path: root/win/tclWinPipe.c

/*
 * tclWinPipe.c --
 *
 *	This file implements the Windows-specific exec pipeline functions, the
 *	"pipe" channel driver, and the "pid" Tcl command.
 *
 * Copyright (c) 1996-1997 by 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 "tclWinInt.h"

#include <sys/stat.h>

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

static int initialized = 0;

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

TCL_DECLARE_MUTEX(pipeMutex)

/*
 * The following defines identify the various types of applications that run
 * under windows. There is special case code for the various types.
 */

#define APPL_NONE	0
#define APPL_DOS	1
#define APPL_WIN3X	2
#define APPL_WIN32	3

/*
 * The following constants and structures are used to encapsulate the state of
 * various types of files used in a pipeline. This used to have a 1 && 2 that
 * supported Win32s.
 */

#define WIN_FILE	3	/* Basic Win32 file. */

/*
 * This structure encapsulates the common state associated with all file types
 * used in a pipeline.
 */

typedef struct WinFile {
    int type;			/* One of the file types defined above. */
    HANDLE handle;		/* Open file handle. */
} WinFile;

/*
 * This list is used to map from pids to process handles.
 */

typedef struct ProcInfo {
    HANDLE hProcess;
    DWORD dwProcessId;
    struct ProcInfo *nextPtr;
} ProcInfo;

static ProcInfo *procList;

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

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

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

#define PIPE_EOF	(1<<2)	/* Pipe has reached EOF. */
#define PIPE_EXTRABYTE	(1<<3)	/* The reader thread has consumed one byte. */

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

typedef struct PipeInfo {
    struct PipeInfo *nextPtr;	/* Pointer to next registered pipe. */
    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. */
    TclFile readFile;		/* Output from pipe. */
    TclFile writeFile;		/* Input from pipe. */
    TclFile errorFile;		/* Error output from pipe. */
    int numPids;		/* Number of processes attached to pipe. */
    Tcl_Pid *pidPtr;		/* Pids of attached processes. */
    Tcl_ThreadId threadId;	/* Thread to which events should be reported.
				 * This value is used by the reader/writer
				 * threads. */
    HANDLE writeThread;		/* Handle to writer thread. */
    HANDLE readThread;		/* Handle to reader thread. */
    HANDLE writable;		/* Manual-reset event to signal when the
				 * writer thread has finished waiting for the
				 * current buffer to be written. */
    HANDLE readable;		/* Manual-reset event to signal when the
				 * reader thread has finished waiting for
				 * input. */
    HANDLE startWriter;		/* Auto-reset event used by the main thread to
				 * signal when the writer thread should
				 * attempt to write to the pipe. */
    HANDLE stopWriter;		/* Manual-reset event used to alert the reader
				 * thread to fall-out and exit */
    HANDLE startReader;		/* Auto-reset event used by the main thread to
				 * signal when the reader thread should
				 * attempt to read from the pipe. */
    HANDLE stopReader;		/* Manual-reset event used to alert the reader
				 * thread to fall-out and exit */
    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.  */
    char extraByte;		/* Buffer for extra character consumed by
				 * reader thread. This byte is shared with the
				 * reader thread so access must be
				 * synchronized with the readable object. */
} PipeInfo;

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

    PipeInfo *firstPipePtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

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

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

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

static int		ApplicationType(Tcl_Interp *interp,
			    const char *fileName, char *fullName);
static void		BuildCommandLine(const char *executable, int argc,
			    const char **argv, Tcl_DString *linePtr);
static BOOL		HasConsole(void);
static int		PipeBlockModeProc(ClientData instanceData, int mode);
static void		PipeCheckProc(ClientData clientData, int flags);
static int		PipeClose2Proc(ClientData instanceData,
			    Tcl_Interp *interp, int flags);
static int		PipeEventProc(Tcl_Event *evPtr, int flags);
static int		PipeGetHandleProc(ClientData instanceData,
			    int direction, ClientData *handlePtr);
static void		PipeInit(void);
static int		PipeInputProc(ClientData instanceData, char *buf,
			    int toRead, int *errorCode);
static int		PipeOutputProc(ClientData instanceData,
			    const char *buf, int toWrite, int *errorCode);
static DWORD WINAPI	PipeReaderThread(LPVOID arg);
static void		PipeSetupProc(ClientData clientData, int flags);
static void		PipeWatchProc(ClientData instanceData, int mask);
static DWORD WINAPI	PipeWriterThread(LPVOID arg);
static int		TempFileName(TCHAR name[MAX_PATH]);
static int		WaitForRead(PipeInfo *infoPtr, int blocking);
static void		PipeThreadActionProc(ClientData instanceData,
			    int action);

/*
 * This structure describes the channel type structure for command pipe based
 * I/O.
 */

static const Tcl_ChannelType pipeChannelType = {
    "pipe",			/* Type name. */
    TCL_CHANNEL_VERSION_5,	/* v5 channel */
    TCL_CLOSE2PROC,		/* Close proc. */
    PipeInputProc,		/* Input proc. */
    PipeOutputProc,		/* Output proc. */
    NULL,			/* Seek proc. */
    NULL,			/* Set option proc. */
    NULL,			/* Get option proc. */
    PipeWatchProc,		/* Set up notifier to watch the channel. */
    PipeGetHandleProc,		/* Get an OS handle from channel. */
    PipeClose2Proc,		/* close2proc */
    PipeBlockModeProc,		/* Set blocking or non-blocking mode.*/
    NULL,			/* flush proc. */
    NULL,			/* handler proc. */
    NULL,			/* wide seek proc */
    PipeThreadActionProc,	/* thread action proc */
    NULL                       /* truncate */
};

/*
 *----------------------------------------------------------------------
 *
 * PipeInit --
 *
 *	This function initializes the static variables for this file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new event source.
 *
 *----------------------------------------------------------------------
 */

static void
PipeInit(void)
{
    ThreadSpecificData *tsdPtr;

    /*
     * Check the initialized flag first, then check again in the mutex. This
     * is a speed enhancement.
     */

    if (!initialized) {
	Tcl_MutexLock(&pipeMutex);
	if (!initialized) {
	    initialized = 1;
	    procList = NULL;
	}
	Tcl_MutexUnlock(&pipeMutex);
    }

    tsdPtr = (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);
    if (tsdPtr == NULL) {
	tsdPtr = TCL_TSD_INIT(&dataKey);
	tsdPtr->firstPipePtr = NULL;
	Tcl_CreateEventSource(PipeSetupProc, PipeCheckProc, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizePipes --
 *
 *	This function is called from Tcl_FinalizeThread to finalize the
 *	platform specific pipe subsystem.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes the pipe event source.
 *
 *----------------------------------------------------------------------
 */

void
TclpFinalizePipes(void)
{
    ThreadSpecificData *tsdPtr;

    tsdPtr = (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);
    if (tsdPtr != NULL) {
	Tcl_DeleteEventSource(PipeSetupProc, PipeCheckProc, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeSetupProc --
 *
 *	This function is invoked before Tcl_DoOneEvent blocks waiting for an
 *	event.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

void
PipeSetupProc(
    ClientData data,		/* Not used. */
    int flags)			/* Event flags as passed to Tcl_DoOneEvent. */
{
    PipeInfo *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->firstPipePtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (infoPtr->watchMask & TCL_WRITABLE) {
	    if (WaitForSingleObject(infoPtr->writable, 0) != WAIT_TIMEOUT) {
		block = 0;
	    }
	}
	if (infoPtr->watchMask & TCL_READABLE) {
	    if (WaitForRead(infoPtr, 0) >= 0) {
		block = 0;
	    }
	}
    }
    if (!block) {
	Tcl_SetMaxBlockTime(&blockTime);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeCheckProc --
 *
 *	This function is called by Tcl_DoOneEvent to check the pipe event
 *	source for events.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May queue an event.
 *
 *----------------------------------------------------------------------
 */

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

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

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

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

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

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

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

	if (needEvent) {
	    infoPtr->flags |= PIPE_PENDING;
	    evPtr = ckalloc(sizeof(PipeEvent));
	    evPtr->header.proc = PipeEventProc;
	    evPtr->infoPtr = infoPtr;
	    Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinMakeFile --
 *
 *	This function constructs a new TclFile from a given data and type
 *	value.
 *
 * Results:
 *	Returns a newly allocated WinFile as a TclFile.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclWinMakeFile(
    HANDLE handle)		/* Type-specific data. */
{
    WinFile *filePtr;

    filePtr = ckalloc(sizeof(WinFile));
    filePtr->type = WIN_FILE;
    filePtr->handle = handle;

    return (TclFile)filePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TempFileName --
 *
 *	Gets a temporary file name and deals with the fact that the temporary
 *	file path provided by Windows may not actually exist if the TMP or
 *	TEMP environment variables refer to a non-existent directory.
 *
 * Results:
 *	0 if error, non-zero otherwise. If non-zero is returned, the name
 *	buffer will be filled with a name that can be used to construct a
 *	temporary file.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
TempFileName(
    TCHAR name[MAX_PATH])	/* Buffer in which name for temporary file
				 * gets stored. */
{
    const TCHAR *prefix = TEXT("TCL");
    if (GetTempPath(MAX_PATH, name) != 0) {
	if (GetTempFileName(name, prefix, 0, name) != 0) {
	    return 1;
	}
    }
    name[0] = '.';
    name[1] = '\0';
    return GetTempFileName(name, prefix, 0, name);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpMakeFile --
 *
 *	Make a TclFile from a channel.
 *
 * Results:
 *	Returns a new TclFile or NULL on failure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpMakeFile(
    Tcl_Channel channel,	/* Channel to get file from. */
    int direction)		/* Either TCL_READABLE or TCL_WRITABLE. */
{
    HANDLE handle;

    if (Tcl_GetChannelHandle(channel, direction,
	    (ClientData *) &handle) == TCL_OK) {
	return TclWinMakeFile(handle);
    } else {
	return (TclFile) NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpOpenFile --
 *
 *	This function opens files for use in a pipeline.
 *
 * Results:
 *	Returns a newly allocated TclFile structure containing the file
 *	handle.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpOpenFile(
    const char *path,		/* The name of the file to open. */
    int mode)			/* In what mode to open the file? */
{
    HANDLE handle;
    DWORD accessMode, createMode, shareMode, flags;
    Tcl_DString ds;
    const TCHAR *nativePath;

    /*
     * Map the access bits to the NT access mode.
     */

    switch (mode & (O_RDONLY | O_WRONLY | O_RDWR)) {
    case O_RDONLY:
	accessMode = GENERIC_READ;
	break;
    case O_WRONLY:
	accessMode = GENERIC_WRITE;
	break;
    case O_RDWR:
	accessMode = (GENERIC_READ | GENERIC_WRITE);
	break;
    default:
	TclWinConvertError(ERROR_INVALID_FUNCTION);
	return NULL;
    }

    /*
     * Map the creation flags to the NT create mode.
     */

    switch (mode & (O_CREAT | O_EXCL | O_TRUNC)) {
    case (O_CREAT | O_EXCL):
    case (O_CREAT | O_EXCL | O_TRUNC):
	createMode = CREATE_NEW;
	break;
    case (O_CREAT | O_TRUNC):
	createMode = CREATE_ALWAYS;
	break;
    case O_CREAT:
	createMode = OPEN_ALWAYS;
	break;
    case O_TRUNC:
    case (O_TRUNC | O_EXCL):
	createMode = TRUNCATE_EXISTING;
	break;
    default:
	createMode = OPEN_EXISTING;
	break;
    }

    nativePath = Tcl_WinUtfToTChar(path, -1, &ds);

    /*
     * If the file is not being created, use the existing file attributes.
     */

    flags = 0;
    if (!(mode & O_CREAT)) {
	flags = GetFileAttributes(nativePath);
	if (flags == 0xFFFFFFFF) {
	    flags = 0;
	}
    }

    /*
     * Set up the file sharing mode.  We want to allow simultaneous access.
     */

    shareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;

    /*
     * Now we get to create the file.
     */

    handle = CreateFile(nativePath, accessMode, shareMode,
	    NULL, createMode, flags, NULL);
    Tcl_DStringFree(&ds);

    if (handle == INVALID_HANDLE_VALUE) {
	DWORD err;

	err = GetLastError();
	if ((err & 0xffffL) == ERROR_OPEN_FAILED) {
	    err = (mode & O_CREAT) ? ERROR_FILE_EXISTS : ERROR_FILE_NOT_FOUND;
	}
	TclWinConvertError(err);
	return NULL;
    }

    /*
     * Seek to the end of file if we are writing.
     */

    if (mode & (O_WRONLY|O_APPEND)) {
	SetFilePointer(handle, 0, NULL, FILE_END);
    }

    return TclWinMakeFile(handle);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateTempFile --
 *
 *	This function opens a unique file with the property that it will be
 *	deleted when its file handle is closed. The temporary file is created
 *	in the system temporary directory.
 *
 * Results:
 *	Returns a valid TclFile, or NULL on failure.
 *
 * Side effects:
 *	Creates a new temporary file.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpCreateTempFile(
    const char *contents)	/* String to write into temp file, or NULL. */
{
    TCHAR name[MAX_PATH];
    const char *native;
    Tcl_DString dstring;
    HANDLE handle;

    if (TempFileName(name) == 0) {
	return NULL;
    }

    handle = CreateFile(name,
	    GENERIC_READ | GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,
	    FILE_ATTRIBUTE_TEMPORARY|FILE_FLAG_DELETE_ON_CLOSE, NULL);
    if (handle == INVALID_HANDLE_VALUE) {
	goto error;
    }

    /*
     * Write the file out, doing line translations on the way.
     */

    if (contents != NULL) {
	DWORD result, length;
	const char *p;
	int toCopy;

	/*
	 * Convert the contents from UTF to native encoding
	 */

	native = Tcl_UtfToExternalDString(NULL, contents, -1, &dstring);

	toCopy = Tcl_DStringLength(&dstring);
	for (p = native; toCopy > 0; p++, toCopy--) {
	    if (*p == '\n') {
		length = p - native;
		if (length > 0) {
		    if (!WriteFile(handle, native, length, &result, NULL)) {
			goto error;
		    }
		}
		if (!WriteFile(handle, "\r\n", 2, &result, NULL)) {
		    goto error;
		}
		native = p+1;
	    }
	}
	length = p - native;
	if (length > 0) {
	    if (!WriteFile(handle, native, length, &result, NULL)) {
		goto error;
	    }
	}
	Tcl_DStringFree(&dstring);
	if (SetFilePointer(handle, 0, NULL, FILE_BEGIN) == 0xFFFFFFFF) {
	    goto error;
	}
    }

    return TclWinMakeFile(handle);

  error:
    /*
     * Free the native representation of the contents if necessary.
     */

    if (contents != NULL) {
	Tcl_DStringFree(&dstring);
    }

    TclWinConvertError(GetLastError());
    CloseHandle(handle);
    DeleteFile(name);
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpTempFileName --
 *
 *	This function returns a unique filename.
 *
 * Results:
 *	Returns a valid Tcl_Obj* with refCount 0, or NULL on failure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclpTempFileName(void)
{
    TCHAR fileName[MAX_PATH];

    if (TempFileName(fileName) == 0) {
	return NULL;
    }

    return TclpNativeToNormalized(fileName);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreatePipe --
 *
 *	Creates an anonymous pipe.
 *
 * Results:
 *	Returns 1 on success, 0 on failure.
 *
 * Side effects:
 *	Creates a pipe.
 *
 *----------------------------------------------------------------------
 */

int
TclpCreatePipe(
    TclFile *readPipe,		/* Location to store file handle for read side
				 * of pipe. */
    TclFile *writePipe)		/* Location to store file handle for write
				 * side of pipe. */
{
    HANDLE readHandle, writeHandle;

    if (CreatePipe(&readHandle, &writeHandle, NULL, 0) != 0) {
	*readPipe = TclWinMakeFile(readHandle);
	*writePipe = TclWinMakeFile(writeHandle);
	return 1;
    }

    TclWinConvertError(GetLastError());
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCloseFile --
 *
 *	Closes a pipeline file handle. These handles are created by
 *	TclpOpenFile, TclpCreatePipe, or TclpMakeFile.
 *
 * Results:
 *	0 on success, -1 on failure.
 *
 * Side effects:
 *	The file is closed and deallocated.
 *
 *----------------------------------------------------------------------
 */

int
TclpCloseFile(
    TclFile file)		/* The file to close. */
{
    WinFile *filePtr = (WinFile *) file;

    switch (filePtr->type) {
    case WIN_FILE:
	/*
	 * 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) != filePtr->handle)
		    && (GetStdHandle(STD_OUTPUT_HANDLE) != filePtr->handle)
		    && (GetStdHandle(STD_ERROR_HANDLE) != filePtr->handle))) {
	    if (filePtr->handle != NULL &&
		    CloseHandle(filePtr->handle) == FALSE) {
		TclWinConvertError(GetLastError());
		ckfree(filePtr);
		return -1;
	    }
	}
	break;

    default:
	Tcl_Panic("TclpCloseFile: unexpected file type");
    }

    ckfree(filePtr);
    return 0;
}

/*
 *--------------------------------------------------------------------------
 *
 * TclpGetPid --
 *
 *	Given a HANDLE to a child process, return the process id for that
 *	child process.
 *
 * Results:
 *	Returns the process id for the child process. If the pid was not known
 *	by Tcl, either because the pid was not created by Tcl or the child
 *	process has already been reaped, -1 is returned.
 *
 * Side effects:
 *	None.
 *
 *--------------------------------------------------------------------------
 */

int
TclpGetPid(
    Tcl_Pid pid)		/* The HANDLE of the child process. */
{
    ProcInfo *infoPtr;

    PipeInit();

