chanPtr->inQueueHead;
    bytesInBuffer = BytesLeft(bufPtr);

    copied = 0;

    if (bytesInBuffer == 0) {
	RecycleBuffer(chanPtr->state, bufPtr, 0);
	chanPtr->inQueueHead = NULL;
	chanPtr->inQueueTail = NULL;
	return 0;
    }

    /*
     * Copy the current chunk into the result buffer.
     */

    if (bytesInBuffer < space) {
	space = bytesInBuffer;
    }

    memcpy(result, RemovePoint(bufPtr), (size_t) space);
    bufPtr->nextRemoved += space;
    copied = space;

    /*
     * We don't care about in-stream EOF characters here as the data read here
     * may still flow through one or more transformations, i.e. is not in its
     * final state yet.
     */

    /*
     * If the current buffer is empty recycle it.
     */

    if (IsBufferEmpty(bufPtr)) {
	chanPtr->inQueueHead = bufPtr->nextPtr;
	if (chanPtr->inQueueHead == NULL) {
	    chanPtr->inQueueTail = NULL;
	}
	RecycleBuffer(chanPtr->state, bufPtr, 0);
    }

    /*
     * Return the number of characters copied into the result buffer.
     */

    return copied;
}

/*
 *----------------------------------------------------------------------
 *
 * DoWrite --
 *
 *	Puts a sequence of characters into an output buffer, may queue the
 *	buffer for output if it gets full, and also remembers whether the
 *	current buffer is ready e.g. if it contains a newline and we are in
 *	line buffering mode.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

static int
DoWrite(
    Channel *chanPtr,		/* The channel to buffer output for. */
    const char *src,		/* Data to write. */
    int srcLen)			/* Number of bytes to write. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */
    ChannelBuffer *outBufPtr;	/* Current output buffer. */
    int foundNewline;		/* Did we find a newline in output? */
    char *dPtr;
    const char *sPtr;		/* Search variables for newline. */
    int crsent;			/* In CRLF eol translation mode, remember the
				 * fact that a CR was output to the channel
				 * without its following NL. */
    int i;			/* Loop index for newline search. */
    int destCopied;		/* How many bytes were used in this
				 * destination buffer to hold the output? */
    int totalDestCopied;	/* How many bytes total were copied to the
				 * channel buffer? */
    int srcCopied;		/* How many bytes were copied from the source
				 * string? */
    char *destPtr;		/* Where in line to copy to? */

    /*
     * If we are in network (or windows) translation mode, record the fact
     * that we have not yet sent a CR to the channel.
     */

    crsent = 0;

    /*
     * Loop filling buffers and flushing them until all output has been
     * consumed.
     */

    srcCopied = 0;
    totalDestCopied = 0;

    while (srcLen > 0) {
	/*
	 * Make sure there is a current output buffer to accept output.
	 */

	if (statePtr->curOutPtr == NULL) {
	    statePtr->curOutPtr = AllocChannelBuffer(statePtr->bufSize);
	}

	outBufPtr = statePtr->curOutPtr;

	destCopied = SpaceLeft(outBufPtr);
	if (destCopied > srcLen) {
	    destCopied = srcLen;
	}

	destPtr = InsertPoint(outBufPtr);
	switch (statePtr->outputTranslation) {
	case TCL_TRANSLATE_LF:
	    srcCopied = destCopied;
	    memcpy(destPtr, src, (size_t) destCopied);
	    break;
	case TCL_TRANSLATE_CR:
	    srcCopied = destCopied;
	    memcpy(destPtr, src, (size_t) destCopied);
	    for (dPtr = destPtr; dPtr < destPtr + destCopied; dPtr++) {
		if (*dPtr == '\n') {
		    *dPtr = '\r';
		}
	    }
	    break;
	case TCL_TRANSLATE_CRLF:
	    for (srcCopied = 0, dPtr = destPtr, sPtr = src;
		    dPtr < destPtr + destCopied;
		    dPtr++, sPtr++, srcCopied++) {
		if (*sPtr == '\n') {
		    if (crsent) {
			*dPtr = '\n';
			crsent = 0;
		    } else {
			*dPtr = '\r';
			crsent = 1;
			sPtr--, srcCopied--;
		    }
		} else {
		    *dPtr = *sPtr;
		}
	    }
	    break;
	case TCL_TRANSLATE_AUTO:
	    Tcl_Panic("Tcl_Write: AUTO output translation mode not supported");
	default:
	    Tcl_Panic("Tcl_Write: unknown output translation mode");
	}

