source: downloads/tcl8.5.2/win/tclWinPipe.c @ 68

/*
 * 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 1.65 2007/02/20 23:24:07 nijtmans Exp $
 */

#include "tclWinInt.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 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(WCHAR 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 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;
    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 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;
    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(
    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(
    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 = (*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|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. */
{
    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;
}

/*
 *----------------------------------------------------------------------
 *
 * 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)
{
    WCHAR fileName[MAX_PATH];

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

    return TclpNativeToNormalized((ClientData) 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((char *) filePtr);
                return -1;
            }
        }
        break;

    default:
        Tcl_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;

    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). */
    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.
             */
            Tcl_Obj *tclExePtr, *pipeDllPtr;
            char *start, *end;
            int i, fileExists;
            Tcl_DString pipeDll;

            if (createFlags != 0) {
                startInfo.wShowWindow = SW_HIDE;
                startInfo.dwFlags |= STARTF_USESHOWWINDOW;
                createFlags = CREATE_NEW_CONSOLE;
            }

            Tcl_DStringInit(&pipeDll);
            Tcl_DStringAppend(&pipeDll, TCL_PIPE_DLL, -1);
            tclExePtr = TclGetObjNameOfExecutable();
            Tcl_IncrRefCount(tclExePtr);
            start = Tcl_GetStringFromObj(tclExePtr, &i);
            for (end = start + (i-1); end > start; end--) {
                if (*end == '/') {
                    break;
                }
            }
            if (*end != '/') {
                Tcl_AppendResult(interp, "no / in executable path name \"",
                        start, "\"", (char *) NULL);
                Tcl_DecrRefCount(tclExePtr);
                Tcl_DStringFree(&pipeDll);
                goto end;
            }
            i = (end - start) + 1;
            pipeDllPtr = Tcl_NewStringObj(start, i);
            Tcl_AppendToObj(pipeDllPtr, Tcl_DStringValue(&pipeDll), -1);
            Tcl_IncrRefCount(pipeDllPtr);
            if (Tcl_FSConvertToPathType(interp, pipeDllPtr) != TCL_OK) {
                Tcl_Panic("Tcl_FSConvertToPathType failed");
            }
            fileExists = (Tcl_FSAccess(pipeDllPtr, F_OK) == 0);
            if (!fileExists) {
                Tcl_AppendResult(interp, "Tcl pipe dll \"",
                        Tcl_DStringValue(&pipeDll), "\" not found",
                        (char *) NULL);
                Tcl_DecrRefCount(tclExePtr);
                Tcl_DecrRefCount(pipeDllPtr);
                Tcl_DStringFree(&pipeDll);
                goto end;
            }
            Tcl_DStringAppend(&cmdLine, Tcl_DStringValue(&pipeDll), -1);
            Tcl_DecrRefCount(tclExePtr);
            Tcl_DecrRefCount(pipeDllPtr);
            Tcl_DStringFree(&pipeDll);
        }
    }

    /*
     * 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,
            (DWORD) 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(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;
    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() 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 = (*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) && (stricmp(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. */
    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.
     */

    Tcl_DStringAppend(&ds, Tcl_DStringValue(linePtr), -1);
    if (Tcl_DStringLength(linePtr) > 0) {
        Tcl_DStringAppend(&ds, " ", 1);
    }

    for (i = 0; i < argc; i++) {
        if (i == 0) {
            arg = executable;
        } else {
            arg = argv[i];
            Tcl_DStringAppend(&ds, " ", 1);
        }

        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) {
            Tcl_DStringAppend(&ds, "\"", 1);
        }
        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));
                Tcl_DStringAppend(&ds, "\\\"", 2);
                start = special + 1;
            }
            if (*special == '\0') {
                break;
            }
            special++;
        }
        Tcl_DStringAppend(&ds, start, (int) (special - start));
        if (quote) {
            Tcl_DStringAppend(&ds, "\"", 1);
        }
    }
    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];
    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;
    infoPtr->channel = (Tcl_Channel) NULL;

    /*
     * 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->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).
     */

    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;
    const 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);
    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, there should be no pending write operations.
             */

            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;

            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. */
    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((unsigned int) 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;
    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 = 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((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(
    HANDLE hProcess,            /* Handle to process */
    DWORD id)                   /* Global process identifier */
{
    ProcInfo *procPtr = (ProcInfo *) 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;
    char buf[TCL_INTEGER_SPACE];

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

            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);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */