path: root/win/tclWinConsole.c

/*
 * tclWinConsole.c --
 *
 *	This file implements the Windows-specific console functions, and the
 *	"console" channel driver.
 *
 * Copyright (c) 1999 by Scriptics Corp.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#include "tclWinInt.h"

/*
 * The following variable is used to tell whether this module has been
 * initialized.
 */

static int initialized = 0;

/*
 * The consoleMutex locks around access to the initialized variable, and it is
 * used to protect background threads from being terminated while they are
 * using APIs that hold locks.
 */

TCL_DECLARE_MUTEX(consoleMutex)

/*
 * Bit masks used in the flags field of the ConsoleInfo structure below.
 */

#define CONSOLE_PENDING	(1<<0)	/* Message is pending in the queue. */
#define CONSOLE_ASYNC	(1<<1)	/* Channel is non-blocking. */

/*
 * Bit masks used in the sharedFlags field of the ConsoleInfo structure below.
 */

#define CONSOLE_EOF	  (1<<2)  /* Console has reached EOF. */
#define CONSOLE_BUFFERED  (1<<3)  /* Data was read into a buffer by the reader
				   * thread. */

#define CONSOLE_BUFFER_SIZE (8*1024)

/*
 * Structure containing handles associated with one of the special console
 * threads.
 */

typedef struct ConsoleThreadInfo {
    HANDLE thread;		/* Handle to reader or writer thread. */
    int threadExiting;		/* Boolean indicating that thread is exiting. */
    HANDLE readyEvent;		/* Manual-reset event to signal _to_ the main
				 * thread when the worker thread has finished
				 * waiting for its normal work to happen. */
    HANDLE startEvent;		/* Auto-reset event used by the main thread to
				 * signal when the thread should attempt to do
				 * its normal work. Additionally this event
				 * used as wait for thread event (init phase). */
    HANDLE stopEvent;		/* Auto-reset event used by the main thread to
				 * signal when the thread should exit. */
} ConsoleThreadInfo;

/*
 * This structure describes per-instance data for a console based channel.
 */

typedef struct ConsoleInfo {
    HANDLE handle;
    int type;
    struct ConsoleInfo *nextPtr;/* Pointer to next registered console. */
    Tcl_Channel channel;	/* Pointer to channel structure. */
    int validMask;		/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which operations are valid on the file. */
    int watchMask;		/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which events should be reported. */
    int flags;			/* State flags, see above for a list. */
    Tcl_ThreadId threadId;	/* Thread to which events should be reported.
				 * This value is used by the reader/writer
				 * threads. */
    ConsoleThreadInfo writer;	/* A specialized thread for handling
				 * asynchronous writes to the console; the
				 * waiting starts when a start event is sent,
				 * and a reset event is sent back to the main
				 * thread when the write is done. A stop event
				 * is used to terminate the thread. */
    ConsoleThreadInfo reader;	/* A specialized thread for handling
				 * asynchronous reads from the console; the
				 * waiting starts when a start event is sent,
				 * and a reset event is sent back to the main
				 * thread when input is available. A stop
				 * event is used to terminate the thread. */
    DWORD writeError;		/* An error caused by the last background
				 * write. Set to 0 if no error has been
				 * detected. This word is shared with the
				 * writer thread so access must be
				 * synchronized with the writable object. */
    char *writeBuf;		/* Current background output buffer. Access is
				 * synchronized with the writable object. */
    int writeBufLen;		/* Size of write buffer. Access is
				 * synchronized with the writable object. */
    int toWrite;		/* Current amount to be written. Access is
				 * synchronized with the writable object. */
    int readFlags;		/* Flags that are shared with the reader
				 * thread. Access is synchronized with the
				 * readable object. */
    int bytesRead;		/* Number of bytes in the buffer. */
    int offset;			/* Number of bytes read out of the buffer. */
    char buffer[CONSOLE_BUFFER_SIZE];
				/* Data consumed by reader thread. */
} ConsoleInfo;

typedef struct ThreadSpecificData {
    /*
     * The following pointer refers to the head of the list of consoles that
     * are being watched for file events.
     */

    ConsoleInfo *firstConsolePtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * The following structure is what is added to the Tcl event queue when
 * console events are generated.
 */

typedef struct ConsoleEvent {
    Tcl_Event header;		/* Information that is standard for all
				 * events. */
    ConsoleInfo *infoPtr;	/* Pointer to console info structure. Note
				 * that we still have to verify that the
				 * console exists before dereferencing this
				 * pointer. */
} ConsoleEvent;

/*
 * Declarations for functions used only in this file.
 */

static int		ConsoleBlockModeProc(ClientData instanceData,
			    int mode);
static void		ConsoleCheckProc(ClientData clientData, int flags);
static int		ConsoleCloseProc(ClientData instanceData,
			    Tcl_Interp *interp);
static int		ConsoleEventProc(Tcl_Event *evPtr, int flags);
static void		ConsoleExitHandler(ClientData clientData);
static int		ConsoleGetHandleProc(ClientData instanceData,
			    int direction, ClientData *handlePtr);
static void		ConsoleInit(void);
static int		ConsoleInputProc(ClientData instanceData, char *buf,
			    int toRead, int *errorCode);
static int		ConsoleOutputProc(ClientData instanceData,
			    const char *buf, int toWrite, int *errorCode);
static DWORD WINAPI	ConsoleReaderThread(LPVOID arg);
static void		ConsoleSetupProc(ClientData clientData, int flags);
static void		ConsoleWatchProc(ClientData instanceData, int mask);
static DWORD WINAPI	ConsoleWriterThread(LPVOID arg);
static void		ProcExitHandler(ClientData clientData);
static int		WaitForRead(ConsoleInfo *infoPtr, int blocking);
static void		ConsoleThreadActionProc(ClientData instanceData,
			    int action);
static BOOL		ReadConsoleBytes(HANDLE hConsole, LPVOID lpBuffer,
			    DWORD nbytes, LPDWORD nbytesread);
static BOOL		WriteConsoleBytes(HANDLE hConsole,
			    const void *lpBuffer, DWORD nbytes,
			    LPDWORD nbyteswritten);
static void		StartChannelThread(ConsoleInfo *infoPtr,
			    ConsoleThreadInfo *threadInfoPtr,
			    LPTHREAD_START_ROUTINE threadProc);
static void		StopChannelThread(ConsoleThreadInfo *threadInfoPtr);

/*
 * This structure describes the channel type structure for command console
 * based IO.
 */

static const Tcl_ChannelType consoleChannelType = {
    "console",			/* Type name. */
    TCL_CHANNEL_VERSION_5,	/* v5 channel */
    ConsoleCloseProc,		/* Close proc. */
    ConsoleInputProc,		/* Input proc. */
    ConsoleOutputProc,		/* Output proc. */
    NULL,			/* Seek proc. */
    NULL,			/* Set option proc. */
    NULL,			/* Get option proc. */
    ConsoleWatchProc,		/* Set up notifier to watch the channel. */
    ConsoleGetHandleProc,	/* Get an OS handle from channel. */
    NULL,			/* close2proc. */
    ConsoleBlockModeProc,	/* Set blocking or non-blocking mode. */
    NULL,			/* Flush proc. */
    NULL,			/* Handler proc. */
    NULL,			/* Wide seek proc. */
    ConsoleThreadActionProc,	/* Thread action proc. */
    NULL			/* Truncation proc. */
};

/*
 *----------------------------------------------------------------------
 *
 * ReadConsoleBytes, WriteConsoleBytes --
 *
 *	Wrapper for ReadConsole{A,W}, that takes and returns number of bytes
 *	instead of number of TCHARS.
 *
 *----------------------------------------------------------------------
 */

static BOOL
ReadConsoleBytes(
    HANDLE hConsole,
    LPVOID lpBuffer,
    DWORD nbytes,
    LPDWORD nbytesread)
{
    DWORD ntchars;
    BOOL result;
    int tcharsize = sizeof(TCHAR);

    /*
     * If user types a Ctrl-Break or Ctrl-C, ReadConsole will return
     * success with ntchars == 0 and GetLastError() will be
     * ERROR_OPERATION_ABORTED. We do not want to treat this case
     * as EOF so we will loop around again. If no Ctrl signal handlers
     * have been established, the default signal OS handler in a separate
     * thread will terminate the program. If a Ctrl signal handler
     * has been established (through an extension for example), it
     * will run and take whatever action it deems appropriate.
     */
    do {
        result = ReadConsole(hConsole, lpBuffer, nbytes / tcharsize, &ntchars,
                             NULL);
    } while (result && ntchars == 0 && GetLastError() == ERROR_OPERATION_ABORTED);
    if (nbytesread != NULL) {
	*nbytesread = ntchars * tcharsize;
    }
    return result;
}

static BOOL
WriteConsoleBytes(
    HANDLE hConsole,
    const void *lpBuffer,
    DWORD nbytes,
    LPDWORD nbyteswritten)
{
    DWORD ntchars;
    BOOL result;
    int tcharsize = sizeof(TCHAR);

    result = WriteConsole(hConsole, lpBuffer, nbytes / tcharsize, &ntchars,
	    NULL);
    if (nbyteswritten != NULL) {
	*nbyteswritten = ntchars * tcharsize;
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleInit --
 *
 *	This function initializes the static variables for this file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new event source.
 *
 *----------------------------------------------------------------------
 */

static void
ConsoleInit(void)
{
    /*
     * Check the initialized flag first, then check again in the mutex. This
     * is a speed enhancement.
     */

    if (!initialized) {
	Tcl_MutexLock(&consoleMutex);
	if (!initialized) {
	    initialized = 1;
	    Tcl_CreateExitHandler(ProcExitHandler, NULL);
	}
	Tcl_MutexUnlock(&consoleMutex);
    }

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

	tsdPtr->firstConsolePtr = NULL;
	Tcl_CreateEventSource(ConsoleSetupProc, ConsoleCheckProc, NULL);
	Tcl_CreateThreadExitHandler(ConsoleExitHandler, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleExitHandler --
 *
 *	This function is called to cleanup the console module before Tcl is
 *	unloaded.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes the console event source.
 *
 *----------------------------------------------------------------------
 */

static void
ConsoleExitHandler(
    ClientData clientData)	/* Old window proc. */
{
    Tcl_DeleteEventSource(ConsoleSetupProc, ConsoleCheckProc, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * ProcExitHandler --
 *
 *	This function is called to cleanup the process list before Tcl is
 *	unloaded.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Resets the process list.
 *
 *----------------------------------------------------------------------
 */

static void
ProcExitHandler(
    ClientData clientData)	/* Old window proc. */
{
    Tcl_MutexLock(&consoleMutex);
    initialized = 0;
    Tcl_MutexUnlock(&consoleMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleSetupProc --
 *
 *	This procedure is invoked before Tcl_DoOneEvent blocks waiting for an
 *	event.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

void
ConsoleSetupProc(
    ClientData data,		/* Not used. */
    int flags)			/* Event flags as passed to Tcl_DoOneEvent. */
{
    ConsoleInfo *infoPtr;
    Tcl_Time blockTime = { 0, 0 };
    int block = 1;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
	return;
    }

    /*
     * Look to see if any events are already pending. If they are, poll.
     */

    for (infoPtr = tsdPtr->firstConsolePtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (infoPtr->watchMask & TCL_WRITABLE) {
	    if (WaitForSingleObject(infoPtr->writer.readyEvent,
		    0) != WAIT_TIMEOUT) {
		block = 0;
	    }
	}
	if (infoPtr->watchMask & TCL_READABLE) {
	    if (WaitForRead(infoPtr, 0) >= 0) {
		block = 0;
	    }
	}
    }
    if (!block) {
	Tcl_SetMaxBlockTime(&blockTime);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleCheckProc --
 *
 *	This procedure is called by Tcl_DoOneEvent to check the console event
 *	source for events.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May queue an event.
 *
 *----------------------------------------------------------------------
 */

static void
ConsoleCheckProc(
    ClientData data,		/* Not used. */
    int flags)			/* Event flags as passed to Tcl_DoOneEvent. */
{
    ConsoleInfo *infoPtr;
    int needEvent;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
	return;
    }

    /*
     * Queue events for any ready consoles that don't already have events
     * queued.
     */

    for (infoPtr = tsdPtr->firstConsolePtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (infoPtr->flags & CONSOLE_PENDING) {
	    continue;
	}

	/*
	 * Queue an event if the console is signaled for reading or writing.
	 */

	needEvent = 0;
	if (infoPtr->watchMask & TCL_WRITABLE) {
	    if (WaitForSingleObject(infoPtr->writer.readyEvent,
		    0) != WAIT_TIMEOUT) {
		needEvent = 1;
	    }
	}

	if (infoPtr->watchMask & TCL_READABLE) {
	    if (WaitForRead(infoPtr, 0) >= 0) {
		needEvent = 1;
	    }
	}

	if (needEvent) {
	    ConsoleEvent *evPtr = ckalloc(sizeof(ConsoleEvent));

	    infoPtr->flags |= CONSOLE_PENDING;
	    evPtr->header.proc = ConsoleEventProc;
	    evPtr->infoPtr = infoPtr;
	    Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleBlockModeProc --
 *
 *	Set blocking or non-blocking mode on channel.
 *
 * Results:
 *	0 if successful, errno when failed.
 *
 * Side effects:
 *	Sets the device into blocking or non-blocking mode.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleBlockModeProc(
    ClientData instanceData,	/* Instance data for channel. */
    int mode)			/* TCL_MODE_BLOCKING or
				 * TCL_MODE_NONBLOCKING. */
{
    ConsoleInfo *infoPtr = instanceData;

    /*
     * Consoles on Windows can not be switched between blocking and
     * nonblocking, hence we have to emulate the behavior. This is done in the
     * input function by checking against a bit in the state. We set or unset
     * the bit here to cause the input function to emulate the correct
     * behavior.
     */

    if (mode == TCL_MODE_NONBLOCKING) {
	infoPtr->flags |= CONSOLE_ASYNC;
    } else {
	infoPtr->flags &= ~CONSOLE_ASYNC;
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * StartChannelThread, StopChannelThread --
 *
 *	Helpers that codify how to ask one of the console service threads to
 *	start and stop.
 *
 *----------------------------------------------------------------------
 */

static void
StartChannelThread(
    ConsoleInfo *infoPtr,
    ConsoleThreadInfo *threadInfoPtr,
    LPTHREAD_START_ROUTINE threadProc)
{
    DWORD id;

    threadInfoPtr->readyEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
    threadInfoPtr->startEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
    threadInfoPtr->threadExiting = FALSE;
    threadInfoPtr->stopEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
    threadInfoPtr->thread = CreateThread(NULL, 256, threadProc, infoPtr, 0,
	    &id);
    SetThreadPriority(threadInfoPtr->thread, THREAD_PRIORITY_HIGHEST);
}

static void
StopChannelThread(
    ConsoleThreadInfo *threadInfoPtr)
{
    DWORD exitCode = 0;

    /*
     * The thread may already have closed on it's own. Check it's exit
     * code.
     */

    GetExitCodeThread(threadInfoPtr->thread, &exitCode);
    if (exitCode == STILL_ACTIVE) {
	/*
	 * Set the stop event so that if the reader thread is blocked in
	 * ConsoleReaderThread on WaitForMultipleEvents, it will exit cleanly.
	 */

	SetEvent(threadInfoPtr->stopEvent);

	/*
	 * Wait at most 20 milliseconds for the reader thread to close.
	 */

	if (WaitForSingleObject(threadInfoPtr->thread, 20) == WAIT_TIMEOUT) {
	    /*
	     * Forcibly terminate the background thread as a last resort.
	     * Note that we need to guard against terminating the thread while
	     * it is in the middle of Tcl_ThreadAlert because it won't be able
	     * to release the notifier lock.
	     *
	     * Also note that terminating threads during their initialization or teardown phase
	     * may result in ntdll.dll's LoaderLock to remain locked indefinitely.
	     * This causes ntdll.dll's LdrpInitializeThread() to deadlock trying to acquire LoaderLock.
	     * LdrpInitializeThread() is executed within new threads to perform
	     * initialization and to execute DllMain() of all loaded dlls.
	     * As a result, all new threads are deadlocked in their initialization phase and never execute,
	     * even though CreateThread() reports successful thread creation.
	     * This results in a very weird process-wide behavior, which is extremely hard to debug.
	     * 
	     * THREADS SHOULD NEVER BE TERMINATED. Period.
	     * 
	     * But for now, check if thread is exiting, and if so, let it die peacefully.
	     */

	    if ( !threadInfoPtr->threadExiting
	      || WaitForSingleObject(threadInfoPtr->thread, 5000) != WAIT_OBJECT_0
	    ) {
		Tcl_MutexLock(&consoleMutex);
		/* BUG: this leaks memory. */
		TerminateThread(threadInfoPtr->thread, 0);
		Tcl_MutexUnlock(&consoleMutex);
	    }
	}
    }

    /*
     * Close all the handles associated with the thread, and set the thread
     * handle field to NULL to mark that the thread has been cleaned up.
     */

    CloseHandle(threadInfoPtr->thread);
    CloseHandle(threadInfoPtr->readyEvent);
    CloseHandle(threadInfoPtr->startEvent);
    CloseHandle(threadInfoPtr->stopEvent);
    threadInfoPtr->thread = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleCloseProc --
 *
 *	Closes a console based IO channel.
 *
 * Results:
 *	0 on success, errno otherwise.
 *
 * Side effects:
 *	Closes the physical channel.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleCloseProc(
    ClientData instanceData,	/* Pointer to ConsoleInfo structure. */
    Tcl_Interp *interp)		/* For error reporting. */
{
    ConsoleInfo *consolePtr = instanceData;
    int errorCode = 0;
    ConsoleInfo *infoPtr, **nextPtrPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * Clean up the background thread if necessary. Note that this must be
     * done before we can close the file, since the thread may be blocking
     * trying to read from the console.
     */

    if (consolePtr->reader.thread) {
	StopChannelThread(&consolePtr->reader);
    }
    consolePtr->validMask &= ~TCL_READABLE;

    /*
     * Wait for the writer thread to finish the current buffer, then terminate
     * the thread and close the handles. If the channel is nonblocking, there
     * should be no pending write operations.
     */

    if (consolePtr->writer.thread) {
	if (consolePtr->toWrite) {
	    /*
	     * We only need to wait if there is something to write. This may
	     * prevent infinite wait on exit. [Python Bug 216289]
	     */

	    WaitForSingleObject(consolePtr->writer.readyEvent, INFINITE);
	}

	StopChannelThread(&consolePtr->writer);
    }
    consolePtr->validMask &= ~TCL_WRITABLE;

    /*
     * Don't close the Win32 handle if the handle is a standard channel during
     * the thread exit process. Otherwise, one thread may kill the stdio of
     * another.
     */

    if (!TclInThreadExit()
	    || ((GetStdHandle(STD_INPUT_HANDLE) != consolePtr->handle)
		&& (GetStdHandle(STD_OUTPUT_HANDLE) != consolePtr->handle)
		&& (GetStdHandle(STD_ERROR_HANDLE) != consolePtr->handle))) {
	if (CloseHandle(consolePtr->handle) == FALSE) {
	    TclWinConvertError(GetLastError());
	    errorCode = errno;
	}
    }

    consolePtr->watchMask &= consolePtr->validMask;

    /*
     * Remove the file from the list of watched files.
     */

    for (nextPtrPtr = &(tsdPtr->firstConsolePtr), infoPtr = *nextPtrPtr;
	    infoPtr != NULL;
	    nextPtrPtr = &infoPtr->nextPtr, infoPtr = *nextPtrPtr) {
	if (infoPtr == (ConsoleInfo *) consolePtr) {
	    *nextPtrPtr = infoPtr->nextPtr;
	    break;
	}
    }
    if (consolePtr->writeBuf != NULL) {
	ckfree(consolePtr->writeBuf);
	consolePtr->writeBuf = 0;
    }
    ckfree(consolePtr);

    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleInputProc --
 *
 *	Reads input from the IO channel into the buffer given. Returns count
 *	of how many bytes were actually read, and an error indication.
 *
 * Results:
 *	A count of how many bytes were read is returned and an error
 *	indication is returned in an output argument.
 *
 * Side effects:
 *	Reads input from the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleInputProc(
    ClientData instanceData,	/* Console state. */
    char *buf,			/* Where to store data read. */
    int bufSize,		/* How much space is available in the
				 * buffer? */
    int *errorCode)		/* Where to store error code. */
{
    ConsoleInfo *infoPtr = instanceData;
    DWORD count, bytesRead = 0;
    int result;

