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tclWinChan.c

/* 
 * tclWinChan.c
 *
 *    Channel drivers for Windows channels based on files, command
 *    pipes and TCP sockets.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclWinChan.c,v 1.30.2.4 2005/06/23 15:05:22 kennykb Exp $
 */

#include "tclWinInt.h"
#include "tclIO.h"

/*
 * State flags used in the info structures below.
 */

#define FILE_PENDING    (1<<0)      /* Message is pending in the queue. */
#define FILE_ASYNC      (1<<1)      /* Channel is non-blocking. */
#define FILE_APPEND     (1<<2)      /* File is in append mode. */

#define FILE_TYPE_SERIAL  (FILE_TYPE_PIPE+1)
#define FILE_TYPE_CONSOLE (FILE_TYPE_PIPE+2)

/*
 * The following structure contains per-instance data for a file based channel.
 */

typedef struct FileInfo {
    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. */
    HANDLE handle;            /* Input/output file. */
    struct FileInfo *nextPtr; /* Pointer to next registered file. */
    int dirty;                  /* Boolean flag. Set if the OS may have data
                         * pending on the channel */
} FileInfo;

typedef struct ThreadSpecificData {
    /*
     * List of all file channels currently open.
     */

    FileInfo *firstFilePtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

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

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

/*
 * Static routines for this file:
 */

static int        FileBlockProc _ANSI_ARGS_((ClientData instanceData,
                      int mode));
static void       FileChannelExitHandler _ANSI_ARGS_((
                        ClientData clientData));
static void       FileCheckProc _ANSI_ARGS_((ClientData clientData,
                      int flags));
static int        FileCloseProc _ANSI_ARGS_((ClientData instanceData,
                        Tcl_Interp *interp));
static int        FileEventProc _ANSI_ARGS_((Tcl_Event *evPtr, 
                      int flags));
static int        FileGetHandleProc _ANSI_ARGS_((ClientData instanceData,
                        int direction, ClientData *handlePtr));
static ThreadSpecificData *FileInit _ANSI_ARGS_((void));
static int        FileInputProc _ANSI_ARGS_((ClientData instanceData,
                            char *buf, int toRead, int *errorCode));
static int        FileOutputProc _ANSI_ARGS_((ClientData instanceData,
                      CONST char *buf, int toWrite, int *errorCode));
static int        FileSeekProc _ANSI_ARGS_((ClientData instanceData,
                      long offset, int mode, int *errorCode));
static Tcl_WideInt      FileWideSeekProc _ANSI_ARGS_((ClientData instanceData,
                      Tcl_WideInt offset, int mode, int *errorCode));
static void       FileSetupProc _ANSI_ARGS_((ClientData clientData,
                      int flags));
static void       FileWatchProc _ANSI_ARGS_((ClientData instanceData,
                        int mask));
static void             FileThreadActionProc _ANSI_ARGS_ ((
                     ClientData instanceData, int action));

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

static Tcl_ChannelType fileChannelType = {
    "file",             /* Type name. */
    TCL_CHANNEL_VERSION_4,    /* v4 channel */
    FileCloseProc,            /* Close proc. */
    FileInputProc,            /* Input proc. */
    FileOutputProc,           /* Output proc. */
    FileSeekProc,       /* Seek proc. */
    NULL,               /* Set option proc. */
    NULL,               /* Get option proc. */
    FileWatchProc,            /* Set up the notifier to watch the channel. */
    FileGetHandleProc,        /* Get an OS handle from channel. */
    NULL,               /* close2proc. */
    FileBlockProc,            /* Set blocking or non-blocking mode.*/
    NULL,               /* flush proc. */
    NULL,               /* handler proc. */
    FileWideSeekProc,         /* Wide seek proc. */
    FileThreadActionProc,     /* Thread action proc. */
};

#ifdef HAVE_NO_SEH

/*
 * Unlike Borland and Microsoft, we don't register exception handlers
 * by pushing registration records onto the runtime stack.  Instead, we
 * register them by creating an EXCEPTION_REGISTRATION within the activation
 * record.
 */

typedef struct EXCEPTION_REGISTRATION {
    struct EXCEPTION_REGISTRATION* link;
    EXCEPTION_DISPOSITION (*handler)( struct _EXCEPTION_RECORD*, void*,
                              struct _CONTEXT*, void* );
    void* ebp;
    void* esp;
    int status;
} EXCEPTION_REGISTRATION;

#endif

/*
 *----------------------------------------------------------------------
 *
 * FileInit --
 *
 *    This function creates the window used to simulate file events.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Creates a new window and creates an exit handler. 
 *
 *----------------------------------------------------------------------
 */

static ThreadSpecificData *
FileInit()
{
    ThreadSpecificData *tsdPtr =
      (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);
    if (tsdPtr == NULL) {
      tsdPtr = TCL_TSD_INIT(&dataKey);
      tsdPtr->firstFilePtr = NULL;
      Tcl_CreateEventSource(FileSetupProc, FileCheckProc, NULL);
      Tcl_CreateThreadExitHandler(FileChannelExitHandler, NULL);
    }
    return tsdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * FileChannelExitHandler --
 *
 *    This function is called to cleanup the channel driver before
 *    Tcl is unloaded.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Destroys the communication window.
 *
 *----------------------------------------------------------------------
 */

static void
FileChannelExitHandler(clientData)
    ClientData clientData;    /* Old window proc */
{
    Tcl_DeleteEventSource(FileSetupProc, FileCheckProc, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * FileSetupProc --
 *
 *    This procedure is invoked before Tcl_DoOneEvent blocks waiting
 *    for an event.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

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

    if (!(flags & TCL_FILE_EVENTS)) {
      return;
    }
    
    /*
     * Check to see if there is a ready file.  If so, poll.
     */

    for (infoPtr = tsdPtr->firstFilePtr; infoPtr != NULL; 
          infoPtr = infoPtr->nextPtr) {
      if (infoPtr->watchMask) {
          Tcl_SetMaxBlockTime(&blockTime);
          break;
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileCheckProc --
 *
 *    This procedure is called by Tcl_DoOneEvent to check the file
 *    event source for events. 
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    May queue an event.
 *
 *----------------------------------------------------------------------
 */

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

    if (!(flags & TCL_FILE_EVENTS)) {
      return;
    }
    
    /*
     * Queue events for any ready files that don't already have events
     * queued (caused by persistent states that won't generate WinSock
     * events).
     */

    for (infoPtr = tsdPtr->firstFilePtr; infoPtr != NULL; 
          infoPtr = infoPtr->nextPtr) {
      if (infoPtr->watchMask && !(infoPtr->flags & FILE_PENDING)) {
          infoPtr->flags |= FILE_PENDING;
          evPtr = (FileEvent *) ckalloc(sizeof(FileEvent));
          evPtr->header.proc = FileEventProc;
          evPtr->infoPtr = infoPtr;
          Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
      }
    }
}

/*----------------------------------------------------------------------
 *
 * FileEventProc --
 *
 *    This function is invoked by Tcl_ServiceEvent when a file event
 *    reaches the front of the event queue.  This procedure invokes
 *    Tcl_NotifyChannel on the file.
 *
 * 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
FileEventProc(evPtr, flags)
    Tcl_Event *evPtr;         /* Event to service. */
    int flags;                /* Flags that indicate what events to
                         * handle, such as TCL_FILE_EVENTS. */
{
    FileEvent *fileEvPtr = (FileEvent *)evPtr;
    FileInfo *infoPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

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

    for (infoPtr = tsdPtr->firstFilePtr; infoPtr != NULL;
          infoPtr = infoPtr->nextPtr) {
      if (fileEvPtr->infoPtr == infoPtr) {
          infoPtr->flags &= ~(FILE_PENDING);
          Tcl_NotifyChannel(infoPtr->channel, infoPtr->watchMask);
          break;
      }
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileBlockProc --
 *
 *    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
FileBlockProc(instanceData, mode)
    ClientData instanceData;  /* Instance data for channel. */
    int mode;                 /* TCL_MODE_BLOCKING or
                                 * TCL_MODE_NONBLOCKING. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    
    /*
     * Files 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 |= FILE_ASYNC;
    } else {
      infoPtr->flags &= ~(FILE_ASYNC);
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * FileCloseProc --
 *
 *    Closes the IO channel.
 *
 * Results:
 *    0 if successful, the value of errno if failed.
 *
 * Side effects:
 *    Closes the physical channel
 *
 *----------------------------------------------------------------------
 */

static int
FileCloseProc(instanceData, interp)
    ClientData instanceData;  /* Pointer to FileInfo structure. */
    Tcl_Interp *interp;       /* Not used. */
{
    FileInfo *fileInfoPtr = (FileInfo *) instanceData;
    FileInfo *infoPtr;
    ThreadSpecificData *tsdPtr;
    int errorCode = 0;

    /*
     * Remove the file from the watch list.
     */

    FileWatchProc(instanceData, 0);

    /*
     * 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) != fileInfoPtr->handle)
            && (GetStdHandle(STD_OUTPUT_HANDLE) != fileInfoPtr->handle)
            && (GetStdHandle(STD_ERROR_HANDLE) != fileInfoPtr->handle))) {
      if (CloseHandle(fileInfoPtr->handle) == FALSE) {
          TclWinConvertError(GetLastError());
          errorCode = errno;
      }
    }

    /*
     * See if this FileInfo* is still on the thread local list.
     */
    tsdPtr = TCL_TSD_INIT(&dataKey);
    for (infoPtr = tsdPtr->firstFilePtr; infoPtr != NULL; 
          infoPtr = infoPtr->nextPtr) {
      if (infoPtr == fileInfoPtr) {
            /*
             * This channel exists on the thread local list. It should
             * have been removed by an earlier Thread Action call,
             * but do that now since just deallocating fileInfoPtr would
             * leave an deallocated pointer on the thread local list.
             */
          FileThreadActionProc(fileInfoPtr,TCL_CHANNEL_THREAD_REMOVE);
            break;
        }
    }
    ckfree((char *)fileInfoPtr);
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * FileSeekProc --
 *
 *    Seeks on a file-based channel. Returns the new position.
 *
 * Results:
 *    -1 if failed, the new position if successful. If failed, it
 *    also sets *errorCodePtr to the error code.
 *
 * Side effects:
 *    Moves the location at which the channel will be accessed in
 *    future operations.
 *
 *----------------------------------------------------------------------
 */

static int
FileSeekProc(instanceData, offset, mode, errorCodePtr)
    ClientData instanceData;  /* File state. */
    long offset;        /* Offset to seek to. */
    int mode;                 /* Relative to where should we seek? */
    int *errorCodePtr;        /* To store error code. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    DWORD moveMethod;
    DWORD newPos, newPosHigh;
    DWORD oldPos, oldPosHigh;

    *errorCodePtr = 0;
    if (mode == SEEK_SET) {
        moveMethod = FILE_BEGIN;
    } else if (mode == SEEK_CUR) {
        moveMethod = FILE_CURRENT;
    } else {
        moveMethod = FILE_END;
    }

    /*
     * Save our current place in case we need to roll-back the seek.
     */
    oldPosHigh = (DWORD)0;
    oldPos = SetFilePointer(infoPtr->handle, (LONG)0, &oldPosHigh,
          FILE_CURRENT);
    if (oldPos == INVALID_SET_FILE_POINTER) {
      DWORD winError = GetLastError();
      if (winError != NO_ERROR) {
          TclWinConvertError(winError);
          *errorCodePtr = errno;
          return -1;
      }
    }

    newPosHigh = (DWORD)(offset < 0 ? -1 : 0);
    newPos = SetFilePointer(infoPtr->handle, (LONG) offset, &newPosHigh,
                      moveMethod);
    if (newPos == INVALID_SET_FILE_POINTER) {
      DWORD winError = GetLastError();
      if (winError != NO_ERROR) {
          TclWinConvertError(winError);
          *errorCodePtr = errno;
          return -1;
      }
    }

    /*
     * Check for expressability in our return type, and roll-back otherwise.
     */
    if (newPosHigh != 0) {
      *errorCodePtr = EOVERFLOW;
      SetFilePointer(infoPtr->handle, (LONG)oldPos, &oldPosHigh, FILE_BEGIN);
      return -1;
    }
    return (int) newPos;
}

/*
 *----------------------------------------------------------------------
 *
 * FileWideSeekProc --
 *
 *    Seeks on a file-based channel. Returns the new position.
 *
 * Results:
 *    -1 if failed, the new position if successful. If failed, it
 *    also sets *errorCodePtr to the error code.
 *
 * Side effects:
 *    Moves the location at which the channel will be accessed in
 *    future operations.
 *
 *----------------------------------------------------------------------
 */

static Tcl_WideInt
FileWideSeekProc(instanceData, offset, mode, errorCodePtr)
    ClientData instanceData;  /* File state. */
    Tcl_WideInt offset;       /* Offset to seek to. */
    int mode;                 /* Relative to where should we seek? */
    int *errorCodePtr;        /* To store error code. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    DWORD moveMethod;
    DWORD newPos, newPosHigh;

    *errorCodePtr = 0;
    if (mode == SEEK_SET) {
        moveMethod = FILE_BEGIN;
    } else if (mode == SEEK_CUR) {
        moveMethod = FILE_CURRENT;
    } else {
        moveMethod = FILE_END;
    }

    newPosHigh = (DWORD)(offset >> 32);
    newPos = SetFilePointer(infoPtr->handle, (LONG) offset, &newPosHigh,
                      moveMethod);
    if (newPos == INVALID_SET_FILE_POINTER) {
      DWORD winError = GetLastError();
      if (winError != NO_ERROR) {
          TclWinConvertError(winError);
          *errorCodePtr = errno;
          return -1;
      }
    }
    return ((Tcl_WideInt) newPos) | (((Tcl_WideInt) newPosHigh) << 32);
}

/*
 *----------------------------------------------------------------------
 *
 * FileInputProc --
 *
 *    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
FileInputProc(instanceData, buf, bufSize, errorCode)
    ClientData instanceData;        /* File 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. */
{
    FileInfo *infoPtr;
    DWORD bytesRead;

    *errorCode = 0;
    infoPtr = (FileInfo *) instanceData;

    /*
     * Note that we will block on reads from a console buffer until a
     * full line has been entered.  The only way I know of to get
     * around this is to write a console driver.  We should probably
     * do this at some point, but for now, we just block.  The same
     * problem exists for files being read over the network.
     */

    if (ReadFile(infoPtr->handle, (LPVOID) buf, (DWORD) bufSize, &bytesRead,
            (LPOVERLAPPED) NULL) != FALSE) {
      return bytesRead;
    }
    
    TclWinConvertError(GetLastError());
    *errorCode = errno;
    if (errno == EPIPE) {
      return 0;
    }
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileOutputProc --
 *
 *    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
FileOutputProc(instanceData, buf, toWrite, errorCode)
    ClientData instanceData;        /* File state. */
    CONST char *buf;                /* The data buffer. */
    int toWrite;              /* How many bytes to write? */
    int *errorCode;                 /* Where to store error code. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    DWORD bytesWritten;
    
    *errorCode = 0;

    /*
     * If we are writing to a file that was opened with O_APPEND, we need to
     * seek to the end of the file before writing the current buffer.
     */

    if (infoPtr->flags & FILE_APPEND) {
        SetFilePointer(infoPtr->handle, 0, NULL, FILE_END);
    }

    if (WriteFile(infoPtr->handle, (LPVOID) buf, (DWORD) toWrite, &bytesWritten,
            (LPOVERLAPPED) NULL) == FALSE) {
        TclWinConvertError(GetLastError());
        *errorCode = errno;
        return -1;
    }
    infoPtr->dirty = 1;
    return bytesWritten;
}

/*
 *----------------------------------------------------------------------
 *
 * FileWatchProc --
 *
 *    Called by the notifier to set up to watch for events on this
 *    channel.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static void
FileWatchProc(instanceData, mask)
    ClientData instanceData;        /* File state. */
    int mask;                       /* What events to watch for; OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    Tcl_Time blockTime = { 0, 0 };

    /*
     * Since the file is always ready for events, we set the block time
     * to zero so we will poll.
     */

    infoPtr->watchMask = mask & infoPtr->validMask;
    if (infoPtr->watchMask) {
      Tcl_SetMaxBlockTime(&blockTime);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileGetHandleProc --
 *
 *    Called from Tcl_GetChannelHandle to retrieve OS handles from
 *    a file 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
FileGetHandleProc(instanceData, direction, handlePtr)
    ClientData instanceData;  /* The file state. */
    int direction;            /* TCL_READABLE or TCL_WRITABLE */
    ClientData *handlePtr;    /* Where to store the handle.  */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;

    if (direction & infoPtr->validMask) {
      *handlePtr = (ClientData) infoPtr->handle;
      return TCL_OK;
    } else {
      return TCL_ERROR;
    }
}


/*
 *----------------------------------------------------------------------
 *
 * TclpOpenFileChannel --
 *
 *    Open an File based channel on Unix systems.
 *
 * Results:
 *    The new channel or NULL. If NULL, the output argument
 *    errorCodePtr is set to a POSIX error.
 *
 * Side effects:
 *    May open the channel and may cause creation of a file on the
 *    file system.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpOpenFileChannel(interp, pathPtr, mode, permissions)
    Tcl_Interp *interp;             /* Interpreter for error reporting;
                                         * can be NULL. */
    Tcl_Obj *pathPtr;               /* Name of file to open. */
    int mode;                       /* POSIX mode. */
    int permissions;                /* If the open involves creating a
                                         * file, with what modes to create
                                         * it? */
{
    Tcl_Channel channel = 0;
    int channelPermissions;
    DWORD accessMode, createMode, shareMode, flags, consoleParams, type;
    CONST TCHAR *nativeName;
    DCB dcb;
    HANDLE handle;
    char channelName[16 + TCL_INTEGER_SPACE];
    TclFile readFile = NULL;
    TclFile writeFile = NULL;

    nativeName = (TCHAR*) Tcl_FSGetNativePath(pathPtr);
    if (nativeName == NULL) {
      return NULL;
    }
    
    switch (mode & (O_RDONLY | O_WRONLY | O_RDWR)) {
      case O_RDONLY:
          accessMode = GENERIC_READ;
          channelPermissions = TCL_READABLE;
          break;
      case O_WRONLY:
          accessMode = GENERIC_WRITE;
          channelPermissions = TCL_WRITABLE;
          break;
      case O_RDWR:
          accessMode = (GENERIC_READ | GENERIC_WRITE);
          channelPermissions = (TCL_READABLE | TCL_WRITABLE);
          break;
      default:
          panic("TclpOpenFileChannel: invalid mode value");
          break;
    }

    /*
     * 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;
    }

    /*
     * If the file is being created, get the file attributes from the
     * permissions argument, else use the existing file attributes.
     */

    if (mode & O_CREAT) {
        if (permissions & S_IWRITE) {
            flags = FILE_ATTRIBUTE_NORMAL;
        } else {
            flags = FILE_ATTRIBUTE_READONLY;
        }
    } else {
      flags = (*tclWinProcs->getFileAttributesProc)(nativeName);
        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)(nativeName, accessMode, 
          shareMode, NULL, createMode, flags, (HANDLE) NULL);

    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);
      if (interp != (Tcl_Interp *) NULL) {
            Tcl_AppendResult(interp, "couldn't open \"", 
                       Tcl_GetString(pathPtr), "\": ",
                       Tcl_PosixError(interp), (char *) NULL);
        }
        return NULL;
    }
    
    type = GetFileType(handle);

    /*
     * If the file is a character device, we need to try to figure out
     * whether it is a serial port, a console, or something else.  We
     * test for the console case first because this is more common.
     */

    if (type == FILE_TYPE_CHAR) {
      if (GetConsoleMode(handle, &consoleParams)) {
          type = FILE_TYPE_CONSOLE;
      } else {
          dcb.DCBlength = sizeof( DCB ) ;
          if (GetCommState(handle, &dcb)) {
            type = FILE_TYPE_SERIAL;
          }
                
      }
    }

    channel = NULL;

    switch (type) {
    case FILE_TYPE_SERIAL:
      /*
       * Reopen channel for OVERLAPPED operation
       * Normally this shouldn't fail, because the channel exists
       */
      handle = TclWinSerialReopen(handle, nativeName, accessMode);
      if (handle == INVALID_HANDLE_VALUE) {
          TclWinConvertError(GetLastError());
          if (interp != (Tcl_Interp *) NULL) {
            Tcl_AppendResult(interp, "couldn't reopen serial \"",
                  Tcl_GetString(pathPtr), "\": ",
                  Tcl_PosixError(interp), (char *) NULL);
          }
          return NULL;
      }
      channel = TclWinOpenSerialChannel(handle, channelName,
              channelPermissions);
      break;
    case FILE_TYPE_CONSOLE:
      channel = TclWinOpenConsoleChannel(handle, channelName,
              channelPermissions);
      break;
    case FILE_TYPE_PIPE:
      if (channelPermissions & TCL_READABLE) {
          readFile = TclWinMakeFile(handle);
      }
      if (channelPermissions & TCL_WRITABLE) {
          writeFile = TclWinMakeFile(handle);
      }
      channel = TclpCreateCommandChannel(readFile, writeFile, NULL, 0, NULL);
      break;
    case FILE_TYPE_CHAR:
    case FILE_TYPE_DISK:
    case FILE_TYPE_UNKNOWN:
      channel = TclWinOpenFileChannel(handle, channelName,
                              channelPermissions,
                              (mode & O_APPEND) ? FILE_APPEND : 0);
      break;

    default:
      /*
       * The handle is of an unknown type, probably /dev/nul equivalent
       * or possibly a closed handle.  
       */
      
      channel = NULL;
      Tcl_AppendResult(interp, "couldn't open \"", 
                   Tcl_GetString(pathPtr), "\": ",
                   "bad file type", (char *) NULL);
      break;
    }

    return channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeFileChannel --
 *
 *    Creates a Tcl_Channel from an existing platform specific file
 *    handle.
 *
 * Results:
 *    The Tcl_Channel created around the preexisting file.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_MakeFileChannel(rawHandle, mode)
    ClientData rawHandle;     /* OS level handle */
    int mode;                 /* ORed combination of TCL_READABLE and
                                 * TCL_WRITABLE to indicate file mode. */
{
#ifdef HAVE_NO_SEH
    EXCEPTION_REGISTRATION registration;
#endif
    char channelName[16 + TCL_INTEGER_SPACE];
    Tcl_Channel channel = NULL;
    HANDLE handle = (HANDLE) rawHandle;
    HANDLE dupedHandle;
    DCB dcb;
    DWORD consoleParams, type;
    TclFile readFile = NULL;
    TclFile writeFile = NULL;
    BOOL result;

    if (mode == 0) {
      return NULL;
    }

    /*
     * GetFileType() returns FILE_TYPE_UNKNOWN for invalid handles.
     */

    type = GetFileType(handle);

    /*
     * If the file is a character device, we need to try to figure out
     * whether it is a serial port, a console, or something else.  We
     * test for the console case first because this is more common.
     */

    if (type == FILE_TYPE_CHAR) {
      if (GetConsoleMode(handle, &consoleParams)) {
          type = FILE_TYPE_CONSOLE;
      } else {
          dcb.DCBlength = sizeof( DCB ) ;
          if (GetCommState(handle, &dcb)) {
            type = FILE_TYPE_SERIAL;
          }
      }
    }

    switch (type)
    {
    case FILE_TYPE_SERIAL:
      channel = TclWinOpenSerialChannel(handle, channelName, mode);
      break;
    case FILE_TYPE_CONSOLE:
      channel = TclWinOpenConsoleChannel(handle, channelName, mode);
      break;
    case FILE_TYPE_PIPE:
      if (mode & TCL_READABLE)
      {
          readFile = TclWinMakeFile(handle);
      }
      if (mode & TCL_WRITABLE)
      {
          writeFile = TclWinMakeFile(handle);
      }
      channel = TclpCreateCommandChannel(readFile, writeFile, NULL, 0, NULL);
      break;

    case FILE_TYPE_DISK:
    case FILE_TYPE_CHAR:
      channel = TclWinOpenFileChannel(handle, channelName, mode, 0);
      break;
      
    case FILE_TYPE_UNKNOWN:
    default:
      /*
       * The handle is of an unknown type.  Test the validity of this OS
       * handle by duplicating it, then closing the dupe.  The Win32 API
       * doesn't provide an IsValidHandle() function, so we have to emulate
       * it here.  This test will not work on a console handle reliably,
       * which is why we can't test every handle that comes into this
       * function in this way.
       */

      result = DuplicateHandle(GetCurrentProcess(), handle,
            GetCurrentProcess(), &dupedHandle, 0, FALSE,
            DUPLICATE_SAME_ACCESS);

      if (result == 0) {
          /* 
           * Unable to make a duplicate. It's definately invalid at this
           * point.
           */

          return NULL;
      }

      /*
       * Use structured exception handling (Win32 SEH) to protect the close
       * of this duped handle which might throw EXCEPTION_INVALID_HANDLE.
       */

      result = 0;
#ifndef HAVE_NO_SEH
      __try {
          CloseHandle(dupedHandle);
          result = 1;
      } __except (EXCEPTION_EXECUTE_HANDLER) {}
#else
      /*
       * Don't have SEH available, do things the hard way.
       * Note that this needs to be one block of asm, to avoid stack
       * imbalance; also, it is illegal for one asm block to contain 
       * a jump to another.
       */
      
      __asm__ __volatile__ (

          /*
           * Pick up parameters before messing with the stack
           */

          "movl       %[dupedHandle], %%ebx"          "\n\t"

