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path: root/generic/tclProc.c
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/*
 * tclProc.c --
 *
 *	This file contains routines that implement Tcl procedures, including
 *	the "proc" and "uplevel" commands.
 *
 * Copyright (c) 1987-1993 The Regents of the University of California.
 * Copyright (c) 1994-1998 Sun Microsystems, Inc.
 * Copyright (c) 2004-2006 Miguel Sofer
 * Copyright (c) 2007 Daniel A. Steffen <das@users.sourceforge.net>
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#include "tclInt.h"
#include "tclCompile.h"
#include "tclOOInt.h"

/*
 * Variables that are part of the [apply] command implementation and which
 * have to be passed to the other side of the NRE call.
 */

typedef struct {
    int isRootEnsemble;
    Command cmd;
    ExtraFrameInfo efi;
} ApplyExtraData;

/*
 * Prototypes for static functions in this file
 */

static void		DupLambdaInternalRep(Tcl_Obj *objPtr,
			    Tcl_Obj *copyPtr);
static void		FreeLambdaInternalRep(Tcl_Obj *objPtr);
static int		InitArgsAndLocals(Tcl_Interp *interp,
			    Tcl_Obj *procNameObj, int skip);
static void		InitResolvedLocals(Tcl_Interp *interp,
			    ByteCode *codePtr, Var *defPtr,
			    Namespace *nsPtr);
static void		InitLocalCache(Proc *procPtr);
static int		PushProcCallFrame(ClientData clientData,
			    register Tcl_Interp *interp, int objc,
			    Tcl_Obj *const objv[], int isLambda);
static void		ProcBodyDup(Tcl_Obj *srcPtr, Tcl_Obj *dupPtr);
static void		ProcBodyFree(Tcl_Obj *objPtr);
static int		ProcWrongNumArgs(Tcl_Interp *interp, int skip);
static void		MakeProcError(Tcl_Interp *interp,
			    Tcl_Obj *procNameObj);
static void		MakeLambdaError(Tcl_Interp *interp,
			    Tcl_Obj *procNameObj);
static int		SetLambdaFromAny(Tcl_Interp *interp, Tcl_Obj *objPtr);

static Tcl_NRPostProc ApplyNR2;
static Tcl_NRPostProc InterpProcNR2;
static Tcl_NRPostProc Uplevel_Callback;

/*
 * The ProcBodyObjType type
 */

const Tcl_ObjType tclProcBodyType = {
    "procbody",			/* name for this type */
    ProcBodyFree,		/* FreeInternalRep function */
    ProcBodyDup,		/* DupInternalRep function */
    NULL,			/* UpdateString function; Tcl_GetString and
				 * Tcl_GetStringFromObj should panic
				 * instead. */
    NULL			/* SetFromAny function; Tcl_ConvertToType
				 * should panic instead. */
};

/*
 * The [upvar]/[uplevel] level reference type. Uses the ptrAndLongRep field,
 * encoding the type of level reference in ptr and the actual parsed out
 * offset in value.
 *
 * Uses the default behaviour throughout, and never disposes of the string
 * rep; it's just a cache type.
 */

static const Tcl_ObjType levelReferenceType = {
    "levelReference",
    NULL, NULL, NULL, NULL
};

/*
 * The type of lambdas. Note that every lambda will *always* have a string
 * representation.
 *
 * Internally, ptr1 is a pointer to a Proc instance that is not bound to a
 * command name, and ptr2 is a pointer to the namespace that the Proc instance
 * will execute within.
 */

static const Tcl_ObjType lambdaType = {
    "lambdaExpr",		/* name */
    FreeLambdaInternalRep,	/* freeIntRepProc */
    DupLambdaInternalRep,	/* dupIntRepProc */
    NULL,			/* updateStringProc */
    SetLambdaFromAny		/* setFromAnyProc */
};

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ProcObjCmd --
 *
 *	This object-based function is invoked to process the "proc" Tcl
 *	command. See the user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	A new procedure gets created.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
int
Tcl_ProcObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    register Interp *iPtr = (Interp *) interp;
    Proc *procPtr;
    const char *fullName;
    const char *procName, *procArgs, *procBody;
    Namespace *nsPtr, *altNsPtr, *cxtNsPtr;
    Tcl_Command cmd;
    Tcl_DString ds;

    if (objc != 4) {
	Tcl_WrongNumArgs(interp, 1, objv, "name args body");
	return TCL_ERROR;
    }

    /*
     * Determine the namespace where the procedure should reside. Unless the
     * command name includes namespace qualifiers, this will be the current
     * namespace.
     */

    fullName = TclGetString(objv[1]);
    TclGetNamespaceForQualName(interp, fullName, NULL, 0,
	    &nsPtr, &altNsPtr, &cxtNsPtr, &procName);

    if (nsPtr == NULL) {
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't create procedure \"%s\": unknown namespace",
		fullName));
	Tcl_SetErrorCode(interp, "TCL", "VALUE", "COMMAND", NULL);
	return TCL_ERROR;
    }
    if (procName == NULL) {
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't create procedure \"%s\": bad procedure name",
		fullName));
	Tcl_SetErrorCode(interp, "TCL", "VALUE", "COMMAND", NULL);
	return TCL_ERROR;
    }
    if ((nsPtr != iPtr->globalNsPtr)
	    && (procName != NULL) && (procName[0] == ':')) {
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't create procedure \"%s\" in non-global namespace with"
		" name starting with \":\"", procName));
	Tcl_SetErrorCode(interp, "TCL", "VALUE", "COMMAND", NULL);
	return TCL_ERROR;
    }

    /*
     * Create the data structure to represent the procedure.
     */

    if (TclCreateProc(interp, nsPtr, procName, objv[2], objv[3],
	    &procPtr) != TCL_OK) {
	Tcl_AddErrorInfo(interp, "\n    (creating proc \"");
	Tcl_AddErrorInfo(interp, procName);
	Tcl_AddErrorInfo(interp, "\")");
	return TCL_ERROR;
    }

    /*
     * Now create a command for the procedure. This will initially be in the
     * current namespace unless the procedure's name included namespace
     * qualifiers. To create the new command in the right namespace, we
     * generate a fully qualified name for it.
     */

    Tcl_DStringInit(&ds);
    if (nsPtr != iPtr->globalNsPtr) {
	Tcl_DStringAppend(&ds, nsPtr->fullName, -1);
	TclDStringAppendLiteral(&ds, "::");
    }
    Tcl_DStringAppend(&ds, procName, -1);

    cmd = Tcl_NRCreateCommand(interp, Tcl_DStringValue(&ds), TclObjInterpProc,
	    TclNRInterpProc, procPtr, TclProcDeleteProc);
    Tcl_DStringFree(&ds);

    /*
     * Now initialize the new procedure's cmdPtr field. This will be used
     * later when the procedure is called to determine what namespace the
     * procedure will run in. This will be different than the current
     * namespace if the proc was renamed into a different namespace.
     */

    procPtr->cmdPtr = (Command *) cmd;

    /*
     * TIP #280: Remember the line the procedure body is starting on. In a
     * bytecode context we ask the engine to provide us with the necessary
     * information. This is for the initialization of the byte code compiler
     * when the body is used for the first time.
     *
     * This code is nearly identical to the #280 code in SetLambdaFromAny, see
     * this file. The differences are the different index of the body in the
     * line array of the context, and the lamdba code requires some special
     * processing. Find a way to factor the common elements into a single
     * function.
     */

    if (iPtr->cmdFramePtr) {
	CmdFrame *contextPtr = TclStackAlloc(interp, sizeof(CmdFrame));

	*contextPtr = *iPtr->cmdFramePtr;
	if (contextPtr->type == TCL_LOCATION_BC) {
	    /*
	     * Retrieve source information from the bytecode, if possible. If
	     * the information is retrieved successfully, context.type will be
	     * TCL_LOCATION_SOURCE and the reference held by
	     * context.data.eval.path will be counted.
	     */

	    TclGetSrcInfoForPc(contextPtr);
	} else if (contextPtr->type == TCL_LOCATION_SOURCE) {
	    /*
	     * The copy into 'context' up above has created another reference
	     * to 'context.data.eval.path'; account for it.
	     */

	    Tcl_IncrRefCount(contextPtr->data.eval.path);
	}

	if (contextPtr->type == TCL_LOCATION_SOURCE) {
	    /*
	     * We can account for source location within a proc only if the
	     * proc body was not created by substitution.
	     */

	    if (contextPtr->line
		    && (contextPtr->nline >= 4) && (contextPtr->line[3] >= 0)) {
		int isNew;
		Tcl_HashEntry *hePtr;
		CmdFrame *cfPtr = ckalloc(sizeof(CmdFrame));

		cfPtr->level = -1;
		cfPtr->type = contextPtr->type;
		cfPtr->line = ckalloc(sizeof(int));
		cfPtr->line[0] = contextPtr->line[3];
		cfPtr->nline = 1;
		cfPtr->framePtr = NULL;
		cfPtr->nextPtr = NULL;

		cfPtr->data.eval.path = contextPtr->data.eval.path;
		Tcl_IncrRefCount(cfPtr->data.eval.path);

		cfPtr->cmd.str.cmd = NULL;
		cfPtr->cmd.str.len = 0;

		hePtr = Tcl_CreateHashEntry(iPtr->linePBodyPtr,
			procPtr, &isNew);
		if (!isNew) {
		    /*
		     * Get the old command frame and release it. See also
		     * TclProcCleanupProc in this file. Currently it seems as
		     * if only the procbodytest::proc command of the testsuite
		     * is able to trigger this situation.
		     */

		    CmdFrame *cfOldPtr = Tcl_GetHashValue(hePtr);

		    if (cfOldPtr->type == TCL_LOCATION_SOURCE) {
			Tcl_DecrRefCount(cfOldPtr->data.eval.path);
			cfOldPtr->data.eval.path = NULL;
		    }
		    ckfree(cfOldPtr->line);
		    cfOldPtr->line = NULL;
		    ckfree(cfOldPtr);
		}
		Tcl_SetHashValue(hePtr, cfPtr);
	    }

	    /*
	     * 'contextPtr' is going out of scope; account for the reference
	     * that it's holding to the path name.
	     */

	    Tcl_DecrRefCount(contextPtr->data.eval.path);
	    contextPtr->data.eval.path = NULL;
	}
	TclStackFree(interp, contextPtr);
    }

    /*
     * Optimize for no-op procs: if the body is not precompiled (like a TclPro
     * procbody), and the argument list is just "args" and the body is empty,
     * define a compileProc to compile a no-op.
     *
     * Notes:
     *	 - cannot be done for any argument list without having different
     *	   compiled/not-compiled behaviour in the "wrong argument #" case, or
     *	   making this code much more complicated. In any case, it doesn't
     *	   seem to make a lot of sense to verify the number of arguments we
     *	   are about to ignore ...
     *	 - could be enhanced to handle also non-empty bodies that contain only
     *	   comments; however, parsing the body will slow down the compilation
     *	   of all procs whose argument list is just _args_
     */

    if (objv[3]->typePtr == &tclProcBodyType) {
	goto done;
    }

    procArgs = TclGetString(objv[2]);

    while (*procArgs == ' ') {
	procArgs++;
    }

    if ((procArgs[0] == 'a') && (strncmp(procArgs, "args", 4) == 0)) {
	int numBytes;

	procArgs +=4;
	while (*procArgs != '\0') {
	    if (*procArgs != ' ') {
		goto done;
	    }
	    procArgs++;
	}

	/*
	 * The argument list is just "args"; check the body
	 */

	procBody = Tcl_GetStringFromObj(objv[3], &numBytes);
	if (TclParseAllWhiteSpace(procBody, numBytes) < numBytes) {
	    goto done;
	}

	/*
	 * The body is just spaces: link the compileProc
	 */

	((Command *) cmd)->compileProc = TclCompileNoOp;
    }

  done:
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclCreateProc --
 *
 *	Creates the data associated with a Tcl procedure definition. This
 *	function knows how to handle two types of body objects: strings and
 *	procbody. Strings are the traditional (and common) value for bodies,
 *	procbody are values created by extensions that have loaded a
 *	previously compiled script.
 *
 * Results:
 *	Returns TCL_OK on success, along with a pointer to a Tcl procedure
 *	definition in procPtrPtr where the cmdPtr field is not initialised.
 *	This definition should be freed by calling TclProcCleanupProc() when
 *	it is no longer needed. Returns TCL_ERROR if anything goes wrong.
 *
 * Side effects:
 *	If anything goes wrong, this function returns an error message in the
 *	interpreter.
 *
 *----------------------------------------------------------------------
 */

int
TclCreateProc(
    Tcl_Interp *interp,		/* Interpreter containing proc. */
    Namespace *nsPtr,		/* Namespace containing this proc. */
    const char *procName,	/* Unqualified name of this proc. */
    Tcl_Obj *argsPtr,		/* Description of arguments. */
    Tcl_Obj *bodyPtr,		/* Command body. */
    Proc **procPtrPtr)		/* Returns: pointer to proc data. */
{
    Interp *iPtr = (Interp *) interp;
    const char **argArray = NULL;

    register Proc *procPtr;
    int i, length, result, numArgs;
    const char *args, *bytes, *p;
    register CompiledLocal *localPtr = NULL;
    Tcl_Obj *defPtr;
    int precompiled = 0;

    if (bodyPtr->typePtr == &tclProcBodyType) {
	/*
	 * Because the body is a TclProProcBody, the actual body is already
	 * compiled, and it is not shared with anyone else, so it's OK not to
	 * unshare it (as a matter of fact, it is bad to unshare it, because
	 * there may be no source code).
	 *
	 * We don't create and initialize a Proc structure for the procedure;
	 * rather, we use what is in the body object. We increment the ref
	 * count of the Proc struct since the command (soon to be created)
	 * will be holding a reference to it.
	 */

	procPtr = bodyPtr->internalRep.otherValuePtr;
	procPtr->iPtr = iPtr;
	procPtr->refCount++;
	precompiled = 1;
    } else {
	/*
	 * If the procedure's body object is shared because its string value
	 * is identical to, e.g., the body of another procedure, we must
	 * create a private copy for this procedure to use. Such sharing of
	 * procedure bodies is rare but can cause problems. A procedure body
	 * is compiled in a context that includes the number of "slots"
	 * allocated by the compiler for local variables. There is a local
	 * variable slot for each formal parameter (the
	 * "procPtr->numCompiledLocals = numArgs" assignment below). This
	 * means that the same code can not be shared by two procedures that
	 * have a different number of arguments, even if their bodies are
	 * identical. Note that we don't use Tcl_DuplicateObj since we would
	 * not want any bytecode internal representation.
	 */

	if (Tcl_IsShared(bodyPtr)) {
	    Tcl_Obj *sharedBodyPtr = bodyPtr;

	    bytes = TclGetStringFromObj(bodyPtr, &length);
	    bodyPtr = Tcl_NewStringObj(bytes, length);

	    /*
	     * TIP #280.
	     * Ensure that the continuation line data for the original body is
	     * not lost and applies to the new body as well.
	     */

	    TclContinuationsCopy(bodyPtr, sharedBodyPtr);
	}

	/*
	 * Create and initialize a Proc structure for the procedure. We
	 * increment the ref count of the procedure's body object since there
	 * will be a reference to it in the Proc structure.
	 */

	Tcl_IncrRefCount(bodyPtr);

	procPtr = ckalloc(sizeof(Proc));
	procPtr->iPtr = iPtr;
	procPtr->refCount = 1;
	procPtr->bodyPtr = bodyPtr;
	procPtr->numArgs = 0;	/* Actual argument count is set below. */
	procPtr->numCompiledLocals = 0;
	procPtr->firstLocalPtr = NULL;
	procPtr->lastLocalPtr = NULL;
    }

    /*
     * Break up the argument list into argument specifiers, then process each
     * argument specifier. If the body is precompiled, processing is limited
     * to checking that the parsed argument is consistent with the one stored
     * in the Proc.
     *
     * THIS FAILS IF THE ARG LIST OBJECT'S STRING REP CONTAINS NULS.
     */

    args = TclGetStringFromObj(argsPtr, &length);
    result = Tcl_SplitList(interp, args, &numArgs, &argArray);
    if (result != TCL_OK) {
	goto procError;
    }

    if (precompiled) {
	if (numArgs > procPtr->numArgs) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "procedure \"%s\": arg list contains %d entries, "
		    "precompiled header expects %d", procName, numArgs,
		    procPtr->numArgs));
	    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
		    "BYTECODELIES", NULL);
	    goto procError;
	}
	localPtr = procPtr->firstLocalPtr;
    } else {
	procPtr->numArgs = numArgs;
	procPtr->numCompiledLocals = numArgs;
    }

    for (i = 0; i < numArgs; i++) {
	int fieldCount, nameLength, valueLength;
	const char **fieldValues;

	/*
	 * Now divide the specifier up into name and default.
	 */

	result = Tcl_SplitList(interp, argArray[i], &fieldCount,
		&fieldValues);
	if (result != TCL_OK) {
	    goto procError;
	}
	if (fieldCount > 2) {
	    ckfree(fieldValues);
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "too many fields in argument specifier \"%s\"",
		    argArray[i]));
	    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
		    "FORMALARGUMENTFORMAT", NULL);
	    goto procError;
	}
	if ((fieldCount == 0) || (*fieldValues[0] == 0)) {
	    ckfree(fieldValues);
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
		    "argument with no name", -1));
	    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
		    "FORMALARGUMENTFORMAT", NULL);
	    goto procError;
	}

	nameLength = strlen(fieldValues[0]);
	if (fieldCount == 2) {
	    valueLength = strlen(fieldValues[1]);
	} else {
	    valueLength = 0;
	}

	/*
	 * Check that the formal parameter name is a scalar.
	 */

	p = fieldValues[0];
	while (*p != '\0') {
	    if (*p == '(') {
		const char *q = p;
		do {
		    q++;
		} while (*q != '\0');
		q--;
		if (*q == ')') {	/* We have an array element. */
		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			    "formal parameter \"%s\" is an array element",
			    fieldValues[0]));
		    ckfree(fieldValues);
		    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
			    "FORMALARGUMENTFORMAT", NULL);
		    goto procError;
		}
	    } else if ((*p == ':') && (*(p+1) == ':')) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"formal parameter \"%s\" is not a simple name",
			fieldValues[0]));
		ckfree(fieldValues);
		Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
			"FORMALARGUMENTFORMAT", NULL);
		goto procError;
	    }
	    p++;
	}

	if (precompiled) {
	    /*
	     * Compare the parsed argument with the stored one. Note that the
	     * only flag value that makes sense at this point is VAR_ARGUMENT
	     * (its value was kept the same as pre VarReform to simplify
	     * tbcload's processing of older byetcodes).
	     *
	     * The only other flag vlaue that is important to retrieve from
	     * precompiled procs is VAR_TEMPORARY (also unchanged). It is
	     * needed later when retrieving the variable names.
	     */

	    if ((localPtr->nameLength != nameLength)
		    || (strcmp(localPtr->name, fieldValues[0]))
		    || (localPtr->frameIndex != i)
		    || !(localPtr->flags & VAR_ARGUMENT)
		    || (localPtr->defValuePtr == NULL && fieldCount == 2)
		    || (localPtr->defValuePtr != NULL && fieldCount != 2)) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"procedure \"%s\": formal parameter %d is "
			"inconsistent with precompiled body", procName, i));
		ckfree(fieldValues);
		Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
			"BYTECODELIES", NULL);
		goto procError;
	    }

	    /*
	     * Compare the default value if any.
	     */

	    if (localPtr->defValuePtr != NULL) {
		int tmpLength;
		const char *tmpPtr = TclGetStringFromObj(localPtr->defValuePtr,
			&tmpLength);

		if ((valueLength != tmpLength) ||
			strncmp(fieldValues[1], tmpPtr, (size_t) tmpLength)) {
		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			    "procedure \"%s\": formal parameter \"%s\" has "
			    "default value inconsistent with precompiled body",
			    procName, fieldValues[0]));
		    ckfree(fieldValues);
		    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
			    "BYTECODELIES", NULL);
		    goto procError;
		}
	    }
	    if ((i == numArgs - 1)
		    && (localPtr->nameLength == 4)
		    && (localPtr->name[0] == 'a')
		    && (strcmp(localPtr->name, "args") == 0)) {
		localPtr->flags |= VAR_IS_ARGS;
	    }

	    localPtr = localPtr->nextPtr;
	} else {
	    /*
	     * Allocate an entry in the runtime procedure frame's array of
	     * local variables for the argument.
	     */

	    localPtr = ckalloc(TclOffset(CompiledLocal, name) + nameLength+1);
	    if (procPtr->firstLocalPtr == NULL) {
		procPtr->firstLocalPtr = procPtr->lastLocalPtr = localPtr;
	    } else {
		procPtr->lastLocalPtr->nextPtr = localPtr;
		procPtr->lastLocalPtr = localPtr;
	    }
	    localPtr->nextPtr = NULL;
	    localPtr->nameLength = nameLength;
	    localPtr->frameIndex = i;
	    localPtr->flags = VAR_ARGUMENT;
	    localPtr->resolveInfo = NULL;

	    if (fieldCount == 2) {
		localPtr->defValuePtr =
			Tcl_NewStringObj(fieldValues[1], valueLength);
		Tcl_IncrRefCount(localPtr->defValuePtr);
	    } else {
		localPtr->defValuePtr = NULL;
	    }
	    memcpy(localPtr->name, fieldValues[0], nameLength + 1);
	    if ((i == numArgs - 1)
		    && (localPtr->nameLength == 4)
		    && (localPtr->name[0] == 'a')
		    && (strcmp(localPtr->name, "args") == 0)) {
		localPtr->flags |= VAR_IS_ARGS;
	    }
	}

	ckfree(fieldValues);
    }

    *procPtrPtr = procPtr;
    ckfree(argArray);
    return TCL_OK;

  procError:
    if (precompiled) {
	procPtr->refCount--;
    } else {
	Tcl_DecrRefCount(bodyPtr);
	while (procPtr->firstLocalPtr != NULL) {
	    localPtr = procPtr->firstLocalPtr;
	    procPtr->firstLocalPtr = localPtr->nextPtr;

	    defPtr = localPtr->defValuePtr;
	    if (defPtr != NULL) {
		Tcl_DecrRefCount(defPtr);
	    }

	    ckfree(localPtr);
	}
	ckfree(procPtr);
    }
    if (argArray != NULL) {
	ckfree(argArray);
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetFrame --
 *
 *	Given a description of a procedure frame, such as the first argument
 *	to an "uplevel" or "upvar" command, locate the call frame for the
 *	appropriate level of procedure.
 *
 * Results:
 *	The return value is -1 if an error occurred in finding the frame (in
 *	this case an error message is left in the interp's result). 1 is
 *	returned if string was either a number or a number preceded by "#" and
 *	it specified a valid frame. 0 is returned if string isn't one of the
 *	two things above (in this case, the lookup acts as if string were
 *	"1"). The variable pointed to by framePtrPtr is filled in with the
 *	address of the desired frame (unless an error occurs, in which case it
 *	isn't modified).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TclGetFrame(
    Tcl_Interp *interp,		/* Interpreter in which to find frame. */
    const char *name,		/* String describing frame. */
    CallFrame **framePtrPtr)	/* Store pointer to frame here (or NULL if
				 * global frame indicated). */
{
    register Interp *iPtr = (Interp *) interp;
    int curLevel, level, result;
    CallFrame *framePtr;

    /*
     * Parse string to figure out which level number to go to.
     */

    result = 1;
    curLevel = iPtr->varFramePtr->level;
    if (*name== '#') {
	if (Tcl_GetInt(interp, name+1, &level) != TCL_OK || level < 0) {
	    goto levelError;
	}
    } else if (isdigit(UCHAR(*name))) { /* INTL: digit */
	if (Tcl_GetInt(interp, name, &level) != TCL_OK) {
	    goto levelError;
	}
	level = curLevel - level;
    } else {
	level = curLevel - 1;
	result = 0;
    }

    /*
     * Figure out which frame to use, and return it to the caller.
     */

    for (framePtr = iPtr->varFramePtr; framePtr != NULL;
	    framePtr = framePtr->callerVarPtr) {
	if (framePtr->level == level) {
	    break;
	}
    }
    if (framePtr == NULL) {
	goto levelError;
    }

    *framePtrPtr = framePtr;
    return result;

  levelError:
    Tcl_SetObjResult(interp, Tcl_ObjPrintf("bad level \"%s\"", name));
    Tcl_SetErrorCode(interp, "TCL", "VALUE", "STACKLEVEL", NULL);
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * TclObjGetFrame --
 *
 *	Given a description of a procedure frame, such as the first argument
 *	to an "uplevel" or "upvar" command, locate the call frame for the
 *	appropriate level of procedure.
 *
 * Results:
 *	The return value is -1 if an error occurred in finding the frame (in
 *	this case an error message is left in the interp's result). 1 is
 *	returned if objPtr was either a number or a number preceded by "#" and
 *	it specified a valid frame. 0 is returned if objPtr isn't one of the
 *	two things above (in this case, the lookup acts as if objPtr were
 *	"1"). The variable pointed to by framePtrPtr is filled in with the
 *	address of the desired frame (unless an error occurs, in which case it
 *	isn't modified).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TclObjGetFrame(
    Tcl_Interp *interp,		/* Interpreter in which to find frame. */
    Tcl_Obj *objPtr,		/* Object describing frame. */
    CallFrame **framePtrPtr)	/* Store pointer to frame here (or NULL if
				 * global frame indicated). */
{
    register Interp *iPtr = (Interp *) interp;
    int curLevel, level, result;
    CallFrame *framePtr;
    const char *name;

    /*
     * Parse object to figure out which level number to go to.
     */

    result = 1;
    curLevel = iPtr->varFramePtr->level;
    if (objPtr == NULL) {
	name = "1";
	goto haveLevel1;
    }

    name = TclGetString(objPtr);
    if (objPtr->typePtr == &levelReferenceType) {
	if (objPtr->internalRep.ptrAndLongRep.ptr != NULL) {
	    level = curLevel - objPtr->internalRep.ptrAndLongRep.value;
	} else {
	    level = objPtr->internalRep.ptrAndLongRep.value;
	}
	if (level < 0) {
	    goto levelError;
	}
	/* TODO: Consider skipping the typePtr checks */
    } else if (objPtr->typePtr == &tclIntType
#ifndef NO_WIDE_TYPE
	    || objPtr->typePtr == &tclWideIntType
#endif
	    ) {
	if (TclGetIntFromObj(NULL, objPtr, &level) != TCL_OK || level < 0) {
	    goto levelError;
	}
	level = curLevel - level;
    } else if (*name == '#') {
	if (Tcl_GetInt(interp, name+1, &level) != TCL_OK || level < 0) {
	    goto levelError;
	}

	/*
	 * Cache for future reference.
	 *
	 * TODO: Use the new ptrAndLongRep intrep
	 */