    *errorCode = 0;

    /*
     * Synchronize with the reader thread.
     */

    result = WaitForRead(infoPtr, (infoPtr->flags & CONSOLE_ASYNC) ? 0 : 1);

    /*
     * If an error occurred, return immediately.
     */

    if (result == -1) {
	*errorCode = errno;
	return -1;
    }

    if (infoPtr->readFlags & CONSOLE_BUFFERED) {
	/*
	 * Data is stored in the buffer.
	 */

	if (bufSize < (infoPtr->bytesRead - infoPtr->offset)) {
	    memcpy(buf, &infoPtr->buffer[infoPtr->offset], (size_t) bufSize);
	    bytesRead = bufSize;
	    infoPtr->offset += bufSize;
	} else {
	    memcpy(buf, &infoPtr->buffer[infoPtr->offset], (size_t) bufSize);
	    bytesRead = infoPtr->bytesRead - infoPtr->offset;

	    /*
	     * Reset the buffer.
	     */

	    infoPtr->readFlags &= ~CONSOLE_BUFFERED;
	    infoPtr->offset = 0;
	}

	return bytesRead;
    }

    /*
     * Attempt to read bufSize bytes. The read will return immediately if
     * there is any data available. Otherwise it will block until at least one
     * byte is available or an EOF occurs.
     */

    if (ReadConsoleBytes(infoPtr->handle, (LPVOID) buf, (DWORD) bufSize,
	    &count) == TRUE) {
	/*
	 * TODO: This potentially writes beyond the limits specified
	 * by the caller.  In practice this is harmless, since all writes
	 * are into ChannelBuffers, and those have padding, but still
	 * ought to remove this, unless some Windows wizard can give
	 * a reason not to.
	 */
	buf[count] = '\0';
	return count;
    }

    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleOutputProc --
 *
 *	Writes the given output on the IO channel. Returns count of how many
 *	characters were actually written, and an error indication.
 *
 * Results:
 *	A count of how many characters were written is returned and an error
 *	indication is returned in an output argument.
 *
 * Side effects:
 *	Writes output on the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleOutputProc(
    ClientData instanceData,	/* Console state. */
    const char *buf,		/* The data buffer. */
    int toWrite,		/* How many bytes to write? */
    int *errorCode)		/* Where to store error code. */
{
    ConsoleInfo *infoPtr = instanceData;
    ConsoleThreadInfo *threadInfo = &infoPtr->reader;
    DWORD bytesWritten, timeout;

    *errorCode = 0;
    timeout = (infoPtr->flags & CONSOLE_ASYNC) ? 0 : INFINITE;
    if (WaitForSingleObject(threadInfo->readyEvent,timeout) == WAIT_TIMEOUT) {
	/*
	 * The writer thread is blocked waiting for a write to complete and
	 * the channel is in non-blocking mode.
	 */

	errno = EWOULDBLOCK;
	goto error;
    }

    /*
     * Check for a background error on the last write.
     */

    if (infoPtr->writeError) {
	TclWinConvertError(infoPtr->writeError);
	infoPtr->writeError = 0;
	goto error;
    }

    if (infoPtr->flags & CONSOLE_ASYNC) {
	/*
	 * The console is non-blocking, so copy the data into the output
	 * buffer and restart the writer thread.
	 */

	if (toWrite > infoPtr->writeBufLen) {
	    /*
	     * Reallocate the buffer to be large enough to hold the data.
	     */

	    if (infoPtr->writeBuf) {
		ckfree(infoPtr->writeBuf);
	    }
	    infoPtr->writeBufLen = toWrite;
	    infoPtr->writeBuf = ckalloc(toWrite);
	}
	memcpy(infoPtr->writeBuf, buf, (size_t) toWrite);
	infoPtr->toWrite = toWrite;
	ResetEvent(threadInfo->readyEvent);
	SetEvent(threadInfo->startEvent);
	bytesWritten = toWrite;
    } else {
	/*
	 * In the blocking case, just try to write the buffer directly. This
	 * avoids an unnecessary copy.
	 */

	if (WriteConsoleBytes(infoPtr->handle, buf, (DWORD) toWrite,
		&bytesWritten) == FALSE) {
	    TclWinConvertError(GetLastError());
	    goto error;
	}
    }
    return bytesWritten;

  error:
    *errorCode = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleEventProc --
 *
 *	This function is invoked by Tcl_ServiceEvent when a file event reaches
 *	the front of the event queue. This procedure invokes Tcl_NotifyChannel
 *	on the console.
 *
 * Results:
 *	Returns 1 if the event was handled, meaning it should be removed from
 *	the queue. Returns 0 if the event was not handled, meaning it should
 *	stay on the queue. The only time the event isn't handled is if the
 *	TCL_FILE_EVENTS flag bit isn't set.
 *
 * Side effects:
 *	Whatever the notifier callback does.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleEventProc(
    Tcl_Event *evPtr,		/* Event to service. */
    int flags)			/* Flags that indicate what events to handle,
				 * such as TCL_FILE_EVENTS. */
{
    ConsoleEvent *consoleEvPtr = (ConsoleEvent *) evPtr;
    ConsoleInfo *infoPtr;
    int mask;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
	return 0;
    }

    /*
     * Search through the list of watched consoles for the one whose handle
     * matches the event. We do this rather than simply dereferencing the
     * handle in the event so that consoles can be deleted while the event is
     * in the queue.
     */

    for (infoPtr = tsdPtr->firstConsolePtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (consoleEvPtr->infoPtr == infoPtr) {
	    infoPtr->flags &= ~CONSOLE_PENDING;
	    break;
	}
    }

    /*
     * Remove stale events.
     */

    if (!infoPtr) {
	return 1;
    }

    /*
     * Check to see if the console is readable. Note that we can't tell if a
     * console is writable, so we always report it as being writable unless we
     * have detected EOF.
     */

    mask = 0;
    if (infoPtr->watchMask & TCL_WRITABLE) {
	if (WaitForSingleObject(infoPtr->writer.readyEvent,
		0) != WAIT_TIMEOUT) {
	    mask = TCL_WRITABLE;
	}
    }

    if (infoPtr->watchMask & TCL_READABLE) {
	if (WaitForRead(infoPtr, 0) >= 0) {
	    if (infoPtr->readFlags & CONSOLE_EOF) {
		mask = TCL_READABLE;
	    } else {
		mask |= TCL_READABLE;
	    }
	}
    }

    /*
     * Inform the channel of the events.
     */

    Tcl_NotifyChannel(infoPtr->channel, infoPtr->watchMask & mask);
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleWatchProc --
 *
 *	Called by the notifier to set up to watch for events on this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
ConsoleWatchProc(
    ClientData instanceData,	/* Console state. */
    int mask)			/* What events to watch for, OR-ed combination
				 * of TCL_READABLE, TCL_WRITABLE and
				 * TCL_EXCEPTION. */
{
    ConsoleInfo **nextPtrPtr, *ptr;
    ConsoleInfo *infoPtr = instanceData;
    int oldMask = infoPtr->watchMask;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * Since most of the work is handled by the background threads, we just
     * need to update the watchMask and then force the notifier to poll once.
     */

    infoPtr->watchMask = mask & infoPtr->validMask;
    if (infoPtr->watchMask) {
	Tcl_Time blockTime = { 0, 0 };

	if (!oldMask) {
	    infoPtr->nextPtr = tsdPtr->firstConsolePtr;
	    tsdPtr->firstConsolePtr = infoPtr;
	}
	Tcl_SetMaxBlockTime(&blockTime);
    } else if (oldMask) {
	/*
	 * Remove the console from the list of watched consoles.
	 */

	for (nextPtrPtr = &(tsdPtr->firstConsolePtr), ptr = *nextPtrPtr;
		ptr != NULL;
		nextPtrPtr = &ptr->nextPtr, ptr = *nextPtrPtr) {
	    if (infoPtr == ptr) {
		*nextPtrPtr = ptr->nextPtr;
		break;
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle to retrieve OS handles from inside a
 *	command consoleline based channel.
 *
 * Results:
 *	Returns TCL_OK with the fd in handlePtr, or TCL_ERROR if there is no
 *	handle for the specified direction.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
ConsoleGetHandleProc(
    ClientData instanceData,	/* The console state. */
    int direction,		/* TCL_READABLE or TCL_WRITABLE. */
    ClientData *handlePtr)	/* Where to store the handle. */
{
    ConsoleInfo *infoPtr = instanceData;

    *handlePtr = infoPtr->handle;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * WaitForRead --
 *
 *	Wait until some data is available, the console is at EOF or the reader
 *	thread is blocked waiting for data (if the channel is in non-blocking
 *	mode).
 *
 * Results:
 *	Returns 1 if console is readable. Returns 0 if there is no data on the
 *	console, but there is buffered data. Returns -1 if an error occurred.
 *	If an error occurred, the threads may not be synchronized.
 *
 * Side effects:
 *	Updates the shared state flags. If no error occurred, the reader
 *	thread is blocked waiting for a signal from the main thread.
 *
 *----------------------------------------------------------------------
 */

static int
WaitForRead(
    ConsoleInfo *infoPtr,	/* Console state. */
    int blocking)		/* Indicates whether call should be blocking
				 * or not. */
{
    DWORD timeout, count;
    HANDLE *handle = infoPtr->handle;
    ConsoleThreadInfo *threadInfo = &infoPtr->reader;
    INPUT_RECORD input;

    while (1) {
	/*
	 * Synchronize with the reader thread.
	 */

	timeout = blocking ? INFINITE : 0;
	if (WaitForSingleObject(threadInfo->readyEvent,
		timeout) == WAIT_TIMEOUT) {
	    /*
	     * The reader thread is blocked waiting for data and the channel
	     * is in non-blocking mode.
	     */

	    errno = EWOULDBLOCK;
	    return -1;
	}

	/*
	 * At this point, the two threads are synchronized, so it is safe to
	 * access shared state.
	 */

	/*
	 * If the console has hit EOF, it is always readable.
	 */

	if (infoPtr->readFlags & CONSOLE_EOF) {
	    return 1;
	}

	if (PeekConsoleInput(handle, &input, 1, &count) == FALSE) {
	    /*
	     * Check to see if the peek failed because of EOF.
	     */

	    TclWinConvertError(GetLastError());

	    if (errno == EOF) {
		infoPtr->readFlags |= CONSOLE_EOF;
		return 1;
	    }

	    /*
	     * Ignore errors if there is data in the buffer.
	     */

	    if (infoPtr->readFlags & CONSOLE_BUFFERED) {
		return 0;
	    } else {
		return -1;
	    }
	}

	/*
	 * If there is data in the buffer, the console must be readable (since
	 * it is a line-oriented device).
	 */

	if (infoPtr->readFlags & CONSOLE_BUFFERED) {
	    return 1;
	}

	/*
	 * There wasn't any data available, so reset the thread and try again.
	 */

	ResetEvent(threadInfo->readyEvent);
	SetEvent(threadInfo->startEvent);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleReaderThread --
 *
 *	This function runs in a separate thread and waits for input to become
 *	available on a console.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Signals the main thread when input become available. May cause the
 *	main thread to wake up by posting a message. May one line from the
 *	console for each wait operation.
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
ConsoleReaderThread(
    LPVOID arg)
{
    ConsoleInfo *infoPtr = arg;
    HANDLE *handle = infoPtr->handle;
    ConsoleThreadInfo *threadInfo = &infoPtr->reader;
    DWORD waitResult;
    HANDLE wEvents[2];

    /*
     * Notify caller (using startEvent) that this thread is initialized
     */
    SetEvent(threadInfo->startEvent);
    SuspendThread(threadInfo->thread); /* until main thread get an event */

    /*
     * The first event takes precedence.
     */

    wEvents[0] = threadInfo->stopEvent;
    wEvents[1] = threadInfo->startEvent;

    for (;;) {
	/*
	 * Wait for the main thread to signal before attempting to wait.
	 */

	waitResult = WaitForMultipleObjects(2, wEvents, FALSE, INFINITE);

	if (waitResult != (WAIT_OBJECT_0 + 1)) {
	    /*
	     * The start event was not signaled. It must be the stop event or
	     * an error, so exit this thread.
	     */

	    break;
	}

	/*
	 * Look for data on the console, but first ignore any events that are
	 * not KEY_EVENTs.
	 */

	if (ReadConsoleBytes(handle, infoPtr->buffer, CONSOLE_BUFFER_SIZE,
		(LPDWORD) &infoPtr->bytesRead) != FALSE) {
	    /*
	     * Data was stored in the buffer.
	     */

	    infoPtr->readFlags |= CONSOLE_BUFFERED;
	} else {
	    DWORD err = GetLastError();

	    if (err == (DWORD) EOF) {
		infoPtr->readFlags = CONSOLE_EOF;
	    }
	}

	/*
	 * Signal the main thread by signalling the readable event and then
	 * waking up the notifier thread.
	 */

	SetEvent(threadInfo->readyEvent);

	/*
	 * Alert the foreground thread. Note that we need to treat this like a
	 * critical section so the foreground thread does not terminate this
	 * thread while we are holding a mutex in the notifier code.
	 */

	Tcl_MutexLock(&consoleMutex);
	if (infoPtr->threadId != NULL) {
	    /*
	     * TIP #218. When in flight ignore the event, no one will receive
	     * it anyway.
	     */

	    Tcl_ThreadAlert(infoPtr->threadId);
	}
	Tcl_MutexUnlock(&consoleMutex);
    }

    /*
     * Inform caller that this thread should not be terminated, since it is about to exit.
     * See comment in StopChannelThread() for reasons.
    */
    threadInfo->threadExiting = TRUE;

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleWriterThread --
 *
 *	This function runs in a separate thread and writes data onto a
 *	console.
 *
 * Results:
 *	Always returns 0.
 *
 * Side effects:

 *	Signals the main thread when an output operation is completed. May
 *	cause the main thread to wake up by posting a message.
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
ConsoleWriterThread(
    LPVOID arg)
{
    ConsoleInfo *infoPtr = arg;
    HANDLE *handle = infoPtr->handle;
    ConsoleThreadInfo *threadInfo = &infoPtr->writer;
    DWORD count, toWrite, waitResult;
    char *buf;
    HANDLE wEvents[2];

    /*
     * Notify caller (using startEvent) that this thread is initialized
     */
    SetEvent(threadInfo->startEvent);
    SuspendThread(threadInfo->thread); /* until main thread get an event */

    /*
     * The first event takes precedence.
     */

    wEvents[0] = threadInfo->stopEvent;
    wEvents[1] = threadInfo->startEvent;

    for (;;) {
	/*
	 * Wait for the main thread to signal before attempting to write.
	 */

	waitResult = WaitForMultipleObjects(2, wEvents, FALSE, INFINITE);

	if (waitResult != (WAIT_OBJECT_0 + 1)) {
	    /*
	     * The start event was not signaled. It must be the stop event or
	     * an error, so exit this thread.
	     */

	    break;
	}

	buf = infoPtr->writeBuf;
	toWrite = infoPtr->toWrite;

	/*
	 * Loop until all of the bytes are written or an error occurs.
	 */

	while (toWrite > 0) {
	    if (WriteConsoleBytes(handle, buf, (DWORD) toWrite,
		    &count) == FALSE) {
		infoPtr->writeError = GetLastError();
		break;
	    }
	    toWrite -= count;
	    buf += count;
	}

	/*
	 * Signal the main thread by signalling the writable event and then
	 * waking up the notifier thread.
	 */

	SetEvent(threadInfo->readyEvent);

	/*
	 * Alert the foreground thread. Note that we need to treat this like a
	 * critical section so the foreground thread does not terminate this
	 * thread while we are holding a mutex in the notifier code.
	 */

	Tcl_MutexLock(&consoleMutex);
	if (infoPtr->threadId != NULL) {
	    /*
	     * TIP #218. When in flight ignore the event, no one will receive
	     * it anyway.
	     */

	    Tcl_ThreadAlert(infoPtr->threadId);
	}
	Tcl_MutexUnlock(&consoleMutex);
    }

    /*
     * Inform caller that this thread should not be terminated, since it is about to exit.
     * See comment in StopChannelThread() for reasons.
    */
    threadInfo->threadExiting = TRUE;

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinOpenConsoleChannel --
 *
 *	Constructs a Console channel for the specified standard OS handle.
 *	This is a helper function to break up the construction of channels
 *	into File, Console, or Serial.
 *
 * Results:
 *	Returns the new channel, or NULL.
 *
 * Side effects:
 *	May open the channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclWinOpenConsoleChannel(
    HANDLE handle,
    char *channelName,
    int permissions)
{
    char encoding[4 + TCL_INTEGER_SPACE];
    ConsoleInfo *infoPtr;
    DWORD modes, wEventsCnt = 0;
    HANDLE wEvents[2], wEventsPtr = wEvents;

    ConsoleInit();

    /*
     * See if a channel with this handle already exists.
     */

    infoPtr = ckalloc(sizeof(ConsoleInfo));
    memset(infoPtr, 0, sizeof(ConsoleInfo));

    infoPtr->validMask = permissions;
    infoPtr->handle = handle;
    infoPtr->channel = (Tcl_Channel) NULL;

    wsprintfA(encoding, "cp%d", GetConsoleCP());

    infoPtr->threadId = Tcl_GetCurrentThread();

    /*
     * Use the pointer for the name of the result channel. This keeps the
     * channel names unique, since some may share handles (stdin/stdout/stderr
     * for instance).
     */

    sprintf(channelName, "file%" TCL_I_MODIFIER "x", (size_t) infoPtr);

    infoPtr->channel = Tcl_CreateChannel(&consoleChannelType, channelName,
	    infoPtr, permissions);

    if (permissions & TCL_READABLE) {
	/*
	 * Make sure the console input buffer is ready for only character
	 * input notifications and the buffer is set for line buffering. IOW,
	 * we only want to catch when complete lines are ready for reading.
	 */

	GetConsoleMode(infoPtr->handle, &modes);
	modes &= ~(ENABLE_WINDOW_INPUT | ENABLE_MOUSE_INPUT);
	modes |= ENABLE_LINE_INPUT;
	SetConsoleMode(infoPtr->handle, modes);
	StartChannelThread(infoPtr, &infoPtr->reader, ConsoleReaderThread);
	wEvents[wEventsCnt++] = infoPtr->reader.startEvent;
    }

    if (permissions & TCL_WRITABLE) {
	StartChannelThread(infoPtr, &infoPtr->writer, ConsoleWriterThread);
	wEvents[wEventsCnt++] = infoPtr->writer.startEvent;
    }

    /* 
     * Wait for both threads to initialize (using theirs startEvent)
     */
    if (wEventsCnt) {
	WaitForMultipleObjects(wEventsCnt, wEvents, TRUE, 5000);
	/* Resume both waiting threads */
	if (infoPtr->reader.thread)
	    ResumeThread(infoPtr->reader.thread);
	if (infoPtr->writer.thread)
	    ResumeThread(infoPtr->writer.thread);
    }
    /*
     * Files have default translation of AUTO and ^Z eof char, which means
     * that a ^Z will be accepted as EOF when reading.
     */

    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");
#ifdef UNICODE
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-encoding", "unicode");
#else
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-encoding", encoding);
#endif
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * ConsoleThreadActionProc --
 *
 *	Insert or remove any thread local refs to this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Changes thread local list of valid channels.
 *
 *----------------------------------------------------------------------
 */

static void
ConsoleThreadActionProc(
    ClientData instanceData,
    int action)
{
    ConsoleInfo *infoPtr = instanceData;

    /*
     * We do not access firstConsolePtr in the thread structures. This is not
     * for all serials managed by the thread, but only those we are watching.
     * Removal of the filevent handlers before transfer thus takes care of
     * this structure.
     */

    Tcl_MutexLock(&consoleMutex);
    if (action == TCL_CHANNEL_THREAD_INSERT) {
	/*
	 * We can't copy the thread information from the channel when the
	 * channel is created. At this time the channel back pointer has not
	 * been set yet. However in that case the threadId has already been
	 * set by TclpCreateCommandChannel itself, so the structure is still
	 * good.
	 */

	ConsoleInit();
	if (infoPtr->channel != NULL) {
	    infoPtr->threadId = Tcl_GetChannelThread(infoPtr->channel);
	}
    } else {
	infoPtr->threadId = NULL;
    }
    Tcl_MutexUnlock(&consoleMutex);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */