shared_source/c_tcl_base_7_5_w_mods/tclwinpipe.c

/* $Header$ */
/* 
 * 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.
 *
 * RCS: @(#) $Id: tclwinpipe.c,v 1.1.1.1 2001/06/13 04:49:50 dtashley Exp $
 */

#include "tclWinInt.h"

#include <dos.h>
#include <fcntl.h>
#include <io.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 startReader;         /* Auto-reset event used by the main thread to
                                 * signal when the reader thread should attempt
                                 * to read from the pipe. */
    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, 
                            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 void             PipeExitHandler(ClientData clientData);
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, 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 void             ProcExitHandler(ClientData clientData);
static int              TempFileName(WCHAR name[MAX_PATH]);
static int              WaitForRead(PipeInfo *infoPtr, int blocking);

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

static Tcl_ChannelType pipeChannelType = {
    "pipe",                     /* Type name. */
    PipeBlockModeProc,          /* Set blocking or non-blocking mode.*/
    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
};

/*
 *----------------------------------------------------------------------
 *
 * PipeInit --
 *
 *      This function initializes the static variables for this file.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Creates a new event source.
 *
 *----------------------------------------------------------------------
 */

static void
PipeInit()
{
    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_CreateExitHandler(ProcExitHandler, NULL);
        }
        Tcl_MutexUnlock(&pipeMutex);
    }

    tsdPtr = (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);
    if (tsdPtr == NULL) {
        tsdPtr = TCL_TSD_INIT(&dataKey);
        tsdPtr->firstPipePtr = NULL;
        Tcl_CreateEventSource(PipeSetupProc, PipeCheckProc, NULL);
        Tcl_CreateThreadExitHandler(PipeExitHandler, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeExitHandler --
 *
 *      This function is called to cleanup the pipe module before
 *      Tcl is unloaded.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Removes the pipe event source.
 *
 *----------------------------------------------------------------------
 */

static void
PipeExitHandler(
    ClientData clientData)      /* Old window proc */
{
    Tcl_DeleteEventSource(PipeSetupProc, PipeCheckProc, 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(&pipeMutex);
    initialized = 0;
    Tcl_MutexUnlock(&pipeMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * PipeSetupProc --
 *
 *      This procedure 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;
    WinFile *filePtr;
    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) {
            filePtr = (WinFile*) infoPtr->writeFile;
            if (WaitForSingleObject(infoPtr->writable, 0) != WAIT_TIMEOUT) {
                block = 0;
            }
        }
        if (infoPtr->watchMask & TCL_READABLE) {
            filePtr = (WinFile*) infoPtr->readFile;
            if (WaitForRead(infoPtr, 0) >= 0) {
                block = 0;
            }
        }
    }
    if (!block) {
        Tcl_SetMaxBlockTime(&blockTime);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeCheckProc --
 *
 *      This procedure 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;
    WinFile *filePtr;
    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;
        filePtr = (WinFile*) infoPtr->writeFile;
        if ((infoPtr->watchMask & TCL_WRITABLE) &&
                (WaitForSingleObject(infoPtr->writable, 0) != WAIT_TIMEOUT)) {
            needEvent = 1;
        }
        
        filePtr = (WinFile*) infoPtr->readFile;
        if ((infoPtr->watchMask & TCL_READABLE) &&
                (WaitForRead(infoPtr, 0) >= 0)) {
            needEvent = 1;
        }

        if (needEvent) {
            infoPtr->flags |= PIPE_PENDING;
            evPtr = (PipeEvent *) 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 = (WinFile *) 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(name)
    WCHAR name[MAX_PATH];       /* Buffer in which name for temporary 
                                 * file gets stored. */
{
    TCHAR *prefix;

    prefix = (tclWinProcs->useWide) ? (TCHAR *) L"TCL" : (TCHAR *) "TCL";
    if ((*tclWinProcs->getTempPathProc)(MAX_PATH, name) != 0) {
        if ((*tclWinProcs->getTempFileNameProc)((TCHAR *) name, prefix, 0, 
                name) != 0) {
            return 1;
        }
    }
    if (tclWinProcs->useWide) {
        ((WCHAR *) name)[0] = '.';
        ((WCHAR *) name)[1] = '\0';
    } else {
        ((char *) name)[0] = '.';
        ((char *) name)[1] = '\0';
    }
    return (*tclWinProcs->getTempFileNameProc)((TCHAR *) 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(channel, direction)
    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(path, mode)
    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;
    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 = (*tclWinProcs->getFileAttributesProc)(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 = (*tclWinProcs->createFileProc)(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) {
        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(contents)
    CONST char *contents;       /* String to write into temp file, or NULL. */
{
    WCHAR name[MAX_PATH];
    CONST char *native;
    Tcl_DString dstring;
    HANDLE handle;

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

    handle = (*tclWinProcs->createFileProc)((TCHAR *) 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;

        /*
         * Convert the contents from UTF to native encoding
         */
        native = Tcl_UtfToExternalDString(NULL, contents, -1, &dstring);
        
        for (p = native; *p != '\0'; p++) {
            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);
    (*tclWinProcs->deleteFileProc)((TCHAR *) name);
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * 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 exit process.  Otherwise, one thread may kill the
             * stdio of another.
             */

            if (!TclInExit() 
                    || ((GetStdHandle(STD_INPUT_HANDLE) != filePtr->handle)
                            && (GetStdHandle(STD_OUTPUT_HANDLE) != filePtr->handle)
                            && (GetStdHandle(STD_ERROR_HANDLE) != filePtr->handle))) {
                if (CloseHandle(filePtr->handle) == FALSE) {
                    TclWinConvertError(GetLastError());
                    ckfree((char *) filePtr);
                    return -1;
                }
            }
            break;

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

    ckfree((char *) 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.
 *
 *--------------------------------------------------------------------------
 */

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

    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. */
    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 procedure is successful, pidPtr
                                 * is filled with the process id of the child
                                 * process. */
{
    int result, applType, createFlags;
    Tcl_DString cmdLine;        /* Complete command line (TCHAR). */
    STARTUPINFOA 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_AppendResult(interp, "couldn't duplicate input handle: ",
                Tcl_PosixError(interp), (char *) NULL);
        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_AppendResult(interp, "couldn't duplicate output handle: ",
                Tcl_PosixError(interp), (char *) NULL);
        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_AppendResult(interp, "couldn't duplicate error handle: ",
                Tcl_PosixError(interp), (char *) NULL);
        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;
            Tcl_DStringAppend(&cmdLine, "cmd.exe /c ", -1);
        } else {
            createFlags = DETACHED_PROCESS;
        } 
    } else {
        if (HasConsole()) {
            createFlags = 0;
        } else {
            createFlags = DETACHED_PROCESS;
        }
        
        if (applType == APPL_DOS) {
            /*
             * Under Windows 95, 16-bit DOS applications do not work well 
             * with pipes:
             *
             * 1. EOF on a pipe between a detached 16-bit DOS application 
             * and another application is not seen at the other
             * end of the pipe, so the listening process blocks forever on 
             * reads.  This inablity to detect EOF happens when either a 
             * 16-bit app or the 32-bit app is the listener.  
             *
             * 2. If a 16-bit DOS application (detached or not) blocks when 
             * writing to a pipe, it will never wake up again, and it
             * eventually brings the whole system down around it.
             *
             * The 16-bit application is run as a normal process inside
             * of a hidden helper console app, and this helper may be run
             * as a detached process.  If any of the stdio handles is
             * a pipe, the helper application accumulates information 
             * into temp files and forwards it to or from the DOS 
             * application as appropriate.  This means that DOS apps 
             * must receive EOF from a stdin pipe before they will actually
             * begin, and must finish generating stdout or stderr before 
             * the data will be sent to the next stage of the pipe.
             *
             * The helper app should be located in the same directory as
             * the tcl dll.
             */

            if (createFlags != 0) {
                startInfo.wShowWindow = SW_HIDE;
                startInfo.dwFlags |= STARTF_USESHOWWINDOW;
                createFlags = CREATE_NEW_CONSOLE;
            }
            Tcl_DStringAppend(&cmdLine, "tclpip" STRINGIFY(TCL_MAJOR_VERSION) 
                    STRINGIFY(TCL_MINOR_VERSION) ".dll ", -1);
        }
    }
    
    /*
     * 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 ((*tclWinProcs->createProcessProc)(NULL, 
            (TCHAR *) Tcl_DStringValue(&cmdLine), NULL, NULL, TRUE, 
            createFlags, NULL, NULL, &startInfo, &procInfo) == 0) {
        TclWinConvertError(GetLastError());
        Tcl_AppendResult(interp, "couldn't execute \"", argv[0],
                "\": ", Tcl_PosixError(interp), (char *) NULL);
        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()
{
    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 procedure 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(interp, originalName, fullName)
    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;
    TCHAR *nativeName;
    WCHAR nativeFullPath[MAX_PATH];
    static 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() procedure 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 = (*tclWinProcs->searchPathProc)(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 = (*tclWinProcs->getFileAttributesProc)((TCHAR *) nativeFullPath);
        if ((attr == 0xffffffff) || (attr & FILE_ATTRIBUTE_DIRECTORY)) {
            continue;
        }
        strcpy(fullName, Tcl_WinTCharToUtf((TCHAR *) nativeFullPath, -1, &ds));
        Tcl_DStringFree(&ds);

        ext = strrchr(fullName, '.');
        if ((ext != NULL) && (stricmp(ext, ".bat") == 0)) {
            applType = APPL_DOS;
            break;
        }
        
        hFile = (*tclWinProcs->createFileProc)((TCHAR *) 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) && (strcmp(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_AppendResult(interp, "couldn't execute \"", originalName,
                "\": ", Tcl_PosixError(interp), (char *) NULL);
        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.
         */

        (*tclWinProcs->getShortPathNameProc)((TCHAR *) nativeFullPath, 
                nativeFullPath, MAX_PATH);
        strcpy(fullName, Tcl_WinTCharToUtf((TCHAR *) 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. */
    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.
     */
    
    Tcl_DStringAppend(&ds, Tcl_DStringValue(linePtr), -1);
    
    for (i = 0; i < argc; i++) {
        if (i == 0) {
            arg = executable;
        } else {
            arg = argv[i];
            Tcl_DStringAppend(&ds, " ", 1);
        }

        quote = 0;
        if (argv[i][0] == '\0') {
            quote = 1;
        } else {
            for (start = argv[i]; *start != '\0'; start++) {
                if (isspace(*start)) { /* INTL: ISO space. */
                    quote = 1;
                    break;
                }
            }
        }
        if (quote) {
            Tcl_DStringAppend(&ds, "\"", 1);
        }

        start = arg;        
        for (special = arg; ; ) {
            if ((*special == '\\') && 
                    (special[1] == '\\' || special[1] == '"')) {
                Tcl_DStringAppend(&ds, start, special - start);
                start = special;
                while (1) {
                    special++;
                    if (*special == '"') {
                        /* 
                         * N backslashes followed a quote -> insert 
                         * N * 2 + 1 backslashes then a quote.
                         */

                        Tcl_DStringAppend(&ds, start, special - start);
                        break;
                    }
                    if (*special != '\\') {
                        break;
                    }
                }
                Tcl_DStringAppend(&ds, start, special - start);
                start = special;
            }
            if (*special == '"') {
                Tcl_DStringAppend(&ds, start, special - start);
                Tcl_DStringAppend(&ds, "\\\"", 2);
                start = special + 1;
            }
            if (*special == '\0') {
                break;
            }
            special++;
        }
        Tcl_DStringAppend(&ds, start, special - start);
        if (quote) {
            Tcl_DStringAppend(&ds, "\"", 1);
        }
    }
    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];
    int channelId;
    DWORD id;
    PipeInfo *infoPtr = (PipeInfo *) ckalloc((unsigned) 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;

    /*
     * Use one of the fds associated with the channel as the
     * channel id.
     */

    if (readFile) {
        channelId = (int) ((WinFile*)readFile)->handle;
    } else if (writeFile) {
        channelId = (int) ((WinFile*)writeFile)->handle;
    } else if (errorFile) {
        channelId = (int) ((WinFile*)errorFile)->handle;
    } else {
        channelId = 0;
    }

    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->readThread = CreateThread(NULL, 8000, PipeReaderThread,
                infoPtr, 0, &id);
        SetThreadPriority(infoPtr->readThread, THREAD_PRIORITY_HIGHEST); 
        infoPtr->validMask |= TCL_READABLE;
    } else {
        infoPtr->readThread = 0;
    }
    if (writeFile != NULL) {
        /*
         * Start the background writeer thwrite.
         */

        infoPtr->writable = CreateEvent(NULL, TRUE, TRUE, NULL);
        infoPtr->startWriter = CreateEvent(NULL, FALSE, FALSE, NULL);
        infoPtr->writeThread = CreateThread(NULL, 8000, 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).
     */

    wsprintfA(channelName, "file%lx", infoPtr);
    infoPtr->channel = Tcl_CreateChannel(&pipeChannelType, channelName,
            (ClientData) 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((Tcl_Interp *) NULL, infoPtr->channel,
            "-translation", "auto");
    Tcl_SetChannelOption((Tcl_Interp *) NULL, infoPtr->channel,
            "-eofchar", "\032 {}");
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * 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;
    Tcl_ChannelType *chanTypePtr;
    int i;
    char buf[TCL_INTEGER_SPACE];

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

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

    pipePtr = (PipeInfo *) Tcl_GetChannelInstanceData(chan);
    for (i = 0; i < pipePtr->numPids; i++) {
        wsprintfA(buf, "%lu", TclpGetPid(pipePtr->pidPtr[i]));
        Tcl_AppendElement(interp, buf);
        Tcl_DetachPids(1, &(pipePtr->pidPtr[i]));
    }
    if (pipePtr->numPids > 0) {
        ckfree((char *) 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);

    errorCode = 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) {
            /*
             * Forcibly terminate the background thread.  We cannot rely on the
             * thread to cleanly terminate itself because we have no way of
             * closing the pipe handle without blocking in the case where the
             * thread is in the middle of an I/O operation.  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);
            TerminateThread(pipePtr->readThread, 0);

            /*
             * Wait for the thread to terminate.  This ensures that we are
             * completely cleaned up before we leave this function. 
             */

            WaitForSingleObject(pipePtr->readThread, INFINITE);
            Tcl_MutexUnlock(&pipeMutex);

            CloseHandle(pipePtr->readThread);
            CloseHandle(pipePtr->readable);
            CloseHandle(pipePtr->startReader);
            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)) {
        /*
         * 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 (pipePtr->writeThread) {
            WaitForSingleObject(pipePtr->writable, INFINITE);

            /*
             * Forcibly terminate the background thread.  We cannot rely on the
             * thread to cleanly terminate itself because we have no way of
             * closing the pipe handle without blocking in the case where the
             * thread is in the middle of an I/O operation.  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);
            TerminateThread(pipePtr->writeThread, 0);

            /*
             * Wait for the thread to terminate.  This ensures that we are
             * completely cleaned up before we leave this function. 
             */

            WaitForSingleObject(pipePtr->writeThread, INFINITE);
            Tcl_MutexUnlock(&pipeMutex);


            CloseHandle(pipePtr->writeThread);
            CloseHandle(pipePtr->writable);
            CloseHandle(pipePtr->startWriter);
            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;
        }
    }

    /*
     * Wrap the error file into a channel and give it to the cleanup
     * routine.
     */

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

        filePtr = (WinFile*)pipePtr->errorFile;
        errChan = Tcl_MakeFileChannel((ClientData) filePtr->handle,
                TCL_READABLE);
        ckfree((char *) filePtr);
    } else {
        errChan = NULL;
    }

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

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

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

    ckfree((char*) 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. */
    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, 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 procedure 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;
    WinFile *filePtr;
    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.
     */

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

    filePtr = (WinFile*) ((PipeInfo*)infoPtr)->readFile;
    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, **prevPtrPtr;
    int flags;
    Tcl_Pid result;
    DWORD ret;

    PipeInit();

    /*
     * If no pid is specified, do nothing.
     */
    
    if (pid == 0) {
        *statPtr = 0;
        return 0;
    }

    /*
     * Find the process on the process list.
     */

    Tcl_MutexLock(&pipeMutex);
    prevPtrPtr = &procList;
    for (infoPtr = procList; infoPtr != NULL;
            prevPtrPtr = &infoPtr->nextPtr, infoPtr = infoPtr->nextPtr) {
         if (infoPtr->hProcess == (HANDLE) pid) {
            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) {
            return 0;
        } else {
            result = 0;
        }
    } else if (ret != WAIT_FAILED) {
        GetExitCodeProcess(infoPtr->hProcess, (DWORD*)statPtr);
        *statPtr = ((*statPtr << 8) & 0xff00);
        result = pid;
    } else {
        errno = ECHILD;
        *statPtr = ECHILD;
        result = (Tcl_Pid) -1;
    }

    /*
     * Remove the process from the process list and close the process handle.
     */

    CloseHandle(infoPtr->hProcess);
    *prevPtrPtr = infoPtr->nextPtr;
    ckfree((char*)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(hProcess, id)
    HANDLE hProcess;           /* Handle to process */
    DWORD id;                  /* Global process identifier */
{
    ProcInfo *procPtr = (ProcInfo *) ckalloc(sizeof(ProcInfo));
    procPtr->hProcess = hProcess;
    procPtr->dwProcessId = id;
    Tcl_MutexLock(&pipeMutex);
    procPtr->nextPtr = procList;
    procList = procPtr;
    Tcl_MutexUnlock(&pipeMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PidObjCmd --
 *
 *      This procedure 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;
    Tcl_ChannelType *chanTypePtr;
    PipeInfo *pipePtr;
    int i;
    Tcl_Obj *resultPtr;
    char buf[TCL_INTEGER_SPACE];

    if (objc > 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "?channelId?");
        return TCL_ERROR;
    }
    if (objc == 1) {
        resultPtr = Tcl_GetObjResult(interp);
        wsprintfA(buf, "%lu", (unsigned long) getpid());
        Tcl_SetStringObj(resultPtr, buf, -1);
    } 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_GetObjResult(interp);
        for (i = 0; i < pipePtr->numPids; i++) {
            wsprintfA(buf, "%lu", TclpGetPid(pipePtr->pidPtr[i]));
            Tcl_ListObjAppendElement(/*interp*/ NULL, resultPtr,
                    Tcl_NewStringObj(buf, -1));
        }
    }
    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.
 *
 *----------------------------------------------------------------------
 */

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

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

        WaitForSingleObject(infoPtr->startReader, INFINITE);

        /*
         * 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);
        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;

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

        WaitForSingleObject(infoPtr->startWriter, INFINITE);

        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);
        Tcl_ThreadAlert(infoPtr->threadId);
        Tcl_MutexUnlock(&pipeMutex);
    }
    return 0;
}

/* End of tclwinpipe.c */