/*
 * 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
 *	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.
 *	generic/tclNotify.c.
 *
 * 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.
 * 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 1.12.2.11 2005/07/05 15:09:13 dgp Exp $
 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.12.2.12 2005/07/26 04:12:33 dgp Exp $
 */

#ifndef HAVE_COREFOUNDATION /* Darwin/Mac OS X CoreFoundation notifier
                             * is in tclMacOSXNotify.c */
#ifndef HAVE_COREFOUNDATION	/* Darwin/Mac OS X CoreFoundation notifier is
				 * in tclMacOSXNotify.c */
#include "tclInt.h"
#include <signal.h> 

/*
 * This code does deep stub magic to allow replacement of the notifier at
 * runtime.
 */

extern TclStubs tclStubs;
extern Tcl_NotifierProcs tclOriginalNotifier;

/*
 * This structure is used to keep track of the notifier info for a 
 * a registered file.
 * This structure is used to keep track of the notifier info for 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
    int readyMask;		/* Mask of events that have been seen since
				 * the last time file handlers were invoked
				 * for this file. */
    Tcl_FileProc *proc;		/* Function 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.
 * 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). */
    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.
 * 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.  
 * 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 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
    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 
    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 
				/* 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. */
    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. */
				 * Used as condition flag together with waitCV
				 * above. */
#endif
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

#ifdef TCL_THREADS
/*
 * The following static indicates the number of threads that have
 * initialized notifiers.
 * 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.
 * The following variable points to the head of a doubly-linked list 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
 * 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
 * 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.
 * 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. 
 * 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.
 * initializing the triggerPipe and right before the notifier thread
 * terminates.
 */

static Tcl_Condition notifierCV;

/*
 * The pollState bits
 * 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
 *		variable. It is checked by the notifier before it does select.
 *		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.
 *	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.
 */

}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FinalizeNotifier --
 *
 *	This function is called to cleanup the notifier state before
 *	a thread is terminated.
 *	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.
 *	May terminate the background notifier thread if this is the last
 *	notifier instance.
 *
 *----------------------------------------------------------------------
 */

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 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) {
	    Tcl_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]
	 * 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);
	}

}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AlertNotifier --
 *
 *	Wake up the specified notifier from any thread. This routine
 *	is called by the platform independent notifier code whenever
 *	Wake up the specified notifier from any thread. This routine is called
 *	by the platform independent notifier code whenever the Tcl_ThreadAlert
 *	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.
 *	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
 *	Signals the notifier condition variable for the specified notifier.
 *	notifier.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AlertNotifier(clientData)
    ClientData clientData;

}

/*
 *----------------------------------------------------------------------
 *
 * 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.
 *	This function 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.
 *
 *----------------------------------------------------------------------
 */

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.
     * 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_CreateFileHandler --
 *
 *	This procedure registers a file handler with the select notifier.
 *	This function registers a file handler with the select notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new file handler structure.
 *
 *----------------------------------------------------------------------
 */

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. */
				 * TCL_WRITABLE, and TCL_EXCEPTION: indicates
				 * conditions under which proc should be
				 * called. */
    Tcl_FileProc *proc;		/* Function 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);

}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteFileHandler --
 *
 *	Cancel a previously-arranged callback arrangement for
 *	Cancel a previously-arranged callback arrangement for a file.
 *	a file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered on file, remove it.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteFileHandler(fd)
    int fd;		/* Stream id for which to remove callback procedure. */
    int fd;			/* Stream id for which to remove callback
				 * function. */
{
    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) {
	    prevPtr = filePtr, filePtr = filePtr->nextPtr) {
	if (filePtr == NULL) {
	    return;
	}
	if (filePtr->fd == fd) {
	    break;
	}
    }

}

/*
 *----------------------------------------------------------------------
 *
 * 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.
 *	This function is called by Tcl_ServiceEvent when a file event reaches
 *	the front of the event queue. This function 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.
 *	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.
 *	Whatever the file handler's callback function 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 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.
     * 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
	 * 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
	 *    the queued event:  it will be zeroed when a new
	 *    file handler is created for the newly opened file.
	 *    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.
 *	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 -1 if the select would block forever, otherwise returns 0.
 *	returns 0.
 *
 * Side effects:
 *	Queues file events that are detected by the select.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WaitForEvent(timePtr)
    Tcl_Time *timePtr;		/* Maximum block time, or NULL. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr;
    int mask;
    Tcl_Time myTime;
#ifdef TCL_THREADS
    int waitForFiles;
    Tcl_Time *myTimePtr;
#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. */
     * 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
#endif /* TCL_THREADS */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_WaitForEvent != tclOriginalNotifier.waitForEventProc) {
	return tclStubs.tcl_WaitForEvent(timePtr);
    }

    /*
     * Set up the timeout structure.  Note that if there are no events to
     * check for, we return with a negative result rather than blocking
     * 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.
     * forever.
     */

    if (timePtr != NULL) {
	/*
	/* TIP #233 (Virtualized Time). Is virtual time in effect ?
	 * And do we actually have something to scale ? If yes to both
	 * then we call the handler to do this scaling */
	 * TIP #233 (Virtualized Time). Is virtual time in effect? And do we
	 * actually have something to scale? If yes to both then we call the
	 * handler to do this scaling.
	 */

	myTime.sec  = timePtr->sec;
	myTime.usec = timePtr->usec;

	if (myTime.sec != 0 || myTime.usec != 0) {
	    (*tclScaleTimeProcPtr) (&myTime, tclTimeClientData);
	}

#ifdef TCL_THREADS
	myTimePtr = &myTime;
#else
	timeout.tv_sec  = myTime.sec;
	timeout.tv_sec = myTime.sec;
	timeout.tv_usec = myTime.usec;
	timeoutPtr      = &timeout;
#endif
	timeoutPtr = &timeout;
#endif /* TCL_THREADS */

#ifndef TCL_THREADS
    } 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.
	 * 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;
#endif
#endif /* !TCL_THREADS */
    } else {
#ifdef TCL_THREADS
	myTimePtr = NULL;
#else
	timeoutPtr = NULL;
#endif
#endif /* TCL_THREADS */
    }

#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 (myTimePtr != NULL && myTimePtr->sec == 0 && myTimePtr->usec == 0) {
	/*
	 * 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.
	 * 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;
	myTimePtr = 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.
	 * 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, myTimePtr);
	Tcl_ConditionWait(&tsdPtr->waitCV, &notifierMutex, myTimePtr);
    }
    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
	 * 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),
    numFound = select(tsdPtr->numFdBits, &(tsdPtr->readyMasks.readable),
	    &(tsdPtr->readyMasks.writable), &(tsdPtr->readyMasks.exceptional),
		       &(tsdPtr->readyMasks.exceptional),
		       timeoutPtr );
	    timeoutPtr);

    /*
     * Some systems don't clear the masks after an error, so
     * we have to do it here.
     * 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 ) );
	FD_ZERO(&(tsdPtr->readyMasks.readable));
	FD_ZERO(&(tsdPtr->readyMasks.writable));
	FD_ZERO(&(tsdPtr->readyMasks.exceptional));
    }
#endif
#endif /* TCL_THREADS */

    /*
     * Queue all detected file events before returning.
     */

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

	}

	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.
	 * 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
#endif /* TCL_THREADS */
    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
 *	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.
 *	thread is monitoring.
 *
 * Result:
 *	None.  Once started, this routine never exits.  It dies with
 *	the overall process.
 *	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.
 *	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. */

#else
    if (ioctl(receivePipe, (int) FIONBIO, &status) < 0) {
	Tcl_Panic("NotifierThreadProc: could not make receive pipe non blocking.");
    }
    if (ioctl(fds[1], (int) FIONBIO, &status) < 0) {
	Tcl_Panic("NotifierThreadProc: could not make trigger pipe non blocking.");
    }
#endif
#endif /* FIONBIO */

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

    Tcl_MutexLock(&notifierMutex);
    triggerPipe = fds[1];

    while (1) {
	FD_ZERO(&readableMask);
	FD_ZERO(&writableMask);
	FD_ZERO(&exceptionalMask);

	/*
	 * Compute the logical OR of the select masks from all the
	 * waiting notifiers.
	 * 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))) {

		}
	    }
	    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.
		 * 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);

		}
	    }

	    if (found || (tsdPtr->pollState & POLL_DONE)) {
		tsdPtr->eventReady = 1;
		if (tsdPtr->onList) {
		    /*
		     * Remove the ThreadSpecificData structure of this
		     * thread from the waiting list. This prevents us from
		     * continuously spining on select until the other
		     * threads runs and services the file event.
		     * Remove the ThreadSpecificData structure of this thread
		     * from the waiting list. This prevents us from
		     * continuously spining on select until the other threads
		     * runs and services the file event.
		     */

		    if (tsdPtr->prevPtr) {
			tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
		    } else {
			waitingListPtr = tsdPtr->nextPtr;
		    }

		Tcl_ConditionNotify(&tsdPtr->waitCV);
	    }
	}
	Tcl_MutexUnlock(&notifierMutex);

	/*
	 * Consume the next byte from the notifier pipe if the pipe was
	 * readable.  Note that there may be multiple bytes pending, but
	 * to avoid a race condition we only read one at a time.
	 * readable. Note that there may be multiple bytes pending, but to
	 * avoid a race condition we only read one at a time.
	 */

	if (FD_ISSET(receivePipe, &readableMask)) {
	    i = read(receivePipe, buf, 1);

	    if ((i == 0) || ((i == 1) && (buf[0] == 'q'))) {
		/*
		 * Someone closed the write end of the pipe or sent us a
		 * Quit message [Bug: 4139] and then closed the write end
		 * of the pipe so we need to shut down the notifier thread.
		 * Someone closed the write end of the pipe or sent us a Quit
		 * message [Bug: 4139] and then closed the write end of the
		 * pipe so we need to shut down the notifier thread.
		 */

		break;
	    }
	}
    }

    /*
     * Clean up the read end of the pipe and signal any threads waiting on
     * termination of the notifier thread.
     */

    close(receivePipe);
    Tcl_MutexLock(&notifierMutex);
    triggerPipe = -1;
    Tcl_ConditionNotify(&notifierCV);
    Tcl_MutexUnlock(&notifierMutex);

    TclpThreadExit (0);
}
#endif
#endif /* TCL_THREADS */

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