          /*
           * Construct an EXCEPTION_REGISTRATION to protect the
           * call to CloseHandle
           */
          "leal       %[registration], %%edx"         "\n\t"
          "movl       %%fs:0,         %%eax"          "\n\t"
          "movl       %%eax,          0x0(%%edx)"     "\n\t" /* link */
          "leal       1f,             %%eax"          "\n\t"
          "movl       %%eax,          0x4(%%edx)"     "\n\t" /* handler */
          "movl       %%ebp,          0x8(%%edx)"     "\n\t" /* ebp */
          "movl       %%esp,          0xc(%%edx)"     "\n\t" /* esp */
          "movl       $0,             0x10(%%edx)"    "\n\t" /* status */
      
          /* Link the EXCEPTION_REGISTRATION on the chain */
          
          "movl       %%edx,          %%fs:0"         "\n\t"
          
          /* Call CloseHandle( dupedHandle ) */
          
          "pushl      %%ebx"                          "\n\t"
          "call       _CloseHandle@4"                 "\n\t"
          
          /* 
           * Come here on normal exit.  Recover the EXCEPTION_REGISTRATION
           * and put a TRUE status return into it.
           */
          
          "movl       %%fs:0,         %%edx"          "\n\t"
          "movl   $1,         %%eax"            "\n\t"
          "movl       %%eax,          0x10(%%edx)"    "\n\t"
          "jmp        2f"                             "\n"
          
          /*
           * Come here on an exception.  Recover the EXCEPTION_REGISTRATION
           */
          
          "1:"                                        "\t"
          "movl       %%fs:0,         %%edx"          "\n\t"
          "movl       0x8(%%edx),     %%edx"          "\n\t"
          
          /* 
           * Come here however we exited.  Restore context from the
           * EXCEPTION_REGISTRATION in case the stack is unbalanced.
           */
          
          "2:"                                        "\t"
          "movl       0xc(%%edx),     %%esp"          "\n\t"
          "movl       0x8(%%edx),     %%ebp"          "\n\t"
          "movl       0x0(%%edx),     %%eax"          "\n\t"
          "movl       %%eax,          %%fs:0"         "\n\t"
          
          :
          /* No outputs */
          :
          [registration]  "m"     (registration),
          [dupedHandle]   "m"     (dupedHandle)
          :
          "%eax", "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory"
          );
      result = registration.status;

#endif
      if (result == FALSE) {
          return NULL;
      }

      /* Fall through, the handle is valid. */

      /*
       * Create the undefined channel, anyways, because we know the handle
       * is valid to something.
       */

      channel = TclWinOpenFileChannel(handle, channelName, mode, 0);
    }

    return channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetDefaultStdChannel --
 *
 *    Constructs a channel for the specified standard OS handle.
 *
 * Results:
 *    Returns the specified default standard channel, or NULL.
 *
 * Side effects:
 *    May cause the creation of a standard channel and the underlying
 *    file.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpGetDefaultStdChannel(type)
    int type;                 /* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR. */
{
    Tcl_Channel channel;
    HANDLE handle;
    int mode;
    char *bufMode;
    DWORD handleId;           /* Standard handle to retrieve. */


    switch (type) {
      case TCL_STDIN:
          handleId = STD_INPUT_HANDLE;
          mode = TCL_READABLE;
          bufMode = "line";
          break;
      case TCL_STDOUT:
          handleId = STD_OUTPUT_HANDLE;
          mode = TCL_WRITABLE;
          bufMode = "line";
          break;
      case TCL_STDERR:
          handleId = STD_ERROR_HANDLE;
          mode = TCL_WRITABLE;
          bufMode = "none";
          break;
      default:
          panic("TclGetDefaultStdChannel: Unexpected channel type");
          break;
    }

    handle = GetStdHandle(handleId);

    /*
     * Note that we need to check for 0 because Windows may return 0 if this
     * is not a console mode application, even though this is not a valid
     * handle.
     */

    if ((handle == INVALID_HANDLE_VALUE) || (handle == 0)) {
      return (Tcl_Channel) NULL;
    }

    channel = Tcl_MakeFileChannel(handle, mode);

    if (channel == NULL) {
      return (Tcl_Channel) NULL;
    }

    /*
     * Set up the normal channel options for stdio handles.
     */

    if ((Tcl_SetChannelOption((Tcl_Interp *) NULL, channel, "-translation",
            "auto") == TCL_ERROR)
          || (Tcl_SetChannelOption((Tcl_Interp *) NULL, channel, "-eofchar",
                "\032 {}") == TCL_ERROR)
          || (Tcl_SetChannelOption((Tcl_Interp *) NULL, channel,
                "-buffering", bufMode) == TCL_ERROR)) {
        Tcl_Close((Tcl_Interp *) NULL, channel);
        return (Tcl_Channel) NULL;
    }
    return channel;
}



/*
 *----------------------------------------------------------------------
 *
 * TclWinOpenFileChannel --
 *
 *    Constructs a File channel for the specified standard OS handle.
 *      This is a helper function to break up the construction of 
 *      channels into File, Console, or Serial.
 *
 * Results:
 *    Returns the new channel, or NULL.
 *
 * Side effects:
 *    May open the channel and may cause creation of a file on the
 *    file system.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclWinOpenFileChannel(handle, channelName, permissions, appendMode)
    HANDLE handle;
    char *channelName;
    int permissions;
    int appendMode;
{
    FileInfo *infoPtr;
    ThreadSpecificData *tsdPtr;

    tsdPtr = FileInit();

    /*
     * See if a channel with this handle already exists.
     */
    
    for (infoPtr = tsdPtr->firstFilePtr; infoPtr != NULL; 
       infoPtr = infoPtr->nextPtr) {
      if (infoPtr->handle == (HANDLE) handle) {
          return (permissions == infoPtr->validMask) ? infoPtr->channel : NULL;
      }
    }

    infoPtr = (FileInfo *) ckalloc((unsigned) sizeof(FileInfo));
    /* TIP #218. Removed the code inserting the new structure
     * into the global list. This is now handled in the thread
     * action callbacks, and only there.
     */
    infoPtr->nextPtr = NULL;
    infoPtr->validMask = permissions;
    infoPtr->watchMask = 0;
    infoPtr->flags = appendMode;
    infoPtr->handle = handle;
    infoPtr->dirty = 0;
    wsprintfA(channelName, "file%lx", (int) infoPtr);
    
    infoPtr->channel = Tcl_CreateChannel(&fileChannelType, channelName,
          (ClientData) infoPtr, permissions);
    
    /*
     * Files have default translation of AUTO and ^Z eof char, which
     * means that a ^Z will be accepted as EOF when reading.
     */
    
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");

    return infoPtr->channel;
}


/*
 *----------------------------------------------------------------------
 *
 * TclWinFlushDirtyChannels --
 *
 *    Flush all dirty channels to disk, so that requesting the
 *    size of any file returns the correct value.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Information is actually written to disk now, rather than
 *    later.  Don't call this too often, or there will be a 
 *    performance hit (i.e. only call when we need to ask for
 *    the size of a file).
 *
 *----------------------------------------------------------------------
 */

void
TclWinFlushDirtyChannels ()
{
    FileInfo *infoPtr;
    ThreadSpecificData *tsdPtr;

    tsdPtr = FileInit();

    /*
     * Flush all channels which are dirty, i.e. may have data pending
     * in the OS
     */
    
    for (infoPtr = tsdPtr->firstFilePtr;
       infoPtr != NULL; 
       infoPtr = infoPtr->nextPtr) {
      if (infoPtr->dirty) {
          FlushFileBuffers(infoPtr->handle);
          infoPtr->dirty = 0;
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileThreadActionProc --
 *
 *    Insert or remove any thread local refs to this channel.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Changes thread local list of valid channels.
 *
 *----------------------------------------------------------------------
 */

static void
FileThreadActionProc (instanceData, action)
     ClientData instanceData;
     int action;
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileInfo *infoPtr = (FileInfo *) instanceData;

    if (action == TCL_CHANNEL_THREAD_INSERT) {
        infoPtr->nextPtr = tsdPtr->firstFilePtr;
      tsdPtr->firstFilePtr = infoPtr;
    } else {
        FileInfo **nextPtrPtr;
      int removed = 0;

      for (nextPtrPtr = &(tsdPtr->firstFilePtr); (*nextPtrPtr) != NULL;
           nextPtrPtr = &((*nextPtrPtr)->nextPtr)) {
          if ((*nextPtrPtr) == infoPtr) {
              (*nextPtrPtr) = infoPtr->nextPtr;
            removed = 1;
            break;
          }
      }

      /*
       * This could happen if the channel was created in one thread
       * and then moved to another without updating the thread
       * local data in each thread.
       */

      if (!removed) {
          panic("file info ptr not on thread channel list");
      }
    }
}

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