    Tcl_MutexLock(&pipeMutex);
    for (infoPtr = procList; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
	if (infoPtr->hProcess == (HANDLE) pid) {
	    Tcl_MutexUnlock(&pipeMutex);
	    return infoPtr->dwProcessId;
	}
    }
    Tcl_MutexUnlock(&pipeMutex);
    return (unsigned long) -1;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateProcess --
 *
 *	Create a child process that has the specified files as its standard
 *	input, output, and error. The child process runs asynchronously under
 *	Windows NT and Windows 9x, and runs with the same environment
 *	variables as the creating process.
 *
 *	The complete Windows search path is searched to find the specified
 *	executable. If an executable by the given name is not found,
 *	automatically tries appending ".com", ".exe", and ".bat" to the
 *	executable name.
 *
 * Results:
 *	The return value is TCL_ERROR and an error message is left in the
 *	interp's result if there was a problem creating the child process.
 *	Otherwise, the return value is TCL_OK and *pidPtr is filled with the
 *	process id of the child process.
 *
 * Side effects:
 *	A process is created.
 *
 *----------------------------------------------------------------------
 */

int
TclpCreateProcess(
    Tcl_Interp *interp,		/* Interpreter in which to leave errors that
				 * occurred when creating the child process.
				 * Error messages from the child process
				 * itself are sent to errorFile. */
    int argc,			/* Number of arguments in following array. */
    const char **argv,		/* Array of argument strings. argv[0] contains
				 * the name of the executable converted to
				 * native format (using the
				 * Tcl_TranslateFileName call). Additional
				 * arguments have not been converted. */
    TclFile inputFile,		/* If non-NULL, gives the file to use as input
				 * for the child process. If inputFile file is
				 * not readable or is NULL, the child will
				 * receive no standard input. */
    TclFile outputFile,		/* If non-NULL, gives the file that receives
				 * output from the child process. If
				 * outputFile file is not writeable or is
				 * NULL, output from the child will be
				 * discarded. */
    TclFile errorFile,		/* If non-NULL, gives the file that receives
				 * errors from the child process. If errorFile
				 * file is not writeable or is NULL, errors
				 * from the child will be discarded. errorFile
				 * may be the same as outputFile. */
    Tcl_Pid *pidPtr)		/* If this function is successful, pidPtr is
				 * filled with the process id of the child
				 * process. */
{
    int result, applType, createFlags;
    Tcl_DString cmdLine;	/* Complete command line (TCHAR). */
    STARTUPINFO startInfo;
    PROCESS_INFORMATION procInfo;
    SECURITY_ATTRIBUTES secAtts;
    HANDLE hProcess, h, inputHandle, outputHandle, errorHandle;
    char execPath[MAX_PATH * TCL_UTF_MAX];
    WinFile *filePtr;

    PipeInit();

    applType = ApplicationType(interp, argv[0], execPath);
    if (applType == APPL_NONE) {
	return TCL_ERROR;
    }

    result = TCL_ERROR;
    Tcl_DStringInit(&cmdLine);
    hProcess = GetCurrentProcess();

    /*
     * STARTF_USESTDHANDLES must be used to pass handles to child process.
     * Using SetStdHandle() and/or dup2() only works when a console mode
     * parent process is spawning an attached console mode child process.
     */

    ZeroMemory(&startInfo, sizeof(startInfo));
    startInfo.cb = sizeof(startInfo);
    startInfo.dwFlags	= STARTF_USESTDHANDLES;
    startInfo.hStdInput	= INVALID_HANDLE_VALUE;
    startInfo.hStdOutput= INVALID_HANDLE_VALUE;
    startInfo.hStdError = INVALID_HANDLE_VALUE;

    secAtts.nLength = sizeof(SECURITY_ATTRIBUTES);
    secAtts.lpSecurityDescriptor = NULL;
    secAtts.bInheritHandle = TRUE;

    /*
     * We have to check the type of each file, since we cannot duplicate some
     * file types.
     */

    inputHandle = INVALID_HANDLE_VALUE;
    if (inputFile != NULL) {
	filePtr = (WinFile *)inputFile;
	if (filePtr->type == WIN_FILE) {
	    inputHandle = filePtr->handle;
	}
    }
    outputHandle = INVALID_HANDLE_VALUE;
    if (outputFile != NULL) {
	filePtr = (WinFile *)outputFile;
	if (filePtr->type == WIN_FILE) {
	    outputHandle = filePtr->handle;
	}
    }
    errorHandle = INVALID_HANDLE_VALUE;
    if (errorFile != NULL) {
	filePtr = (WinFile *)errorFile;
	if (filePtr->type == WIN_FILE) {
	    errorHandle = filePtr->handle;
	}
    }

    /*
     * Duplicate all the handles which will be passed off as stdin, stdout and
     * stderr of the child process. The duplicate handles are set to be
     * inheritable, so the child process can use them.
     */

    if (inputHandle == INVALID_HANDLE_VALUE) {
	/*
	 * If handle was not set, stdin should return immediate EOF. Under
	 * Windows95, some applications (both 16 and 32 bit!) cannot read from
	 * the NUL device; they read from console instead. When running tk,
	 * this is fatal because the child process would hang forever waiting
	 * for EOF from the unmapped console window used by the helper
	 * application.
	 *
	 * Fortunately, the helper application detects a closed pipe as an
	 * immediate EOF and can pass that information to the child process.
	 */

	if (CreatePipe(&startInfo.hStdInput, &h, &secAtts, 0) != FALSE) {
	    CloseHandle(h);
	}
    } else {
	DuplicateHandle(hProcess, inputHandle, hProcess, &startInfo.hStdInput,
		0, TRUE, DUPLICATE_SAME_ACCESS);
    }
    if (startInfo.hStdInput == INVALID_HANDLE_VALUE) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"couldn't duplicate input handle: %s",
		Tcl_PosixError(interp)));
	goto end;
    }

    if (outputHandle == INVALID_HANDLE_VALUE) {
	/*
	 * If handle was not set, output should be sent to an infinitely deep
	 * sink. Under Windows 95, some 16 bit applications cannot have stdout
	 * redirected to NUL; they send their output to the console instead.
	 * Some applications, like "more" or "dir /p", when outputting
	 * multiple pages to the console, also then try and read from the
	 * console to go the next page. When running tk, this is fatal because
	 * the child process would hang forever waiting for input from the
	 * unmapped console window used by the helper application.
	 *
	 * Fortunately, the helper application will detect a closed pipe as a
	 * sink.
	 */

	if ((TclWinGetPlatformId() == VER_PLATFORM_WIN32_WINDOWS)
		&& (applType == APPL_DOS)) {
	    if (CreatePipe(&h, &startInfo.hStdOutput, &secAtts, 0) != FALSE) {
		CloseHandle(h);
	    }
	} else {
	    startInfo.hStdOutput = CreateFileA("NUL:", GENERIC_WRITE, 0,
		    &secAtts, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
	}
    } else {
	DuplicateHandle(hProcess, outputHandle, hProcess,
		&startInfo.hStdOutput, 0, TRUE, DUPLICATE_SAME_ACCESS);
    }
    if (startInfo.hStdOutput == INVALID_HANDLE_VALUE) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"couldn't duplicate output handle: %s",
		Tcl_PosixError(interp)));
	goto end;
    }

    if (errorHandle == INVALID_HANDLE_VALUE) {
	/*
	 * If handle was not set, errors should be sent to an infinitely deep
	 * sink.
	 */

	startInfo.hStdError = CreateFileA("NUL:", GENERIC_WRITE, 0,
		&secAtts, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    } else {
	DuplicateHandle(hProcess, errorHandle, hProcess, &startInfo.hStdError,
		0, TRUE, DUPLICATE_SAME_ACCESS);
    }
    if (startInfo.hStdError == INVALID_HANDLE_VALUE) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"couldn't duplicate error handle: %s",
		Tcl_PosixError(interp)));
	goto end;
    }

    /*
     * If we do not have a console window, then we must run DOS and WIN32
     * console mode applications as detached processes. This tells the loader
     * that the child application should not inherit the console, and that it
     * should not create a new console window for the child application. The
     * child application should get its stdio from the redirection handles
     * provided by this application, and run in the background.
     *
     * If we are starting a GUI process, they don't automatically get a
     * console, so it doesn't matter if they are started as foreground or
     * detached processes. The GUI window will still pop up to the foreground.
     */

    if (TclWinGetPlatformId() == VER_PLATFORM_WIN32_NT) {
	if (HasConsole()) {
	    createFlags = 0;
	} else if (applType == APPL_DOS) {
	    /*
	     * Under NT, 16-bit DOS applications will not run unless they can
	     * be attached to a console. If we are running without a console,
	     * run the 16-bit program as an normal process inside of a hidden
	     * console application, and then run that hidden console as a
	     * detached process.
	     */

	    startInfo.wShowWindow = SW_HIDE;
	    startInfo.dwFlags |= STARTF_USESHOWWINDOW;
	    createFlags = CREATE_NEW_CONSOLE;
	    TclDStringAppendLiteral(&cmdLine, "cmd.exe /c");
	} else {
	    createFlags = DETACHED_PROCESS;
	}
    } else {
	if (HasConsole()) {
	    createFlags = 0;
	} else {
	    createFlags = DETACHED_PROCESS;
	}

	if (applType == APPL_DOS) {
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
		    "DOS application process not supported on this platform",
		    -1));
	    Tcl_SetErrorCode(interp, "TCL", "OPERATION", "EXEC", "DOS_APP",
		    NULL);
	    goto end;
	}
    }

    /*
     * cmdLine gets the full command line used to invoke the executable,
     * including the name of the executable itself. The command line arguments
     * in argv[] are stored in cmdLine separated by spaces. Special characters
     * in individual arguments from argv[] must be quoted when being stored in
     * cmdLine.
     *
     * When calling any application, bear in mind that arguments that specify
     * a path name are not converted. If an argument contains forward slashes
     * as path separators, it may or may not be recognized as a path name,
     * depending on the program. In general, most applications accept forward
     * slashes only as option delimiters and backslashes only as paths.
     *
     * Additionally, when calling a 16-bit dos or windows application, all
     * path names must use the short, cryptic, path format (e.g., using
     * ab~1.def instead of "a b.default").
     */