	/*
	 * The current buffer is ready for output if it is full, or if it
	 * contains a newline and this channel is line-buffered, or if it
	 * contains any output and this channel is unbuffered.
	 */

	outBufPtr->nextAdded += destCopied;
	if (!GotFlag(statePtr, BUFFER_READY)) {
	    if (IsBufferFull(outBufPtr)) {
		SetFlag(statePtr, BUFFER_READY);
	    } else if (GotFlag(statePtr, CHANNEL_LINEBUFFERED)) {
		for (sPtr = src, i = 0, foundNewline = 0;
			(i < srcCopied) && (!foundNewline);
			i++, sPtr++) {
		    if (*sPtr == '\n') {
			foundNewline = 1;
			break;
		    }
		}
		if (foundNewline) {
		    SetFlag(statePtr, BUFFER_READY);
		}
	    } else if (GotFlag(statePtr, CHANNEL_UNBUFFERED)) {
		SetFlag(statePtr, BUFFER_READY);
	    }
	}

	totalDestCopied += srcCopied;
	src += srcCopied;
	srcLen -= srcCopied;

	if (GotFlag(statePtr, BUFFER_READY)) {
	    if (FlushChannel(NULL, chanPtr, 0) != 0) {
		return -1;
	    }
	}
    } /* Closes "while" */

    return totalDestCopied;
}

/*
 *----------------------------------------------------------------------
 *
 * CopyEventProc --
 *
 *	This routine is invoked as a channel event handler for the background
 *	copy operation. It is just a trivial wrapper around the CopyData
 *	routine.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
CopyEventProc(
    ClientData clientData,
    int mask)
{
    (void) CopyData((CopyState *) clientData, mask);
}

/*
 *----------------------------------------------------------------------
 *
 * StopCopy --
 *
 *	This routine halts a copy that is in progress.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes any pending channel handlers and restores the blocking and
 *	buffering modes of the channels. The CopyState is freed.
 *
 *----------------------------------------------------------------------
 */

static void
StopCopy(
    CopyState *csPtr)		/* State for bg copy to stop . */
{
    ChannelState *inStatePtr, *outStatePtr;
    int nonBlocking;

    if (!csPtr) {
	return;
    }

    inStatePtr = csPtr->readPtr->state;
    outStatePtr = csPtr->writePtr->state;

    /*
     * Restore the old blocking mode and output buffering mode.
     */

    nonBlocking = csPtr->readFlags & CHANNEL_NONBLOCKING;
    if (nonBlocking != (inStatePtr->flags & CHANNEL_NONBLOCKING)) {
	SetBlockMode(NULL, csPtr->readPtr,
		nonBlocking ? TCL_MODE_NONBLOCKING : TCL_MODE_BLOCKING);
    }
    if (csPtr->readPtr != csPtr->writePtr) {
	nonBlocking = csPtr->writeFlags & CHANNEL_NONBLOCKING;
	if (nonBlocking != (outStatePtr->flags & CHANNEL_NONBLOCKING)) {
	    SetBlockMode(NULL, csPtr->writePtr,
		    nonBlocking ? TCL_MODE_NONBLOCKING : TCL_MODE_BLOCKING);
	}
    }
    ResetFlag(outStatePtr, CHANNEL_LINEBUFFERED | CHANNEL_UNBUFFERED);
    outStatePtr->flags |=
	    csPtr->writeFlags & (CHANNEL_LINEBUFFERED | CHANNEL_UNBUFFERED);

    if (csPtr->cmdPtr) {
	Tcl_DeleteChannelHandler((Tcl_Channel) csPtr->readPtr, CopyEventProc,
		csPtr);
	if (csPtr->readPtr != csPtr->writePtr) {
	    Tcl_DeleteChannelHandler((Tcl_Channel) csPtr->writePtr,
		    CopyEventProc, csPtr);
	}
	TclDecrRefCount(csPtr->cmdPtr);
    }
    inStatePtr->csPtrR = NULL;
    outStatePtr->csPtrW = NULL;
    ckfree((char *) csPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * StackSetBlockMode --
 *
 *	This function sets the blocking mode for a channel, iterating through
 *	each channel in a stack and updates the state flags.
 *
 * Results:
 *	0 if OK, result code from failed blockModeProc otherwise.
 *
 * Side effects:
 *	Modifies the blocking mode of the channel and possibly generates an
 *	error.
 *
 *----------------------------------------------------------------------
 */

static int
StackSetBlockMode(
    Channel *chanPtr,		/* Channel to modify. */
    int mode)			/* One of TCL_MODE_BLOCKING or
				 * TCL_MODE_NONBLOCKING. */
{
    int result = 0;
    Tcl_DriverBlockModeProc *blockModeProc;

    /*
     * Start at the top of the channel stack
     */

    chanPtr = chanPtr->state->topChanPtr;
    while (chanPtr != NULL) {
	blockModeProc = Tcl_ChannelBlockModeProc(chanPtr->typePtr);
	if (blockModeProc != NULL) {
	    result = blockModeProc(chanPtr->instanceData, mode);
	    if (result != 0) {
		Tcl_SetErrno(result);
		return result;
	    }
	}
	chanPtr = chanPtr->downChanPtr;
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * SetBlockMode --
 *
 *	This function sets the blocking mode for a channel and updates the
 *	state flags.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Modifies the blocking mode of the channel and possibly generates an
 *	error.
 *
 *----------------------------------------------------------------------
 */

static int
SetBlockMode(
    Tcl_Interp *interp,		/* Interp for error reporting. */
    Channel *chanPtr,		/* Channel to modify. */
    int mode)			/* One of TCL_MODE_BLOCKING or
				 * TCL_MODE_NONBLOCKING. */
{
    int result = 0;
    ChannelState *statePtr = chanPtr->state;
				/* State info for channel */

    result = StackSetBlockMode(chanPtr, mode);
    if (result != 0) {
	if (interp != NULL) {
	    /*
	     * TIP #219.
	     * Move error messages put by the driver into the bypass area and
	     * put them into the regular interpreter result. Fall back to the
	     * regular message if nothing was found in the bypass.
	     *
	     * Note that we cannot have a message in the interpreter bypass
	     * area, StackSetBlockMode is restricted to the channel bypass.
	     * We still need the interp as the destination of the move.
	     */

	    if (!TclChanCaughtErrorBypass(interp, (Tcl_Channel) chanPtr)) {
		Tcl_AppendResult(interp, "error setting blocking mode: ",
			Tcl_PosixError(interp), NULL);
	    }
	} else {
	    /*
	     * TIP #219.
	     * If we have no interpreter to put a bypass message into we have
	     * to clear it, to prevent its propagation and use in other places
	     * unrelated to the actual occurence of the problem.
	     */

	    Tcl_SetChannelError((Tcl_Channel) chanPtr, NULL);
	}
	return TCL_ERROR;
    }
    if (mode == TCL_MODE_BLOCKING) {
	ResetFlag(statePtr, CHANNEL_NONBLOCKING | BG_FLUSH_SCHEDULED);
    } else {
	SetFlag(statePtr, CHANNEL_NONBLOCKING);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelNames --
 *
 *	Return the names of all open channels in the interp.
 *
 * Results:
 *	TCL_OK or TCL_ERROR.
 *
 * Side effects:
 *	Interp result modified with list of channel names.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelNames(
    Tcl_Interp *interp)		/* Interp for error reporting. */
{
    return Tcl_GetChannelNamesEx(interp, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelNamesEx --
 *
 *	Return the names of open channels in the interp filtered filtered
 *	through a pattern. If pattern is NULL, it returns all the open
 *	channels.
 *
 * Results:
 *	TCL_OK or TCL_ERROR.
 *
 * Side effects:
 *	Interp result modified with list of channel names.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelNamesEx(
    Tcl_Interp *interp,		/* Interp for error reporting. */
    const char *pattern)	/* Pattern to filter on. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ChannelState *statePtr;
    const char *name;		/* Name for channel */
    Tcl_Obj *resultPtr;		/* Pointer to result object */
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Tcl_HashSearch hSearch;	/* Search variable. */

    if (interp == NULL) {
	return TCL_OK;
    }

    /*
     * Get the channel table that stores the channels registered for this
     * interpreter.
     */

    hTblPtr = GetChannelTable(interp);
    TclNewObj(resultPtr);
    if ((pattern != NULL) && TclMatchIsTrivial(pattern)
	    && !((pattern[0] == 's') && (pattern[1] == 't')
	    && (pattern[2] == 'd'))) {
	if ((Tcl_FindHashEntry(hTblPtr, pattern) != NULL)
		&& (Tcl_ListObjAppendElement(interp, resultPtr,
		Tcl_NewStringObj(pattern, -1)) != TCL_OK)) {
	    goto error;
	}
	goto done;
    }
    for (hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch); hPtr != NULL;
	    hPtr = Tcl_NextHashEntry(&hSearch)) {

	statePtr = ((Channel *) Tcl_GetHashValue(hPtr))->state;
	if (statePtr->topChanPtr == (Channel *) tsdPtr->stdinChannel) {
	    name = "stdin";
	} else if (statePtr->topChanPtr == (Channel *) tsdPtr->stdoutChannel) {
	    name = "stdout";
	} else if (statePtr->topChanPtr == (Channel *) tsdPtr->stderrChannel) {
	    name = "stderr";
	} else {
	    /*
	     * This is also stored in Tcl_GetHashKey(hTblPtr, hPtr), but it's
	     * simpler to just grab the name from the statePtr.
	     */

	    name = statePtr->channelName;
	}

	if (((pattern == NULL) || Tcl_StringMatch(name, pattern)) &&
		(Tcl_ListObjAppendElement(interp, resultPtr,
			Tcl_NewStringObj(name, -1)) != TCL_OK)) {
	error:
	    TclDecrRefCount(resultPtr);
	    return TCL_ERROR;
	}
    }

  done:
    Tcl_SetObjResult(interp, resultPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_IsChannelRegistered --
 *
 *	Checks whether the channel is associated with the interp. See also
 *	Tcl_RegisterChannel and Tcl_UnregisterChannel.
 *
 * Results:
 *	0 if the channel is not registered in the interpreter, 1 else.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_IsChannelRegistered(
    Tcl_Interp *interp,		/* The interp to query of the channel */
    Tcl_Channel chan)		/* The channel to check */
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of the real channel. */

    /*
     * Always check bottom-most channel in the stack. This is the one that
     * gets registered.
     */

    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    statePtr = chanPtr->state;

    hTblPtr = Tcl_GetAssocData(interp, "tclIO", NULL);
    if (hTblPtr == NULL) {
	return 0;
    }
    hPtr = Tcl_FindHashEntry(hTblPtr, statePtr->channelName);
    if (hPtr == NULL) {
	return 0;
    }
    if ((Channel *) Tcl_GetHashValue(hPtr) != chanPtr) {
	return 0;
    }

    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_IsChannelShared --
 *
 *	Checks whether the channel is shared by multiple interpreters.
 *
 * Results:
 *	A boolean value (0 = Not shared, 1 = Shared).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_IsChannelShared(
    Tcl_Channel chan)		/* The channel to query */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
				/* State of real channel structure. */

    return ((statePtr->refCount > 1) ? 1 : 0);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_IsChannelExisting --
 *
 *	Checks whether a channel of the given name exists in the
 *	(thread)-global list of all channels. See Tcl_GetChannelNamesEx for
 *	function exposed at the Tcl level.
 *
 * Results:
 *	A boolean value (0 = Does not exist, 1 = Does exist).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_IsChannelExisting(
    const char *chanName)	/* The name of the channel to look for. */
{
    ChannelState *statePtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    const char *name;
    int chanNameLen;

    chanNameLen = strlen(chanName);
    for (statePtr = tsdPtr->firstCSPtr; statePtr != NULL;
	    statePtr = statePtr->nextCSPtr) {
	if (statePtr->topChanPtr == (Channel *) tsdPtr->stdinChannel) {
	    name = "stdin";
	} else if (statePtr->topChanPtr == (Channel *) tsdPtr->stdoutChannel) {
	    name = "stdout";
	} else if (statePtr->topChanPtr == (Channel *) tsdPtr->stderrChannel) {
	    name = "stderr";
	} else {
	    name = statePtr->channelName;
	}

	if ((*chanName == *name) &&
		(memcmp(name, chanName, (size_t) chanNameLen + 1) == 0)) {
	    return 1;
	}
    }

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelName --
 *
 *	Return the name of the channel type.
 *
 * Results:
 *	A pointer the name of the channel type.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

const char *
Tcl_ChannelName(
    const Tcl_ChannelType *chanTypePtr) /* Pointer to channel type. */
{
    return chanTypePtr->typeName;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelVersion --
 *
 *	Return the of version of the channel type.
 *
 * Results:
 *	One of the TCL_CHANNEL_VERSION_* constants from tcl.h
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_ChannelTypeVersion
Tcl_ChannelVersion(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (chanTypePtr->version == TCL_CHANNEL_VERSION_2) {
	return TCL_CHANNEL_VERSION_2;
    } else if (chanTypePtr->version == TCL_CHANNEL_VERSION_3) {
	return TCL_CHANNEL_VERSION_3;
    } else if (chanTypePtr->version == TCL_CHANNEL_VERSION_4) {
	return TCL_CHANNEL_VERSION_4;
    } else if (chanTypePtr->version == TCL_CHANNEL_VERSION_5) {
	return TCL_CHANNEL_VERSION_5;
    } else {
	/*
	 * In <v2 channel versions, the version field is occupied by the
	 * Tcl_DriverBlockModeProc
	 */

	return TCL_CHANNEL_VERSION_1;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * HaveVersion --
 *
 *	Return whether a channel type is (at least) of a given version.
 *
 * Results:
 *	True if the minimum version is exceeded by the version actually
 *	present.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
HaveVersion(
    const Tcl_ChannelType *chanTypePtr,
    Tcl_ChannelTypeVersion minimumVersion)
{
    Tcl_ChannelTypeVersion actualVersion = Tcl_ChannelVersion(chanTypePtr);

    return (PTR2INT(actualVersion)) >= (PTR2INT(minimumVersion));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelBlockModeProc --
 *
 *	Return the Tcl_DriverBlockModeProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------- */

Tcl_DriverBlockModeProc *
Tcl_ChannelBlockModeProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_2)) {
	return chanTypePtr->blockModeProc;
    } else {
	/*
	 * The v1 structure had the blockModeProc in a different place.
	 */

	return (Tcl_DriverBlockModeProc *) chanTypePtr->version;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelCloseProc --
 *
 *	Return the Tcl_DriverCloseProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverCloseProc *
Tcl_ChannelCloseProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->closeProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelClose2Proc --
 *
 *	Return the Tcl_DriverClose2Proc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverClose2Proc *
Tcl_ChannelClose2Proc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->close2Proc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelInputProc --
 *
 *	Return the Tcl_DriverInputProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverInputProc *
Tcl_ChannelInputProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->inputProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelOutputProc --
 *
 *	Return the Tcl_DriverOutputProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverOutputProc *
Tcl_ChannelOutputProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->outputProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelSeekProc --
 *
 *	Return the Tcl_DriverSeekProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverSeekProc *
Tcl_ChannelSeekProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->seekProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelSetOptionProc --
 *
 *	Return the Tcl_DriverSetOptionProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverSetOptionProc *
Tcl_ChannelSetOptionProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->setOptionProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelGetOptionProc --
 *
 *	Return the Tcl_DriverGetOptionProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverGetOptionProc *
Tcl_ChannelGetOptionProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->getOptionProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelWatchProc --
 *
 *	Return the Tcl_DriverWatchProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverWatchProc *
Tcl_ChannelWatchProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->watchProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelGetHandleProc --
 *
 *	Return the Tcl_DriverGetHandleProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverGetHandleProc *
Tcl_ChannelGetHandleProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    return chanTypePtr->getHandleProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelFlushProc --
 *
 *	Return the Tcl_DriverFlushProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverFlushProc *
Tcl_ChannelFlushProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_2)) {
	return chanTypePtr->flushProc;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelHandlerProc --
 *
 *	Return the Tcl_DriverHandlerProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverHandlerProc *
Tcl_ChannelHandlerProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_2)) {
	return chanTypePtr->handlerProc;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelWideSeekProc --
 *
 *	Return the Tcl_DriverWideSeekProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverWideSeekProc *
Tcl_ChannelWideSeekProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_3)) {
	return chanTypePtr->wideSeekProc;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelThreadActionProc --
 *
 *	TIP #218, Channel Thread Actions. Return the
 *	Tcl_DriverThreadActionProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverThreadActionProc *
Tcl_ChannelThreadActionProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_4)) {
	return chanTypePtr->threadActionProc;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetChannelErrorInterp --
 *
 *	TIP #219, Tcl Channel Reflection API.
 *	Store an error message for the I/O system.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Discards a previously stored message.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetChannelErrorInterp(
    Tcl_Interp *interp,		/* Interp to store the data into. */
    Tcl_Obj *msg)		/* Error message to store. */
{
    Interp *iPtr = (Interp *) interp;

    if (iPtr->chanMsg != NULL) {
	TclDecrRefCount(iPtr->chanMsg);
	iPtr->chanMsg = NULL;
    }

    if (msg != NULL) {
	iPtr->chanMsg = FixLevelCode(msg);
	Tcl_IncrRefCount(iPtr->chanMsg);
    }
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetChannelError --
 *
 *	TIP #219, Tcl Channel Reflection API.
 *	Store an error message for the I/O system.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Discards a previously stored message.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetChannelError(
    Tcl_Channel chan,		/* Channel to store the data into. */
    Tcl_Obj *msg)		/* Error message to store. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;

    if (statePtr->chanMsg != NULL) {
	TclDecrRefCount(statePtr->chanMsg);
	statePtr->chanMsg = NULL;
    }

    if (msg != NULL) {
	statePtr->chanMsg = FixLevelCode(msg);
	Tcl_IncrRefCount(statePtr->chanMsg);
    }
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * FixLevelCode --
 *
 *	TIP #219, Tcl Channel Reflection API.
 *	Scans an error message for bad -code / -level directives. Returns a
 *	modified copy with such directives corrected, and the input if it had
 *	no problems.
 *
 * Results:
 *	A Tcl_Obj*
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static Tcl_Obj *
FixLevelCode(
    Tcl_Obj *msg)
{
    int explicitResult, numOptions, lc, lcn;
    Tcl_Obj **lv, **lvn;
    int res, i, j, val, lignore, cignore;
    int newlevel = -1, newcode = -1;

    /* ASSERT msg != NULL */

    /*
     * Process the caught message.
     *
     * Syntax = (option value)... ?message?
     *
     * Bad message syntax causes a panic, because the other side uses
     * Tcl_GetReturnOptions and list construction functions to marshall the
     * information. Hence an error means that we've got serious breakage.
     */

    res = Tcl_ListObjGetElements(NULL, msg, &lc, &lv);
    if (res != TCL_OK) {
	Tcl_Panic("Tcl_SetChannelError(Interp): Bad syntax of message");
    }

    explicitResult = (1 == (lc % 2));
    numOptions = lc - explicitResult;

    /*
     * No options, nothing to do.
     */

    if (numOptions == 0) {
	return msg;
    }

    /*
     * Check for -code x, x != 1|error, and -level x, x != 0
     */

    for (i = 0; i < numOptions; i += 2) {
	if (0 == strcmp(TclGetString(lv[i]), "-code")) {
	    /*
	     * !"error", !integer, integer != 1 (numeric code for error)
	     */

	    res = TclGetIntFromObj(NULL, lv[i+1], &val);
	    if (((res == TCL_OK) && (val != 1)) || ((res != TCL_OK) &&
		    (0 != strcmp(TclGetString(lv[i+1]), "error")))) {
		newcode = 1;
	    }
	} else if (0 == strcmp(TclGetString(lv[i]), "-level")) {
	    /*
	     * !integer, integer != 0
	     */

	    res = TclGetIntFromObj(NULL, lv [i+1], &val);
	    if ((res != TCL_OK) || (val != 0)) {
		newlevel = 0;
	    }
	}
    }

    /*
     * -code, -level are either not present or ok. Nothing to do.
     */

    if ((newlevel < 0) && (newcode < 0)) {
	return msg;
    }

    lcn = numOptions;
    if (explicitResult) {
	lcn ++;
    }
    if (newlevel >= 0) {
	lcn += 2;
    }
    if (newcode >= 0) {
	lcn += 2;
    }

    lvn = (Tcl_Obj **) ckalloc(lcn * sizeof(Tcl_Obj *));

    /*
     * New level/code information is spliced into the first occurence of
     * -level, -code, further occurences are ignored. The options cannot be
     * not present, we would not come here. Options which are ok are simply
     * copied over.
     */

    lignore = cignore = 0;
    for (i=0, j=0; i<numOptions; i+=2) {
	if (0 == strcmp(TclGetString(lv[i]), "-level")) {
	    if (newlevel >= 0) {
		lvn[j++] = lv[i];
		lvn[j++] = Tcl_NewIntObj(newlevel);
		newlevel = -1;
		lignore = 1;
		continue;
	    } else if (lignore) {
		continue;
	    }
	} else if (0 == strcmp(TclGetString(lv[i]), "-code")) {
	    if (newcode >= 0) {
		lvn[j++] = lv[i];
		lvn[j++] = Tcl_NewIntObj(newcode);
		newcode = -1;
		cignore = 1;
		continue;
	    } else if (cignore) {
		continue;
	    }
	}

	/*
	 * Keep everything else, possibly copied down.
	 */

	lvn[j++] = lv[i];
	lvn[j++] = lv[i+1];
    }
    if (newlevel >= 0) {
	Tcl_Panic("Defined newlevel not used in rewrite");
    }
    if (newcode >= 0) {
	Tcl_Panic("Defined newcode not used in rewrite");
    }

    if (explicitResult) {
	lvn[j++] = lv[i];
    }

    msg = Tcl_NewListObj(j, lvn);

    ckfree((char *) lvn);
    return msg;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelErrorInterp --
 *
 *	TIP #219, Tcl Channel Reflection API.
 *	Return the message stored by the channel driver.
 *
 * Results:
 *	Tcl error message object.
 *
 * Side effects:
 *	Resets the stored data to NULL.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_GetChannelErrorInterp(
    Tcl_Interp *interp,		/* Interp to query. */
    Tcl_Obj **msg)		/* Place for error message. */
{
    Interp *iPtr = (Interp *) interp;

    *msg = iPtr->chanMsg;
    iPtr->chanMsg = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelError --
 *
 *	TIP #219, Tcl Channel Reflection API.
 *	Return the message stored by the channel driver.
 *
 * Results:
 *	Tcl error message object.
 *
 * Side effects:
 *	Resets the stored data to NULL.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_GetChannelError(
    Tcl_Channel chan,		/* Channel to query. */
    Tcl_Obj **msg)		/* Place for error message. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;

    *msg = statePtr->chanMsg;
    statePtr->chanMsg = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ChannelTruncateProc --
 *
 *	TIP #208 (subsection relating to truncation, based on TIP #206).
 *	Return the Tcl_DriverTruncateProc of the channel type.
 *
 * Results:
 *	A pointer to the proc.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_DriverTruncateProc *
Tcl_ChannelTruncateProc(
    const Tcl_ChannelType *chanTypePtr)
				/* Pointer to channel type. */
{
    if (HaveVersion(chanTypePtr, TCL_CHANNEL_VERSION_5)) {
	return chanTypePtr->truncateProc;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * DupChannelIntRep --
 *
 *	Initialize the internal representation of a new Tcl_Obj to a copy of
 *	the internal representation of an existing string object.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	copyPtr's internal rep is set to a copy of srcPtr's internal
 *	representation.
 *
 *----------------------------------------------------------------------
 */

static void
DupChannelIntRep(
    register Tcl_Obj *srcPtr,	/* Object with internal rep to copy. Must have
				 * an internal rep of type "Channel". */
    register Tcl_Obj *copyPtr)	/* Object with internal rep to set. Must not
				 * currently have an internal rep.*/
{
    ChannelState *statePtr  = GET_CHANNELSTATE(srcPtr);
    Interp       *interpPtr = GET_CHANNELINTERP(srcPtr);

    SET_CHANNELSTATE(copyPtr, statePtr);
    SET_CHANNELINTERP(copyPtr, interpPtr);
    Tcl_Preserve(statePtr);
    copyPtr->typePtr = &tclChannelType;
}

/*
 *----------------------------------------------------------------------
 *
 * SetChannelFromAny --
 *
 *	Create an internal representation of type "Channel" for an object.
 *
 * Results:
 *	This operation always succeeds and returns TCL_OK.
 *
 * Side effects:
 *	Any old internal reputation for objPtr is freed and the internal
 *	representation is set to "Channel".
 *
 *----------------------------------------------------------------------
 */

static int
SetChannelFromAny(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    register Tcl_Obj *objPtr)	/* The object to convert. */
{
    ChannelState *statePtr;
    Interp       *interpPtr;

    if (objPtr->typePtr == &tclChannelType) {
	/*
	 * The channel is valid until any call to DetachChannel occurs.
	 * Ensure consistency checks are done.
	 */

	statePtr = GET_CHANNELSTATE(objPtr);
	interpPtr = GET_CHANNELINTERP(objPtr);
	if (GotFlag(statePtr, CHANNEL_TAINTED|CHANNEL_CLOSED)) {
	    ResetFlag(statePtr, CHANNEL_TAINTED);
	    Tcl_Release(statePtr);
	    UpdateStringOfChannel(objPtr);
	    objPtr->typePtr = NULL;
	} else if (interpPtr != (Interp*) interp) {
	    Tcl_Release(statePtr);
	    UpdateStringOfChannel(objPtr);
	    objPtr->typePtr = NULL;
	}
    }
    if (objPtr->typePtr != &tclChannelType) {
	Tcl_Channel chan;

	/*
	 * We need a valid string with which to check for a valid channel, but
	 * make sure not to free internal rep until validated. [Bug 1847044]
	 */

	if ((objPtr->typePtr != NULL) && (objPtr->bytes == NULL)) {
	    objPtr->typePtr->updateStringProc(objPtr);
	}

	chan = Tcl_GetChannel(interp, objPtr->bytes, NULL);
	if (chan == NULL) {
	    return TCL_ERROR;
	}

	TclFreeIntRep(objPtr);
	statePtr = ((Channel *) chan)->state;
	Tcl_Preserve(statePtr);
	SET_CHANNELSTATE(objPtr, statePtr);
	SET_CHANNELINTERP(objPtr, interp);
	objPtr->typePtr = &tclChannelType;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateStringOfChannel --
 *
 *	Update the string representation for an object whose internal
 *	representation is "Channel".
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The object's string may be set by converting its Unicode represention
 *	to UTF format.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateStringOfChannel(
    Tcl_Obj *objPtr)		/* Object with string rep to update. */
{
    if (objPtr->bytes == NULL) {
	ChannelState *statePtr = GET_CHANNELSTATE(objPtr);
	const char *name = statePtr->channelName;

	if (name) {
	    size_t len = strlen(name);

	    objPtr->bytes = (char *) ckalloc(len + 1);
	    objPtr->length = len;
	    memcpy(objPtr->bytes, name, len);
	} else {
	    objPtr->bytes = tclEmptyStringRep;
	    objPtr->length = 0;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FreeChannelIntRep --
 *
 *	Release statePtr storage.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May cause state to be freed.
 *
 *----------------------------------------------------------------------
 */

static void
FreeChannelIntRep(
    Tcl_Obj *objPtr)		/* Object with internal rep to free. */
{
    Tcl_Release(GET_CHANNELSTATE(objPtr));
}

#if 0
/*
 * For future debugging work, a simple function to print the flags of a
 * channel in semi-readable form.
 */

static int
DumpFlags(
    char *str,
    int flags)
{
    char buf[20];
    int i = 0;

#define ChanFlag(chr,bit) (buf[i++] = ((flags & (bit)) ? (chr) : '_'))

    ChanFlag('r', TCL_READABLE);
    ChanFlag('w', TCL_WRITABLE);
    ChanFlag('n', CHANNEL_NONBLOCKING);
    ChanFlag('l', CHANNEL_LINEBUFFERED);
    ChanFlag('u', CHANNEL_UNBUFFERED);
    ChanFlag('R', BUFFER_READY);
    ChanFlag('F', BG_FLUSH_SCHEDULED);
    ChanFlag('c', CHANNEL_CLOSED);
    ChanFlag('E', CHANNEL_EOF);
    ChanFlag('S', CHANNEL_STICKY_EOF);
    ChanFlag('B', CHANNEL_BLOCKED);
    ChanFlag('/', INPUT_SAW_CR);
    ChanFlag('*', INPUT_NEED_NL);
    ChanFlag('D', CHANNEL_DEAD);
    ChanFlag('R', CHANNEL_RAW_MODE);
#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
    ChanFlag('T', CHANNEL_TIMER_FEV);
    ChanFlag('H', CHANNEL_HAS_MORE_DATA);
#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
    ChanFlag('x', CHANNEL_INCLOSE);

    buf[i] ='\0';

    fprintf(stderr, "%s: %s\n", str, buf);
    return 0;
}
#endif

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */