/*

 * tclMacOSXNotify.c --

 *

 *	This file contains the implementation of a merged CFRunLoop/select()

 *	based 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.

 * Copyright 2001, Apple Computer, Inc.

 * Copyright (c) 2005-2007 Daniel A. Steffen <das@users.sourceforge.net>

 *

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

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

 *

 * RCS: @(#) $Id: tclMacOSXNotify.c,v 1.1.2.12 2007/04/29 02:21:33 das Exp $

 */

#include "tclInt.h"

#include "tclPort.h"

#ifdef HAVE_COREFOUNDATION	/* Traditional unix select-based notifier is

				 * in tclUnixNotfy.c */

#include <CoreFoundation/CoreFoundation.h>

#include <pthread.h>

extern TclStubs tclStubs;

extern Tcl_NotifierProcs tclOriginalNotifier;

/*

 * 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;		/* 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.

 */

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). */

    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

				 * notifierLock before accessing these

				 * fields. */

    CFRunLoopSourceRef runLoopSource;

				/* Any other thread alerts a notifier that an

				 * event is ready to be processed by signaling

				 * this CFRunLoopSource. */

    CFRunLoopRef runLoop;	/* This thread's CFRunLoop, needs to be woken

				 * up whenever the runLoopSource is

				 * signaled. */

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

				 * processed. */

} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*

 * The following static indicates the number of threads that have initialized

 * notifiers.

 *

 * You must hold the notifierInitLock before accessing this variable.

 */

static int notifierCount = 0;

/*

 * 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 notifierLock 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 notifierLock lock before writing to the pipe.

 */

static int triggerPipe = -1;

static int receivePipe = -1; /* Output end of triggerPipe */

/*

 * We use the Darwin-native spinlock API rather than pthread mutexes for

 * notifier locking: this radically simplifies the implementation and lowers

 * overhead. Note that these are not pure spinlocks, they employ various

 * strategies to back off and relinquish the processor, making them immune to

 * most priority-inversion livelocks (c.f. 'man 3 OSSpinLockLock' and Darwin

 * sources: xnu/osfmk/{ppc,i386}/commpage/spinlocks.s).

 */

#if defined(HAVE_LIBKERN_OSATOMIC_H) && defined(HAVE_OSSPINLOCKLOCK)

/*

 * Use OSSpinLock API where available (Tiger or later).

 */

#include <libkern/OSAtomic.h>

#if defined(HAVE_WEAK_IMPORT) && MAC_OS_X_VERSION_MIN_REQUIRED < 1040

/*

 * Support for weakly importing spinlock API.

 */

#define WEAK_IMPORT_SPINLOCKLOCK

#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050

#define VOLATILE volatile

#else

#define VOLATILE

#endif

#ifndef bool

#define bool int

#endif

extern void OSSpinLockLock(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

extern void OSSpinLockUnlock(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

extern bool OSSpinLockTry(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

extern void _spin_lock(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

extern void _spin_unlock(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

extern bool _spin_lock_try(VOLATILE OSSpinLock *lock) WEAK_IMPORT_ATTRIBUTE;

static void (* lockLock)(VOLATILE OSSpinLock *lock) = NULL;

static void (* lockUnlock)(VOLATILE OSSpinLock *lock) = NULL;

static bool (* lockTry)(VOLATILE OSSpinLock *lock) = NULL;

#undef VOLATILE

static pthread_once_t spinLockLockInitControl = PTHREAD_ONCE_INIT;

static void SpinLockLockInit(void) {

    lockLock   = OSSpinLockLock   != NULL ? OSSpinLockLock   : _spin_lock;

    lockUnlock = OSSpinLockUnlock != NULL ? OSSpinLockUnlock : _spin_unlock;

    lockTry    = OSSpinLockTry    != NULL ? OSSpinLockTry    : _spin_lock_try;

    if (lockLock == NULL || lockUnlock == NULL) {

	Tcl_Panic("SpinLockLockInit: no spinlock API available");

    }

}

#define SpinLockLock(p) 	lockLock(p)

#define SpinLockUnlock(p)	lockUnlock(p)

#define SpinLockTry(p)  	lockTry(p)

#else

#define SpinLockLock(p) 	OSSpinLockLock(p)

#define SpinLockUnlock(p)	OSSpinLockUnlock(p)

#define SpinLockTry(p)  	OSSpinLockTry(p)

#endif /* HAVE_WEAK_IMPORT */

#define SPINLOCK_INIT   	OS_SPINLOCK_INIT

#else

/*

 * Otherwise, use commpage spinlock SPI directly.

 */

typedef uint32_t OSSpinLock;

extern void _spin_lock(OSSpinLock *lock);

extern void _spin_unlock(OSSpinLock *lock);

extern int  _spin_lock_try(OSSpinLock *lock);

#define SpinLockLock(p) 	_spin_lock(p)

#define SpinLockUnlock(p)	_spin_unlock(p)

#define SpinLockTry(p)  	_spin_lock_try(p)

#define SPINLOCK_INIT   	0

#endif /* HAVE_LIBKERN_OSATOMIC_H && HAVE_OSSPINLOCKLOCK */

/*

 * These spinlocks lock access to the global notifier state.

 */

static OSSpinLock notifierInitLock = SPINLOCK_INIT;

static OSSpinLock notifierLock     = SPINLOCK_INIT;

/*

 * Macros abstracting notifier locking/unlocking

 */

#define LOCK_NOTIFIER_INIT	SpinLockLock(&notifierInitLock)

#define UNLOCK_NOTIFIER_INIT	SpinLockUnlock(&notifierInitLock)

#define LOCK_NOTIFIER		SpinLockLock(&notifierLock)

#define UNLOCK_NOTIFIER		SpinLockUnlock(&notifierLock)

/*

 * 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 pthread_t notifierThread;

/*

 * Custom run loop mode containing only the run loop source for the

 * notifier thread.

 */

#ifndef TCL_EVENTS_ONLY_RUN_LOOP_MODE

#define TCL_EVENTS_ONLY_RUN_LOOP_MODE "com.tcltk.tclEventsOnlyRunLoopMode"

#endif

#ifdef __CONSTANT_CFSTRINGS__

#define tclEventsOnlyRunLoopMode CFSTR(TCL_EVENTS_ONLY_RUN_LOOP_MODE)

#else

static CFStringRef tclEventsOnlyRunLoopMode = NULL;

#endif

/*

 * Static routines defined in this file.

 */

static void	NotifierThreadProc(ClientData clientData)

	__attribute__ ((__noreturn__));

static int	FileHandlerEventProc(Tcl_Event *evPtr, int flags);

#ifdef HAVE_PTHREAD_ATFORK

static int	atForkInit = 0;

static void	AtForkPrepare(void);

static void	AtForkParent(void);

static void	AtForkChild(void);

#if defined(HAVE_WEAK_IMPORT) && MAC_OS_X_VERSION_MIN_REQUIRED < 1040

/* Support for weakly importing pthread_atfork. */

#define WEAK_IMPORT_PTHREAD_ATFORK

extern int pthread_atfork(void (*prepare)(void), void (*parent)(void),

                          void (*child)(void)) WEAK_IMPORT_ATTRIBUTE;

#endif /* HAVE_WEAK_IMPORT */

#endif /* HAVE_PTHREAD_ATFORK */

/*

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

 *

 * Tcl_InitNotifier --

 *

 *	Initializes the platform specific notifier state.

 *

 * Results:

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

 *

 * Side effects:

 *	None.

 *

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

 */

ClientData

Tcl_InitNotifier(void)

{

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    tsdPtr->eventReady = 0;

#ifdef WEAK_IMPORT_SPINLOCKLOCK

    /*

     * Initialize support for weakly imported spinlock API.

     */

    if (pthread_once(&spinLockLockInitControl, SpinLockLockInit)) {

	Tcl_Panic("Tcl_InitNotifier: pthread_once failed");

    }

#endif

#ifndef __CONSTANT_CFSTRINGS__

    if (!tclEventsOnlyRunLoopMode) {

	tclEventsOnlyRunLoopMode = CFSTR(TCL_EVENTS_ONLY_RUN_LOOP_MODE);

    }

#endif

    /*

     * Initialize CFRunLoopSource and add it to CFRunLoop of this thread.

     */

    if (!tsdPtr->runLoop) {

	CFRunLoopRef runLoop = CFRunLoopGetCurrent();

	CFRunLoopSourceRef runLoopSource;

	CFRunLoopSourceContext runLoopSourceContext;

	bzero(&runLoopSourceContext, sizeof(CFRunLoopSourceContext));

	runLoopSourceContext.info = tsdPtr;

	runLoopSource = CFRunLoopSourceCreate(NULL, 0, &runLoopSourceContext);

	if (!runLoopSource) {

	    Tcl_Panic("Tcl_InitNotifier: could not create CFRunLoopSource");

	}

	CFRunLoopAddSource(runLoop, runLoopSource, kCFRunLoopCommonModes);

	CFRunLoopAddSource(runLoop, runLoopSource, tclEventsOnlyRunLoopMode);

	tsdPtr->runLoopSource = runLoopSource;

	tsdPtr->runLoop = runLoop;

    }

    LOCK_NOTIFIER_INIT;

#ifdef HAVE_PTHREAD_ATFORK

    /*

     * Install pthread_atfork handlers to reinitialize the notifier in the

     * child of a fork.

     */

    if (

#ifdef WEAK_IMPORT_PTHREAD_ATFORK

	    pthread_atfork != NULL &&

#endif

	    !atForkInit) {

	int result = pthread_atfork(AtForkPrepare, AtForkParent, AtForkChild);

	if (result) {

	    Tcl_Panic("Tcl_InitNotifier: pthread_atfork failed");

	}

	atForkInit = 1;

    }

#endif

    if (notifierCount == 0) {

	int fds[2], status;

	/*

	 * Initialize trigger pipe.

	 */

	if (pipe(fds) != 0) {

	    Tcl_Panic("Tcl_InitNotifier: could not create trigger pipe");

	}

	status = fcntl(fds[0], F_GETFL);

	status |= O_NONBLOCK;

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

	    Tcl_Panic("Tcl_InitNotifier: could not make receive pipe non blocking");

	}

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

	status |= O_NONBLOCK;

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

	    Tcl_Panic("Tcl_InitNotifier: could not make trigger pipe non blocking");

	}

	receivePipe = fds[0];

	triggerPipe = fds[1];

	/*

	 * Create notifier thread lazily in Tcl_WaitForEvent() to avoid

	 * interfering with fork() followed immediately by execve()

	 * (cannot execve() when more than one thread is present).

	 */

	notifierThread = 0;

    }

    notifierCount++;

    UNLOCK_NOTIFIER_INIT;

    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.

 *

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

 */

void

Tcl_FinalizeNotifier(

    ClientData clientData)		/* Not used. */

{

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    LOCK_NOTIFIER_INIT;

    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) {

	    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]

	 */

	write(triggerPipe, "q", 1);

	close(triggerPipe);

	if (notifierThread) {

	    result = pthread_join(notifierThread, NULL);

	    if (result) {

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

	    }

	    notifierThread = 0;

	}

	close(receivePipe);

	triggerPipe = -1;

    }

    UNLOCK_NOTIFIER_INIT;

    LOCK_NOTIFIER;		/* for concurrency with Tcl_AlertNotifier */

    if (tsdPtr->runLoop) {

	tsdPtr->runLoop = NULL;

	/*

	 * Remove runLoopSource from all CFRunLoops and release it.

	 */

	CFRunLoopSourceInvalidate(tsdPtr->runLoopSource);

	CFRelease(tsdPtr->runLoopSource);

	tsdPtr->runLoopSource = NULL;

    }

    UNLOCK_NOTIFIER;

}

/*

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

 *

 * 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.

 *

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

 */

void

Tcl_AlertNotifier(

    ClientData clientData)

{

    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) clientData;

    LOCK_NOTIFIER;

    if (tsdPtr->runLoop) {

	tsdPtr->eventReady = 1;

	CFRunLoopSourceSignal(tsdPtr->runLoopSource);

	CFRunLoopWakeUp(tsdPtr->runLoop);

    }

    UNLOCK_NOTIFIER;

}

/*

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

 *

 * Tcl_SetTimer --

 *

 *	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(

    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.

 *

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

 */

void

Tcl_ServiceModeHook(

    int mode)			/* Either TCL_SERVICE_ALL, or

				 * TCL_SERVICE_NONE. */

{

}

/*

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

 *

 * Tcl_CreateFileHandler --

 *

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

 *

 * Results:

 *	None.

 *

 * Side effects:

 *	Creates a new file handler structure.

 *

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

 */

void

Tcl_CreateFileHandler(

    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,		/* 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);

	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.

 *

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

 */

void

Tcl_DeleteFileHandler(

    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) {

	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 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.

 *

 * Side effects:

 *	Whatever the file handler's callback function does.

 *

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

 */

static int

FileHandlerEventProc(

    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.

 *

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

 */

int

Tcl_WaitForEvent(

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

{

    FileHandler *filePtr;

    FileHandlerEvent *fileEvPtr;

    int mask;

    int waitForFiles;

    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

	return tclStubs.tcl_WaitForEvent(timePtr);

    }

    /*

     * Start notifier thread if necessary.

     */

    LOCK_NOTIFIER_INIT;

    if (!notifierCount) {

        Tcl_Panic("Tcl_WaitForEvent: notifier not initialized");

    }

    if (!notifierThread) {

	int result;

	pthread_attr_t attr;

	pthread_attr_init(&attr);

	pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM);

	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

	pthread_attr_setstacksize(&attr, 60 * 1024);

	result = pthread_create(&notifierThread, &attr,

		(void * (*)(void *))NotifierThreadProc, NULL);

	pthread_attr_destroy(&attr);

	if (result || !notifierThread) {

	    Tcl_Panic("Tcl_WaitForEvent: unable to start notifier thread");

	}

    }

    UNLOCK_NOTIFIER_INIT;

    /*

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

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

     */

    LOCK_NOTIFIER;

    if (!tsdPtr->runLoop) {

        Tcl_Panic("Tcl_WaitForEvent: CFRunLoop not initialized");

    }

    waitForFiles = (tsdPtr->numFdBits > 0);

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

	 */

	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) {

	CFTimeInterval waitTime;

	CFStringRef runLoopMode;

	if (timePtr == NULL) {

	    waitTime = 1.0e10; /* Wait forever, as per CFRunLoop.c */

	} else {

	    waitTime = timePtr->sec + 1.0e-6 * timePtr->usec;

	}

	/*

	 * If the run loop is already running (e.g. if Tcl_WaitForEvent was

	 * called recursively), re-run it in a custom run loop mode containing

	 * only the source for the notifier thread, otherwise wakeups from other

	 * sources added to the common run loop modes might get lost.

	 */

	if ((runLoopMode = CFRunLoopCopyCurrentMode(tsdPtr->runLoop))) {

	    CFRelease(runLoopMode);

	    runLoopMode = tclEventsOnlyRunLoopMode;

	} else {

	    runLoopMode = kCFRunLoopDefaultMode;

	}

	UNLOCK_NOTIFIER;

	CFRunLoopRunInMode(runLoopMode, waitTime, TRUE);

	LOCK_NOTIFIER;

    }

    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);

    }

    /*

     * 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;

	}

	/*