    BuildCommandLine(execPath, argc, argv, &cmdLine);

    if (CreateProcess(NULL, (TCHAR *) Tcl_DStringValue(&cmdLine),
	    NULL, NULL, TRUE, (DWORD) createFlags, NULL, NULL, &startInfo,
	    &procInfo) == 0) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf("couldn't execute \"%s\": %s",
		argv[0], Tcl_PosixError(interp)));
	goto end;
    }

    /*
     * This wait is used to force the OS to give some time to the DOS process.
     */

    if (applType == APPL_DOS) {
	WaitForSingleObject(procInfo.hProcess, 50);
    }

    /*
     * "When an application spawns a process repeatedly, a new thread instance
     * will be created for each process but the previous instances may not be
     * cleaned up. This results in a significant virtual memory loss each time
     * the process is spawned. If there is a WaitForInputIdle() call between
     * CreateProcess() and CloseHandle(), the problem does not occur." PSS ID
     * Number: Q124121
     */

    WaitForInputIdle(procInfo.hProcess, 5000);
    CloseHandle(procInfo.hThread);

    *pidPtr = (Tcl_Pid) procInfo.hProcess;
    if (*pidPtr != 0) {
	TclWinAddProcess(procInfo.hProcess, procInfo.dwProcessId);
    }
    result = TCL_OK;

  end:
    Tcl_DStringFree(&cmdLine);
    if (startInfo.hStdInput != INVALID_HANDLE_VALUE) {
	CloseHandle(startInfo.hStdInput);
    }
    if (startInfo.hStdOutput != INVALID_HANDLE_VALUE) {
	CloseHandle(startInfo.hStdOutput);
    }
    if (startInfo.hStdError != INVALID_HANDLE_VALUE) {
	CloseHandle(startInfo.hStdError);
    }
    return result;
}


/*
 *----------------------------------------------------------------------
 *
 * HasConsole --
 *
 *	Determines whether the current application is attached to a console.
 *
 * Results:
 *	Returns TRUE if this application has a console, else FALSE.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static BOOL
HasConsole(void)
{
    HANDLE handle;

    handle = CreateFileA("CONOUT$", GENERIC_WRITE, FILE_SHARE_WRITE,
	    NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

    if (handle != INVALID_HANDLE_VALUE) {
	CloseHandle(handle);
	return TRUE;
    } else {
	return FALSE;
    }
}

/*
 *--------------------------------------------------------------------
 *
 * ApplicationType --
 *
 *	Search for the specified program and identify if it refers to a DOS,
 *	Windows 3.X, or Win32 program.	Used to determine how to invoke a
 *	program, or if it can even be invoked.
 *
 *	It is possible to almost positively identify DOS and Windows
 *	applications that contain the appropriate magic numbers. However, DOS
 *	.com files do not seem to contain a magic number; if the program name
 *	ends with .com and could not be identified as a Windows .com file, it
 *	will be assumed to be a DOS application, even if it was just random
 *	data. If the program name does not end with .com, no such assumption
 *	is made.
 *
 *	The Win32 function GetBinaryType incorrectly identifies any junk file
 *	that ends with .exe as a dos executable and some executables that
 *	don't end with .exe as not executable. Plus it doesn't exist under
 *	win95, so I won't feel bad about reimplementing functionality.
 *
 * Results:
 *	The return value is one of APPL_DOS, APPL_WIN3X, or APPL_WIN32 if the
 *	filename referred to the corresponding application type. If the file
 *	name could not be found or did not refer to any known application
 *	type, APPL_NONE is returned and an error message is left in interp.
 *	.bat files are identified as APPL_DOS.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
ApplicationType(
    Tcl_Interp *interp,		/* Interp, for error message. */
    const char *originalName,	/* Name of the application to find. */
    char fullName[])		/* Filled with complete path to
				 * application. */
{
    int applType, i, nameLen, found;
    HANDLE hFile;
    TCHAR *rest;
    char *ext;
    char buf[2];
    DWORD attr, read;
    IMAGE_DOS_HEADER header;
    Tcl_DString nameBuf, ds;
    const TCHAR *nativeName;
    TCHAR nativeFullPath[MAX_PATH];
    static const char extensions[][5] = {"", ".com", ".exe", ".bat"};

    /*
     * Look for the program as an external program. First try the name as it
     * is, then try adding .com, .exe, and .bat, in that order, to the name,
     * looking for an executable.
     *
     * Using the raw SearchPath() function doesn't do quite what is necessary.
     * If the name of the executable already contains a '.' character, it will
     * not try appending the specified extension when searching (in other
     * words, SearchPath will not find the program "a.b.exe" if the arguments
     * specified "a.b" and ".exe"). So, first look for the file as it is
     * named. Then manually append the extensions, looking for a match.
     */

    applType = APPL_NONE;
    Tcl_DStringInit(&nameBuf);
    Tcl_DStringAppend(&nameBuf, originalName, -1);
    nameLen = Tcl_DStringLength(&nameBuf);

    for (i = 0; i < (int) (sizeof(extensions) / sizeof(extensions[0])); i++) {
	Tcl_DStringSetLength(&nameBuf, nameLen);
	Tcl_DStringAppend(&nameBuf, extensions[i], -1);
	nativeName = Tcl_WinUtfToTChar(Tcl_DStringValue(&nameBuf),
		Tcl_DStringLength(&nameBuf), &ds);
	found = SearchPath(NULL, nativeName, NULL, MAX_PATH,
		nativeFullPath, &rest);
	Tcl_DStringFree(&ds);
	if (found == 0) {
	    continue;
	}

	/*
	 * Ignore matches on directories or data files, return if identified a
	 * known type.
	 */

	attr = GetFileAttributes(nativeFullPath);
	if ((attr == 0xffffffff) || (attr & FILE_ATTRIBUTE_DIRECTORY)) {
	    continue;
	}
	strcpy(fullName, Tcl_WinTCharToUtf(nativeFullPath, -1, &ds));
	Tcl_DStringFree(&ds);

	ext = strrchr(fullName, '.');
	if ((ext != NULL) && (strcasecmp(ext, ".bat") == 0)) {
	    applType = APPL_DOS;
	    break;
	}

	hFile = CreateFile(nativeFullPath,
		GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL, NULL);
	if (hFile == INVALID_HANDLE_VALUE) {
	    continue;
	}

	header.e_magic = 0;
	ReadFile(hFile, (void *) &header, sizeof(header), &read, NULL);
	if (header.e_magic != IMAGE_DOS_SIGNATURE) {
	    /*
	     * Doesn't have the magic number for relocatable executables. If
	     * filename ends with .com, assume it's a DOS application anyhow.
	     * Note that we didn't make this assumption at first, because some
	     * supposed .com files are really 32-bit executables with all the
	     * magic numbers and everything.
	     */

	    CloseHandle(hFile);
	    if ((ext != NULL) && (strcasecmp(ext, ".com") == 0)) {
		applType = APPL_DOS;
		break;
	    }
	    continue;
	}
	if (header.e_lfarlc != sizeof(header)) {
	    /*
	     * All Windows 3.X and Win32 and some DOS programs have this value
	     * set here. If it doesn't, assume that since it already had the
	     * other magic number it was a DOS application.
	     */

	    CloseHandle(hFile);
	    applType = APPL_DOS;
	    break;
	}

	/*
	 * The DWORD at header.e_lfanew points to yet another magic number.
	 */

	buf[0] = '\0';
	SetFilePointer(hFile, header.e_lfanew, NULL, FILE_BEGIN);
	ReadFile(hFile, (void *) buf, 2, &read, NULL);
	CloseHandle(hFile);

	if ((buf[0] == 'N') && (buf[1] == 'E')) {
	    applType = APPL_WIN3X;
	} else if ((buf[0] == 'P') && (buf[1] == 'E')) {
	    applType = APPL_WIN32;
	} else {
	    /*
	     * Strictly speaking, there should be a test that there is an 'L'
	     * and 'E' at buf[0..1], to identify the type as DOS, but of
	     * course we ran into a DOS executable that _doesn't_ have the
	     * magic number - specifically, one compiled using the Lahey
	     * Fortran90 compiler.
	     */

	    applType = APPL_DOS;
	}
	break;
    }
    Tcl_DStringFree(&nameBuf);

    if (applType == APPL_NONE) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf("couldn't execute \"%s\": %s",
		originalName, Tcl_PosixError(interp)));
	return APPL_NONE;
    }

    if ((applType == APPL_DOS) || (applType == APPL_WIN3X)) {
	/*
	 * Replace long path name of executable with short path name for
	 * 16-bit applications. Otherwise the application may not be able to
	 * correctly parse its own command line to separate off the
	 * application name from the arguments.
	 */

	GetShortPathName(nativeFullPath, nativeFullPath, MAX_PATH);
	strcpy(fullName, Tcl_WinTCharToUtf(nativeFullPath, -1, &ds));
	Tcl_DStringFree(&ds);
    }
    return applType;
}

/*
 *----------------------------------------------------------------------
 *
 * BuildCommandLine --
 *
 *	The command line arguments are stored in linePtr separated by spaces,
 *	in a form that CreateProcess() understands. Special characters in
 *	individual arguments from argv[] must be quoted when being stored in
 *	cmdLine.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
BuildCommandLine(
    const char *executable,	/* Full path of executable (including
				 * extension). Replacement for argv[0]. */
    int argc,			/* Number of arguments. */
    const char **argv,		/* Argument strings in UTF. */
    Tcl_DString *linePtr)	/* Initialized Tcl_DString that receives the
				 * command line (TCHAR). */
{
    const char *arg, *start, *special;
    int quote, i;
    Tcl_DString ds;

    Tcl_DStringInit(&ds);

    /*
     * Prime the path. Add a space separator if we were primed with something.
     */

    TclDStringAppendDString(&ds, linePtr);
    if (Tcl_DStringLength(linePtr) > 0) {
	TclDStringAppendLiteral(&ds, " ");
    }

    for (i = 0; i < argc; i++) {
	if (i == 0) {
	    arg = executable;
	} else {
	    arg = argv[i];
	    TclDStringAppendLiteral(&ds, " ");
	}

	quote = 0;
	if (arg[0] == '\0') {
	    quote = 1;
	} else {
	    int count;
	    Tcl_UniChar ch;

	    for (start = arg; *start != '\0'; start += count) {
		count = Tcl_UtfToUniChar(start, &ch);
		if (Tcl_UniCharIsSpace(ch)) {	/* INTL: ISO space. */
		    quote = 1;
		    break;
		}
	    }
	}
	if (quote) {
	    TclDStringAppendLiteral(&ds, "\"");
	}
	start = arg;
	for (special = arg; ; ) {
	    if ((*special == '\\') && (special[1] == '\\' ||
		    special[1] == '"' || (quote && special[1] == '\0'))) {
		Tcl_DStringAppend(&ds, start, (int) (special - start));
		start = special;
		while (1) {
		    special++;
		    if (*special == '"' || (quote && *special == '\0')) {
			/*
			 * N backslashes followed a quote -> insert N * 2 + 1
			 * backslashes then a quote.
			 */

			Tcl_DStringAppend(&ds, start,
				(int) (special - start));
			break;
		    }
		    if (*special != '\\') {
			break;
		    }
		}
		Tcl_DStringAppend(&ds, start, (int) (special - start));
		start = special;
	    }
	    if (*special == '"') {
		Tcl_DStringAppend(&ds, start, (int) (special - start));
		TclDStringAppendLiteral(&ds, "\\\"");
		start = special + 1;
	    }
	    if (*special == '\0') {
		break;
	    }
	    special++;
	}
	Tcl_DStringAppend(&ds, start, (int) (special - start));
	if (quote) {
	    TclDStringAppendLiteral(&ds, "\"");
	}
    }
    Tcl_DStringFree(linePtr);
    Tcl_WinUtfToTChar(Tcl_DStringValue(&ds), Tcl_DStringLength(&ds), linePtr);
    Tcl_DStringFree(&ds);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateCommandChannel --
 *
 *	This function is called by Tcl_OpenCommandChannel to perform the
 *	platform specific channel initialization for a command channel.
 *
 * Results:
 *	Returns a new channel or NULL on failure.
 *
 * Side effects:
 *	Allocates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpCreateCommandChannel(
    TclFile readFile,		/* If non-null, gives the file for reading. */
    TclFile writeFile,		/* If non-null, gives the file for writing. */
    TclFile errorFile,		/* If non-null, gives the file where errors
				 * can be read. */
    int numPids,		/* The number of pids in the pid array. */
    Tcl_Pid *pidPtr)		/* An array of process identifiers. */
{
    char channelName[16 + TCL_INTEGER_SPACE];
    DWORD id;
    PipeInfo *infoPtr = ckalloc(sizeof(PipeInfo));

    PipeInit();

    infoPtr->watchMask = 0;
    infoPtr->flags = 0;
    infoPtr->readFlags = 0;
    infoPtr->readFile = readFile;
    infoPtr->writeFile = writeFile;
    infoPtr->errorFile = errorFile;
    infoPtr->numPids = numPids;
    infoPtr->pidPtr = pidPtr;
    infoPtr->writeBuf = 0;
    infoPtr->writeBufLen = 0;
    infoPtr->writeError = 0;
    infoPtr->channel = NULL;

    infoPtr->validMask = 0;

    infoPtr->threadId = Tcl_GetCurrentThread();

    if (readFile != NULL) {
	/*
	 * Start the background reader thread.
	 */

	infoPtr->readable = CreateEvent(NULL, TRUE, TRUE, NULL);
	infoPtr->startReader = CreateEvent(NULL, FALSE, FALSE, NULL);
	infoPtr->stopReader = CreateEvent(NULL, TRUE, FALSE, NULL);
	infoPtr->readThread = CreateThread(NULL, 256, PipeReaderThread,
		infoPtr, 0, &id);
	SetThreadPriority(infoPtr->readThread, THREAD_PRIORITY_HIGHEST);
	infoPtr->validMask |= TCL_READABLE;
    } else {
	infoPtr->readThread = 0;
    }
    if (writeFile != NULL) {
	/*
	 * Start the background writer thread.
	 */

	infoPtr->writable = CreateEvent(NULL, TRUE, TRUE, NULL);
	infoPtr->startWriter = CreateEvent(NULL, FALSE, FALSE, NULL);
	infoPtr->stopWriter = CreateEvent(NULL, TRUE, FALSE, NULL);
	infoPtr->writeThread = CreateThread(NULL, 256, PipeWriterThread,
		infoPtr, 0, &id);
	SetThreadPriority(infoPtr->readThread, THREAD_PRIORITY_HIGHEST);
	infoPtr->validMask |= TCL_WRITABLE;
    }

    /*
     * For backward compatibility with previous versions of Tcl, we use
     * "file%d" as the base name for pipes even though it would be more
     * natural to use "pipe%d". Use the pointer to keep the channel names
     * unique, in case channels share handles (stdin/stdout).
     */

    sprintf(channelName, "file%" TCL_I_MODIFIER "x", (size_t) infoPtr);
    infoPtr->channel = Tcl_CreateChannel(&pipeChannelType, channelName,
	    infoPtr, infoPtr->validMask);

    /*
     * Pipes have AUTO translation mode on Windows and ^Z eof char, which
     * means that a ^Z will be appended to them at close. This is needed for
     * Windows programs that expect a ^Z at EOF.
     */

    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreatePipe --
 *
 *	System dependent interface to create a pipe for the [chan pipe]
 *	command. Stolen from TclX.
 *
 * Results:
 *	TCL_OK or TCL_ERROR.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_CreatePipe(
    Tcl_Interp *interp,		/* Errors returned in result.*/
    Tcl_Channel *rchan,		/* Where to return the read side. */
    Tcl_Channel *wchan,		/* Where to return the write side. */
    int flags)			/* Reserved for future use. */
{
    HANDLE readHandle, writeHandle;
    SECURITY_ATTRIBUTES sec;

    sec.nLength = sizeof(SECURITY_ATTRIBUTES);
    sec.lpSecurityDescriptor = NULL;
    sec.bInheritHandle = FALSE;

    if (!CreatePipe(&readHandle, &writeHandle, &sec, 0)) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"pipe creation failed: %s", Tcl_PosixError(interp)));
	return TCL_ERROR;
    }

    *rchan = Tcl_MakeFileChannel((ClientData) readHandle, TCL_READABLE);
    Tcl_RegisterChannel(interp, *rchan);

    *wchan = Tcl_MakeFileChannel((ClientData) writeHandle, TCL_WRITABLE);
    Tcl_RegisterChannel(interp, *wchan);

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetAndDetachPids --
 *
 *	Stores a list of the command PIDs for a command channel in the
 *	interp's result.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Modifies the interp's result.
 *
 *----------------------------------------------------------------------
 */

void
TclGetAndDetachPids(
    Tcl_Interp *interp,
    Tcl_Channel chan)
{
    PipeInfo *pipePtr;
    const Tcl_ChannelType *chanTypePtr;
    Tcl_Obj *pidsObj;
    int i;

    /*
     * Punt if the channel is not a command channel.
     */

    chanTypePtr = Tcl_GetChannelType(chan);
    if (chanTypePtr != &pipeChannelType) {
	return;
    }

    pipePtr = Tcl_GetChannelInstanceData(chan);
    TclNewObj(pidsObj);
    for (i = 0; i < pipePtr->numPids; i++) {
	Tcl_ListObjAppendElement(NULL, pidsObj,
		Tcl_NewWideIntObj((unsigned)
			TclpGetPid(pipePtr->pidPtr[i])));
	Tcl_DetachPids(1, &pipePtr->pidPtr[i]);
    }
    Tcl_SetObjResult(interp, pidsObj);
    if (pipePtr->numPids > 0) {
	ckfree(pipePtr->pidPtr);
	pipePtr->numPids = 0;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeBlockModeProc --
 *
 *	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
PipeBlockModeProc(
    ClientData instanceData,	/* Instance data for channel. */
    int mode)			/* TCL_MODE_BLOCKING or
				 * TCL_MODE_NONBLOCKING. */
{
    PipeInfo *infoPtr = (PipeInfo *) instanceData;

    /*
     * Pipes 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 |= PIPE_ASYNC;
    } else {
	infoPtr->flags &= ~(PIPE_ASYNC);
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeClose2Proc --
 *
 *	Closes a pipe based IO channel.
 *
 * Results:
 *	0 on success, errno otherwise.
 *
 * Side effects:
 *	Closes the physical channel.
 *
 *----------------------------------------------------------------------
 */

static int
PipeClose2Proc(
    ClientData instanceData,	/* Pointer to PipeInfo structure. */
    Tcl_Interp *interp,		/* For error reporting. */
    int flags)			/* Flags that indicate which side to close. */
{
    PipeInfo *pipePtr = (PipeInfo *) instanceData;
    Tcl_Channel errChan;
    int errorCode, result;
    PipeInfo *infoPtr, **nextPtrPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    DWORD exitCode;

    errorCode = 0;
    result = 0;

    if ((!flags || flags == TCL_CLOSE_READ) && (pipePtr->readFile != NULL)) {
	/*
	 * 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 pipe.
	 */

	if (pipePtr->readThread) {
	    /*
	     * The thread may already have closed on its own. Check its exit
	     * code.
	     */

	    GetExitCodeThread(pipePtr->readThread, &exitCode);

	    if (exitCode == STILL_ACTIVE) {
		/*
		 * Set the stop event so that if the reader thread is blocked
		 * in PipeReaderThread on WaitForMultipleEvents, it will exit
		 * cleanly.
		 */

		SetEvent(pipePtr->stopReader);

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

		if (WaitForSingleObject(pipePtr->readThread,
			20) == WAIT_TIMEOUT) {
		    /*
		     * The thread must be blocked waiting for the pipe to
		     * become readable in ReadFile(). There isn't a clean way
		     * to exit the thread from this condition. We should
		     * terminate the child process instead to get the reader
		     * thread to fall out of ReadFile with a FALSE. (below) is
		     * not the correct way to do this, but will stay here
		     * until a better solution is found.
		     *
		     * 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.
		     */

		    Tcl_MutexLock(&pipeMutex);

		    /* BUG: this leaks memory */
		    TerminateThread(pipePtr->readThread, 0);
		    Tcl_MutexUnlock(&pipeMutex);
		}
	    }

	    CloseHandle(pipePtr->readThread);
	    CloseHandle(pipePtr->readable);
	    CloseHandle(pipePtr->startReader);
	    CloseHandle(pipePtr->stopReader);
	    pipePtr->readThread = NULL;
	}
	if (TclpCloseFile(pipePtr->readFile) != 0) {
	    errorCode = errno;
	}
	pipePtr->validMask &= ~TCL_READABLE;
	pipePtr->readFile = NULL;
    }
    if ((!flags || flags & TCL_CLOSE_WRITE)
	    && (pipePtr->writeFile != NULL)) {
	if (pipePtr->writeThread) {
	    /*
	     * Wait for the  writer thread to finish the  current buffer, then
	     * terminate the thread  and close the handles. If  the channel is
	     * nonblocking but blocked during  exit, bail out since the worker
	     * thread is not interruptible and we want TIP#398-fast-exit.
	     */
	    if (TclInExit()
		&& (pipePtr->flags & PIPE_ASYNC)) {

		/* give it a chance to leave honorably */
		SetEvent(pipePtr->stopWriter);

		if (WaitForSingleObject(pipePtr->writable, 0) == WAIT_TIMEOUT) {
		    return EAGAIN;
		}

	    } else {

		WaitForSingleObject(pipePtr->writable, INFINITE);

	    }

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

	    GetExitCodeThread(pipePtr->writeThread, &exitCode);

	    if (exitCode == STILL_ACTIVE) {
		/*
		 * Set the stop event so that if the reader thread is blocked
		 * in PipeReaderThread on WaitForMultipleEvents, it will exit
		 * cleanly.
		 */

		SetEvent(pipePtr->stopWriter);

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

		if (WaitForSingleObject(pipePtr->writeThread,
			20) == WAIT_TIMEOUT) {
		    /*
		     * The thread must be blocked waiting for the pipe to
		     * consume input in WriteFile(). There isn't a clean way
		     * to exit the thread from this condition. We should
		     * terminate the child process instead to get the writer
		     * thread to fall out of WriteFile with a FALSE. (below)
		     * is not the correct way to do this, but will stay here
		     * until a better solution is found.
		     *
		     * 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.
		     */

		    Tcl_MutexLock(&pipeMutex);

		    /* BUG: this leaks memory */
		    TerminateThread(pipePtr->writeThread, 0);
		    Tcl_MutexUnlock(&pipeMutex);
		}
	    }

	    CloseHandle(pipePtr->writeThread);
	    CloseHandle(pipePtr->writable);
	    CloseHandle(pipePtr->startWriter);
	    CloseHandle(pipePtr->stopWriter);
	    pipePtr->writeThread = NULL;
	}
	if (TclpCloseFile(pipePtr->writeFile) != 0) {
	    if (errorCode == 0) {
		errorCode = errno;
	    }
	}
	pipePtr->validMask &= ~TCL_WRITABLE;
	pipePtr->writeFile = NULL;
    }

    pipePtr->watchMask &= pipePtr->validMask;

    /*
     * Don't free the channel if any of the flags were set.
     */

    if (flags) {
	return errorCode;
    }

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

    for (nextPtrPtr = &(tsdPtr->firstPipePtr), infoPtr = *nextPtrPtr;
	    infoPtr != NULL;
	    nextPtrPtr = &infoPtr->nextPtr, infoPtr = *nextPtrPtr) {
	if (infoPtr == (PipeInfo *)pipePtr) {
	    *nextPtrPtr = infoPtr->nextPtr;
	    break;
	}
    }

    if ((pipePtr->flags & PIPE_ASYNC) || TclInExit()) {
	/*
	 * If the channel is non-blocking or Tcl is being cleaned up, just
	 * detach the children PIDs, reap them (important if we are in a
	 * dynamic load module), and discard the errorFile.
	 */

	Tcl_DetachPids(pipePtr->numPids, pipePtr->pidPtr);
	Tcl_ReapDetachedProcs();

	if (pipePtr->errorFile) {
	    if (TclpCloseFile(pipePtr->errorFile) != 0) {
		if (errorCode == 0) {
		    errorCode = errno;
		}
	    }
	}
	result = 0;
    } else {
	/*
	 * Wrap the error file into a channel and give it to the cleanup
	 * routine.
	 */

	if (pipePtr->errorFile) {
	    WinFile *filePtr = (WinFile *) pipePtr->errorFile;

	    errChan = Tcl_MakeFileChannel((ClientData) filePtr->handle,
		    TCL_READABLE);
	    ckfree(filePtr);
	} else {
	    errChan = NULL;
	}

	result = TclCleanupChildren(interp, pipePtr->numPids,
		pipePtr->pidPtr, errChan);
    }

    if (pipePtr->numPids > 0) {
	ckfree(pipePtr->pidPtr);
    }

    if (pipePtr->writeBuf != NULL) {
	ckfree(pipePtr->writeBuf);
    }

    ckfree(pipePtr);

    if (errorCode == 0) {
	return result;
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeInputProc --
 *
 *	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
PipeInputProc(
    ClientData instanceData,	/* Pipe 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. */
{
    PipeInfo *infoPtr = (PipeInfo *) instanceData;
    WinFile *filePtr = (WinFile*) infoPtr->readFile;
    DWORD count, bytesRead = 0;
    int result;

    *errorCode = 0;
    /*
     * Synchronize with the reader thread.
     */

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

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

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

    if (infoPtr->readFlags & PIPE_EXTRABYTE) {
	/*
	 * The reader thread consumed 1 byte as a side effect of waiting so we
	 * need to move it into the buffer.
	 */

	*buf = infoPtr->extraByte;
	infoPtr->readFlags &= ~PIPE_EXTRABYTE;
	buf++;
	bufSize--;
	bytesRead = 1;

	/*
	 * If further read attempts would block, return what we have.
	 */

	if (result == 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 (ReadFile(filePtr->handle, (LPVOID) buf, (DWORD) bufSize, &count,
	    (LPOVERLAPPED) NULL) == TRUE) {
	return bytesRead + count;
    } else if (bytesRead) {
	/*
	 * Ignore errors if we have data to return.
	 */

	return bytesRead;
    }

    TclWinConvertError(GetLastError());
    if (errno == EPIPE) {
	infoPtr->readFlags |= PIPE_EOF;
	return 0;
    }
    *errorCode = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeOutputProc --
 *
 *	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
PipeOutputProc(
    ClientData instanceData,	/* Pipe state. */
    const char *buf,		/* The data buffer. */
    int toWrite,		/* How many bytes to write? */
    int *errorCode)		/* Where to store error code. */
{
    PipeInfo *infoPtr = (PipeInfo *) instanceData;
    WinFile *filePtr = (WinFile*) infoPtr->writeFile;
    DWORD bytesWritten, timeout;

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

	errno = EAGAIN;
	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 & PIPE_ASYNC) {
	/*
	 * The pipe 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(infoPtr->writable);
	SetEvent(infoPtr->startWriter);
	bytesWritten = toWrite;
    } else {
	/*
	 * In the blocking case, just try to write the buffer directly. This
	 * avoids an unnecessary copy.
	 */

	if (WriteFile(filePtr->handle, (LPVOID) buf, (DWORD) toWrite,
		&bytesWritten, (LPOVERLAPPED) NULL) == FALSE) {
	    TclWinConvertError(GetLastError());
	    goto error;
	}
    }
    return bytesWritten;

  error:
    *errorCode = errno;
    return -1;

}

/*
 *----------------------------------------------------------------------
 *
 * PipeEventProc --
 *
 *	This function is invoked by Tcl_ServiceEvent when a file event reaches
 *	the front of the event queue. This function invokes Tcl_NotifyChannel
 *	on the pipe.
 *
 * 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
PipeEventProc(
    Tcl_Event *evPtr,		/* Event to service. */
    int flags)			/* Flags that indicate what events to
				 * handle, such as TCL_FILE_EVENTS. */
{
    PipeEvent *pipeEvPtr = (PipeEvent *)evPtr;
    PipeInfo *infoPtr;
    int mask;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

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

    for (infoPtr = tsdPtr->firstPipePtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (pipeEvPtr->infoPtr == infoPtr) {
	    infoPtr->flags &= ~(PIPE_PENDING);
	    break;
	}
    }

    /*
     * Remove stale events.
     */

    if (!infoPtr) {
	return 1;
    }

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

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

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

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

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

static void
PipeWatchProc(
    ClientData instanceData,	/* Pipe state. */
    int mask)			/* What events to watch for, OR-ed combination
				 * of TCL_READABLE, TCL_WRITABLE and
				 * TCL_EXCEPTION. */
{
    PipeInfo **nextPtrPtr, *ptr;
    PipeInfo *infoPtr = (PipeInfo *) 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->firstPipePtr;
	    tsdPtr->firstPipePtr = infoPtr;
	}
	Tcl_SetMaxBlockTime(&blockTime);
    } else {
	if (oldMask) {
	    /*
	     * Remove the pipe from the list of watched pipes.
	     */

	    for (nextPtrPtr = &(tsdPtr->firstPipePtr), ptr = *nextPtrPtr;
		    ptr != NULL;
		    nextPtrPtr = &ptr->nextPtr, ptr = *nextPtrPtr) {
		if (infoPtr == ptr) {
		    *nextPtrPtr = ptr->nextPtr;
		    break;
		}
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle to retrieve OS handles from inside a
 *	command pipeline 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
PipeGetHandleProc(
    ClientData instanceData,	/* The pipe state. */
    int direction,		/* TCL_READABLE or TCL_WRITABLE */
    ClientData *handlePtr)	/* Where to store the handle.  */
{
    PipeInfo *infoPtr = (PipeInfo *) instanceData;
    WinFile *filePtr;

    if (direction == TCL_READABLE && infoPtr->readFile) {
	filePtr = (WinFile*) infoPtr->readFile;
	*handlePtr = (ClientData) filePtr->handle;
	return TCL_OK;
    }
    if (direction == TCL_WRITABLE && infoPtr->writeFile) {
	filePtr = (WinFile*) infoPtr->writeFile;
	*handlePtr = (ClientData) filePtr->handle;
	return TCL_OK;
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_WaitPid --
 *
 *	Emulates the waitpid system call.
 *
 * Results:
 *	Returns 0 if the process is still alive, -1 on an error, or the pid on
 *	a clean close.
 *
 * Side effects:
 *	Unless WNOHANG is set and the wait times out, the process information
 *	record will be deleted and the process handle will be closed.
 *
 *----------------------------------------------------------------------
 */

Tcl_Pid
Tcl_WaitPid(
    Tcl_Pid pid,
    int *statPtr,
    int options)
{
    ProcInfo *infoPtr = NULL, **prevPtrPtr;
    DWORD flags;
    Tcl_Pid result;
    DWORD ret, exitCode;

    PipeInit();

    /*
     * If no pid is specified, do nothing.
     */

    if (pid == 0) {
	*statPtr = 0;
	return 0;
    }

    /*
     * Find the process and cut it from the process list.
     */

    Tcl_MutexLock(&pipeMutex);
    prevPtrPtr = &procList;
    for (infoPtr = procList; infoPtr != NULL;
	    prevPtrPtr = &infoPtr->nextPtr, infoPtr = infoPtr->nextPtr) {
	 if (infoPtr->hProcess == (HANDLE) pid) {
	    *prevPtrPtr = infoPtr->nextPtr;
	    break;
	}
    }
    Tcl_MutexUnlock(&pipeMutex);

    /*
     * If the pid is not one of the processes we know about (we started it)
     * then do nothing.
     */

    if (infoPtr == NULL) {
	*statPtr = 0;
	return 0;
    }

    /*
     * Officially "wait" for it to finish. We either poll (WNOHANG) or wait
     * for an infinite amount of time.
     */

    if (options & WNOHANG) {
	flags = 0;
    } else {
	flags = INFINITE;
    }
    ret = WaitForSingleObject(infoPtr->hProcess, flags);
    if (ret == WAIT_TIMEOUT) {
	*statPtr = 0;
	if (options & WNOHANG) {
	    /*
	     * Re-insert this infoPtr back on the list.
	     */

	    Tcl_MutexLock(&pipeMutex);
	    infoPtr->nextPtr = procList;
	    procList = infoPtr;
	    Tcl_MutexUnlock(&pipeMutex);
	    return 0;
	} else {
	    result = 0;
	}
    } else if (ret == WAIT_OBJECT_0) {
	GetExitCodeProcess(infoPtr->hProcess, &exitCode);

	/*
	 * Does the exit code look like one of the exception codes?
	 */

	switch (exitCode) {
	case EXCEPTION_FLT_DENORMAL_OPERAND:
	case EXCEPTION_FLT_DIVIDE_BY_ZERO:
	case EXCEPTION_FLT_INEXACT_RESULT:
	case EXCEPTION_FLT_INVALID_OPERATION:
	case EXCEPTION_FLT_OVERFLOW:
	case EXCEPTION_FLT_STACK_CHECK:
	case EXCEPTION_FLT_UNDERFLOW:
	case EXCEPTION_INT_DIVIDE_BY_ZERO:
	case EXCEPTION_INT_OVERFLOW:
	    *statPtr = 0xC0000000 | SIGFPE;
	    break;

	case EXCEPTION_PRIV_INSTRUCTION:
	case EXCEPTION_ILLEGAL_INSTRUCTION:
	    *statPtr = 0xC0000000 | SIGILL;
	    break;

	case EXCEPTION_ACCESS_VIOLATION:
	case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
	case EXCEPTION_STACK_OVERFLOW:
	case EXCEPTION_NONCONTINUABLE_EXCEPTION:
	case EXCEPTION_INVALID_DISPOSITION:
	case EXCEPTION_GUARD_PAGE:
	case EXCEPTION_INVALID_HANDLE:
	    *statPtr = 0xC0000000 | SIGSEGV;
	    break;

	case EXCEPTION_DATATYPE_MISALIGNMENT:
	    *statPtr = 0xC0000000 | SIGBUS;
	    break;

	case EXCEPTION_BREAKPOINT:
	case EXCEPTION_SINGLE_STEP:
	    *statPtr = 0xC0000000 | SIGTRAP;
	    break;

	case CONTROL_C_EXIT:
	    *statPtr = 0xC0000000 | SIGINT;
	    break;

	default:
	    /*
	     * Non-exceptional, normal, exit code. Note that the exit code is
	     * truncated to a signed short range [-32768,32768) whether it
	     * fits into this range or not.
	     *
	     * BUG: Even though the exit code is a DWORD, it is understood by
	     * convention to be a signed integer, yet there isn't enough room
	     * to fit this into the POSIX style waitstatus mask without
	     * truncating it.
	     */

	    *statPtr = exitCode;
	    break;
	}
	result = pid;
    } else {
	errno = ECHILD;
	*statPtr = 0xC0000000 | ECHILD;
	result = (Tcl_Pid) -1;
    }

    /*
     * Officially close the process handle.
     */

    CloseHandle(infoPtr->hProcess);
    ckfree(infoPtr);

    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinAddProcess --
 *
 *	Add a process to the process list so that we can use Tcl_WaitPid on
 *	the process.
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Adds the specified process handle to the process list so Tcl_WaitPid
 *	knows about it.
 *
 *----------------------------------------------------------------------
 */

void
TclWinAddProcess(
    void *hProcess,		/* Handle to process */
    unsigned long id)		/* Global process identifier */
{
    ProcInfo *procPtr = ckalloc(sizeof(ProcInfo));

    PipeInit();

    procPtr->hProcess = hProcess;
    procPtr->dwProcessId = id;
    Tcl_MutexLock(&pipeMutex);
    procPtr->nextPtr = procList;
    procList = procPtr;
    Tcl_MutexUnlock(&pipeMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PidObjCmd --
 *
 *	This function is invoked to process the "pid" Tcl command. See the
 *	user documentation for details on what it does.
 *
 * Results:
 *	A standard Tcl result.
 *
 * Side effects:
 *	See the user documentation.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
int
Tcl_PidObjCmd(
    ClientData dummy,		/* Not used. */
    Tcl_Interp *interp,		/* Current interpreter. */
    int objc,			/* Number of arguments. */
    Tcl_Obj *const *objv)	/* Argument strings. */
{
    Tcl_Channel chan;
    const Tcl_ChannelType *chanTypePtr;
    PipeInfo *pipePtr;
    int i;
    Tcl_Obj *resultPtr;

    if (objc > 2) {
	Tcl_WrongNumArgs(interp, 1, objv, "?channelId?");
	return TCL_ERROR;
    }
    if (objc == 1) {
	Tcl_SetObjResult(interp, Tcl_NewWideIntObj((unsigned) getpid()));
    } else {
	chan = Tcl_GetChannel(interp, Tcl_GetStringFromObj(objv[1], NULL),
		NULL);
	if (chan == (Tcl_Channel) NULL) {
	    return TCL_ERROR;
	}
	chanTypePtr = Tcl_GetChannelType(chan);
	if (chanTypePtr != &pipeChannelType) {
	    return TCL_OK;
	}

	pipePtr = (PipeInfo *) Tcl_GetChannelInstanceData(chan);
	resultPtr = Tcl_NewObj();
	for (i = 0; i < pipePtr->numPids; i++) {
	    Tcl_ListObjAppendElement(/*interp*/ NULL, resultPtr,
		    Tcl_NewWideIntObj((unsigned)
			    TclpGetPid(pipePtr->pidPtr[i])));
	}
	Tcl_SetObjResult(interp, resultPtr);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * WaitForRead --
 *
 *	Wait until some data is available, the pipe is at EOF or the reader
 *	thread is blocked waiting for data (if the channel is in non-blocking
 *	mode).
 *
 * Results:
 *	Returns 1 if pipe is readable. Returns 0 if there is no data on the
 *	pipe, 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 and may consume 1 byte of data from the
 *	pipe. If no error occurred, the reader thread is blocked waiting for a
 *	signal from the main thread.
 *
 *----------------------------------------------------------------------
 */

static int
WaitForRead(
    PipeInfo *infoPtr,		/* Pipe state. */
    int blocking)		/* Indicates whether call should be blocking
				 * or not. */
{
    DWORD timeout, count;
    HANDLE *handle = ((WinFile *) infoPtr->readFile)->handle;

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

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

	    errno = EAGAIN;
	    return -1;
	}

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

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

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

	/*
	 * Check to see if there is any data sitting in the pipe.
	 */

	if (PeekNamedPipe(handle, (LPVOID) NULL, (DWORD) 0,
		(LPDWORD) NULL, &count, (LPDWORD) NULL) != TRUE) {
	    TclWinConvertError(GetLastError());

	    /*
	     * Check to see if the peek failed because of EOF.
	     */

	    if (errno == EPIPE) {
		infoPtr->readFlags |= PIPE_EOF;
		return 1;
	    }

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

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

	/*
	 * We found some data in the pipe, so it must be readable.
	 */

	if (count > 0) {
	    return 1;
	}

	/*
	 * The pipe isn't readable, but there is some data sitting in the
	 * buffer, so return immediately.
	 */

	if (infoPtr->readFlags & PIPE_EXTRABYTE) {
	    return 0;
	}

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

	ResetEvent(infoPtr->readable);
	SetEvent(infoPtr->startReader);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeReaderThread --
 *
 *	This function runs in a separate thread and waits for input to become
 *	available on a pipe.
 *
 * 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 consume one byte from
 *	the pipe for each wait operation. Will cause a memory leak of ~4k, if
 *	forcefully terminated with TerminateThread().
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
PipeReaderThread(
    LPVOID arg)
{
    PipeInfo *infoPtr = (PipeInfo *)arg;
    HANDLE *handle = ((WinFile *) infoPtr->readFile)->handle;
    DWORD count, err;
    int done = 0;
    HANDLE wEvents[2];
    DWORD waitResult;

    wEvents[0] = infoPtr->stopReader;
    wEvents[1] = infoPtr->startReader;

    while (!done) {
	/*
	 * Wait for the main thread to signal before attempting to wait on the
	 * pipe becoming readable.
	 */

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

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

	    break;
	}

	/*
	 * Try waiting for 0 bytes. This will block until some data is
	 * available on NT, but will return immediately on Win 95. So, if no
	 * data is available after the first read, we block until we can read
	 * a single byte off of the pipe.
	 */

	if (ReadFile(handle, NULL, 0, &count, NULL) == FALSE ||
		PeekNamedPipe(handle, NULL, 0, NULL, &count, NULL) == FALSE) {
	    /*
	     * The error is a result of an EOF condition, so set the EOF bit
	     * before signalling the main thread.
	     */

	    err = GetLastError();
	    if (err == ERROR_BROKEN_PIPE) {
		infoPtr->readFlags |= PIPE_EOF;
		done = 1;
	    } else if (err == ERROR_INVALID_HANDLE) {
		break;
	    }
	} else if (count == 0) {
	    if (ReadFile(handle, &(infoPtr->extraByte), 1, &count, NULL)
		    != FALSE) {
		/*
		 * One byte was consumed as a side effect of waiting for the
		 * pipe to become readable.
		 */

		infoPtr->readFlags |= PIPE_EXTRABYTE;
	    } else {
		err = GetLastError();
		if (err == ERROR_BROKEN_PIPE) {
		    /*
		     * The error is a result of an EOF condition, so set the
		     * EOF bit before signalling the main thread.
		     */

		    infoPtr->readFlags |= PIPE_EOF;
		    done = 1;
		} else if (err == ERROR_INVALID_HANDLE) {
		    break;
		}
	    }
	}


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

	SetEvent(infoPtr->readable);

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

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

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeWriterThread --
 *
 *	This function runs in a separate thread and writes data onto a pipe.
 *
 * 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
PipeWriterThread(
    LPVOID arg)
{
    PipeInfo *infoPtr = (PipeInfo *)arg;
    HANDLE *handle = ((WinFile *) infoPtr->writeFile)->handle;
    DWORD count, toWrite;
    char *buf;
    int done = 0;
    HANDLE wEvents[2];
    DWORD waitResult;

    wEvents[0] = infoPtr->stopWriter;
    wEvents[1] = infoPtr->startWriter;

    while (!done) {
	/*
	 * 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 might be the stop event or
	     * an error, so exit.
	     */

	    if (waitResult == WAIT_OBJECT_0) {
		SetEvent(infoPtr->writable);
	    }

	    break;
	}

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

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

	while (toWrite > 0) {
	    if (WriteFile(handle, buf, toWrite, &count, NULL) == FALSE) {
		infoPtr->writeError = GetLastError();
		done = 1;
		break;
	    } else {
		toWrite -= count;
		buf += count;
	    }
	}

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

	SetEvent(infoPtr->writable);

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

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

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeThreadActionProc --
 *
 *	Insert or remove any thread local refs to this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Changes thread local list of valid channels.
 *
 *----------------------------------------------------------------------
 */

static void
PipeThreadActionProc(
    ClientData instanceData,
    int action)
{
    PipeInfo *infoPtr = (PipeInfo *) instanceData;

    /*
     * We do not access firstPipePtr in the thread structures. This is not for
     * all pipes 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(&pipeMutex);
    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.
	 */

	PipeInit();
	if (infoPtr->channel != NULL) {
	    infoPtr->threadId = Tcl_GetChannelThread(infoPtr->channel);
	}
    } else {
	infoPtr->threadId = NULL;
    }
    Tcl_MutexUnlock(&pipeMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpOpenTemporaryFile --
 *
 *	Creates a temporary file, possibly based on the supplied bits and
 *	pieces of template supplied in the first three arguments. If the
 *	fourth argument is non-NULL, it contains a Tcl_Obj to store the name
 *	of the temporary file in (and it is caller's responsibility to clean
 *	up). If the fourth argument is NULL, try to arrange for the temporary
 *	file to go away once it is no longer needed.
 *
 * Results:
 *	A read-write Tcl Channel open on the file.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpOpenTemporaryFile(
    Tcl_Obj *dirObj,
    Tcl_Obj *basenameObj,
    Tcl_Obj *extensionObj,
    Tcl_Obj *resultingNameObj)
{
    TCHAR name[MAX_PATH];
    char *namePtr;
    HANDLE handle;
    DWORD flags = FILE_ATTRIBUTE_TEMPORARY;
    int length, counter, counter2;
    Tcl_DString buf;

    if (!resultingNameObj) {
	flags |= FILE_FLAG_DELETE_ON_CLOSE;
    }

    namePtr = (char *) name;
    length = GetTempPath(MAX_PATH, name);
    if (length == 0) {
	goto gotError;
    }
    namePtr += length * sizeof(TCHAR);
    if (basenameObj) {
	const char *string = Tcl_GetStringFromObj(basenameObj, &length);

	Tcl_WinUtfToTChar(string, length, &buf);
	memcpy(namePtr, Tcl_DStringValue(&buf), Tcl_DStringLength(&buf));
	namePtr += Tcl_DStringLength(&buf);
	Tcl_DStringFree(&buf);
    } else {
	const TCHAR *baseStr = TEXT("TCL");
	int length = 3 * sizeof(TCHAR);

	memcpy(namePtr, baseStr, length);
	namePtr += length;
    }
    counter = TclpGetClicks() % 65533;
    counter2 = 1024;			/* Only try this many times! Prevents
					 * an infinite loop. */

    do {
	char number[TCL_INTEGER_SPACE + 4];

	sprintf(number, "%d.TMP", counter);
	counter = (unsigned short) (counter + 1);
	Tcl_WinUtfToTChar(number, strlen(number), &buf);
	Tcl_DStringSetLength(&buf, Tcl_DStringLength(&buf) + 1);
	memcpy(namePtr, Tcl_DStringValue(&buf), Tcl_DStringLength(&buf) + 1);
	Tcl_DStringFree(&buf);

	handle = CreateFile(name,
		GENERIC_READ|GENERIC_WRITE, 0, NULL, CREATE_NEW, flags, NULL);
    } while (handle == INVALID_HANDLE_VALUE
	    && --counter2 > 0
	    && GetLastError() == ERROR_FILE_EXISTS);
    if (handle == INVALID_HANDLE_VALUE) {
	goto gotError;
    }

    if (resultingNameObj) {
	Tcl_Obj *tmpObj = TclpNativeToNormalized(name);

	Tcl_AppendObjToObj(resultingNameObj, tmpObj);
	TclDecrRefCount(tmpObj);
    }

    return Tcl_MakeFileChannel((ClientData) handle,
	    TCL_READABLE|TCL_WRITABLE);

  gotError:
    TclWinConvertError(GetLastError());
    return NULL;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */