/*
 * tclSelectNotfy.c --
 *
 *	This file contains the implementation of the select()-based generic
 *	Unix notifier, which is the lowest-level part of the Tcl event loop.
 *	This file works together with generic/tclNotify.c.
 *
 * Copyright © 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.
 */

#include "tclInt.h"
#ifndef HAVE_COREFOUNDATION	/* Darwin/Mac OS X CoreFoundation notifier is
				 * in tclMacOSXNotify.c */
#if (!defined(NOTIFIER_EPOLL) && !defined(NOTIFIER_KQUEUE)) || !TCL_THREADS

#include <signal.h>

/*
 * 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. */
    void *clientData;		/* Argument to pass to proc. */
    struct FileHandler *nextPtr;/* Next in list of all files we care about. */
} FileHandler;

/*
 * The following structure contains a set of select() masks to track readable,
 * writable, and exception conditions.
 */

typedef struct {
    fd_set readable;
    fd_set writable;
    fd_set exception;
} SelectMasks;

/*
 * The following structure is what is added to the Tcl event queue when file
 * handlers are ready to fire.
 */

typedef struct {
    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 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). */
#if TCL_THREADS
    int onList;			/* True if it is in this list */
    unsigned int pollState;	/* pollState is used to implement a polling
				 * handshake between each thread and the
				 * notifier thread. Bits defined below. */
    struct ThreadSpecificData *nextPtr, *prevPtr;
				/* All threads that are currently waiting on
				 * an event have their ThreadSpecificData
				 * structure on a doubly-linked listed formed
				 * from these pointers. You must hold the
				 * notifierMutex lock before accessing these
				 * fields. */
#ifdef __CYGWIN__
    void *event;		/* Any other thread alerts a notifier that an
				 * event is ready to be processed by sending
				 * this event. */
    void *hwnd;			/* Messaging window. */
#else /* !__CYGWIN__ */
    pthread_cond_t waitCV;	/* Any other thread alerts a notifier that an
				 * event is ready to be processed by signaling
				 * this condition variable. */
#endif /* __CYGWIN__ */
    int waitCVinitialized;	/* Variable to flag initialization of the
				 * structure. */
    int eventReady;		/* True if an event is ready to be processed.
				 * Used as condition flag together with waitCV
				 * above. */
#endif /* TCL_THREADS */
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

#if TCL_THREADS
/*
 * The following static indicates the number of threads that have initialized
 * notifiers.
 *
 * You must hold the notifierMutex lock before accessing this variable.
 */

static int notifierCount = 0;

/*
 * The following variable points to the head of a doubly-linked list of
 * ThreadSpecificData structures for all threads that are currently waiting on
 * an event.
 *
 * You must hold the notifierMutex lock before accessing this list.
 */

static ThreadSpecificData *waitingListPtr = NULL;

/*
 * The notifier thread spends all its time in select() waiting for a file
 * descriptor associated with one of the threads on the waitingListPtr list to
 * do something interesting. But if the contents of the waitingListPtr list
 * ever changes, we need to wake up and restart the select() system call. You
 * can wake up the notifier thread by writing a single byte to the file
 * descriptor defined below. This file descriptor is the input-end of a pipe
 * and the notifier thread is listening for data on the output-end of the same
 * pipe. Hence writing to this file descriptor will cause the select() system
 * call to return and wake up the notifier thread.
 *
 * You must hold the notifierMutex lock before writing to the pipe.
 */

static int triggerPipe = -1;
static int otherPipe = -1;

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

static pthread_mutex_t notifierInitMutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t notifierMutex     = PTHREAD_MUTEX_INITIALIZER;
/*
 * The following static indicates if the notifier thread is running.
 *
 * You must hold the notifierInitMutex before accessing this variable.
 */

static int notifierThreadRunning = 0;

/*
 * The following static flag indicates that async handlers are pending.
 */

static int asyncPending = 0;

/*
 * The notifier thread signals the notifierCV when it has finished
 * initializing the triggerPipe and right before the notifier thread
 * terminates. This condition is used to deal with the signal mask, too.
 */

static pthread_cond_t notifierCV = PTHREAD_COND_INITIALIZER;

/*
 * The pollState bits:
 *
 * POLL_WANT is set by each thread before it waits on its condition variable.
 *	It is checked by the notifier before it does select.
 *
 * POLL_DONE is set by the notifier if it goes into select after seeing
 *	POLL_WANT. The idea is to ensure it tries a select with the same bits
 *	the initial thread had set.
 */

#define POLL_WANT	0x1
#define POLL_DONE	0x2

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

static Tcl_ThreadId notifierThread;

/*
 * Signal mask information for notifier thread.
 */

static sigset_t notifierSigMask;
#ifndef HAVE_PSELECT
static sigset_t allSigMask;
#endif /* HAVE_PSELECT */

#endif /* TCL_THREADS */

/*
 * Static routines defined in this file.
 */

#if TCL_THREADS
static TCL_NORETURN void NotifierThreadProc(void *clientData);
#if defined(HAVE_PTHREAD_ATFORK)
static int atForkInit = 0;
static void		AtForkChild(void);
#endif /* HAVE_PTHREAD_ATFORK */
#endif /* TCL_THREADS */
static int		FileHandlerEventProc(Tcl_Event *evPtr, int flags);

/*
 * Import of critical bits of Windows API when building threaded with Cygwin.
 */

#if defined(__CYGWIN__)
#ifdef __cplusplus
extern "C" {
#endif
typedef struct {
    void *hwnd;			/* Messaging window. */
    unsigned int *message;	/* Message payload. */
    size_t wParam;		/* Event-specific "word" parameter. */
    size_t lParam;		/* Event-specific "long" parameter. */
    int time;			/* Event timestamp. */
    int x;			/* Event location (where meaningful). */
    int y;
    int lPrivate;
} MSG;

typedef struct {
    unsigned int style;
    void *lpfnWndProc;
    int cbClsExtra;
    int cbWndExtra;
    void *hInstance;
    void *hIcon;
    void *hCursor;
    void *hbrBackground;
    const void *lpszMenuName;
    const void *lpszClassName;
} WNDCLASSW;

#ifdef __clang__
#pragma clang diagnostic ignored "-Wignored-attributes"
#endif
extern void __stdcall	CloseHandle(void *);
extern void *__stdcall	CreateEventW(void *, unsigned char, unsigned char,
			    void *);
extern void *__stdcall	CreateWindowExW(void *, const void *, const void *,
			    unsigned int, int, int, int, int, void *, void *,
			    void *, void *);
extern unsigned int __stdcall	DefWindowProcW(void *, int, void *, void *);
extern unsigned char __stdcall	DestroyWindow(void *);
extern int __stdcall	DispatchMessageW(const MSG *);
extern unsigned char __stdcall	GetMessageW(MSG *, void *, int, int);
extern void __stdcall	MsgWaitForMultipleObjects(unsigned int, void *,
			    unsigned char, unsigned int, unsigned int);
extern unsigned char __stdcall	PeekMessageW(MSG *, void *, int, int, int);
extern unsigned char __stdcall	PostMessageW(void *, unsigned int, void *,
				    void *);
extern void __stdcall	PostQuitMessage(int);
extern void *__stdcall	RegisterClassW(const WNDCLASSW *);
extern unsigned char __stdcall	ResetEvent(void *);
extern unsigned char __stdcall	TranslateMessage(const MSG *);

/*
 * Threaded-cygwin specific constants and functions in this file:
 */

#if TCL_THREADS && defined(__CYGWIN__)
static const wchar_t className[] = L"TclNotifier";
static unsigned int __stdcall	NotifierProc(void *hwnd, unsigned int message,
			    void *wParam, void *lParam);
#endif /* TCL_THREADS && defined(__CYGWIN__) */
#ifdef __cplusplus
}
#endif
#endif /* TCL_THREADS && __CYGWIN__ */

/*
 * Incorporate the base notifier implementation.
 */

#include "tclUnixNotfy.c"

/*
 *----------------------------------------------------------------------
 *
 * TclpInitNotifier --
 *
 *	Initializes the platform specific notifier state.
 *
 * Results:
 *	Returns a handle to the notifier state for this thread.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

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

#if TCL_THREADS
    tsdPtr->eventReady = 0;

    /*
     * Initialize thread specific condition variable for this thread.
     */

    if (tsdPtr->waitCVinitialized == 0) {
#ifdef __CYGWIN__
	WNDCLASSW clazz;

	clazz.style = 0;
	clazz.cbClsExtra = 0;
	clazz.cbWndExtra = 0;
	clazz.hInstance = TclWinGetTclInstance();
	clazz.hbrBackground = NULL;
	clazz.lpszMenuName = NULL;
	clazz.lpszClassName = className;
	clazz.lpfnWndProc = (void *)NotifierProc;
	clazz.hIcon = NULL;
	clazz.hCursor = NULL;

	RegisterClassW(&clazz);
	tsdPtr->hwnd = CreateWindowExW(NULL, clazz.lpszClassName,
		clazz.lpszClassName, 0, 0, 0, 0, 0, NULL, NULL,
		clazz.hInstance, NULL);
	tsdPtr->event = CreateEventW(NULL, 1 /* manual */,
		0 /* !signaled */, NULL);
#else /* !__CYGWIN__ */
	pthread_cond_init(&tsdPtr->waitCV, NULL);
#endif /* __CYGWIN__ */
	tsdPtr->waitCVinitialized = 1;
    }

    pthread_mutex_lock(&notifierInitMutex);
#if defined(HAVE_PTHREAD_ATFORK)
    /*
     * Install pthread_atfork handlers to clean up the notifier in the child
     * of a fork.
     */

    if (!atForkInit) {
	int result = pthread_atfork(NULL, NULL, AtForkChild);

	if (result) {
	    Tcl_Panic("Tcl_InitNotifier: %s", "pthread_atfork failed");
	}
	atForkInit = 1;
    }
#endif /* HAVE_PTHREAD_ATFORK */

    notifierCount++;
    pthread_mutex_unlock(&notifierInitMutex);
#endif /* TCL_THREADS */

    return tsdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizeNotifier --
 *
 *	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
TclpFinalizeNotifier(
    TCL_UNUSED(void *))
{
#if TCL_THREADS
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    pthread_mutex_lock(&notifierInitMutex);
    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 && triggerPipe != -1) {
	if (write(triggerPipe, "q", 1) != 1) {
	    Tcl_Panic("Tcl_FinalizeNotifier: %s",
		    "unable to write 'q' to triggerPipe");
	}
	close(triggerPipe);
	pthread_mutex_lock(&notifierMutex);
	while(triggerPipe != -1) {
	    pthread_cond_wait(&notifierCV, &notifierMutex);
	}
	pthread_mutex_unlock(&notifierMutex);
	if (notifierThreadRunning) {
	    int result = pthread_join((pthread_t) notifierThread, NULL);

	    if (result) {
		Tcl_Panic("Tcl_FinalizeNotifier: %s",
			"unable to join notifier thread");
	    }
	    notifierThreadRunning = 0;

	    /*
	     * If async marks are outstanding, perform actions now.
	     */
	    if (asyncPending) {
		asyncPending = 0;
		TclAsyncMarkFromNotifier();
	    }
	}
    }

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

#ifdef __CYGWIN__
    DestroyWindow(tsdPtr->hwnd);
    CloseHandle(tsdPtr->event);
#else /* !__CYGWIN__ */
    pthread_cond_destroy(&tsdPtr->waitCV);
#endif /* __CYGWIN__ */
    tsdPtr->waitCVinitialized = 0;

    pthread_mutex_unlock(&notifierInitMutex);
#endif /* TCL_THREADS */
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateFileHandler --
 *
 *	This function registers a file handler with the select notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new file handler structure.
 *
 *----------------------------------------------------------------------
 */

void
TclpCreateFileHandler(
    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. */
    void *clientData)		/* Arbitrary data to pass to proc. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileHandler *filePtr = LookUpFileHandler(tsdPtr, fd, NULL);

    if (filePtr == NULL) {
	filePtr = (FileHandler *) Tcl_Alloc(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.exception);
    } else {
	FD_CLR(fd, &tsdPtr->checkMasks.exception);
    }
    if (tsdPtr->numFdBits <= fd) {
	tsdPtr->numFdBits = fd + 1;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpDeleteFileHandler --
 *
 *	Cancel a previously-arranged callback arrangement for a file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered on file, remove it.
 *
 *----------------------------------------------------------------------
 */

void
TclpDeleteFileHandler(
    int fd)			/* Stream id for which to remove callback
				 * function. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileHandler *filePtr, *prevPtr;
    int i;

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

    filePtr = LookUpFileHandler(tsdPtr, fd, &prevPtr);
    if (filePtr == NULL) {
	return;
    }

    /*
     * 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.exception);
    }

    /*
     * Find current max fd.
     */

    if (fd + 1 == tsdPtr->numFdBits) {
	int 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.exception)) {
		numFdBits = i + 1;
		break;
	    }
	}
	tsdPtr->numFdBits = numFdBits;
    }

    /*
     * Clean up information in the callback record.
     */

    if (prevPtr == NULL) {
	tsdPtr->firstFileHandlerPtr = filePtr->nextPtr;
    } else {
	prevPtr->nextPtr = filePtr->nextPtr;
    }
    Tcl_Free(filePtr);
}

#if TCL_THREADS && defined(__CYGWIN__)

static unsigned int __stdcall
NotifierProc(
    void *hwnd,
    unsigned int message,
    void *wParam,
    void *lParam)
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (message != 1024) {
	return DefWindowProcW(hwnd, message, wParam, lParam);
    }

    /*
     * Process all of the runnable events.
     */

    tsdPtr->eventReady = 1;
    Tcl_ServiceAll();
    return 0;
}
#endif /* TCL_THREADS && __CYGWIN__ */

/*
 *----------------------------------------------------------------------
 *
 * TclpWaitForEvent --
 *
 *	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
TclpWaitForEvent(
    const Tcl_Time *timePtr)	/* Maximum block time, or NULL. */
{
    FileHandler *filePtr;
    int mask;
    Tcl_Time vTime;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
#if TCL_THREADS
    int waitForFiles;
#   ifdef __CYGWIN__
    MSG msg;
#   endif /* __CYGWIN__ */
#else /* !TCL_THREADS */
    /*
     * 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 /* TCL_THREADS */

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

    if (timePtr != 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.
	 */

	if (timePtr->sec != 0 || timePtr->usec != 0) {
	    vTime = *timePtr;
	    TclScaleTime(&vTime);
	    timePtr = &vTime;
	}
#if !TCL_THREADS
	timeout.tv_sec = timePtr->sec;
	timeout.tv_usec = timePtr->usec;
	timeoutPtr = &timeout;
    } else if (tsdPtr->numFdBits == 0) {
	/*
	 * If there are no threads, no timeout, and no fds registered, then
	 * there are no events possible and we must avoid deadlock.  Note that
	 * this is not entirely correct because there might be a signal that
	 * could interrupt the select call, but we don't handle that case if
	 * we aren't using threads.
	 */

	return -1;
    } else {
	timeoutPtr = NULL;
#endif /* !TCL_THREADS */
    }

#if TCL_THREADS
    /*
     * Start notifier thread and place this thread on the list of interested
     * threads, signal the notifier thread, and wait for a response or a
     * timeout.
     */

    StartNotifierThread("Tcl_WaitForEvent");

    pthread_mutex_lock(&notifierMutex);

    if (timePtr != NULL && timePtr->sec == 0 && (timePtr->usec == 0
#if defined(__APPLE__) && defined(__LP64__)
	    /*
	     * On 64-bit Darwin, pthread_cond_timedwait() appears to have a
	     * bug that causes it to wait forever when passed an absolute time
	     * which has already been exceeded by the system time; as a
	     * workaround, when given a very brief timeout, just do a poll.
	     * [Bug 1457797]
	     */
	    || timePtr->usec < 10
#endif /* __APPLE__ && __LP64__ */
	    )) {
	/*
	 * 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 {
	waitForFiles = (tsdPtr->numFdBits > 0);
	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;

	if ((write(triggerPipe, "", 1) == -1) && (errno != EAGAIN)) {
	    Tcl_Panic("Tcl_WaitForEvent: %s",
		    "unable to write to triggerPipe");
	}
    }

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

    if (!tsdPtr->eventReady) {
#ifdef __CYGWIN__
	if (!PeekMessageW(&msg, NULL, 0, 0, 0)) {
	    long long timeout;

	    if (timePtr) {
		timeout = timePtr->sec * 1000 + timePtr->usec / 1000;
		if (timeout > UINT_MAX) {
		    timeout = UINT_MAX;
		}
	    } else {
		timeout = UINT_MAX;
	    }
	    pthread_mutex_unlock(&notifierMutex);
	    MsgWaitForMultipleObjects(1, &tsdPtr->event, 0, (unsigned int)timeout, 1279);
	    pthread_mutex_lock(&notifierMutex);
	}
#else /* !__CYGWIN__ */
	if (timePtr != NULL) {
	    Tcl_Time now;
	    struct timespec ptime;

	    Tcl_GetTime(&now);
	    ptime.tv_sec = timePtr->sec + now.sec +
		    (timePtr->usec + now.usec) / 1000000;
	    ptime.tv_nsec = 1000 * ((timePtr->usec + now.usec) % 1000000);

	    pthread_cond_timedwait(&tsdPtr->waitCV, &notifierMutex, &ptime);
	} else {
	    pthread_cond_wait(&tsdPtr->waitCV, &notifierMutex);
	}
#endif /* __CYGWIN__ */
    }
    tsdPtr->eventReady = 0;

#ifdef __CYGWIN__
    while (PeekMessageW(&msg, NULL, 0, 0, 0)) {
	/*
	 * Retrieve and dispatch the message.
	 */

	unsigned int result = GetMessageW(&msg, NULL, 0, 0);

	if (result == 0) {
	    PostQuitMessage((int)msg.wParam);
	    /* What to do here? */
	} else if (result != (unsigned int) -1) {
	    TranslateMessage(&msg);
	    DispatchMessageW(&msg);
	}
    }
    ResetEvent(tsdPtr->event);
#endif /* __CYGWIN__ */

    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;
	if ((write(triggerPipe, "", 1) == -1) && (errno != EAGAIN)) {
	    Tcl_Panic("Tcl_WaitForEvent: %s",
		    "unable to write to triggerPipe");
	}
    }
#else /* !TCL_THREADS */
    tsdPtr->readyMasks = tsdPtr->checkMasks;
    numFound = select(tsdPtr->numFdBits, &tsdPtr->readyMasks.readable,
	    &tsdPtr->readyMasks.writable, &tsdPtr->readyMasks.exception,
	    timeoutPtr);

    /*
     * Some systems don't clear the masks after an error, so we have to do it
     * here.
     */

    if (numFound == -1) {
	FD_ZERO(&tsdPtr->readyMasks.readable);
	FD_ZERO(&tsdPtr->readyMasks.writable);
	FD_ZERO(&tsdPtr->readyMasks.exception);
    }
#endif /* TCL_THREADS */

    /*
     * 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.exception)) {
	    mask |= TCL_EXCEPTION;
	}

	if (!mask) {
	    continue;
	}

	/*
	 * Don't bother to queue an event if the mask was previously non-zero
	 * since an event must still be on the queue.
	 */

	if (filePtr->readyMask == 0) {
	    FileHandlerEvent *fileEvPtr =
		    (FileHandlerEvent *) Tcl_Alloc(sizeof(FileHandlerEvent));

	    fileEvPtr->header.proc = FileHandlerEventProc;
	    fileEvPtr->fd = filePtr->fd;
	    Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
	}
	filePtr->readyMask = mask;
    }
#if TCL_THREADS
    pthread_mutex_unlock(&notifierMutex);
#endif /* TCL_THREADS */
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclAsyncNotifier --
 *
 *	This procedure sets the async mark of an async handler to a
 *	given value, if it is called from the notifier thread.
 *
 * Result:
 *	True, when the handler will be marked, false otherwise.
 *
 * Side effetcs:
 *	The trigger pipe is written when called from the notifier
 *	thread.
 *
 *----------------------------------------------------------------------
 */

int
TclAsyncNotifier(
    int sigNumber,		/* Signal number. */
    TCL_UNUSED(Tcl_ThreadId),	/* Target thread. */
    TCL_UNUSED(void *),	/* Notifier data. */
    int *flagPtr,		/* Flag to mark. */
    int value)			/* Value of mark. */
{
#if TCL_THREADS
    /*
     * WARNING:
     * This code most likely runs in a signal handler. Thus,
     * only few async-signal-safe system calls are allowed,
     * e.g. pthread_self(), sem_post(), write().
     */

    if (pthread_equal(pthread_self(), (pthread_t) notifierThread)) {
	if (notifierThreadRunning) {
	    *flagPtr = value;
	    if (!asyncPending) {
		asyncPending = 1;
		if (write(triggerPipe, "S", 1) != 1) {
		    asyncPending = 0;
		    return 0;
		};
	    }
	    return 1;
	}
	return 0;
    }

    /*
     * Re-send the signal to the notifier thread.
     */

    pthread_kill((pthread_t) notifierThread, sigNumber);
#else
    (void)sigNumber;
    (void)flagPtr;
    (void)value;
#endif
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * NotifierThreadProc --
 *
 *	This routine is the initial (and only) function executed by the
 *	special notifier thread. Its job is to wait for file descriptors to
 *	become readable or writable or to have an exception condition and then
 *	to notify other threads who are interested in this information by
 *	signalling a condition variable. Other threads can signal this
 *	notifier thread of a change in their interests by writing a single
 *	byte to a special pipe that the notifier thread is monitoring.
 *
 * Result:
 *	None. Once started, this routine normally never exits and usually dies
 *	with the overall process, but it can be shut down if the Tcl library
 *	is finalized.
 *
 * Side effects:
 *	The trigger pipe used to signal the notifier thread is created when
 *	the notifier thread first starts.
 *
 *----------------------------------------------------------------------
 */

#if TCL_THREADS
static TCL_NORETURN void
NotifierThreadProc(
    TCL_UNUSED(void *))
{
    ThreadSpecificData *tsdPtr;
    fd_set readableMask;
    fd_set writableMask;
    fd_set exceptionMask;
    int i, fds[2], receivePipe, ret;
    long found;
    struct timeval poll = {0, 0}, *timePtr;
    char buf[2];
    int numFdBits = 0;

    if (pipe(fds) != 0) {
	Tcl_Panic("NotifierThreadProc: %s", "could not create trigger pipe");
    }

    /*
     * Ticket [c6897e6e6a].
     */

    if (fds[0] >= FD_SETSIZE || fds[1] >= FD_SETSIZE) {
	Tcl_Panic("NotifierThreadProc: %s", "too many open files");
    }

    receivePipe = fds[0];

    if (TclUnixSetBlockingMode(receivePipe, TCL_MODE_NONBLOCKING) < 0) {
	Tcl_Panic("NotifierThreadProc: %s",
		"could not make receive pipe non blocking");
    }
    if (TclUnixSetBlockingMode(fds[1], TCL_MODE_NONBLOCKING) < 0) {
	Tcl_Panic("NotifierThreadProc: %s",
		"could not make trigger pipe non blocking");
    }
    if (fcntl(receivePipe, F_SETFD, FD_CLOEXEC) < 0) {
	Tcl_Panic("NotifierThreadProc: %s",
		"could not make receive pipe close-on-exec");
    }
    if (fcntl(fds[1], F_SETFD, FD_CLOEXEC) < 0) {
	Tcl_Panic("NotifierThreadProc: %s",
		"could not make trigger pipe close-on-exec");
    }

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

    pthread_mutex_lock(&notifierMutex);
    triggerPipe = fds[1];
    otherPipe = fds[0];

    /*
     * Signal any threads that are waiting.
     */

    pthread_cond_broadcast(&notifierCV);
    pthread_mutex_unlock(&notifierMutex);

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

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

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

	pthread_mutex_lock(&notifierMutex);
	timePtr = NULL;
	for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
	    for (i = tsdPtr->numFdBits-1; i >= 0; --i) {
		if (FD_ISSET(i, &tsdPtr->checkMasks.readable)) {
		    FD_SET(i, &readableMask);
		}
		if (FD_ISSET(i, &tsdPtr->checkMasks.writable)) {
		    FD_SET(i, &writableMask);
		}
		if (FD_ISSET(i, &tsdPtr->checkMasks.exception)) {
		    FD_SET(i, &exceptionMask);
		}
	    }
	    if (tsdPtr->numFdBits > numFdBits) {
		numFdBits = tsdPtr->numFdBits;
	    }
	    if (tsdPtr->pollState & POLL_WANT) {
		/*
		 * Here we make sure we go through select() with the same mask
		 * bits that were present when the thread tried to poll.
		 */

		tsdPtr->pollState |= POLL_DONE;
		timePtr = &poll;
	    }
	}
	pthread_mutex_unlock(&notifierMutex);

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

	if (receivePipe >= numFdBits) {
	    numFdBits = receivePipe + 1;
	}
	FD_SET(receivePipe, &readableMask);

	/*
	 * Signals are unblocked only during select().
	 */

#ifdef HAVE_PSELECT
	{
	    struct timespec tspec, *tspecPtr;

	    if (timePtr == NULL) {
		tspecPtr = NULL;
	    } else {
		tspecPtr = &tspec;
		tspecPtr->tv_sec = timePtr->tv_sec;
		tspecPtr->tv_nsec = timePtr->tv_usec * 1000;
	    }
	    ret = pselect(numFdBits, &readableMask, &writableMask,
		    &exceptionMask, tspecPtr, &notifierSigMask);
	}
#else
	pthread_sigmask(SIG_SETMASK, &notifierSigMask, NULL);
	ret = select(numFdBits, &readableMask, &writableMask, &exceptionMask,
		timePtr);
	pthread_sigmask(SIG_BLOCK, &allSigMask, NULL);
#endif

	if (ret == -1) {
	    /*
	     * In case a signal was caught during select(),
	     * perform work on async handlers now.
	     */
	    if (errno == EINTR && asyncPending) {
		asyncPending = 0;
		TclAsyncMarkFromNotifier();
	    }

	    /*
	     * Try again immediately on select() error.
	     */
	    continue;
	}

	/*
	 * Alert any threads that are waiting on a ready file descriptor.
	 */

	pthread_mutex_lock(&notifierMutex);
	for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
	    found = 0;

	    for (i = tsdPtr->numFdBits - 1; i >= 0; --i) {
		if (FD_ISSET(i, &tsdPtr->checkMasks.readable)
			&& FD_ISSET(i, &readableMask)) {
		    FD_SET(i, &tsdPtr->readyMasks.readable);
		    found = 1;
		}
		if (FD_ISSET(i, &tsdPtr->checkMasks.writable)
			&& FD_ISSET(i, &writableMask)) {
		    FD_SET(i, &tsdPtr->readyMasks.writable);
		    found = 1;
		}
		if (FD_ISSET(i, &tsdPtr->checkMasks.exception)
			&& FD_ISSET(i, &exceptionMask)) {
		    FD_SET(i, &tsdPtr->readyMasks.exception);
		    found = 1;
		}
	    }

	    if (found || (tsdPtr->pollState & POLL_DONE)) {
		AlertSingleThread(tsdPtr);
	    }
	}
	pthread_mutex_unlock(&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.
	 */

	do {
	    i = (int)read(receivePipe, buf, 1);
	    if (i <= 0) {
		break;
	    } else 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.
		 */

		break;
	    }
	} while (1);

	if (asyncPending) {
	    asyncPending = 0;
	    TclAsyncMarkFromNotifier();
	}

	if ((i == 0) || (buf[0] == 'q')) {
	    break;
	}
    }

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

    close(receivePipe);
    pthread_mutex_lock(&notifierMutex);
    triggerPipe = -1;
    otherPipe = -1;
    pthread_cond_broadcast(&notifierCV);
    pthread_mutex_unlock(&notifierMutex);

    TclpThreadExit(0);
}
#endif /* TCL_THREADS */

#endif /* (!NOTIFIER_EPOLL && !NOTIFIER_KQUEUE) || !TCL_THREADS */
#else
TCL_MAC_EMPTY_FILE(unix_tclSelectNotfy_c)
#endif /* !HAVE_COREFOUNDATION */

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */