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tclNotify.c

/*
 * tclNotify.c --
 *
 *    This file implements the generic portion of the Tcl notifier. The
 *    notifier is lowest-level part of the event system. It manages an event
 *    queue that holds Tcl_Event structures. The platform specific portion
 *    of the notifier is defined in the tcl*Notify.c files in each platform
 *    directory.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 * Copyright (c) 1998 by Scriptics Corporation.
 * Copyright (c) 2003 by Kevin B. Kenny.  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: tclNotify.c,v 1.25 2006/09/25 15:02:54 dkf Exp $
 */

#include "tclInt.h"

extern TclStubs tclStubs;

/*
 * For each event source (created with Tcl_CreateEventSource) there is a
 * structure of the following type:
 */

typedef struct EventSource {
    Tcl_EventSetupProc *setupProc;
    Tcl_EventCheckProc *checkProc;
    ClientData clientData;
    struct EventSource *nextPtr;
} EventSource;

/*
 * The following structure keeps track of the state of the notifier on a
 * per-thread basis. The first three elements keep track of the event queue.
 * In addition to the first (next to be serviced) and last events in the
 * queue, we keep track of a "marker" event. This provides a simple priority
 * mechanism whereby events can be inserted at the front of the queue but
 * behind all other high-priority events already in the queue (this is used
 * for things like a sequence of Enter and Leave events generated during a
 * grab in Tk). These elements are protected by the queueMutex so that any
 * thread can queue an event on any notifier. Note that all of the values in
 * this structure will be initialized to 0.
 */

typedef struct ThreadSpecificData {
    Tcl_Event *firstEventPtr; /* First pending event, or NULL if none. */
    Tcl_Event *lastEventPtr;  /* Last pending event, or NULL if none. */
    Tcl_Event *markerEventPtr;      /* Last high-priority event in queue, or NULL
                         * if none. */
    Tcl_Mutex queueMutex;     /* Mutex to protect access to the previous
                         * three fields. */
    int serviceMode;          /* One of TCL_SERVICE_NONE or
                         * TCL_SERVICE_ALL. */
    int blockTimeSet;         /* 0 means there is no maximum block time:
                         * block forever. */
    Tcl_Time blockTime;       /* If blockTimeSet is 1, gives the maximum
                         * elapsed time for the next block. */
    int inTraversal;          /* 1 if Tcl_SetMaxBlockTime is being called
                         * during an event source traversal. */
    EventSource *firstEventSourcePtr;
                        /* Pointer to first event source in list of
                         * event sources for this thread. */
    Tcl_ThreadId threadId;    /* Thread that owns this notifier instance. */
    ClientData clientData;    /* Opaque handle for platform specific
                         * notifier. */
    int initialized;          /* 1 if notifier has been initialized. */
    struct ThreadSpecificData *nextPtr;
                        /* Next notifier in global list of notifiers.
                         * Access is controlled by the listLock global
                         * mutex. */
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * Global list of notifiers. Access to this list is controlled by the listLock
 * mutex. If this becomes a performance bottleneck, this could be replaced
 * with a hashtable.
 */

static ThreadSpecificData *firstNotifierPtr = NULL;
TCL_DECLARE_MUTEX(listLock)

/*
 * Declarations for routines used only in this file.
 */

static void       QueueEvent(ThreadSpecificData *tsdPtr,
                      Tcl_Event* evPtr, Tcl_QueuePosition position);

/*
 *----------------------------------------------------------------------
 *
 * TclInitNotifier --
 *
 *    Initialize the thread local data structures for the notifier
 *    subsystem.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Adds the current thread to the global list of notifiers.
 *
 *----------------------------------------------------------------------
 */

void
TclInitNotifier(void)
{
    ThreadSpecificData *tsdPtr;
    Tcl_ThreadId threadId = Tcl_GetCurrentThread();

    Tcl_MutexLock(&listLock);
    for (tsdPtr = firstNotifierPtr; tsdPtr && tsdPtr->threadId != threadId;
          tsdPtr = tsdPtr->nextPtr) {
      /* Empty loop body. */
    }

    if (NULL == tsdPtr) {
      /*
       * Notifier not yet initialized in this thread.
       */

      tsdPtr = TCL_TSD_INIT(&dataKey);
      tsdPtr->threadId = threadId;
      tsdPtr->clientData = tclStubs.tcl_InitNotifier();
      tsdPtr->initialized = 1;
      tsdPtr->nextPtr = firstNotifierPtr;
      firstNotifierPtr = tsdPtr;
    }
    Tcl_MutexUnlock(&listLock);
}

/*
 *----------------------------------------------------------------------
 *
 * TclFinalizeNotifier --
 *
 *    Finalize the thread local data structures for the notifier subsystem.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Removes the notifier associated with the current thread from the
 *    global notifier list. This is done only if the notifier was
 *    initialized for this thread by call to TclInitNotifier(). This is
 *    always true for threads which have been seeded with an Tcl
 *    interpreter, since the call to Tcl_CreateInterp will, among other
 *    things, call TclInitializeSubsystems() and this one will, in turn,
 *    call the TclInitNotifier() for the thread. For threads created without
 *    the Tcl interpreter, though, nobody is explicitly nor implicitly
 *    calling the TclInitNotifier hence, TclFinalizeNotifier should not be
 *    performed at all.
 *
 *----------------------------------------------------------------------
 */

void
TclFinalizeNotifier(void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    ThreadSpecificData **prevPtrPtr;
    Tcl_Event *evPtr, *hold;

    if (!tsdPtr->initialized) {
      return;           /* Notifier not initialized for the current thread */
    }

    Tcl_MutexLock(&(tsdPtr->queueMutex));
    for (evPtr = tsdPtr->firstEventPtr; evPtr != NULL; ) {
      hold = evPtr;
      evPtr = evPtr->nextPtr;
      ckfree((char *) hold);
    }
    tsdPtr->firstEventPtr = NULL;
    tsdPtr->lastEventPtr = NULL;
    Tcl_MutexUnlock(&(tsdPtr->queueMutex));

    Tcl_MutexLock(&listLock);

    if (tclStubs.tcl_FinalizeNotifier) {
      tclStubs.tcl_FinalizeNotifier(tsdPtr->clientData);
    }
    Tcl_MutexFinalize(&(tsdPtr->queueMutex));
    for (prevPtrPtr = &firstNotifierPtr; *prevPtrPtr != NULL;
          prevPtrPtr = &((*prevPtrPtr)->nextPtr)) {
      if (*prevPtrPtr == tsdPtr) {
          *prevPtrPtr = tsdPtr->nextPtr;
          break;
      }
    }
    tsdPtr->initialized = 0;

    Tcl_MutexUnlock(&listLock);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetNotifier --
 *
 *    Install a set of alternate functions for use with the notifier. In
 *    particular, this can be used to install the Xt-based notifier for use
 *    with the Browser plugin.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Overstomps part of the stub vector. This relies on hooks added to the
 *    default functions in case those are called directly (i.e., not through
 *    the stub table.)
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetNotifier(
    Tcl_NotifierProcs *notifierProcPtr)
{
#if !defined(__WIN32__) /* UNIX */
    tclStubs.tcl_CreateFileHandler = notifierProcPtr->createFileHandlerProc;
    tclStubs.tcl_DeleteFileHandler = notifierProcPtr->deleteFileHandlerProc;
#endif
    tclStubs.tcl_SetTimer = notifierProcPtr->setTimerProc;
    tclStubs.tcl_WaitForEvent = notifierProcPtr->waitForEventProc;
    tclStubs.tcl_InitNotifier = notifierProcPtr->initNotifierProc;
    tclStubs.tcl_FinalizeNotifier = notifierProcPtr->finalizeNotifierProc;
    tclStubs.tcl_AlertNotifier = notifierProcPtr->alertNotifierProc;
    tclStubs.tcl_ServiceModeHook = notifierProcPtr->serviceModeHookProc;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateEventSource --
 *
 *    This function is invoked to create a new source of events. The source
 *    is identified by a function that gets invoked during Tcl_DoOneEvent to
 *    check for events on that source and queue them.
 *
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    SetupProc and checkProc will be invoked each time that Tcl_DoOneEvent
 *    runs out of things to do. SetupProc will be invoked before
 *    Tcl_DoOneEvent calls select or whatever else it uses to wait for
 *    events. SetupProc typically calls functions like Tcl_SetMaxBlockTime
 *    to indicate what to wait for.
 *
 *    CheckProc is called after select or whatever operation was actually
 *    used to wait. It figures out whether anything interesting actually
 *    happened (e.g. by calling Tcl_AsyncReady), and then calls
 *    Tcl_QueueEvent to queue any events that are ready.
 *
 *    Each of these functions is passed two arguments, e.g.
 *          (*checkProc)(ClientData clientData, int flags));
 *    ClientData is the same as the clientData argument here, and flags is a
 *    combination of things like TCL_FILE_EVENTS that indicates what events
 *    are of interest: setupProc and checkProc use flags to figure out
 *    whether their events are relevant or not.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateEventSource(
    Tcl_EventSetupProc *setupProc,
                        /* Function to invoke to figure out what to
                         * wait for. */
    Tcl_EventCheckProc *checkProc,
                        /* Function to call after waiting to see what
                         * happened. */
    ClientData clientData)    /* One-word argument to pass to setupProc and
                         * checkProc. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    EventSource *sourcePtr = (EventSource *) ckalloc(sizeof(EventSource));

    sourcePtr->setupProc = setupProc;
    sourcePtr->checkProc = checkProc;
    sourcePtr->clientData = clientData;
    sourcePtr->nextPtr = tsdPtr->firstEventSourcePtr;
    tsdPtr->firstEventSourcePtr = sourcePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteEventSource --
 *
 *    This function is invoked to delete the source of events given by proc
 *    and clientData.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The given event source is cancelled, so its function will never again
 *    be called. If no such source exists, nothing happens.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteEventSource(
    Tcl_EventSetupProc *setupProc,
                        /* Function to invoke to figure out what to
                         * wait for. */
    Tcl_EventCheckProc *checkProc,
                        /* Function to call after waiting to see what
                         * happened. */
    ClientData clientData)    /* One-word argument to pass to setupProc and
                         * checkProc. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    EventSource *sourcePtr, *prevPtr;

    for (sourcePtr = tsdPtr->firstEventSourcePtr, prevPtr = NULL;
          sourcePtr != NULL;
          prevPtr = sourcePtr, sourcePtr = sourcePtr->nextPtr) {
      if ((sourcePtr->setupProc != setupProc)
            || (sourcePtr->checkProc != checkProc)
            || (sourcePtr->clientData != clientData)) {
          continue;
      }
      if (prevPtr == NULL) {
          tsdPtr->firstEventSourcePtr = sourcePtr->nextPtr;
      } else {
          prevPtr->nextPtr = sourcePtr->nextPtr;
      }
      ckfree((char *) sourcePtr);
      return;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_QueueEvent --
 *
 *    Queue an event on the event queue associated with the current thread.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_QueueEvent(
    Tcl_Event* evPtr,         /* Event to add to queue. The storage space
                         * must have been allocated the caller with
                         * malloc (ckalloc), and it becomes the
                         * property of the event queue. It will be
                         * freed after the event has been handled. */
    Tcl_QueuePosition position)     /* One of TCL_QUEUE_TAIL, TCL_QUEUE_HEAD,
                         * TCL_QUEUE_MARK. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    QueueEvent(tsdPtr, evPtr, position);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ThreadQueueEvent --
 *
 *    Queue an event on the specified thread's event queue.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ThreadQueueEvent(
    Tcl_ThreadId threadId,    /* Identifier for thread to use. */
    Tcl_Event *evPtr,         /* Event to add to queue. The storage space
                         * must have been allocated the caller with
                         * malloc (ckalloc), and it becomes the
                         * property of the event queue. It will be
                         * freed after the event has been handled. */
    Tcl_QueuePosition position)     /* One of TCL_QUEUE_TAIL, TCL_QUEUE_HEAD,
                         * TCL_QUEUE_MARK. */
{
    ThreadSpecificData *tsdPtr;

    /*
     * Find the notifier associated with the specified thread.
     */

    Tcl_MutexLock(&listLock);
    for (tsdPtr = firstNotifierPtr; tsdPtr && tsdPtr->threadId != threadId;
          tsdPtr = tsdPtr->nextPtr) {
      /* Empty loop body. */
    }

    /*
     * Queue the event if there was a notifier associated with the thread.
     */

    if (tsdPtr) {
      QueueEvent(tsdPtr, evPtr, position);
    }
    Tcl_MutexUnlock(&listLock);
}

/*
 *----------------------------------------------------------------------
 *
 * QueueEvent --
 *
 *    Insert an event into the specified thread's event queue at one of
 *    three positions: the head, the tail, or before a floating marker.
 *    Events inserted before the marker will be processed in first-in-
 *    first-out order, but before any events inserted at the tail of the
 *    queue. Events inserted at the head of the queue will be processed in
 *    last-in-first-out order.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static void
QueueEvent(
    ThreadSpecificData *tsdPtr,     /* Handle to thread local data that indicates
                         * which event queue to use. */
    Tcl_Event *evPtr,         /* Event to add to queue.  The storage space
                         * must have been allocated the caller with
                         * malloc (ckalloc), and it becomes the
                         * property of the event queue. It will be
                         * freed after the event has been handled. */
    Tcl_QueuePosition position)     /* One of TCL_QUEUE_TAIL, TCL_QUEUE_HEAD,
                         * TCL_QUEUE_MARK. */
{
    Tcl_MutexLock(&(tsdPtr->queueMutex));
    if (position == TCL_QUEUE_TAIL) {
      /*
       * Append the event on the end of the queue.
       */

      evPtr->nextPtr = NULL;
      if (tsdPtr->firstEventPtr == NULL) {
          tsdPtr->firstEventPtr = evPtr;
      } else {
          tsdPtr->lastEventPtr->nextPtr = evPtr;
      }
      tsdPtr->lastEventPtr = evPtr;
    } else if (position == TCL_QUEUE_HEAD) {
      /*
       * Push the event on the head of the queue.
       */

      evPtr->nextPtr = tsdPtr->firstEventPtr;
      if (tsdPtr->firstEventPtr == NULL) {
          tsdPtr->lastEventPtr = evPtr;
      }
      tsdPtr->firstEventPtr = evPtr;
    } else if (position == TCL_QUEUE_MARK) {
      /*
       * Insert the event after the current marker event and advance the
       * marker to the new event.
       */

      if (tsdPtr->markerEventPtr == NULL) {
          evPtr->nextPtr = tsdPtr->firstEventPtr;
          tsdPtr->firstEventPtr = evPtr;
      } else {
          evPtr->nextPtr = tsdPtr->markerEventPtr->nextPtr;
          tsdPtr->markerEventPtr->nextPtr = evPtr;
      }
      tsdPtr->markerEventPtr = evPtr;
      if (evPtr->nextPtr == NULL) {
          tsdPtr->lastEventPtr = evPtr;
      }
    }
    Tcl_MutexUnlock(&(tsdPtr->queueMutex));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteEvents --
 *
 *    Calls a function for each event in the queue and deletes those for
 *    which the function returns 1. Events for which the function returns 0
 *    are left in the queue. Operates on the queue associated with the
 *    current thread.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Potentially removes one or more events from the event queue.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteEvents(
    Tcl_EventDeleteProc *proc,      /* The function to call. */
    ClientData clientData)          /* The type-specific data. */
{
    Tcl_Event *evPtr;         /* Pointer to the event being examined */
    Tcl_Event *prevPtr;       /* Pointer to evPtr's predecessor, or NULL if
                         * evPtr designates the first event in the
                         * queue for the thread. */
    Tcl_Event* hold;

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    Tcl_MutexLock(&(tsdPtr->queueMutex));

    /*
     * Walk the queue of events for the thread, applying 'proc' to each to
     * decide whether to eliminate the event.
     */

    prevPtr = NULL;
    evPtr = tsdPtr->firstEventPtr;
    while (evPtr != NULL) {
      if ((*proc)(evPtr, clientData) == 1) {
          /*
           * This event should be deleted. Unlink it.
           */

          if (prevPtr == NULL) {
            tsdPtr->firstEventPtr = evPtr->nextPtr;
          } else {
            prevPtr->nextPtr = evPtr->nextPtr;
          }

          /*
           * Update 'last' and 'marker' events if either has been deleted.
           */

          if (evPtr->nextPtr == NULL) {
            tsdPtr->lastEventPtr = prevPtr;
          }
          if (tsdPtr->markerEventPtr == evPtr) {
            tsdPtr->markerEventPtr = prevPtr;
          }

          /*
           * Delete the event data structure.
           */

          hold = evPtr;
          evPtr = evPtr->nextPtr;
          ckfree((char *) hold);
      } else {
          /*
           * Event is to be retained.
           */

          prevPtr = evPtr;
          evPtr = evPtr->nextPtr;
      }
    }
    Tcl_MutexUnlock(&(tsdPtr->queueMutex));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ServiceEvent --
 *
 *    Process one event from the event queue, or invoke an asynchronous
 *    event handler. Operates on event queue for current thread.
 *
 * Results:
 *    The return value is 1 if the function actually found an event to
 *    process. If no processing occurred, then 0 is returned.
 *
 * Side effects:
 *    Invokes all of the event handlers for the highest priority event in
 *    the event queue. May collapse some events into a single event or
 *    discard stale events.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ServiceEvent(
    int flags)                /* Indicates what events should be processed.
                         * May be any combination of TCL_WINDOW_EVENTS
                         * TCL_FILE_EVENTS, TCL_TIMER_EVENTS, or other
                         * flags defined elsewhere. Events not
                         * matching this will be skipped for
                         * processing later. */
{
    Tcl_Event *evPtr, *prevPtr;
    Tcl_EventProc *proc;
    int result;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * Asynchronous event handlers are considered to be the highest priority
     * events, and so must be invoked before we process events on the event
     * queue.
     */

    if (Tcl_AsyncReady()) {
      (void) Tcl_AsyncInvoke(NULL, 0);
      return 1;
    }

    /*
     * No event flags is equivalent to TCL_ALL_EVENTS.
     */

    if ((flags & TCL_ALL_EVENTS) == 0) {
      flags |= TCL_ALL_EVENTS;
    }

    /*
     * Loop through all the events in the queue until we find one that can
     * actually be handled.
     */

    Tcl_MutexLock(&(tsdPtr->queueMutex));
    for (evPtr = tsdPtr->firstEventPtr; evPtr != NULL;
          evPtr = evPtr->nextPtr) {
      /*
       * Call the handler for the event. If it actually handles the event
       * then free the storage for the event. There are two tricky things
       * here, both stemming from the fact that the event code may be
       * re-entered while servicing the event:
       *
       * 1. Set the "proc" field to NULL.  This is a signal to ourselves
       *    that we shouldn't reexecute the handler if the event loop is
       *    re-entered.
       * 2. When freeing the event, must search the queue again from the
       *    front to find it. This is because the event queue could change
       *    almost arbitrarily while handling the event, so we can't depend
       *    on pointers found now still being valid when the handler
       *    returns.
       */

      proc = evPtr->proc;
      if (proc == NULL) {
          continue;
      }
      evPtr->proc = NULL;

      /*
       * Release the lock before calling the event function. This allows
       * other threads to post events if we enter a recursive event loop in
       * this thread. Note that we are making the assumption that if the
       * proc returns 0, the event is still in the list.
       */

      Tcl_MutexUnlock(&(tsdPtr->queueMutex));
      result = (*proc)(evPtr, flags);
      Tcl_MutexLock(&(tsdPtr->queueMutex));

      if (result) {
          /*
           * The event was processed, so remove it from the queue.
           */

          if (tsdPtr->firstEventPtr == evPtr) {
            tsdPtr->firstEventPtr = evPtr->nextPtr;
            if (evPtr->nextPtr == NULL) {
                tsdPtr->lastEventPtr = NULL;
            }
            if (tsdPtr->markerEventPtr == evPtr) {
                tsdPtr->markerEventPtr = NULL;
            }
          } else {
            for (prevPtr = tsdPtr->firstEventPtr;
                  prevPtr && prevPtr->nextPtr != evPtr;
                  prevPtr = prevPtr->nextPtr) {
                /* Empty loop body. */
            }
            if (prevPtr) {
                prevPtr->nextPtr = evPtr->nextPtr;
                if (evPtr->nextPtr == NULL) {
                  tsdPtr->lastEventPtr = prevPtr;
                }
                if (tsdPtr->markerEventPtr == evPtr) {
                  tsdPtr->markerEventPtr = prevPtr;
                }
            } else {
                evPtr = NULL;
            }
          }
          if (evPtr) {
            ckfree((char *) evPtr);
          }
          Tcl_MutexUnlock(&(tsdPtr->queueMutex));
          return 1;
      } else {
          /*
           * The event wasn't actually handled, so we have to restore the
           * proc field to allow the event to be attempted again.
           */

          evPtr->proc = proc;
      }
    }
    Tcl_MutexUnlock(&(tsdPtr->queueMutex));
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetServiceMode --
 *
 *    This routine returns the current service mode of the notifier.
 *
 * Results:
 *    Returns either TCL_SERVICE_ALL or TCL_SERVICE_NONE.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetServiceMode(void)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    return tsdPtr->serviceMode;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetServiceMode --
 *
 *    This routine sets the current service mode of the tsdPtr->
 *
 * Results:
 *    Returns the previous service mode.
 *
 * Side effects:
 *    Invokes the notifier service mode hook function.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_SetServiceMode(
    int mode)                 /* New service mode: TCL_SERVICE_ALL or
                         * TCL_SERVICE_NONE */
{
    int oldMode;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    oldMode = tsdPtr->serviceMode;
    tsdPtr->serviceMode = mode;
    if (tclStubs.tcl_ServiceModeHook) {
      tclStubs.tcl_ServiceModeHook(mode);
    }
    return oldMode;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetMaxBlockTime --
 *
 *    This function is invoked by event sources to tell the notifier how
 *    long it may block the next time it blocks. The timePtr argument gives
 *    a maximum time; the actual time may be less if some other event source
 *    requested a smaller time.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    May reduce the length of the next sleep in the tsdPtr->
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetMaxBlockTime(
    Tcl_Time *timePtr)        /* Specifies a maximum elapsed time for the
                         * next blocking operation in the event
                         * tsdPtr-> */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!tsdPtr->blockTimeSet || (timePtr->sec < tsdPtr->blockTime.sec)
          || ((timePtr->sec == tsdPtr->blockTime.sec)
          && (timePtr->usec < tsdPtr->blockTime.usec))) {
      tsdPtr->blockTime = *timePtr;
      tsdPtr->blockTimeSet = 1;
    }

    /*
     * If we are called outside an event source traversal, set the timeout
     * immediately.
     */

    if (!tsdPtr->inTraversal) {
      if (tsdPtr->blockTimeSet) {
          Tcl_SetTimer(&tsdPtr->blockTime);
      } else {
          Tcl_SetTimer(NULL);
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DoOneEvent --
 *
 *    Process a single event of some sort. If there's no work to do, wait
 *    for an event to occur, then process it.
 *
 * Results:
 *    The return value is 1 if the function actually found an event to
 *    process. If no processing occurred, then 0 is returned (this can
 *    happen if the TCL_DONT_WAIT flag is set or if there are no event
 *    handlers to wait for in the set specified by flags).
 *
 * Side effects:
 *    May delay execution of process while waiting for an event, unless
 *    TCL_DONT_WAIT is set in the flags argument. Event sources are invoked
 *    to check for and queue events. Event handlers may produce arbitrary
 *    side effects.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DoOneEvent(
    int flags)                /* Miscellaneous flag values: may be any
                         * combination of TCL_DONT_WAIT,
                         * TCL_WINDOW_EVENTS, TCL_FILE_EVENTS,
                         * TCL_TIMER_EVENTS, TCL_IDLE_EVENTS, or
                         * others defined by event sources. */
{
    int result = 0, oldMode;
    EventSource *sourcePtr;
    Tcl_Time *timePtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * The first thing we do is to service any asynchronous event handlers.
     */

    if (Tcl_AsyncReady()) {
      (void) Tcl_AsyncInvoke(NULL, 0);
      return 1;
    }

    /*
     * No event flags is equivalent to TCL_ALL_EVENTS.
     */

    if ((flags & TCL_ALL_EVENTS) == 0) {
      flags |= TCL_ALL_EVENTS;
    }

    /*
     * Set the service mode to none so notifier event routines won't try to
     * service events recursively.
     */

    oldMode = tsdPtr->serviceMode;
    tsdPtr->serviceMode = TCL_SERVICE_NONE;

    /*
     * The core of this function is an infinite loop, even though we only
     * service one event. The reason for this is that we may be processing
     * events that don't do anything inside of Tcl.
     */

    while (1) {
      /*
       * If idle events are the only things to service, skip the main part
       * of the loop and go directly to handle idle events (i.e. don't wait
       * even if TCL_DONT_WAIT isn't set).
       */

      if ((flags & TCL_ALL_EVENTS) == TCL_IDLE_EVENTS) {
          flags = TCL_IDLE_EVENTS | TCL_DONT_WAIT;
          goto idleEvents;
      }

      /*
       * Ask Tcl to service a queued event, if there are any.
       */

      if (Tcl_ServiceEvent(flags)) {
          result = 1;
          break;
      }

      /*
       * If TCL_DONT_WAIT is set, be sure to poll rather than blocking,
       * otherwise reset the block time to infinity.
       */

      if (flags & TCL_DONT_WAIT) {
          tsdPtr->blockTime.sec = 0;
          tsdPtr->blockTime.usec = 0;
          tsdPtr->blockTimeSet = 1;
      } else {
          tsdPtr->blockTimeSet = 0;
      }

      /*
       * Set up all the event sources for new events. This will cause the
       * block time to be updated if necessary.
       */

      tsdPtr->inTraversal = 1;
      for (sourcePtr = tsdPtr->firstEventSourcePtr; sourcePtr != NULL;
            sourcePtr = sourcePtr->nextPtr) {
          if (sourcePtr->setupProc) {
            (sourcePtr->setupProc)(sourcePtr->clientData, flags);
          }
      }
      tsdPtr->inTraversal = 0;

      if ((flags & TCL_DONT_WAIT) || tsdPtr->blockTimeSet) {
          timePtr = &tsdPtr->blockTime;
      } else {
          timePtr = NULL;
      }

      /*
       * Wait for a new event or a timeout. If Tcl_WaitForEvent returns -1,
       * we should abort Tcl_DoOneEvent.
       */

      result = Tcl_WaitForEvent(timePtr);
      if (result < 0) {
          result = 0;
          break;
      }

      /*
       * Check all the event sources for new events.
       */

      for (sourcePtr = tsdPtr->firstEventSourcePtr; sourcePtr != NULL;
            sourcePtr = sourcePtr->nextPtr) {
          if (sourcePtr->checkProc) {
            (sourcePtr->checkProc)(sourcePtr->clientData, flags);
          }
      }

      /*
       * Check for events queued by the notifier or event sources.
       */

      if (Tcl_ServiceEvent(flags)) {
          result = 1;
          break;
      }

      /*
       * We've tried everything at this point, but nobody we know about had
       * anything to do. Check for idle events. If none, either quit or go
       * back to the top and try again.
       */

    idleEvents:
      if (flags & TCL_IDLE_EVENTS) {
          if (TclServiceIdle()) {
            result = 1;
            break;
          }
      }
      if (flags & TCL_DONT_WAIT) {
          break;
      }

      /*
       * If Tcl_WaitForEvent has returned 1, indicating that one system
       * event has been dispatched (and thus that some Tcl code might have
       * been indirectly executed), we break out of the loop. We do this to
       * give VwaitCmd for instance a chance to check if that system event
       * had the side effect of changing the variable (so the vwait can
       * return and unwind properly).
       *
       * NB: We will process idle events if any first, because otherwise we
       *     might never do the idle events if the notifier always gets
       *     system events.
       */

      if (result) {
          break;
      }
    }

    tsdPtr->serviceMode = oldMode;
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ServiceAll --
 *
 *    This routine checks all of the event sources, processes events that
 *    are on the Tcl event queue, and then calls the any idle handlers.
 *    Platform specific notifier callbacks that generate events should call
 *    this routine before returning to the system in order to ensure that
 *    Tcl gets a chance to process the new events.
 *
 * Results:
 *    Returns 1 if an event or idle handler was invoked, else 0.
 *
 * Side effects:
 *    Anything that an event or idle handler may do.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ServiceAll(void)
{
    int result = 0;
    EventSource *sourcePtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tsdPtr->serviceMode == TCL_SERVICE_NONE) {
      return result;
    }

    /*
     * We need to turn off event servicing like we to in Tcl_DoOneEvent, to
     * avoid recursive calls.
     */

    tsdPtr->serviceMode = TCL_SERVICE_NONE;

    /*
     * Check async handlers first.
     */

    if (Tcl_AsyncReady()) {
      (void) Tcl_AsyncInvoke(NULL, 0);
    }

    /*
     * Make a single pass through all event sources, queued events, and idle
     * handlers. Note that we wait to update the notifier timer until the end
     * so we can avoid multiple changes.
     */

    tsdPtr->inTraversal = 1;
    tsdPtr->blockTimeSet = 0;

    for (sourcePtr = tsdPtr->firstEventSourcePtr; sourcePtr != NULL;
          sourcePtr = sourcePtr->nextPtr) {
      if (sourcePtr->setupProc) {
          (sourcePtr->setupProc)(sourcePtr->clientData, TCL_ALL_EVENTS);
      }
    }
    for (sourcePtr = tsdPtr->firstEventSourcePtr; sourcePtr != NULL;
          sourcePtr = sourcePtr->nextPtr) {
      if (sourcePtr->checkProc) {
          (sourcePtr->checkProc)(sourcePtr->clientData, TCL_ALL_EVENTS);
      }
    }

    while (Tcl_ServiceEvent(0)) {
      result = 1;
    }
    if (TclServiceIdle()) {
      result = 1;
    }

    if (!tsdPtr->blockTimeSet) {
      Tcl_SetTimer(NULL);
    } else {
      Tcl_SetTimer(&tsdPtr->blockTime);
    }
    tsdPtr->inTraversal = 0;
    tsdPtr->serviceMode = TCL_SERVICE_ALL;
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ThreadAlert --
 *
 *    This function wakes up the notifier associated with the specified
 *    thread (if there is one).
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ThreadAlert(
    Tcl_ThreadId threadId)    /* Identifier for thread to use. */
{
    ThreadSpecificData *tsdPtr;

    /*
     * Find the notifier associated with the specified thread. Note that we
     * need to hold the listLock while calling Tcl_AlertNotifier to avoid a
     * race condition where the specified thread might destroy its notifier.
     */

    Tcl_MutexLock(&listLock);
    for (tsdPtr = firstNotifierPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
      if (tsdPtr->threadId == threadId) {
          if (tclStubs.tcl_AlertNotifier) {
            tclStubs.tcl_AlertNotifier(tsdPtr->clientData);
          }
          break;
      }
    }
    Tcl_MutexUnlock(&listLock);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */

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