/*

 * tclUnixNotify.c --

 *

 *	This file contains the implementation of the select-based

 *	Unix-specific notifier, which is the lowest-level part of the

 *	Tcl event loop.  This file works together with

 *	../generic/tclNotify.c.

 *

 * Copyright (c) 1995-1997 Sun Microsystems, Inc.

 * Portions Copyright (c) 2007-2008 Nokia Corporation and/or its subsidiaries. All rights reserved.  

 *

 * See the file "license.terms" for information on usage and redistribution

 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.

 *

 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.11.2.16 2006/08/22 17:45:02 andreas_kupries Exp $

 */

#include "tclInt.h"

#include "tclPort.h"

#if defined(__SYMBIAN32__) && defined(__WINSCW__)

#include "tclSymbianGlobals.h"

#define dataKey getdataKey(8)

#endif 

#ifndef HAVE_COREFOUNDATION /* Darwin/Mac OS X CoreFoundation notifier

                             * is in tclMacOSXNotify.c */

#ifndef __SYMBIAN32__  // added to prevent link errors on armv5

#include <signal.h> 

#endif

extern TclStubs tclStubs;

extern Tcl_NotifierProcs tclOriginalNotifier;

/*

 * This structure is used to keep track of the notifier info for a 

 * a registered file.

 */

typedef struct FileHandler {

    int fd;

    int mask;			/* Mask of desired events: TCL_READABLE,

				 * etc. */

    int readyMask;		/* Mask of events that have been seen since the

				 * last time file handlers were invoked for

				 * this file. */

    Tcl_FileProc *proc;		/* Procedure to call, in the style of

				 * Tcl_CreateFileHandler. */

    ClientData clientData;	/* Argument to pass to proc. */

    struct FileHandler *nextPtr;/* Next in list of all files we care about. */

} FileHandler;

/*

 * The following structure is what is added to the Tcl event queue when

 * file handlers are ready to fire.

 */

typedef struct FileHandlerEvent {

    Tcl_Event header;		/* Information that is standard for

				 * all events. */

    int fd;			/* File descriptor that is ready.  Used

				 * to find the FileHandler structure for

				 * the file (can't point directly to the

				 * FileHandler structure because it could

				 * go away while the event is queued). */

} FileHandlerEvent;

/*

 *

 * The following structure contains a set of select() masks to track

 * readable, writable, and exceptional conditions.

 */

typedef struct SelectMasks {

    fd_set readable;

    fd_set writable;

    fd_set exceptional;

} SelectMasks;

/*

 * The following static structure contains the state information for the

 * select based implementation of the Tcl notifier.  One of these structures

 * is created for each thread that is using the notifier.  

 */

typedef struct ThreadSpecificData {

    FileHandler *firstFileHandlerPtr;

				/* Pointer to head of file handler list. */

    SelectMasks checkMasks;	/* This structure is used to build up the masks

				 * to be used in the next call to select.

				 * Bits are set in response to calls to

				 * Tcl_CreateFileHandler. */

    SelectMasks readyMasks;	/* This array reflects the readable/writable

				 * conditions that were found to exist by the

				 * last call to select. */

    int numFdBits;		/* Number of valid bits in checkMasks

				 * (one more than highest fd for which

				 * Tcl_WatchFile has been called). */

#ifdef TCL_THREADS

    int onList;			/* True if it is in this list */

    unsigned int pollState;	/* pollState is used to implement a polling 

				 * handshake between each thread and the

				 * notifier thread. Bits defined below. */

    struct ThreadSpecificData *nextPtr, *prevPtr;

                                /* All threads that are currently waiting on 

                                 * an event have their ThreadSpecificData

                                 * structure on a doubly-linked listed formed

                                 * from these pointers.  You must hold the

                                 * notifierMutex lock before accessing these

                                 * fields. */

    Tcl_Condition waitCV;     /* Any other thread alerts a notifier

				 * that an event is ready to be processed

				 * by signaling this condition variable. */

    int eventReady;           /* True if an event is ready to be processed.

                               * Used as condition flag together with

                               * waitCV above. */

#endif

} ThreadSpecificData;

#if !defined(__SYMBIAN32__) || !defined(__WINSCW__)

static Tcl_ThreadDataKey dataKey;

#endif

#ifdef TCL_THREADS

/*

 * The following static indicates the number of threads that have

 * initialized notifiers.

 *

 * You must hold the notifierMutex lock before accessing this variable.

 */

static int notifierCount = 0;

/*

 * The following variable points to the head of a doubly-linked list of 

 * of ThreadSpecificData structures for all threads that are currently

 * waiting on an event.

 *

 * You must hold the notifierMutex lock before accessing this list.

 */

static ThreadSpecificData *waitingListPtr = NULL;

/*

 * The notifier thread spends all its time in select() waiting for a

 * file descriptor associated with one of the threads on the waitingListPtr

 * list to do something interesting.  But if the contents of the

 * waitingListPtr list ever changes, we need to wake up and restart

 * the select() system call.  You can wake up the notifier thread by

 * writing a single byte to the file descriptor defined below.  This

 * file descriptor is the input-end of a pipe and the notifier thread is

 * listening for data on the output-end of the same pipe.  Hence writing

 * to this file descriptor will cause the select() system call to return

 * and wake up the notifier thread.

 *

 * You must hold the notifierMutex lock before accessing this list.

 */

static int triggerPipe = -1;

/*

 * The notifierMutex locks access to all of the global notifier state. 

 */

TCL_DECLARE_MUTEX(notifierMutex)

/*

 * The notifier thread signals the notifierCV when it has finished

 * initializing the triggerPipe and right before the notifier

 * thread terminates.

 */

static Tcl_Condition notifierCV;

/*

 * The pollState bits

 *	POLL_WANT is set by each thread before it waits on its condition

 *		variable.  It is checked by the notifier before it does

 *		select.

 *	POLL_DONE is set by the notifier if it goes into select after

 *		seeing POLL_WANT.  The idea is to ensure it tries a select

 *		with the same bits the initial thread had set.

 */

#define POLL_WANT	0x1

#define POLL_DONE	0x2

/*

 * This is the thread ID of the notifier thread that does select.

 */

static Tcl_ThreadId notifierThread;

#endif

/*

 * Static routines defined in this file.

 */

#ifdef TCL_THREADS

static void	NotifierThreadProc _ANSI_ARGS_((ClientData clientData));

#endif

static int	FileHandlerEventProc _ANSI_ARGS_((Tcl_Event *evPtr,

		    int flags));

/*

 *----------------------------------------------------------------------

 *

 * Tcl_InitNotifier --

 *

 *	Initializes the platform specific notifier state.

 *

 * Results:

 *	Returns a handle to the notifier state for this thread..

 *

 * Side effects:

 *	None.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C ClientData

Tcl_InitNotifier()

{

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

#ifdef TCL_THREADS

    tsdPtr->eventReady = 0;

    /*

     * Start the Notifier thread if necessary.

     */

    Tcl_MutexLock(&notifierMutex);

    if (notifierCount == 0) {

	if (TclpThreadCreate(&notifierThread, NotifierThreadProc, NULL,

		     TCL_THREAD_STACK_DEFAULT, TCL_THREAD_JOINABLE) != TCL_OK) {

	    panic("Tcl_InitNotifier: unable to start notifier thread");

	}

    }

    notifierCount++;

    /*

     * Wait for the notifier pipe to be created.

     */

    while (triggerPipe < 0) {

	Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);

    }

    Tcl_MutexUnlock(&notifierMutex);

#endif

    return (ClientData) tsdPtr;

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_FinalizeNotifier --

 *

 *	This function is called to cleanup the notifier state before

 *	a thread is terminated.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	May terminate the background notifier thread if this is the

 *	last notifier instance.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_FinalizeNotifier(clientData)

    ClientData clientData;		/* Not used. */

{

#ifdef TCL_THREADS

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    Tcl_MutexLock(&notifierMutex);

    notifierCount--;

    /*

     * If this is the last thread to use the notifier, close the notifier

     * pipe and wait for the background thread to terminate.

     */

    if (notifierCount == 0) {

	int result;

	if (triggerPipe < 0) {

	    panic("Tcl_FinalizeNotifier: notifier pipe not initialized");

	}

	/*

	 * Send "q" message to the notifier thread so that it will

	 * terminate.  The notifier will return from its call to select()

	 * and notice that a "q" message has arrived, it will then close

	 * its side of the pipe and terminate its thread.  Note the we can

	 * not just close the pipe and check for EOF in the notifier

	 * thread because if a background child process was created with

	 * exec, select() would not register the EOF on the pipe until the

	 * child processes had terminated. [Bug: 4139] [Bug: 1222872]

	 */

	write(triggerPipe, "q", 1);

	close(triggerPipe);

	while(triggerPipe >= 0) {

	    Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);

	}

	result = Tcl_JoinThread(notifierThread, NULL);

	if (result) {

	    Tcl_Panic("Tcl_FinalizeNotifier: unable to join notifier thread");

	}

    }

    /*

     * Clean up any synchronization objects in the thread local storage.

     */

    Tcl_ConditionFinalize(&(tsdPtr->waitCV));

    Tcl_MutexUnlock(&notifierMutex);

#endif

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_AlertNotifier --

 *

 *	Wake up the specified notifier from any thread. This routine

 *	is called by the platform independent notifier code whenever

 *	the Tcl_ThreadAlert routine is called.  This routine is

 *	guaranteed not to be called on a given notifier after

 *	Tcl_FinalizeNotifier is called for that notifier.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	Signals the notifier condition variable for the specified

 *	notifier.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_AlertNotifier(clientData)

    ClientData clientData;

{

#ifdef TCL_THREADS

    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) clientData;

    Tcl_MutexLock(&notifierMutex);

    tsdPtr->eventReady = 1;

    Tcl_ConditionNotify(&tsdPtr->waitCV);

    Tcl_MutexUnlock(&notifierMutex);

#endif

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_SetTimer --

 *

 *	This procedure sets the current notifier timer value.  This

 *	interface is not implemented in this notifier because we are

 *	always running inside of Tcl_DoOneEvent.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	None.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_SetTimer(timePtr)

    Tcl_Time *timePtr;		/* Timeout value, may be NULL. */

{

    /*

     * The interval timer doesn't do anything in this implementation,

     * because the only event loop is via Tcl_DoOneEvent, which passes

     * timeout values to Tcl_WaitForEvent.

     */

    if (tclStubs.tcl_SetTimer != tclOriginalNotifier.setTimerProc) {

	tclStubs.tcl_SetTimer(timePtr);

    }

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_ServiceModeHook --

 *

 *	This function is invoked whenever the service mode changes.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	None.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_ServiceModeHook(mode)

    int mode;			/* Either TCL_SERVICE_ALL, or

				 * TCL_SERVICE_NONE. */

{

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_CreateFileHandler --

 *

 *	This procedure registers a file handler with the select notifier.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	Creates a new file handler structure.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_CreateFileHandler(fd, mask, proc, clientData)

    int fd;			/* Handle of stream to watch. */

    int mask;			/* OR'ed combination of TCL_READABLE,

				 * TCL_WRITABLE, and TCL_EXCEPTION:

				 * indicates conditions under which

				 * proc should be called. */

    Tcl_FileProc *proc;		/* Procedure to call for each

				 * selected event. */

    ClientData clientData;	/* Arbitrary data to pass to proc. */

{

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    FileHandler *filePtr;

    if (tclStubs.tcl_CreateFileHandler != tclOriginalNotifier.createFileHandlerProc) {

	tclStubs.tcl_CreateFileHandler(fd, mask, proc, clientData);

	return;

    }

    for (filePtr = tsdPtr->firstFileHandlerPtr; filePtr != NULL;

	 filePtr = filePtr->nextPtr) {

	if (filePtr->fd == fd) {

	    break;

	}

    }

    if (filePtr == NULL) {

	filePtr = (FileHandler*) ckalloc(sizeof(FileHandler));

	filePtr->fd = fd;

	filePtr->readyMask = 0;

	filePtr->nextPtr = tsdPtr->firstFileHandlerPtr;

	tsdPtr->firstFileHandlerPtr = filePtr;

    }

    filePtr->proc = proc;

    filePtr->clientData = clientData;

    filePtr->mask = mask;

    /*

     * Update the check masks for this file.

     */

    if ( mask & TCL_READABLE ) {

	FD_SET( fd, &(tsdPtr->checkMasks.readable) );

    } else {

	FD_CLR( fd, &(tsdPtr->checkMasks.readable) );

    }

    if ( mask & TCL_WRITABLE ) {

	FD_SET( fd, &(tsdPtr->checkMasks.writable) );

    } else {

	FD_CLR( fd, &(tsdPtr->checkMasks.writable) );

    }

    if ( mask & TCL_EXCEPTION ) {

	FD_SET( fd, &(tsdPtr->checkMasks.exceptional) );

    } else {

	FD_CLR( fd, &(tsdPtr->checkMasks.exceptional) );

    }

    if (tsdPtr->numFdBits <= fd) {

	tsdPtr->numFdBits = fd+1;

    }

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_DeleteFileHandler --

 *

 *	Cancel a previously-arranged callback arrangement for

 *	a file.

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	If a callback was previously registered on file, remove it.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C void

Tcl_DeleteFileHandler(fd)

    int fd;		/* Stream id for which to remove callback procedure. */

{

    FileHandler *filePtr, *prevPtr;

    int i;

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_DeleteFileHandler != tclOriginalNotifier.deleteFileHandlerProc) {

	tclStubs.tcl_DeleteFileHandler(fd);

	return;

    }

    /*

     * Find the entry for the given file (and return if there isn't one).

     */

    for (prevPtr = NULL, filePtr = tsdPtr->firstFileHandlerPtr; ;

	 prevPtr = filePtr, filePtr = filePtr->nextPtr) {

	if (filePtr == NULL) {

	    return;

	}

	if (filePtr->fd == fd) {

	    break;

	}

    }

    /*

     * Update the check masks for this file.

     */

    if (filePtr->mask & TCL_READABLE) {

	FD_CLR( fd, &(tsdPtr->checkMasks.readable) );

    }

    if (filePtr->mask & TCL_WRITABLE) {

	FD_CLR( fd, &(tsdPtr->checkMasks.writable) );

    }

    if (filePtr->mask & TCL_EXCEPTION) {

	FD_CLR( fd, &(tsdPtr->checkMasks.exceptional) );

    }

    /*

     * Find current max fd.

     */

    if (fd+1 == tsdPtr->numFdBits) {

	tsdPtr->numFdBits = 0;

	for (i = fd-1; i >= 0; i--) {

	    if ( FD_ISSET( i, &(tsdPtr->checkMasks.readable) )

		 || FD_ISSET( i, &(tsdPtr->checkMasks.writable) )

		 || FD_ISSET( i, &(tsdPtr->checkMasks.exceptional ) ) ) {

		tsdPtr->numFdBits = i+1;

		break;

	    }

	}

    }

    /*

     * Clean up information in the callback record.

     */

    if (prevPtr == NULL) {

	tsdPtr->firstFileHandlerPtr = filePtr->nextPtr;

    } else {

	prevPtr->nextPtr = filePtr->nextPtr;

    }

    ckfree((char *) filePtr);

}

/*

 *----------------------------------------------------------------------

 *

 * FileHandlerEventProc --

 *

 *	This procedure is called by Tcl_ServiceEvent when a file event

 *	reaches the front of the event queue.  This procedure is

 *	responsible for actually handling the event by invoking the

 *	callback for the file handler.

 *

 * 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 file handler's callback procedure does.

 *

 *----------------------------------------------------------------------

 */

static int

FileHandlerEventProc(evPtr, flags)

    Tcl_Event *evPtr;		/* Event to service. */

    int flags;			/* Flags that indicate what events to

				 * handle, such as TCL_FILE_EVENTS. */

{

    int mask;

    FileHandler *filePtr;

    FileHandlerEvent *fileEvPtr = (FileHandlerEvent *) evPtr;

    ThreadSpecificData *tsdPtr;

    if (!(flags & TCL_FILE_EVENTS)) {

	return 0;

    }

    /*

     * Search through the file handlers to find the one whose handle matches

     * the event.  We do this rather than keeping a pointer to the file

     * handler directly in the event, so that the handler can be deleted

     * while the event is queued without leaving a dangling pointer.

     */

    tsdPtr = TCL_TSD_INIT(&dataKey);

    for (filePtr = tsdPtr->firstFileHandlerPtr; filePtr != NULL;

	 filePtr = filePtr->nextPtr) {

	if (filePtr->fd != fileEvPtr->fd) {

	    continue;

	}

	/*

	 * The code is tricky for two reasons:

	 * 1. The file handler's desired events could have changed

	 *    since the time when the event was queued, so AND the

	 *    ready mask with the desired mask.

	 * 2. The file could have been closed and re-opened since

	 *    the time when the event was queued.  This is why the

	 *    ready mask is stored in the file handler rather than

	 *    the queued event:  it will be zeroed when a new

	 *    file handler is created for the newly opened file.

	 */

	mask = filePtr->readyMask & filePtr->mask;

	filePtr->readyMask = 0;

	if (mask != 0) {

	    (*filePtr->proc)(filePtr->clientData, mask);

	}

	break;

    }

    return 1;

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_WaitForEvent --

 *

 *	This function is called by Tcl_DoOneEvent to wait for new

 *	events on the message queue.  If the block time is 0, then

 *	Tcl_WaitForEvent just polls without blocking.

 *

 * Results:

 *	Returns -1 if the select would block forever, otherwise

 *	returns 0.

 *

 * Side effects:

 *	Queues file events that are detected by the select.

 *

 *----------------------------------------------------------------------

 */

EXPORT_C int

Tcl_WaitForEvent(timePtr)

    Tcl_Time *timePtr;		/* Maximum block time, or NULL. */

{

    FileHandler *filePtr;

    FileHandlerEvent *fileEvPtr;

    int mask;

#ifdef TCL_THREADS

    int waitForFiles;

#else

    /* Impl. notes: timeout & timeoutPtr are used if, and only if

     * threads are not enabled. They are the arguments for the regular

     * select() used when the core is not thread-enabled. */

    struct timeval timeout, *timeoutPtr;

    int numFound;

#endif

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_WaitForEvent != tclOriginalNotifier.waitForEventProc) {

	return tclStubs.tcl_WaitForEvent(timePtr);

    }

#ifndef TCL_THREADS

    /*

     * Set up the timeout structure.  Note that if there are no events to

     * check for, we return with a negative result rather than blocking

     * forever.

     */

    if (timePtr) {

	timeout.tv_sec = timePtr->sec;

	timeout.tv_usec = timePtr->usec;

	timeoutPtr = &timeout;

    } else if (tsdPtr->numFdBits == 0) {

	/*

	 * If there are no threads, no timeout, and no fds registered,

	 * then there are no events possible and we must avoid deadlock.

	 * Note that this is not entirely correct because there might

	 * be a signal that could interrupt the select call, but we

	 * don't handle that case if we aren't using threads.

	 */

	return -1;

    } else {

	timeoutPtr = NULL;

    }

#endif

#ifdef TCL_THREADS

    /*

     * Place this thread on the list of interested threads, signal the

     * notifier thread, and wait for a response or a timeout.

     */

    Tcl_MutexLock(&notifierMutex);

    waitForFiles = (tsdPtr->numFdBits > 0);

    if (timePtr != NULL && timePtr->sec == 0 && (timePtr->usec == 0

#if defined(__APPLE__) && defined(__LP64__)

	    /*

	     * On 64-bit Darwin, pthread_cond_timedwait() appears to have a bug

	     * that causes it to wait forever when passed an absolute time which

	     * has already been exceeded by the system time; as a workaround,

	     * when given a very brief timeout, just do a poll. [Bug 1457797]

	     */

	    || timePtr->usec < 10

#endif

	    )) {

	/*

	 * Cannot emulate a polling select with a polling condition variable.

	 * Instead, pretend to wait for files and tell the notifier

	 * thread what we are doing.  The notifier thread makes sure

	 * it goes through select with its select mask in the same state

	 * as ours currently is.  We block until that happens.

	 */

	waitForFiles = 1;

	tsdPtr->pollState = POLL_WANT;

	timePtr = NULL;

    } else {

	tsdPtr->pollState = 0;

    }

    if (waitForFiles) {

        /*

         * Add the ThreadSpecificData structure of this thread to the list

         * of ThreadSpecificData structures of all threads that are waiting

         * on file events.

         */

        tsdPtr->nextPtr = waitingListPtr;

        if (waitingListPtr) {

            waitingListPtr->prevPtr = tsdPtr;

        }

        tsdPtr->prevPtr = 0;

        waitingListPtr = tsdPtr;

	tsdPtr->onList = 1;

	write(triggerPipe, "", 1);

    }

    FD_ZERO( &(tsdPtr->readyMasks.readable) );

    FD_ZERO( &(tsdPtr->readyMasks.writable) );

    FD_ZERO( &(tsdPtr->readyMasks.exceptional) );

    if (!tsdPtr->eventReady) {

        Tcl_ConditionWait(&tsdPtr->waitCV, &notifierMutex, timePtr);

    }

    tsdPtr->eventReady = 0;

    if (waitForFiles && tsdPtr->onList) {

	/*

	 * Remove the ThreadSpecificData structure of this thread from the

	 * waiting list.  Alert the notifier thread to recompute its select

	 * masks - skipping this caused a hang when trying to close a pipe

	 * which the notifier thread was still doing a select on.

	 */

        if (tsdPtr->prevPtr) {

            tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;

        } else {

            waitingListPtr = tsdPtr->nextPtr;

        }

        if (tsdPtr->nextPtr) {

            tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;

        }

        tsdPtr->nextPtr = tsdPtr->prevPtr = NULL;

	tsdPtr->onList = 0;

	write(triggerPipe, "", 1);

    }

#else

    tsdPtr->readyMasks = tsdPtr->checkMasks;

    numFound = select( tsdPtr->numFdBits,

		       &(tsdPtr->readyMasks.readable),

		       &(tsdPtr->readyMasks.writable),

		       &(tsdPtr->readyMasks.exceptional),

		       timeoutPtr );

    /*

     * Some systems don't clear the masks after an error, so

     * we have to do it here.

     */

    if (numFound == -1) {

	FD_ZERO( &(tsdPtr->readyMasks.readable ) );

	FD_ZERO( &(tsdPtr->readyMasks.writable ) );

	FD_ZERO( &(tsdPtr->readyMasks.exceptional ) );

    }

#endif

    /*

     * Queue all detected file events before returning.

     */

    for (filePtr = tsdPtr->firstFileHandlerPtr; (filePtr != NULL);

	 filePtr = filePtr->nextPtr) {

	mask = 0;

	if ( FD_ISSET( filePtr->fd, &(tsdPtr->readyMasks.readable) ) ) {

	    mask |= TCL_READABLE;

	}

	if ( FD_ISSET( filePtr->fd, &(tsdPtr->readyMasks.writable) ) ) {

	    mask |= TCL_WRITABLE;

	}

	if ( FD_ISSET( filePtr->fd, &(tsdPtr->readyMasks.exceptional) ) ) {

	    mask |= TCL_EXCEPTION;

	}

	if (!mask) {

	    continue;

	}

	/*

	 * Don't bother to queue an event if the mask was previously

	 * non-zero since an event must still be on the queue.

	 */

	if (filePtr->readyMask == 0) {

	    fileEvPtr = (FileHandlerEvent *) ckalloc(

		sizeof(FileHandlerEvent));

	    fileEvPtr->header.proc = FileHandlerEventProc;

	    fileEvPtr->fd = filePtr->fd;

	    Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);

	}

	filePtr->readyMask = mask;

    }

#ifdef TCL_THREADS

    Tcl_MutexUnlock(&notifierMutex);

#endif

    return 0;

}

#ifdef TCL_THREADS

/*

 *----------------------------------------------------------------------

 *

 * NotifierThreadProc --

 *

 *	This routine is the initial (and only) function executed by the

 *	special notifier thread.  Its job is to wait for file descriptors

 *	to become readable or writable or to have an exception condition

 *	and then to notify other threads who are interested in this

 *	information by signalling a condition variable.  Other threads

 *	can signal this notifier thread of a change in their interests

 *	by writing a single byte to a special pipe that the notifier

 *	thread is monitoring.

 *

 * Result:

 *	None.  Once started, this routine never exits.  It dies with

 *	the overall process.

 *

 * Side effects:

 *	The trigger pipe used to signal the notifier thread is created

 *	when the notifier thread first starts.

 *

 *----------------------------------------------------------------------

 */

static void

NotifierThreadProc(clientData)

    ClientData clientData;	/* Not used. */

{

    ThreadSpecificData *tsdPtr;

    fd_set readableMask;

    fd_set writableMask;

    fd_set exceptionalMask;

    int fds[2];

    int i, status, numFdBits = 0, receivePipe;

    long found;

    struct timeval poll = {0., 0.}, *timePtr;

    char buf[2];

    if (pipe(fds) != 0) {

	panic("NotifierThreadProc: could not create trigger pipe.");

    }

    receivePipe = fds[0];

#ifndef USE_FIONBIO

    status = fcntl(receivePipe, F_GETFL);

    status |= O_NONBLOCK;

    if (fcntl(receivePipe, F_SETFL, status) < 0) {

	panic("NotifierThreadProc: could not make receive pipe non blocking.");

    }

    status = fcntl(fds[1], F_GETFL);

    status |= O_NONBLOCK;

    if (fcntl(fds[1], F_SETFL, status) < 0) {

	panic("NotifierThreadProc: could not make trigger pipe non blocking.");

    }

#else

    if (ioctl(receivePipe, (int) FIONBIO, &status) < 0) {

	panic("NotifierThreadProc: could not make receive pipe non blocking.");

    }

    if (ioctl(fds[1], (int) FIONBIO, &status) < 0) {

	panic("NotifierThreadProc: could not make trigger pipe non blocking.");

    }

#endif

    /*

     * Install the write end of the pipe into the global variable.

     */

    Tcl_MutexLock(&notifierMutex);

    triggerPipe = fds[1];

    /*

     * Signal any threads that are waiting.

     */

    Tcl_ConditionNotify(&notifierCV);

    Tcl_MutexUnlock(&notifierMutex);

    /*

     * Look for file events and report them to interested threads.

     */

    while (1) {

	FD_ZERO( &readableMask );

	FD_ZERO( &writableMask );

	FD_ZERO( &exceptionalMask );

	/*

	 * Compute the logical OR of the select masks from all the

	 * waiting notifiers.

	 */

	Tcl_MutexLock(&notifierMutex);

	timePtr = NULL;

        for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {

	    for ( i = tsdPtr->numFdBits-1; i >= 0; --i ) {

		if ( FD_ISSET( i, &(tsdPtr->checkMasks.readable) ) ) {

		    FD_SET( i, &readableMask );

		}

		if ( FD_ISSET( i, &(tsdPtr->checkMasks.writable) ) ) {

		    FD_SET( i, &writableMask );

		}

		if ( FD_ISSET( i, &(tsdPtr->checkMasks.exceptional) ) ) {

		    FD_SET( i, &exceptionalMask );

		}

	    }

	    if ( tsdPtr->numFdBits > numFdBits ) {

		numFdBits = tsdPtr->numFdBits;

	    }

	    if (tsdPtr->pollState & POLL_WANT) {

		/*

		 * Here we make sure we go through select() with the same

		 * mask bits that were present when the thread tried to poll.

		 */

		tsdPtr->pollState |= POLL_DONE;

		timePtr = &poll;

	    }

	}

	Tcl_MutexUnlock(&notifierMutex);

	/*

	 * Set up the select mask to include the receive pipe.

	 */

	if ( receivePipe >= numFdBits ) {

	    numFdBits = receivePipe + 1;