	TclFreeIntRep(objPtr);
	objPtr->typePtr = &levelReferenceType;
	objPtr->internalRep.ptrAndLongRep.ptr = NULL;
	objPtr->internalRep.ptrAndLongRep.value = level;
    } else if (isdigit(UCHAR(*name))) { /* INTL: digit */
	if (Tcl_GetInt(interp, name, &level) != TCL_OK) {
	    return -1;
	}

	/*
	 * Cache for future reference.
	 *
	 * TODO: Use the new ptrAndLongRep intrep
	 */

	TclFreeIntRep(objPtr);
	objPtr->typePtr = &levelReferenceType;
	objPtr->internalRep.ptrAndLongRep.ptr = (void *) 1; /* non-NULL */
	objPtr->internalRep.ptrAndLongRep.value = level;
	level = curLevel - level;
    } else {
	/*
	 * Don't cache as the object *isn't* a level reference (might even be
	 * NULL...)
	 */

    haveLevel1:
	level = curLevel - 1;
	result = 0;
    }

    /*
     * Figure out which frame to use, and return it to the caller.
     */

    for (framePtr = iPtr->varFramePtr; framePtr != NULL;
	    framePtr = framePtr->callerVarPtr) {
	if (framePtr->level == level) {
	    break;
	}
    }
    if (framePtr == NULL) {
	goto levelError;
    }
    *framePtrPtr = framePtr;
    return result;

  levelError:
    Tcl_SetObjResult(interp, Tcl_ObjPrintf("bad level \"%s\"", name));
    Tcl_SetErrorCode(interp, "TCL", "VALUE", "STACKLEVEL", NULL);
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UplevelObjCmd --
 *
 *	This object function is invoked to process the "uplevel" Tcl command.
 *	See the user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
Uplevel_Callback(
    ClientData data[],
    Tcl_Interp *interp,
    int result)
{
    CallFrame *savedVarFramePtr = data[0];

    if (result == TCL_ERROR) {
	Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
		"\n    (\"uplevel\" body line %d)", Tcl_GetErrorLine(interp)));
    }

    /*
     * Restore the variable frame, and return.
     */

    ((Interp *)interp)->varFramePtr = savedVarFramePtr;
    return result;
}

	/* ARGSUSED */
int
Tcl_UplevelObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    return Tcl_NRCallObjProc(interp, TclNRUplevelObjCmd, dummy, objc, objv);
}

int
TclNRUplevelObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{

    register Interp *iPtr = (Interp *) interp;
    CmdFrame *invoker = NULL;
    int word = 0;
    int result;
    CallFrame *savedVarFramePtr, *framePtr;
    Tcl_Obj *objPtr;

    if (objc < 2) {
    uplevelSyntax:
	Tcl_WrongNumArgs(interp, 1, objv, "?level? command ?arg ...?");
	return TCL_ERROR;
    }

    /*
     * Find the level to use for executing the command.
     */

    result = TclObjGetFrame(interp, objv[1], &framePtr);
    if (result == -1) {
	return TCL_ERROR;
    }
    objc -= result + 1;
    if (objc == 0) {
	goto uplevelSyntax;
    }
    objv += result + 1;

    /*
     * Modify the interpreter state to execute in the given frame.
     */

    savedVarFramePtr = iPtr->varFramePtr;
    iPtr->varFramePtr = framePtr;

    /*
     * Execute the residual arguments as a command.
     */

    if (objc == 1) {
	/*
	 * TIP #280. Make actual argument location available to eval'd script
	 */

	TclArgumentGet(interp, objv[0], &invoker, &word);
	objPtr = objv[0];

    } else {
	/*
	 * More than one argument: concatenate them together with spaces
	 * between, then evaluate the result. Tcl_EvalObjEx will delete the
	 * object when it decrements its refcount after eval'ing it.
	 */

	objPtr = Tcl_ConcatObj(objc, objv);
    }

    TclNRAddCallback(interp, Uplevel_Callback, savedVarFramePtr, NULL, NULL,
	    NULL);
    return TclNREvalObjEx(interp, objPtr, 0, invoker, word);
}

/*
 *----------------------------------------------------------------------
 *
 * TclFindProc --
 *
 *	Given the name of a procedure, return a pointer to the record
 *	describing the procedure. The procedure will be looked up using the
 *	usual rules: first in the current namespace and then in the global
 *	namespace.
 *
 * Results:
 *	NULL is returned if the name doesn't correspond to any procedure.
 *	Otherwise, the return value is a pointer to the procedure's record. If
 *	the name is found but refers to an imported command that points to a
 *	"real" procedure defined in another namespace, a pointer to that
 *	"real" procedure's structure is returned.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Proc *
TclFindProc(
    Interp *iPtr,		/* Interpreter in which to look. */
    const char *procName)	/* Name of desired procedure. */
{
    Tcl_Command cmd;
    Command *cmdPtr;

    cmd = Tcl_FindCommand((Tcl_Interp *) iPtr, procName, NULL, /*flags*/ 0);
    if (cmd == (Tcl_Command) NULL) {
	return NULL;
    }
    cmdPtr = (Command *) cmd;

    return TclIsProc(cmdPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * TclIsProc --
 *
 *	Tells whether a command is a Tcl procedure or not.
 *
 * Results:
 *	If the given command is actually a Tcl procedure, the return value is
 *	the address of the record describing the procedure. Otherwise the
 *	return value is 0.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Proc *
TclIsProc(
    Command *cmdPtr)		/* Command to test. */
{
    Tcl_Command origCmd = TclGetOriginalCommand((Tcl_Command) cmdPtr);

    if (origCmd != NULL) {
	cmdPtr = (Command *) origCmd;
    }
    if (cmdPtr->deleteProc == TclProcDeleteProc) {
	return cmdPtr->objClientData;
    }
    return NULL;
}

static int
ProcWrongNumArgs(
    Tcl_Interp *interp,
    int skip)
{
    CallFrame *framePtr = ((Interp *)interp)->varFramePtr;
    register Proc *procPtr = framePtr->procPtr;
    register Var *defPtr;
    int localCt = procPtr->numCompiledLocals, numArgs, i;
    Tcl_Obj **desiredObjs;
    const char *final = NULL;

    /*
     * Build up desired argument list for Tcl_WrongNumArgs
     */

    numArgs = framePtr->procPtr->numArgs;
    desiredObjs = TclStackAlloc(interp,
	    (int) sizeof(Tcl_Obj *) * (numArgs+1));

    if (framePtr->isProcCallFrame & FRAME_IS_LAMBDA) {
	desiredObjs[0] = Tcl_NewStringObj("lambdaExpr", -1);
    } else {
	((Interp *) interp)->ensembleRewrite.numInsertedObjs -= skip - 1;

#ifdef AVOID_HACKS_FOR_ITCL
	desiredObjs[0] = framePtr->objv[skip-1];
#else
	desiredObjs[0] = Tcl_NewListObj(skip, framePtr->objv);
#endif /* AVOID_HACKS_FOR_ITCL */
    }
    Tcl_IncrRefCount(desiredObjs[0]);

    defPtr = (Var *) (&framePtr->localCachePtr->varName0 + localCt);
    for (i=1 ; i<=numArgs ; i++, defPtr++) {
	Tcl_Obj *argObj;
	Tcl_Obj *namePtr = localName(framePtr, i-1);

	if (defPtr->value.objPtr != NULL) {
	    TclNewObj(argObj);
	    Tcl_AppendStringsToObj(argObj, "?", TclGetString(namePtr), "?", NULL);
	} else if (defPtr->flags & VAR_IS_ARGS) {
	    numArgs--;
	    final = "?arg ...?";
	    break;
	} else {
	    argObj = namePtr;
	    Tcl_IncrRefCount(namePtr);
	}
	desiredObjs[i] = argObj;
    }

    Tcl_ResetResult(interp);
    Tcl_WrongNumArgs(interp, numArgs+1, desiredObjs, final);

    for (i=0 ; i<=numArgs ; i++) {
	Tcl_DecrRefCount(desiredObjs[i]);
    }
    TclStackFree(interp, desiredObjs);
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * TclInitCompiledLocals --
 *
 *	This routine is invoked in order to initialize the compiled locals
 *	table for a new call frame.
 *
 *	DEPRECATED: functionality has been inlined elsewhere; this function
 *	remains to insure binary compatibility with Itcl.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May invoke various name resolvers in order to determine which
 *	variables are being referenced at runtime.
 *
 *----------------------------------------------------------------------
 */

void
TclInitCompiledLocals(
    Tcl_Interp *interp,		/* Current interpreter. */
    CallFrame *framePtr,	/* Call frame to initialize. */
    Namespace *nsPtr)		/* Pointer to current namespace. */
{
    Var *varPtr = framePtr->compiledLocals;
    Tcl_Obj *bodyPtr;
    ByteCode *codePtr;

    bodyPtr = framePtr->procPtr->bodyPtr;
    if (bodyPtr->typePtr != &tclByteCodeType) {
	Tcl_Panic("body object for proc attached to frame is not a byte code type");
    }
    codePtr = bodyPtr->internalRep.otherValuePtr;

    if (framePtr->numCompiledLocals) {
	if (!codePtr->localCachePtr) {
	    InitLocalCache(framePtr->procPtr) ;
	}
	framePtr->localCachePtr = codePtr->localCachePtr;
	framePtr->localCachePtr->refCount++;
    }

    InitResolvedLocals(interp, codePtr, varPtr, nsPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * InitResolvedLocals --
 *
 *	This routine is invoked in order to initialize the compiled locals
 *	table for a new call frame.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May invoke various name resolvers in order to determine which
 *	variables are being referenced at runtime.
 *
 *----------------------------------------------------------------------
 */

static void
InitResolvedLocals(
    Tcl_Interp *interp,		/* Current interpreter. */
    ByteCode *codePtr,
    Var *varPtr,
    Namespace *nsPtr)		/* Pointer to current namespace. */
{
    Interp *iPtr = (Interp *) interp;
    int haveResolvers = (nsPtr->compiledVarResProc || iPtr->resolverPtr);
    CompiledLocal *firstLocalPtr, *localPtr;
    int varNum;
    Tcl_ResolvedVarInfo *resVarInfo;

    /*
     * Find the localPtr corresponding to varPtr
     */

    varNum = varPtr - iPtr->framePtr->compiledLocals;
    localPtr = iPtr->framePtr->procPtr->firstLocalPtr;
    while (varNum--) {
	localPtr = localPtr->nextPtr;
    }

    if (!(haveResolvers && (codePtr->flags & TCL_BYTECODE_RESOLVE_VARS))) {
	goto doInitResolvedLocals;
    }

    /*
     * This is the first run after a recompile, or else the resolver epoch
     * has changed: update the resolver cache.
     */

    firstLocalPtr = localPtr;
    for (; localPtr != NULL; localPtr = localPtr->nextPtr) {
	if (localPtr->resolveInfo) {
	    if (localPtr->resolveInfo->deleteProc) {
		localPtr->resolveInfo->deleteProc(localPtr->resolveInfo);
	    } else {
		ckfree(localPtr->resolveInfo);
	    }
	    localPtr->resolveInfo = NULL;
	}
	localPtr->flags &= ~VAR_RESOLVED;

	if (haveResolvers &&
		!(localPtr->flags & (VAR_ARGUMENT|VAR_TEMPORARY))) {
	    ResolverScheme *resPtr = iPtr->resolverPtr;
	    Tcl_ResolvedVarInfo *vinfo;
	    int result;

	    if (nsPtr->compiledVarResProc) {
		result = nsPtr->compiledVarResProc(nsPtr->interp,
			localPtr->name, localPtr->nameLength,
			(Tcl_Namespace *) nsPtr, &vinfo);
	    } else {
		result = TCL_CONTINUE;
	    }

	    while ((result == TCL_CONTINUE) && resPtr) {
		if (resPtr->compiledVarResProc) {
		    result = resPtr->compiledVarResProc(nsPtr->interp,
			    localPtr->name, localPtr->nameLength,
			    (Tcl_Namespace *) nsPtr, &vinfo);
		}
		resPtr = resPtr->nextPtr;
	    }
	    if (result == TCL_OK) {
		localPtr->resolveInfo = vinfo;
		localPtr->flags |= VAR_RESOLVED;
	    }
	}
    }
    localPtr = firstLocalPtr;
    codePtr->flags &= ~TCL_BYTECODE_RESOLVE_VARS;

    /*
     * Initialize the array of local variables stored in the call frame. Some
     * variables may have special resolution rules. In that case, we call
     * their "resolver" procs to get our hands on the variable, and we make
     * the compiled local a link to the real variable.
     */

  doInitResolvedLocals:
    for (; localPtr != NULL; varPtr++, localPtr = localPtr->nextPtr) {
	varPtr->flags = 0;
	varPtr->value.objPtr = NULL;

	/*
	 * Now invoke the resolvers to determine the exact variables that
	 * should be used.
	 */

	resVarInfo = localPtr->resolveInfo;
	if (resVarInfo && resVarInfo->fetchProc) {
	    register Var *resolvedVarPtr = (Var *)
		    resVarInfo->fetchProc(interp, resVarInfo);

	    if (resolvedVarPtr) {
		if (TclIsVarInHash(resolvedVarPtr)) {
		    VarHashRefCount(resolvedVarPtr)++;
		}
		varPtr->flags = VAR_LINK;
		varPtr->value.linkPtr = resolvedVarPtr;
	    }
	}
    }
}

void
TclFreeLocalCache(
    Tcl_Interp *interp,
    LocalCache *localCachePtr)
{
    int i;
    Tcl_Obj **namePtrPtr = &localCachePtr->varName0;

    for (i = 0; i < localCachePtr->numVars; i++, namePtrPtr++) {
	register Tcl_Obj *objPtr = *namePtrPtr;

	/*
	 * Note that this can be called with interp==NULL, on interp deletion.
	 * In that case, the literal table and objects go away on their own.
	 */

	if (objPtr) {
	    if (interp) {
		TclReleaseLiteral(interp, objPtr);
	    } else {
		Tcl_DecrRefCount(objPtr);
	    }
	}
    }
    ckfree(localCachePtr);
}

static void
InitLocalCache(
    Proc *procPtr)
{
    Interp *iPtr = procPtr->iPtr;
    ByteCode *codePtr = procPtr->bodyPtr->internalRep.otherValuePtr;
    int localCt = procPtr->numCompiledLocals;
    int numArgs = procPtr->numArgs, i = 0;

    Tcl_Obj **namePtr;
    Var *varPtr;
    LocalCache *localCachePtr;
    CompiledLocal *localPtr;
    int new;

    /*
     * Cache the names and initial values of local variables; store the
     * cache in both the framePtr for this execution and in the codePtr
     * for future calls.
     */

    localCachePtr = ckalloc(sizeof(LocalCache)
	    + (localCt - 1) * sizeof(Tcl_Obj *)
	    + numArgs * sizeof(Var));

    namePtr = &localCachePtr->varName0;
    varPtr = (Var *) (namePtr + localCt);
    localPtr = procPtr->firstLocalPtr;
    while (localPtr) {
	if (TclIsVarTemporary(localPtr)) {
	    *namePtr = NULL;
	} else {
	    *namePtr = TclCreateLiteral(iPtr, localPtr->name,
		    localPtr->nameLength, /* hash */ (unsigned int) -1,
		    &new, /* nsPtr */ NULL, 0, NULL);
	    Tcl_IncrRefCount(*namePtr);
	}

	if (i < numArgs) {
	    varPtr->flags = (localPtr->flags & VAR_IS_ARGS);
	    varPtr->value.objPtr = localPtr->defValuePtr;
	    varPtr++;
	    i++;
	}
	namePtr++;
	localPtr = localPtr->nextPtr;
    }
    codePtr->localCachePtr = localCachePtr;
    localCachePtr->refCount = 1;
    localCachePtr->numVars = localCt;
}

/*
 *----------------------------------------------------------------------
 *
 * InitArgsAndLocals --
 *
 *	This routine is invoked in order to initialize the arguments and other
 *	compiled locals table for a new call frame.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Allocates memory on the stack for the compiled local variables, the
 *	caller is responsible for freeing them. Initialises all variables. May
 *	invoke various name resolvers in order to determine which variables
 *	are being referenced at runtime.
 *
 *----------------------------------------------------------------------
 */

static int
InitArgsAndLocals(
    register Tcl_Interp *interp,/* Interpreter in which procedure was
				 * invoked. */
    Tcl_Obj *procNameObj,	/* Procedure name for error reporting. */
    int skip)			/* Number of initial arguments to be skipped,
				 * i.e., words in the "command name". */
{
    CallFrame *framePtr = ((Interp *)interp)->varFramePtr;
    register Proc *procPtr = framePtr->procPtr;
    ByteCode *codePtr = procPtr->bodyPtr->internalRep.otherValuePtr;
    register Var *varPtr, *defPtr;
    int localCt = procPtr->numCompiledLocals, numArgs, argCt, i, imax;
    Tcl_Obj *const *argObjs;

    /*
     * Make sure that the local cache of variable names and initial values has
     * been initialised properly .
     */

    if (localCt) {
	if (!codePtr->localCachePtr) {
	    InitLocalCache(procPtr) ;
	}
	framePtr->localCachePtr = codePtr->localCachePtr;
	framePtr->localCachePtr->refCount++;
	defPtr = (Var *) (&framePtr->localCachePtr->varName0 + localCt);
    } else {
	defPtr = NULL;
    }

    /*
     * Create the "compiledLocals" array. Make sure it is large enough to hold
     * all the procedure's compiled local variables, including its formal
     * parameters.
     */

    varPtr = TclStackAlloc(interp, (int)(localCt * sizeof(Var)));
    framePtr->compiledLocals = varPtr;
    framePtr->numCompiledLocals = localCt;

    /*
     * Match and assign the call's actual parameters to the procedure's formal
     * arguments. The formal arguments are described by the first numArgs
     * entries in both the Proc structure's local variable list and the call
     * frame's local variable array.
     */

    numArgs = procPtr->numArgs;
    argCt = framePtr->objc - skip;	/* Set it to the number of args to the
					 * procedure. */
    argObjs = framePtr->objv + skip;
    if (numArgs == 0) {
	if (argCt) {
	    goto incorrectArgs;
	} else {
	    goto correctArgs;
	}
    }
    imax = ((argCt < numArgs-1) ? argCt : numArgs-1);
    for (i = 0; i < imax; i++, varPtr++, defPtr ? defPtr++ : defPtr) {
	/*
	 * "Normal" arguments; last formal is special, depends on it being
	 * 'args'.
	 */

	Tcl_Obj *objPtr = argObjs[i];

	varPtr->flags = 0;
	varPtr->value.objPtr = objPtr;
	Tcl_IncrRefCount(objPtr);	/* Local var is a reference. */
    }
    for (; i < numArgs-1; i++, varPtr++, defPtr ? defPtr++ : defPtr) {
	/*
	 * This loop is entered if argCt < (numArgs-1). Set default values;
	 * last formal is special.
	 */

	Tcl_Obj *objPtr = defPtr ? defPtr->value.objPtr : NULL;

	if (!objPtr) {
	    goto incorrectArgs;
	}
	varPtr->flags = 0;
	varPtr->value.objPtr = objPtr;
	Tcl_IncrRefCount(objPtr);	/* Local var reference. */
    }

    /*
     * When we get here, the last formal argument remains to be defined:
     * defPtr and varPtr point to the last argument to be initialized.
     */

    varPtr->flags = 0;
    if (defPtr && defPtr->flags & VAR_IS_ARGS) {
	Tcl_Obj *listPtr = Tcl_NewListObj(argCt-i, argObjs+i);

	varPtr->value.objPtr = listPtr;
	Tcl_IncrRefCount(listPtr);	/* Local var is a reference. */
    } else if (argCt == numArgs) {
	Tcl_Obj *objPtr = argObjs[i];

	varPtr->value.objPtr = objPtr;
	Tcl_IncrRefCount(objPtr);	/* Local var is a reference. */
    } else if ((argCt < numArgs) && defPtr && defPtr->value.objPtr) {
	Tcl_Obj *objPtr = defPtr->value.objPtr;

	varPtr->value.objPtr = objPtr;
	Tcl_IncrRefCount(objPtr);	/* Local var is a reference. */
    } else {
	goto incorrectArgs;
    }
    varPtr++;

    /*
     * Initialise and resolve the remaining compiledLocals. In the absence of
     * resolvers, they are undefined local vars: (flags=0, value=NULL).
     */

  correctArgs:
    if (numArgs < localCt) {
	if (!framePtr->nsPtr->compiledVarResProc
		&& !((Interp *)interp)->resolverPtr) {
	    memset(varPtr, 0, (localCt - numArgs)*sizeof(Var));
	} else {
	    InitResolvedLocals(interp, codePtr, varPtr, framePtr->nsPtr);
	}
    }

    return TCL_OK;

    /*
     * Initialise all compiled locals to avoid problems at DeleteLocalVars.
     */

  incorrectArgs:
    memset(varPtr, 0,
	    ((framePtr->compiledLocals + localCt)-varPtr) * sizeof(Var));
    return ProcWrongNumArgs(interp, skip);
}

/*
 *----------------------------------------------------------------------
 *
 * PushProcCallFrame --
 *
 *	Compiles a proc body if necessary, then pushes a CallFrame suitable
 *	for executing it.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	The proc's body may be recompiled. A CallFrame is pushed, it will have
 *	to be popped by the caller.
 *
 *----------------------------------------------------------------------
 */

static int
PushProcCallFrame(
    ClientData clientData,	/* Record describing procedure to be
				 * interpreted. */
    register Tcl_Interp *interp,/* Interpreter in which procedure was
				 * invoked. */
    int objc,			/* Count of number of arguments to this
				 * procedure. */
    Tcl_Obj *const objv[],	/* Argument value objects. */
    int isLambda)		/* 1 if this is a call by ApplyObjCmd: it
				 * needs special rules for error msg */
{
    Proc *procPtr = clientData;
    Namespace *nsPtr = procPtr->cmdPtr->nsPtr;
    CallFrame *framePtr, **framePtrPtr;
    int result;
    ByteCode *codePtr;

    /*
     * If necessary (i.e. if we haven't got a suitable compilation already
     * cached) compile the procedure's body. The compiler will allocate frame
     * slots for the procedure's non-argument local variables. Note that
     * compiling the body might increase procPtr->numCompiledLocals if new
     * local variables are found while compiling.
     */

    if (procPtr->bodyPtr->typePtr == &tclByteCodeType) {
	Interp *iPtr = (Interp *) interp;

	/*
	 * When we've got bytecode, this is the check for validity. That is,
	 * the bytecode must be for the right interpreter (no cross-leaks!),
	 * the code must be from the current epoch (so subcommand compilation
	 * is up-to-date), the namespace must match (so variable handling
	 * is right) and the resolverEpoch must match (so that new shadowed
	 * commands and/or resolver changes are considered).
	 */

	codePtr = procPtr->bodyPtr->internalRep.otherValuePtr;
	if (((Interp *) *codePtr->interpHandle != iPtr)
		|| (codePtr->compileEpoch != iPtr->compileEpoch)
		|| (codePtr->nsPtr != nsPtr)
		|| (codePtr->nsEpoch != nsPtr->resolverEpoch)) {
	    goto doCompilation;
	}
    } else {
    doCompilation:
	result = TclProcCompileProc(interp, procPtr, procPtr->bodyPtr, nsPtr,
		(isLambda ? "body of lambda term" : "body of proc"),
		TclGetString(objv[isLambda]));
	if (result != TCL_OK) {
	    return result;
	}
    }

    /*
     * Set up and push a new call frame for the new procedure invocation.
     * This call frame will execute in the proc's namespace, which might be
     * different than the current namespace. The proc's namespace is that of
     * its command, which can change if the command is renamed from one
     * namespace to another.
     */

    framePtrPtr = &framePtr;
    result = TclPushStackFrame(interp, (Tcl_CallFrame **) framePtrPtr,
	    (Tcl_Namespace *) nsPtr,
	    (isLambda? (FRAME_IS_PROC|FRAME_IS_LAMBDA) : FRAME_IS_PROC));
    if (result != TCL_OK) {
	return result;
    }

    framePtr->objc = objc;
    framePtr->objv = objv;
    framePtr->procPtr = procPtr;

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclObjInterpProc --
 *
 *	When a Tcl procedure gets invoked during bytecode evaluation, this
 *	object-based routine gets invoked to interpret the procedure.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	Depends on the commands in the procedure.
 *
 *----------------------------------------------------------------------
 */

int
TclObjInterpProc(
    ClientData clientData,	/* Record describing procedure to be
				 * interpreted. */
    register Tcl_Interp *interp,/* Interpreter in which procedure was
				 * invoked. */
    int objc,			/* Count of number of arguments to this
				 * procedure. */
    Tcl_Obj *const objv[])	/* Argument value objects. */
{
    /*
     * Not used much in the core; external interface for iTcl
     */

    return Tcl_NRCallObjProc(interp, TclNRInterpProc, clientData, objc, objv);
}

int
TclNRInterpProc(
    ClientData clientData,	/* Record describing procedure to be
				 * interpreted. */
    register Tcl_Interp *interp,/* Interpreter in which procedure was
				 * invoked. */
    int objc,			/* Count of number of arguments to this
				 * procedure. */
    Tcl_Obj *const objv[])	/* Argument value objects. */
{
    int result = PushProcCallFrame(clientData, interp, objc, objv,
	    /*isLambda*/ 0);

    if (result != TCL_OK) {
	return TCL_ERROR;
    }
    return TclNRInterpProcCore(interp, objv[0], 1, &MakeProcError);
}

/*
 *----------------------------------------------------------------------
 *
 * TclNRInterpProcCore --
 *
 *	When a Tcl procedure, lambda term or anything else that works like a
 *	procedure gets invoked during bytecode evaluation, this object-based
 *	routine gets invoked to interpret the body.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	Nearly anything; depends on the commands in the procedure body.
 *
 *----------------------------------------------------------------------
 */

int
TclNRInterpProcCore(
    register Tcl_Interp *interp,/* Interpreter in which procedure was
				 * invoked. */
    Tcl_Obj *procNameObj,	/* Procedure name for error reporting. */
    int skip,			/* Number of initial arguments to be skipped,
				 * i.e., words in the "command name". */
    ProcErrorProc *errorProc)	/* How to convert results from the script into
				 * results of the overall procedure. */
{
    Interp *iPtr = (Interp *) interp;
    register Proc *procPtr = iPtr->varFramePtr->procPtr;
    int result;
    CallFrame *freePtr;
    ByteCode *codePtr;

    result = InitArgsAndLocals(interp, procNameObj, skip);
    if (result != TCL_OK) {
	freePtr = iPtr->framePtr;
	Tcl_PopCallFrame(interp);	/* Pop but do not free. */
	TclStackFree(interp, freePtr->compiledLocals);
					/* Free compiledLocals. */
	TclStackFree(interp, freePtr);	/* Free CallFrame. */
	return TCL_ERROR;
    }

#if defined(TCL_COMPILE_DEBUG)
    if (tclTraceExec >= 1) {
	register CallFrame *framePtr = iPtr->varFramePtr;
	register int i;

	if (framePtr->isProcCallFrame & FRAME_IS_LAMBDA) {
	    fprintf(stdout, "Calling lambda ");
	} else {
	    fprintf(stdout, "Calling proc ");
	}
	for (i = 0; i < framePtr->objc; i++) {
	    TclPrintObject(stdout, framePtr->objv[i], 15);
	    fprintf(stdout, " ");
	}
	fprintf(stdout, "\n");
	fflush(stdout);
    }
#endif /*TCL_COMPILE_DEBUG*/

#ifdef USE_DTRACE
    if (TCL_DTRACE_PROC_ARGS_ENABLED()) {
	int l = iPtr->varFramePtr->isProcCallFrame & FRAME_IS_LAMBDA ? 1 : 0;
	const char *a[10];
	int i;

	for (i = 0 ; i < 10 ; i++) {
	    a[i] = (l < iPtr->varFramePtr->objc ?
		    TclGetString(iPtr->varFramePtr->objv[l]) : NULL);
	    l++;
	}
	TCL_DTRACE_PROC_ARGS(a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7],
		a[8], a[9]);
    }
    if (TCL_DTRACE_PROC_INFO_ENABLED() && iPtr->cmdFramePtr) {
	Tcl_Obj *info = TclInfoFrame(interp, iPtr->cmdFramePtr);
	const char *a[6]; int i[2];

	TclDTraceInfo(info, a, i);
	TCL_DTRACE_PROC_INFO(a[0], a[1], a[2], a[3], i[0], i[1], a[4], a[5]);
	TclDecrRefCount(info);
    }
    if (TCL_DTRACE_PROC_ENTRY_ENABLED()) {
	int l = iPtr->varFramePtr->isProcCallFrame & FRAME_IS_LAMBDA ? 1 : 0;

	TCL_DTRACE_PROC_ENTRY(l < iPtr->varFramePtr->objc ?
		TclGetString(iPtr->varFramePtr->objv[l]) : NULL,
		iPtr->varFramePtr->objc - l - 1,
		(Tcl_Obj **)(iPtr->varFramePtr->objv + l + 1));
    }
    if (TCL_DTRACE_PROC_ENTRY_ENABLED()) {
	int l = iPtr->varFramePtr->isProcCallFrame & FRAME_IS_LAMBDA ? 1 : 0;

	TCL_DTRACE_PROC_ENTRY(l < iPtr->varFramePtr->objc ?
		TclGetString(iPtr->varFramePtr->objv[l]) : NULL,
		iPtr->varFramePtr->objc - l - 1,
		(Tcl_Obj **)(iPtr->varFramePtr->objv + l + 1));
    }
#endif /* USE_DTRACE */

    /*
     * Invoke the commands in the procedure's body.
     */

    procPtr->refCount++;
    codePtr = procPtr->bodyPtr->internalRep.otherValuePtr;

    TclNRAddCallback(interp, InterpProcNR2, procNameObj, errorProc,
	    NULL, NULL);
    return TclNRExecuteByteCode(interp, codePtr);
}

static int
InterpProcNR2(
    ClientData data[],
    Tcl_Interp *interp,
    int result)
{
    Interp *iPtr = (Interp *) interp;
    Proc *procPtr = iPtr->varFramePtr->procPtr;
    CallFrame *freePtr;
    Tcl_Obj *procNameObj = data[0];
    ProcErrorProc *errorProc = (ProcErrorProc *)data[1];

    if (TCL_DTRACE_PROC_RETURN_ENABLED()) {
	int l = iPtr->varFramePtr->isProcCallFrame & FRAME_IS_LAMBDA ? 1 : 0;

	TCL_DTRACE_PROC_RETURN(l < iPtr->varFramePtr->objc ?
		TclGetString(iPtr->varFramePtr->objv[l]) : NULL, result);
    }
    if (--procPtr->refCount <= 0) {
	TclProcCleanupProc(procPtr);
    }

    /*
     * Process the result code.
     */

    switch (result) {
    case TCL_RETURN:
	/*
	 * If it is a 'return', do the TIP#90 processing now.
	 */

	result = TclUpdateReturnInfo((Interp *) interp);
	break;

    case TCL_CONTINUE:
    case TCL_BREAK:
	/*
	 * It's an error to get to this point from a 'break' or 'continue', so
	 * transform to an error now.
	 */

	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"invoked \"%s\" outside of a loop",
		((result == TCL_BREAK) ? "break" : "continue")));
	Tcl_SetErrorCode(interp, "TCL", "RESULT", "UNEXPECTED", NULL);
	result = TCL_ERROR;

	/*
	 * Fall through to the TCL_ERROR handling code.
	 */

    case TCL_ERROR:
	/*
	 * Now it _must_ be an error, so we need to log it as such. This means
	 * filling out the error trace. Luckily, we just hand this off to the
	 * function handed to us as an argument.
	 */

	errorProc(interp, procNameObj);

    default:
	/*
	 * Process other results (OK and non-standard) by doing nothing
	 * special, skipping directly to the code afterwards that cleans up
	 * associated memory.
	 *
	 * Non-standard results are processed by passing them through quickly.
	 * This means they all work as exceptions, unwinding the stack quickly
	 * and neatly. Who knows how well they are handled by third-party code
	 * though...
	 */

	(void) 0;		/* do nothing */
    }

    if (TCL_DTRACE_PROC_RESULT_ENABLED()) {
	int l = iPtr->varFramePtr->isProcCallFrame & FRAME_IS_LAMBDA ? 1 : 0;
	Tcl_Obj *r = Tcl_GetObjResult(interp);

	TCL_DTRACE_PROC_RESULT(l < iPtr->varFramePtr->objc ?
		TclGetString(iPtr->varFramePtr->objv[l]) : NULL, result,
		TclGetString(r), r);
    }

    /*
     * Free the stack-allocated compiled locals and CallFrame. It is important
     * to pop the call frame without freeing it first: the compiledLocals
     * cannot be freed before the frame is popped, as the local variables must
     * be deleted. But the compiledLocals must be freed first, as they were
     * allocated later on the stack.
     */

    freePtr = iPtr->framePtr;
    Tcl_PopCallFrame(interp);		/* Pop but do not free. */
    TclStackFree(interp, freePtr->compiledLocals);
					/* Free compiledLocals. */
    TclStackFree(interp, freePtr);	/* Free CallFrame. */

    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * TclProcCompileProc --
 *
 *	Called just before a procedure is executed to compile the body to byte
 *	codes. If the type of the body is not "byte code" or if the compile
 *	conditions have changed (namespace context, epoch counters, etc.) then
 *	the body is recompiled. Otherwise, this function does nothing.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May change the internal representation of the body object to compiled
 *	code.
 *
 *----------------------------------------------------------------------
 */

int
TclProcCompileProc(
    Tcl_Interp *interp,		/* Interpreter containing procedure. */
    Proc *procPtr,		/* Data associated with procedure. */
    Tcl_Obj *bodyPtr,		/* Body of proc. (Usually procPtr->bodyPtr,
				 * but could be any code fragment compiled in
				 * the context of this procedure.) */
    Namespace *nsPtr,		/* Namespace containing procedure. */
    const char *description,	/* string describing this body of code. */
    const char *procName)	/* Name of this procedure. */
{
    Interp *iPtr = (Interp *) interp;
    Tcl_CallFrame *framePtr;
    ByteCode *codePtr = bodyPtr->internalRep.otherValuePtr;

    /*
     * If necessary, compile the procedure's body. The compiler will allocate
     * frame slots for the procedure's non-argument local variables. If the
     * ByteCode already exists, make sure it hasn't been invalidated by
     * someone redefining a core command (this might make the compiled code
     * wrong). Also, if the code was compiled in/for a different interpreter,
     * we recompile it. Note that compiling the body might increase
     * procPtr->numCompiledLocals if new local variables are found while
     * compiling.
     *
     * Precompiled procedure bodies, however, are immutable and therefore they
     * are not recompiled, even if things have changed.
     */

    if (bodyPtr->typePtr == &tclByteCodeType) {
	if (((Interp *) *codePtr->interpHandle == iPtr)
		&& (codePtr->compileEpoch == iPtr->compileEpoch)
		&& (codePtr->nsPtr == nsPtr)
		&& (codePtr->nsEpoch == nsPtr->resolverEpoch)) {
	    return TCL_OK;
	}

	if (codePtr->flags & TCL_BYTECODE_PRECOMPILED) {
	    if ((Interp *) *codePtr->interpHandle != iPtr) {
		Tcl_SetObjResult(interp, Tcl_NewStringObj(
			"a precompiled script jumped interps", -1));
		Tcl_SetErrorCode(interp, "TCL", "OPERATION", "PROC",
			"CROSSINTERPBYTECODE", NULL);
		return TCL_ERROR;
	    }
	    codePtr->compileEpoch = iPtr->compileEpoch;
	    codePtr->nsPtr = nsPtr;
	} else {
	    TclFreeIntRep(bodyPtr);
	}
    }

    if (bodyPtr->typePtr != &tclByteCodeType) {
	Tcl_HashEntry *hePtr;

#ifdef TCL_COMPILE_DEBUG
	if (tclTraceCompile >= 1) {
	    /*
	     * Display a line summarizing the top level command we are about
	     * to compile.
	     */

	    Tcl_Obj *message;

	    TclNewLiteralStringObj(message, "Compiling ");
	    Tcl_IncrRefCount(message);
	    Tcl_AppendStringsToObj(message, description, " \"", NULL);
	    Tcl_AppendLimitedToObj(message, procName, -1, 50, NULL);
	    fprintf(stdout, "%s\"\n", TclGetString(message));
	    Tcl_DecrRefCount(message);
	}
#endif

	/*
	 * Plug the current procPtr into the interpreter and coerce the code
	 * body to byte codes. The interpreter needs to know which proc it's
	 * compiling so that it can access its list of compiled locals.
	 *
	 * TRICKY NOTE: Be careful to push a call frame with the proper
	 *   namespace context, so that the byte codes are compiled in the
	 *   appropriate class context.
	 */

	iPtr->compiledProcPtr = procPtr;

	if (procPtr->numCompiledLocals > procPtr->numArgs) {
	    CompiledLocal *clPtr = procPtr->firstLocalPtr;
	    CompiledLocal *lastPtr = NULL;
	    int i, numArgs = procPtr->numArgs;

	    for (i = 0; i < numArgs; i++) {
		lastPtr = clPtr;
		clPtr = clPtr->nextPtr;
	    }

	    if (lastPtr) {
		lastPtr->nextPtr = NULL;
	    } else {
		procPtr->firstLocalPtr = NULL;
	    }
	    procPtr->lastLocalPtr = lastPtr;
	    while (clPtr) {
		CompiledLocal *toFree = clPtr;

		clPtr = clPtr->nextPtr;
		if (toFree->resolveInfo) {
		    if (toFree->resolveInfo->deleteProc) {
			toFree->resolveInfo->deleteProc(toFree->resolveInfo);
		    } else {
			ckfree(toFree->resolveInfo);
		    }
		}
		ckfree(toFree);
	    }
	    procPtr->numCompiledLocals = procPtr->numArgs;
	}

	TclPushStackFrame(interp, &framePtr, (Tcl_Namespace *) nsPtr,
		/* isProcCallFrame */ 0);

	/*
	 * TIP #280: We get the invoking context from the cmdFrame which
	 * was saved by 'Tcl_ProcObjCmd' (using linePBodyPtr).
	 */

	hePtr = Tcl_FindHashEntry(iPtr->linePBodyPtr, (char *) procPtr);

	/*
	 * Constructed saved frame has body as word 0. See Tcl_ProcObjCmd.
	 */

	iPtr->invokeWord = 0;
	iPtr->invokeCmdFramePtr = (hePtr ? Tcl_GetHashValue(hePtr) : NULL);
	tclByteCodeType.setFromAnyProc(interp, bodyPtr);
	iPtr->invokeCmdFramePtr = NULL;
	TclPopStackFrame(interp);
    } else if (codePtr->nsEpoch != nsPtr->resolverEpoch) {
	/*
	 * The resolver epoch has changed, but we only need to invalidate the
	 * resolver cache.
	 */

	codePtr->nsEpoch = nsPtr->resolverEpoch;
	codePtr->flags |= TCL_BYTECODE_RESOLVE_VARS;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * MakeProcError --
 *
 *	Function called by TclObjInterpProc to create the stack information
 *	upon an error from a procedure.
 *
 * Results:
 *	The interpreter's error info trace is set to a value that supplements
 *	the error code.
 *
 * Side effects:
 *	none.
 *
 *----------------------------------------------------------------------
 */

static void
MakeProcError(
    Tcl_Interp *interp,		/* The interpreter in which the procedure was
				 * called. */
    Tcl_Obj *procNameObj)	/* Name of the procedure. Used for error
				 * messages and trace information. */
{
    int overflow, limit = 60, nameLen;
    const char *procName = Tcl_GetStringFromObj(procNameObj, &nameLen);

    overflow = (nameLen > limit);
    Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
	    "\n    (procedure \"%.*s%s\" line %d)",
	    (overflow ? limit : nameLen), procName,
	    (overflow ? "..." : ""), Tcl_GetErrorLine(interp)));
}

/*
 *----------------------------------------------------------------------
 *
 * TclProcDeleteProc --
 *
 *	This function is invoked just before a command procedure is removed
 *	from an interpreter. Its job is to release all the resources allocated
 *	to the procedure.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Memory gets freed, unless the procedure is actively being executed.
 *	In this case the cleanup is delayed until the last call to the current
 *	procedure completes.
 *
 *----------------------------------------------------------------------
 */

void
TclProcDeleteProc(
    ClientData clientData)	/* Procedure to be deleted. */
{
    Proc *procPtr = clientData;

    procPtr->refCount--;
    if (procPtr->refCount <= 0) {
	TclProcCleanupProc(procPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclProcCleanupProc --
 *
 *	This function does all the real work of freeing up a Proc structure.
 *	It's called only when the structure's reference count becomes zero.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Memory gets freed.
 *
 *----------------------------------------------------------------------
 */

void
TclProcCleanupProc(
    register Proc *procPtr)	/* Procedure to be deleted. */
{
    register CompiledLocal *localPtr;
    Tcl_Obj *bodyPtr = procPtr->bodyPtr;
    Tcl_Obj *defPtr;
    Tcl_ResolvedVarInfo *resVarInfo;
    Tcl_HashEntry *hePtr = NULL;
    CmdFrame *cfPtr = NULL;
    Interp *iPtr = procPtr->iPtr;

    if (bodyPtr != NULL) {
	Tcl_DecrRefCount(bodyPtr);
    }
    for (localPtr = procPtr->firstLocalPtr; localPtr != NULL; ) {
	CompiledLocal *nextPtr = localPtr->nextPtr;

	resVarInfo = localPtr->resolveInfo;
	if (resVarInfo) {
	    if (resVarInfo->deleteProc) {
		resVarInfo->deleteProc(resVarInfo);
	    } else {
		ckfree(resVarInfo);
	    }
	}

	if (localPtr->defValuePtr != NULL) {
	    defPtr = localPtr->defValuePtr;
	    Tcl_DecrRefCount(defPtr);
	}
	ckfree(localPtr);
	localPtr = nextPtr;
    }
    ckfree(procPtr);

    /*
     * TIP #280: Release the location data associated with this Proc
     * structure, if any. The interpreter may not exist (For example for
     * procbody structures created by tbcload.
     */

    if (iPtr == NULL) {
	return;
    }

    hePtr = Tcl_FindHashEntry(iPtr->linePBodyPtr, (char *) procPtr);
    if (!hePtr) {
	return;
    }

    cfPtr = Tcl_GetHashValue(hePtr);

    if (cfPtr) {
	if (cfPtr->type == TCL_LOCATION_SOURCE) {
	    Tcl_DecrRefCount(cfPtr->data.eval.path);
	    cfPtr->data.eval.path = NULL;
	}
	ckfree(cfPtr->line);
	cfPtr->line = NULL;
	ckfree(cfPtr);
    }
    Tcl_DeleteHashEntry(hePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * TclUpdateReturnInfo --
 *
 *	This function is called when procedures return, and at other points
 *	where the TCL_RETURN code is used. It examines the returnLevel and
 *	returnCode to determine the real return status.
 *
 * Results:
 *	The return value is the true completion code to use for the procedure
 *	or script, instead of TCL_RETURN.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TclUpdateReturnInfo(
    Interp *iPtr)		/* Interpreter for which TCL_RETURN exception
				 * is being processed. */
{
    int code = TCL_RETURN;

    iPtr->returnLevel--;
    if (iPtr->returnLevel < 0) {
	Tcl_Panic("TclUpdateReturnInfo: negative return level");
    }
    if (iPtr->returnLevel == 0) {
	/*
	 * Now we've reached the level to return the requested -code.
	 * Since iPtr->returnLevel and iPtr->returnCode have completed
	 * their task, we now reset them to default values so that any
	 * bare "return TCL_RETURN" that may follow will work [Bug 2152286].
	 */

	code = iPtr->returnCode;
	iPtr->returnLevel = 1;
	iPtr->returnCode = TCL_OK;
	if (code == TCL_ERROR) {
	    iPtr->flags |= ERR_LEGACY_COPY;
	}
    }
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetObjInterpProc --
 *
 *	Returns a pointer to the TclObjInterpProc function; this is different
 *	from the value obtained from the TclObjInterpProc reference on systems
 *	like Windows where import and export versions of a function exported
 *	by a DLL exist.
 *
 * Results:
 *	Returns the internal address of the TclObjInterpProc function.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

TclObjCmdProcType
TclGetObjInterpProc(void)
{
    return (TclObjCmdProcType) TclObjInterpProc;
}

/*
 *----------------------------------------------------------------------
 *
 * TclNewProcBodyObj --
 *
 *	Creates a new object, of type "procbody", whose internal
 *	representation is the given Proc struct. The newly created object's
 *	reference count is 0.
 *
 * Results:
 *	Returns a pointer to a newly allocated Tcl_Obj, NULL on error.
 *
 * Side effects:
 *	The reference count in the ByteCode attached to the Proc is bumped up
 *	by one, since the internal rep stores a pointer to it.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclNewProcBodyObj(
    Proc *procPtr)		/* the Proc struct to store as the internal
				 * representation. */
{
    Tcl_Obj *objPtr;

    if (!procPtr) {
	return NULL;
    }

    TclNewObj(objPtr);
    if (objPtr) {
	objPtr->typePtr = &tclProcBodyType;
	objPtr->internalRep.otherValuePtr = procPtr;

	procPtr->refCount++;
    }

    return objPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * ProcBodyDup --
 *
 *	Tcl_ObjType's Dup function for the proc body object. Bumps the
 *	reference count on the Proc stored in the internal representation.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets up the object in dupPtr to be a duplicate of the one in srcPtr.
 *
 *----------------------------------------------------------------------
 */

static void
ProcBodyDup(
    Tcl_Obj *srcPtr,		/* Object to copy. */
    Tcl_Obj *dupPtr)		/* Target object for the duplication. */
{
    Proc *procPtr = srcPtr->internalRep.otherValuePtr;

    dupPtr->typePtr = &tclProcBodyType;
    dupPtr->internalRep.otherValuePtr = procPtr;
    procPtr->refCount++;
}

/*
 *----------------------------------------------------------------------
 *
 * ProcBodyFree --
 *
 *	Tcl_ObjType's Free function for the proc body object. The reference
 *	count on its Proc struct is decreased by 1; if the count reaches 0,
 *	the proc is freed.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If the reference count on the Proc struct reaches 0, the struct is
 *	freed.
 *
 *----------------------------------------------------------------------
 */

static void
ProcBodyFree(
    Tcl_Obj *objPtr)		/* The object to clean up. */
{
    Proc *procPtr = objPtr->internalRep.otherValuePtr;

    procPtr->refCount--;
    if (procPtr->refCount <= 0) {
	TclProcCleanupProc(procPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * DupLambdaInternalRep, FreeLambdaInternalRep, SetLambdaFromAny --
 *
 *	How to manage the internal representations of lambda term objects.
 *	Syntactically they look like a two- or three-element list, where the
 *	first element is the formal arguments, the second is the the body, and
 *	the (optional) third is the namespace to execute the lambda term
 *	within (the global namespace is assumed if it is absent).
 *
 *----------------------------------------------------------------------
 */

static void
DupLambdaInternalRep(
    Tcl_Obj *srcPtr,		/* Object with internal rep to copy. */
    register Tcl_Obj *copyPtr)	/* Object with internal rep to set. */
{
    Proc *procPtr = srcPtr->internalRep.twoPtrValue.ptr1;
    Tcl_Obj *nsObjPtr = srcPtr->internalRep.twoPtrValue.ptr2;

    copyPtr->internalRep.twoPtrValue.ptr1 = procPtr;
    copyPtr->internalRep.twoPtrValue.ptr2 = nsObjPtr;

    procPtr->refCount++;
    Tcl_IncrRefCount(nsObjPtr);
    copyPtr->typePtr = &lambdaType;
}

static void
FreeLambdaInternalRep(
    register Tcl_Obj *objPtr)	/* CmdName object with internal representation
				 * to free. */
{
    Proc *procPtr = objPtr->internalRep.twoPtrValue.ptr1;
    Tcl_Obj *nsObjPtr = objPtr->internalRep.twoPtrValue.ptr2;

    procPtr->refCount--;
    if (procPtr->refCount == 0) {
	TclProcCleanupProc(procPtr);
    }
    TclDecrRefCount(nsObjPtr);
    objPtr->typePtr = NULL;
}

static int
SetLambdaFromAny(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    register Tcl_Obj *objPtr)	/* The object to convert. */
{
    Interp *iPtr = (Interp *) interp;
    const char *name;
    Tcl_Obj *argsPtr, *bodyPtr, *nsObjPtr, **objv;
    int isNew, objc, result;
    CmdFrame *cfPtr = NULL;
    Proc *procPtr;

    if (interp == NULL) {
	return TCL_ERROR;
    }

    /*
     * Convert objPtr to list type first; if it cannot be converted, or if its
     * length is not 2, then it cannot be converted to lambdaType.
     */

    result = TclListObjGetElements(NULL, objPtr, &objc, &objv);
    if ((result != TCL_OK) || ((objc != 2) && (objc != 3))) {
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't interpret \"%s\" as a lambda expression",
		Tcl_GetString(objPtr)));
	Tcl_SetErrorCode(interp, "TCL", "VALUE", "LAMBDA", NULL);
	return TCL_ERROR;
    }

    argsPtr = objv[0];
    bodyPtr = objv[1];

    /*
     * Create and initialize the Proc struct. The cmdPtr field is set to NULL
     * to signal that this is an anonymous function.
     */

    name = TclGetString(objPtr);

    if (TclCreateProc(interp, /*ignored nsPtr*/ NULL, name, argsPtr, bodyPtr,
	    &procPtr) != TCL_OK) {
	Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
		"\n    (parsing lambda expression \"%s\")", name));
	return TCL_ERROR;
    }

    /*
     * CAREFUL: TclCreateProc returns refCount==1! [Bug 1578454]
     * procPtr->refCount = 1;
     */

    procPtr->cmdPtr = NULL;

    /*
     * TIP #280: Remember the line the apply body is starting on. In a Byte
     * code context we ask the engine to provide us with the necessary
     * information. This is for the initialization of the byte code compiler
     * when the body is used for the first time.
     *
     * NOTE: The body is the second word in the 'objPtr'. Its location,
     * accessible through 'context.line[1]' (see below) is therefore only the
     * first approximation of the actual line the body is on. We have to use
     * the string rep of the 'objPtr' to determine the exact line. This is
     * available already through 'name'. Use 'TclListLines', see 'switch'
     * (tclCmdMZ.c).
     *
     * This code is nearly identical to the #280 code in Tcl_ProcObjCmd, see
     * this file. The differences are the different index of the body in the
     * line array of the context, and the special processing mentioned in the
     * previous paragraph to track into the list. Find a way to factor the
     * common elements into a single function.
     */

    if (iPtr->cmdFramePtr) {
	CmdFrame *contextPtr = TclStackAlloc(interp, sizeof(CmdFrame));

	*contextPtr = *iPtr->cmdFramePtr;
	if (contextPtr->type == TCL_LOCATION_BC) {
	    /*
	     * Retrieve the source context from the bytecode. This call
	     * accounts for the reference to the source file, if any, held in
	     * 'context.data.eval.path'.
	     */

	    TclGetSrcInfoForPc(contextPtr);
	} else if (contextPtr->type == TCL_LOCATION_SOURCE) {
	    /*
	     * We created a new reference to the source file path name when we
	     * created 'context' above. Account for the reference.
	     */

	    Tcl_IncrRefCount(contextPtr->data.eval.path);

	}

	if (contextPtr->type == TCL_LOCATION_SOURCE) {
	    /*
	     * We can record source location within a lambda only if the body
	     * was not created by substitution.
	     */

	    if (contextPtr->line
		    && (contextPtr->nline >= 2) && (contextPtr->line[1] >= 0)) {
		int buf[2];

		/*
		 * Move from approximation (line of list cmd word) to actual
		 * location (line of 2nd list element).
		 */

		cfPtr = ckalloc(sizeof(CmdFrame));
		TclListLines(objPtr, contextPtr->line[1], 2, buf, NULL);

		cfPtr->level = -1;
		cfPtr->type = contextPtr->type;
		cfPtr->line = ckalloc(sizeof(int));
		cfPtr->line[0] = buf[1];
		cfPtr->nline = 1;
		cfPtr->framePtr = NULL;
		cfPtr->nextPtr = NULL;

		cfPtr->data.eval.path = contextPtr->data.eval.path;
		Tcl_IncrRefCount(cfPtr->data.eval.path);

		cfPtr->cmd.str.cmd = NULL;
		cfPtr->cmd.str.len = 0;
	    }

	    /*
	     * 'contextPtr' is going out of scope. Release the reference that
	     * it's holding to the source file path
	     */

	    Tcl_DecrRefCount(contextPtr->data.eval.path);
	}
	TclStackFree(interp, contextPtr);
    }
    Tcl_SetHashValue(Tcl_CreateHashEntry(iPtr->linePBodyPtr, procPtr,
	    &isNew), cfPtr);

    /*
     * Set the namespace for this lambda: given by objv[2] understood as a
     * global reference, or else global per default.
     */

    if (objc == 2) {
	TclNewLiteralStringObj(nsObjPtr, "::");
    } else {
	const char *nsName = TclGetString(objv[2]);

	if ((*nsName != ':') || (*(nsName+1) != ':')) {
	    TclNewLiteralStringObj(nsObjPtr, "::");
	    Tcl_AppendObjToObj(nsObjPtr, objv[2]);
	} else {
	    nsObjPtr = objv[2];
	}
    }

    Tcl_IncrRefCount(nsObjPtr);

    /*
     * Free the list internalrep of objPtr - this will free argsPtr, but
     * bodyPtr retains a reference from the Proc structure. Then finish the
     * conversion to lambdaType.
     */

    TclFreeIntRep(objPtr);

    objPtr->internalRep.twoPtrValue.ptr1 = procPtr;
    objPtr->internalRep.twoPtrValue.ptr2 = nsObjPtr;
    objPtr->typePtr = &lambdaType;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ApplyObjCmd --
 *
 *	This object-based function is invoked to process the "apply" Tcl
 *	command. See the user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl object result value.
 *
 * Side effects:
 *	Depends on the content of the lambda term (i.e., objv[1]).
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ApplyObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    return Tcl_NRCallObjProc(interp, TclNRApplyObjCmd, dummy, objc, objv);
}

int
TclNRApplyObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    Interp *iPtr = (Interp *) interp;
    Proc *procPtr = NULL;
    Tcl_Obj *lambdaPtr, *nsObjPtr;
    int result, isRootEnsemble;
    Tcl_Namespace *nsPtr;
    ApplyExtraData *extraPtr;

    if (objc < 2) {
	Tcl_WrongNumArgs(interp, 1, objv, "lambdaExpr ?arg ...?");
	return TCL_ERROR;
    }

    /*
     * Set lambdaPtr, convert it to lambdaType in the current interp if
     * necessary.
     */

    lambdaPtr = objv[1];
    if (lambdaPtr->typePtr == &lambdaType) {
	procPtr = lambdaPtr->internalRep.twoPtrValue.ptr1;
    }

#define JOE_EXTENSION 0
/*
 * Note: this code is NOT FUNCTIONAL due to the NR implementation; DO NOT
 * ENABLE! Leaving here as reminder to (a) TIP the suggestion, and (b) adapt
 * the code. (MS)
 */

#if JOE_EXTENSION
    else {
	/*
	 * Joe English's suggestion to allow cmdNames to function as lambdas.
	 * Also requires making tclCmdNameType non-static in tclObj.c
	 */

	Tcl_Obj *elemPtr;
	int numElem;

	if ((lambdaPtr->typePtr == &tclCmdNameType) ||
		(TclListObjGetElements(interp, lambdaPtr, &numElem,
		&elemPtr) == TCL_OK && numElem == 1)) {
	    return Tcl_EvalObjv(interp, objc-1, objv+1, 0);
	}
    }
#endif

    if ((procPtr == NULL) || (procPtr->iPtr != iPtr)) {
	result = SetLambdaFromAny(interp, lambdaPtr);
	if (result != TCL_OK) {
	    return result;
	}
	procPtr = lambdaPtr->internalRep.twoPtrValue.ptr1;
    }

    /*
     * Find the namespace where this lambda should run, and push a call frame
     * for that namespace. Note that TclObjInterpProc() will pop it.
     */

    nsObjPtr = lambdaPtr->internalRep.twoPtrValue.ptr2;
    result = TclGetNamespaceFromObj(interp, nsObjPtr, &nsPtr);
    if (result != TCL_OK) {
	return TCL_ERROR;
    }

    extraPtr = TclStackAlloc(interp, sizeof(ApplyExtraData));
    memset(&extraPtr->cmd, 0, sizeof(Command));
    procPtr->cmdPtr = &extraPtr->cmd;
    extraPtr->cmd.nsPtr = (Namespace *) nsPtr;

    /*
     * TIP#280 (semi-)HACK!
     *
     * Using cmd.clientData to tell [info frame] how to render the lambdaPtr.
     * The InfoFrameCmd will detect this case by testing cmd.hPtr for NULL.
     * This condition holds here because of the memset() above, and nowhere
     * else (in the core). Regular commands always have a valid hPtr, and
     * lambda's never.
     */

    extraPtr->efi.length = 1;
    extraPtr->efi.fields[0].name = "lambda";
    extraPtr->efi.fields[0].proc = NULL;
    extraPtr->efi.fields[0].clientData = lambdaPtr;
    extraPtr->cmd.clientData = &extraPtr->efi;

    isRootEnsemble = (iPtr->ensembleRewrite.sourceObjs == NULL);
    if (isRootEnsemble) {
	iPtr->ensembleRewrite.sourceObjs = objv;
	iPtr->ensembleRewrite.numRemovedObjs = 1;
	iPtr->ensembleRewrite.numInsertedObjs = 0;
    } else {
	iPtr->ensembleRewrite.numInsertedObjs -= 1;
    }
    extraPtr->isRootEnsemble = isRootEnsemble;

    result = PushProcCallFrame(procPtr, interp, objc, objv, 1);
    if (result == TCL_OK) {
	TclNRAddCallback(interp, ApplyNR2, extraPtr, NULL, NULL, NULL);
	result = TclNRInterpProcCore(interp, objv[1], 2, &MakeLambdaError);
    }
    return result;
}

static int
ApplyNR2(
    ClientData data[],
    Tcl_Interp *interp,
    int result)
{
    ApplyExtraData *extraPtr = data[0];

    if (extraPtr->isRootEnsemble) {
	((Interp *) interp)->ensembleRewrite.sourceObjs = NULL;
    }

    TclStackFree(interp, extraPtr);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * MakeLambdaError --
 *
 *	Function called by TclObjInterpProc to create the stack information
 *	upon an error from a lambda term.
 *
 * Results:
 *	The interpreter's error info trace is set to a value that supplements
 *	the error code.
 *
 * Side effects:
 *	none.
 *
 *----------------------------------------------------------------------
 */

static void
MakeLambdaError(
    Tcl_Interp *interp,		/* The interpreter in which the procedure was
				 * called. */
    Tcl_Obj *procNameObj)	/* Name of the procedure. Used for error
				 * messages and trace information. */
{
    int overflow, limit = 60, nameLen;
    const char *procName = Tcl_GetStringFromObj(procNameObj, &nameLen);

    overflow = (nameLen > limit);
    Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
	    "\n    (lambda term \"%.*s%s\" line %d)",
	    (overflow ? limit : nameLen), procName,
	    (overflow ? "..." : ""), Tcl_GetErrorLine(interp)));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DisassembleObjCmd --
 *
 *	Implementation of the "::tcl::unsupported::disassemble" command. This
 *	command is not documented, but will disassemble procedures, lambda
 *	terms and general scripts. Note that will compile terms if necessary
 *	in order to disassemble them.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DisassembleObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const objv[])	/* Argument objects. */
{
    static const char *const types[] = {
	"lambda", "method", "objmethod", "proc", "script", NULL
    };
    enum Types {
	DISAS_LAMBDA, DISAS_CLASS_METHOD, DISAS_OBJECT_METHOD, DISAS_PROC,
	DISAS_SCRIPT
    };
    int idx, result;
    Tcl_Obj *codeObjPtr = NULL;
    Proc *procPtr = NULL;
    Tcl_HashEntry *hPtr;
    Object *oPtr;

    if (objc < 2) {
	Tcl_WrongNumArgs(interp, 1, objv, "type ...");
	return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[1], types, "type", 0, &idx)!=TCL_OK){
	return TCL_ERROR;
    }

    switch ((enum Types) idx) {
    case DISAS_LAMBDA: {
	Command cmd;
	Tcl_Obj *nsObjPtr;
	Tcl_Namespace *nsPtr;

	/*
	 * Compile (if uncompiled) and disassemble a lambda term.
	 */

	if (objc != 3) {
	    Tcl_WrongNumArgs(interp, 2, objv, "lambdaTerm");
	    return TCL_ERROR;
	}
	if (objv[2]->typePtr == &lambdaType) {
	    procPtr = objv[2]->internalRep.twoPtrValue.ptr1;
	}
	if (procPtr == NULL || procPtr->iPtr != (Interp *) interp) {
	    result = SetLambdaFromAny(interp, objv[2]);
	    if (result != TCL_OK) {
		return result;
	    }
	    procPtr = objv[2]->internalRep.twoPtrValue.ptr1;
	}

	memset(&cmd, 0, sizeof(Command));
	nsObjPtr = objv[2]->internalRep.twoPtrValue.ptr2;
	result = TclGetNamespaceFromObj(interp, nsObjPtr, &nsPtr);
	if (result != TCL_OK) {
	    return result;
	}
	cmd.nsPtr = (Namespace *) nsPtr;
	procPtr->cmdPtr = &cmd;
	result = PushProcCallFrame(procPtr, interp, objc, objv, 1);
	if (result != TCL_OK) {
	    return result;
	}
	TclPopStackFrame(interp);
	codeObjPtr = procPtr->bodyPtr;
	break;
    }
    case DISAS_PROC:
	if (objc != 3) {
	    Tcl_WrongNumArgs(interp, 2, objv, "procName");
	    return TCL_ERROR;
	}

	procPtr = TclFindProc((Interp *) interp, TclGetString(objv[2]));
	if (procPtr == NULL) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "\"%s\" isn't a procedure", TclGetString(objv[2])));
	    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "PROC",
		    TclGetString(objv[2]), NULL);
	    return TCL_ERROR;
	}

	/*
	 * Compile (if uncompiled) and disassemble a procedure.
	 */

	result = PushProcCallFrame(procPtr, interp, 2, objv+1, 1);
	if (result != TCL_OK) {
	    return result;
	}
	TclPopStackFrame(interp);
	codeObjPtr = procPtr->bodyPtr;
	break;
    case DISAS_SCRIPT:
	/*
	 * Compile and disassemble a script.
	 */

	if (objc != 3) {
	    Tcl_WrongNumArgs(interp, 2, objv, "script");
	    return TCL_ERROR;
	}
	if (objv[2]->typePtr != &tclByteCodeType) {
	    if (TclSetByteCodeFromAny(interp, objv[2], NULL, NULL) != TCL_OK){
		return TCL_ERROR;
	    }
	}
	codeObjPtr = objv[2];
	break;

    case DISAS_CLASS_METHOD:
	if (objc != 4) {
	    Tcl_WrongNumArgs(interp, 2, objv, "className methodName");
	    return TCL_ERROR;
	}

	/*
	 * Look up the body of a class method.
	 */

	oPtr = (Object *) Tcl_GetObjectFromObj(interp, objv[2]);
	if (oPtr == NULL) {
	    return TCL_ERROR;
	}
	if (oPtr->classPtr == NULL) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "\"%s\" is not a class", TclGetString(objv[2])));
	    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "CLASS",
		    TclGetString(objv[2]), NULL);
	    return TCL_ERROR;
	}
	hPtr = Tcl_FindHashEntry(&oPtr->classPtr->classMethods,
		(char *) objv[3]);
	goto methodBody;
    case DISAS_OBJECT_METHOD:
	if (objc != 4) {
	    Tcl_WrongNumArgs(interp, 2, objv, "objectName methodName");
	    return TCL_ERROR;
	}

	/*
	 * Look up the body of an instance method.
	 */

	oPtr = (Object *) Tcl_GetObjectFromObj(interp, objv[2]);
	if (oPtr == NULL) {
	    return TCL_ERROR;
	}
	if (oPtr->methodsPtr == NULL) {
	    goto unknownMethod;
	}
	hPtr = Tcl_FindHashEntry(oPtr->methodsPtr, (char *) objv[3]);

	/*
	 * Compile (if necessary) and disassemble a method body.
	 */

    methodBody:
	if (hPtr == NULL) {
	unknownMethod:
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		    "unknown method \"%s\"", TclGetString(objv[3])));
	    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "METHOD",
		    TclGetString(objv[3]), NULL);
	    return TCL_ERROR;
	}
	procPtr = TclOOGetProcFromMethod(Tcl_GetHashValue(hPtr));
	if (procPtr == NULL) {
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
		    "body not available for this kind of method", -1));
	    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "DISASSEMBLE",
		    "METHODTYPE", NULL);
	    return TCL_ERROR;
	}
	if (procPtr->bodyPtr->typePtr != &tclByteCodeType) {
	    Command cmd;

	    /*
	     * Yes, this is ugly, but we need to pass the namespace in to the
	     * compiler in two places.
	     */

	    cmd.nsPtr = (Namespace *) oPtr->namespacePtr;
	    procPtr->cmdPtr = &cmd;
	    result = TclProcCompileProc(interp, procPtr, procPtr->bodyPtr,
		    (Namespace *) oPtr->namespacePtr, "body of method",
		    TclGetString(objv[3]));
	    procPtr->cmdPtr = NULL;
	    if (result != TCL_OK) {
		return result;
	    }
	}
	codeObjPtr = procPtr->bodyPtr;
	break;
    default:
	CLANG_ASSERT(0);
    }

    /*
     * Do the actual disassembly.
     */

    if (((ByteCode *) codeObjPtr->internalRep.otherValuePtr)->flags
	    & TCL_BYTECODE_PRECOMPILED) {
	Tcl_SetObjResult(interp, Tcl_NewStringObj(
		"may not disassemble prebuilt bytecode", -1));
	Tcl_SetErrorCode(interp, "TCL", "OPERATION", "DISASSEMBLE",
		"BYTECODE", NULL);
	return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, TclDisassembleByteCodeObj(codeObjPtr));
    return TCL_OK;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */
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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.
 */

#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 int		CloseChannelPart(Tcl_Interp *interp, Channel *chanPtr,
			    int errorCode, int flags);
static int		CloseWrite(Tcl_Interp *interp, Channel *chanPtr);
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, int allowShortReads);
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);
static int              WillRead(Channel *chanPtr);

/*
 * 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
ChanCloseHalf(
    Channel *chanPtr,
    Tcl_Interp *interp,
    int flags)
{
    return chanPtr->typePtr->close2Proc(chanPtr->instanceData, interp, flags);
}

static inline int
ChanRead(
    Channel *chanPtr,
    char *dst,
    int dstSize,
    int *errnoPtr)
{
    if (WillRead(chanPtr) < 0) {
        return -1;
    }

    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 */
    int doflushnb;

    /* Fetch the pre-TIP#398 compatibility flag */ 
    {
        const char *s;
        Tcl_DString ds;
        
        s = TclGetEnv("TCL_FLUSH_NONBLOCKING_ON_EXIT", &ds);
        doflushnb = ((s != NULL) && strcmp(s, "0"));
        if (s != NULL) {
            Tcl_DStringFree(&ds);
        }
    }

    /*
     * 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_DEAD)) {
                continue;
            }
	    if (!GotFlag(statePtr, CHANNEL_INCLOSE | CHANNEL_CLOSED )
                || GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
                ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
		active = 1;
		break;
	    }
	}

	/*
	 * We've found a live (or bg-closing) channel. Close it.
	 */

	if (active) {

	    /*
	     * TIP #398:  by default, we no  longer set the  channel back into
             * blocking  mode.  To  restore  the old  blocking  behavior,  the
             * environment variable  TCL_FLUSH_NONBLOCKING_ON_EXIT must be set
             * and not be "0".
	     */
            if (doflushnb) {
                    /* 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 = ((Channel *) chan)->state;
    CloseCallback *cbPtr;

    cbPtr = 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 = ((Channel *) chan)->state;
    CloseCallback *cbPtr, *cbPrevPtr;

    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(cbPtr);
	    break;
	}
	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 = 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(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(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 (tsdPtr->stdinInitialized
	    && tsdPtr->stdinChannel != NULL
	    && statePtr == ((Channel *)tsdPtr->stdinChannel)->state) {
	if (statePtr->refCount < 2) {
	    statePtr->refCount = 0;
	    tsdPtr->stdinChannel = NULL;
	    return;
	}
    } else if (tsdPtr->stdoutInitialized
	    && tsdPtr->stdoutChannel != NULL
	    && statePtr == ((Channel *)tsdPtr->stdoutChannel)->state) {
	if (statePtr->refCount < 2) {
	    statePtr->refCount = 0;
	    tsdPtr->stdoutChannel = NULL;
	    return;
	}
    } else if (tsdPtr->stderrInitialized
	    && tsdPtr->stderrChannel != NULL
	    && statePtr == ((Channel *)tsdPtr->stderrChannel)->state) {
	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_SetObjResult(interp, Tcl_NewStringObj(
                    "illegal recursive call to close through close-handler"
                    " of channel", -1));
	}
	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_SetObjResult(interp, Tcl_ObjPrintf(
                "can not find channel named \"%s\"", chanName));
	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;
    char *tmp;
    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 = ckalloc(sizeof(Channel));
    statePtr = 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) {
	unsigned len = strlen(chanName) + 1;

	/*
         * Make sure we allocate at least 7 bytes, so it fits for "stdout"
         * later.
         */

	tmp = ckalloc((len < 7) ? 7 : len);
	strcpy(tmp, chanName);
    } else {
	tmp = ckalloc(7);
	tmp[0] = '\0';
    }
    statePtr->channelName = tmp;
    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(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)) {
	strcpy(tmp, "stdin");
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDIN);
	Tcl_RegisterChannel(NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stdoutChannel == NULL) &&
	    (tsdPtr->stdoutInitialized == 1)) {
	strcpy(tmp, "stdout");
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDOUT);
	Tcl_RegisterChannel(NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stderrChannel == NULL) &&
	    (tsdPtr->stderrInitialized == 1)) {
	strcpy(tmp, "stderr");
	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_SetObjResult(interp, Tcl_ObjPrintf(
                    "couldn't find state for channel \"%s\"",
		    Tcl_GetChannelName(prevChan)));
	}
	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_SetObjResult(interp, Tcl_ObjPrintf(
		    "reading and writing both disallowed for channel \"%s\"",
		    Tcl_GetChannelName(prevChan)));
	}
	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_SetObjResult(interp, Tcl_ObjPrintf(
                        "could not flush channel \"%s\"",
			Tcl_GetChannelName(prevChan)));
	    }
	    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 = 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_SetObjResult(interp, Tcl_ObjPrintf(
                            "could not flush channel \"%s\"",
			    Tcl_GetChannelName((Tcl_Channel) chanPtr)));
		}
		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;
    if (!chanPtr->typePtr->getHandleProc) {
        Tcl_SetChannelError(chan, Tcl_ObjPrintf(
                "channel \"%s\" does not support OS handles",
                Tcl_GetChannelName(chan)));
	return TCL_ERROR;
    }
    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 = ckalloc(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(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(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(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_SetObjResult(interp, Tcl_NewStringObj(
                "unable to access channel: invalid channel", -1));
    }
    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.
     */

    Tcl_Preserve(chanPtr);
    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)) {
	    errorCode = 0;
	    goto done;
	}

	/*
	 * 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);
	if (toWrite == 0) {
            written = 0;
	} else {
	    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) && !TclInExit()) {
		    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;
	}

	if (!IsBufferEmpty(bufPtr)) {
	    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) {
	    goto done;
	} 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))) {
	errorCode = CloseChannel(interp, chanPtr, errorCode);
	goto done;
    }

    /*
     * If the write-side of the channel is flagged as closed, delete it when
     * the output queue is empty and there is no output in the current output
     * buffer.
     */

    if (GotFlag(statePtr, CHANNEL_CLOSEDWRITE) &&
	    (statePtr->outQueueHead == NULL) &&
	    ((statePtr->curOutPtr == NULL) ||
	    IsBufferEmpty(statePtr->curOutPtr))) {
	errorCode = CloseChannelPart(interp, chanPtr, errorCode, TCL_CLOSE_WRITE);
	goto done;
    }

  done:
    Tcl_Release(chanPtr);
    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(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(statePtr->channelName);
	    statePtr->channelName = NULL;
	}

	Tcl_FreeEncoding(statePtr->encoding);
	if (statePtr->outputStage != NULL) {
	    ckfree(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;
    int stickyError;

    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_SetObjResult(interp, Tcl_NewStringObj(
                    "illegal recursive call to close through close-handler"
                    " of channel", -1));
	}
	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.
     */

    stickyError = 0;

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

	/*
	 * 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(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 (stickyError != 0) {
	Tcl_SetErrno(stickyError);
	if (interp != NULL) {
	    Tcl_SetObjResult(interp,
			     Tcl_NewStringObj(Tcl_PosixError(interp), -1));
	}
	flushcode = -1;
    }
    if ((flushcode != 0) || (result != 0)) {
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CloseEx --
 *
 *	Closes one side of a channel, read or write.
 *
 * 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. */

    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_SetObjResult(interp, Tcl_ObjPrintf(
                "half-close of channels not supported by %ss",
		chanPtr->typePtr->typeName));
	return TCL_ERROR;
    }

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

    if (chanPtr != statePtr->topChanPtr) {
	Tcl_SetObjResult(interp, Tcl_NewStringObj(
		"half-close not applicable to stack of transformations", -1));
	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_SetObjResult(interp, Tcl_ObjPrintf(
                "Half-close of %s-side not possible, side not opened or"
                " already closed", msg));
	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_SetObjResult(interp, Tcl_NewStringObj(
                    "illegal recursive call to close through close-handler"
                    " of channel", -1));
	}
	return TCL_ERROR;
    }

    if (flags & TCL_CLOSE_READ) {
	/*
	 * Call the finalization code directly. There are no events to handle,
	 * there cannot be for the read-side.
	 */

	return CloseChannelPart(interp, chanPtr, 0, flags);
    } else if (flags & TCL_CLOSE_WRITE) {
	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 CloseWrite().
	     */

	    if (!GotFlag(statePtr, CHANNEL_CLOSEDWRITE)) {
		if (CloseWrite(interp, chanPtr) != TCL_OK) {
		    SetFlag(statePtr, CHANNEL_CLOSEDWRITE);
		    Tcl_Release(statePtr);
		    return TCL_ERROR;
		}
	    }
	}
	SetFlag(statePtr, CHANNEL_CLOSEDWRITE);
	Tcl_Release(statePtr);
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * CloseWrite --
 *
 *	Closes the write side a channel.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	Closes the write side of the channel.
 *
 * NOTE:
 *	CloseWrite removes the channel as far as the user is concerned.
 *	However, the ooutput data structures may continue to exist for a while
 *	longer if it has a background flush scheduled. The device itself is
 *	eventually closed and the channel structures modified, in
 *	CloseChannelPart, below.
 *
 *----------------------------------------------------------------------
 */

static int
CloseWrite(
    Tcl_Interp *interp,		/* Interpreter for errors. */
    Channel *chanPtr)		/* The channel whose write side is being
                                 * closed. May still be used by some
                                 * interpreter */
{
    /* Notes: clear-channel-handlers - write side only ? or keep around, just
     * not called. */
    /* No close cllbacks are run - channel is still open (read side) */

    ChannelState *statePtr = chanPtr->state;
                                /* State of real IO channel. */
    int flushcode;
    int result = 0;

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

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

    /*
     * 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_CLOSEDWRITE);

    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_CLOSEDWRITE in the flags
     * FlushChannel() has called CloseChannelPart(). While we can still access
     * "chan" (no structures were freed), the only place which may still
     * contain a message is the interpreter itself, and "CloseChannelPart" made
     * sure to lift any channel message it generated into it. Hence the NULL
     * argument in the call below.
     */

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

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

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * CloseChannelPart --
 *
 *	Utility procedure to close a channel partially and free associated
 *	resources. If the channel was stacked it will never be run (The higher
 *	level forbid this). If the channel was not stacked, then we will free
 *	all the bits of the chosen side (read, or write) for the TOP channel.
 *
 * Results:
 *	Error code from an unreported error or the driver close2 operation.
 *
 * Side effects:
 *	May free memory, may change the value of errno.
 *
 *----------------------------------------------------------------------
 */

static int
CloseChannelPart(
    Tcl_Interp *interp,		/* Interpreter for errors. */
    Channel *chanPtr,		/* The channel being closed. May still be used
				 * by some interpreter. */
    int errorCode,		/* Status of operation so far. */
    int flags)			/* Flags telling us which side to close. */
{
    ChannelState *statePtr;	/* State of real IO channel. */
    int result;			/* Of calling the close2proc. */

    statePtr = chanPtr->state;

    if (flags & TCL_CLOSE_READ) {
	/*
	 * No more input can be consumed so discard any leftover input.
	 */

	DiscardInputQueued(statePtr, 1);
    } else if (flags & TCL_CLOSE_WRITE) {
	/*
	 * The caller guarantees that there are no more buffers queued for
	 * output.
	 */

	if (statePtr->outQueueHead != NULL) {
	    Tcl_Panic("ClosechanHalf, closed write-side of 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;
	}
    }

    /*
     * Finally do what is asked of us. Close and free the channel driver state
     * for the chosen side of the channel. This may leave a TIP #219 error
     * message in the interp.
     */

    result = ChanCloseHalf(chanPtr, interp, flags);

    /*
     * 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);
	}
    }

    /*
     * TIP #219.
     * Capture error messages put by the driver into the bypass area and put
     * them into the regular interpreter result. See also the bottom of
     * CloseWrite().
     */

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

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

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

    ResetFlag(statePtr, 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(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(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 */
    const 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);
    }
}

static void
WillWrite(
    Channel *chanPtr)
{
    int inputBuffered;

    if ((chanPtr->typePtr->seekProc != NULL) &&
            ((inputBuffered = Tcl_InputBuffered((Tcl_Channel) chanPtr)) > 0)){
        int ignore;

        DiscardInputQueued(chanPtr->state, 0);
        ChanSeek(chanPtr, -inputBuffered, SEEK_CUR, &ignore);
    }
}

static int
WillRead(
    Channel *chanPtr)
{
    if ((chanPtr->typePtr->seekProc != NULL)
            && (Tcl_OutputBuffered((Tcl_Channel) chanPtr) > 0)) {
        if ((chanPtr->state->curOutPtr != NULL)
                && IsBufferReady(chanPtr->state->curOutPtr)) {
            SetFlag(chanPtr->state, BUFFER_READY);
        }
        if (FlushChannel(NULL, chanPtr, 0) != 0) {
            return -1;
        }
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * 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;

    if (srcLen) {
        WillWrite(chanPtr);
    }

    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];

    if (srcLen) {
        WillWrite(chanPtr);
    }

    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;

    TclNewObj(objPtr);
    charsStored = Tcl_GetsObj(chan, objPtr);
    if (charsStored > 0) {
	TclDStringAppendObj(lineRead, objPtr);
    }
    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:
    /*
     * Regenerate the top channel, in case it was changed due to
     * self-modifying reflected transforms.
     */

    chanPtr = statePtr->topChanPtr;

    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:
    /*
     * Regenerate the top channel, in case it was changed due to
     * self-modifying reflected transforms.
     */

    chanPtr = statePtr->topChanPtr;

    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:
    /*
     * Regenerate the top channel, in case it was changed due to
     * self-modifying reflected transforms.
     */

    chanPtr = statePtr->topChanPtr;

    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;
    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;
    spaceLeft = objPtr->length - offset;
    if (dstNeeded > spaceLeft) {
	int length = offset + ((offset < dstNeeded) ? dstNeeded : offset);

	if (Tcl_AttemptSetObjLength(objPtr, length) == 0) {
	    length = offset + dstNeeded;
	    if (Tcl_AttemptSetObjLength(objPtr, length) == 0) {
		dstNeeded = TCL_UTF_MAX - 1 + toRead;
		length = offset + dstNeeded;
		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+1, &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, 0);
}

/*
 *----------------------------------------------------------------------
 *
 * 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