tclunixnotfy.c

tcl是工具命令语言

/*
 * tclUnixNotify.c --
 *
 *	This file contains the implementation of the select-based
 *	Unix-specific notifier, which is the lowest-level part of the
 *	Tcl event loop.  This file works together with
 *	../generic/tclNotify.c.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.11 2002/08/31 06:09:46 das Exp $
 */

#include "tclInt.h"
#include "tclPort.h"
#include <signal.h> 

extern TclStubs tclStubs;

/*
 * This structure is used to keep track of the notifier info for a 
 * a registered file.
 */

typedef struct FileHandler {
    int fd;
    int mask;			/* Mask of desired events: TCL_READABLE,
				 * etc. */
    int readyMask;		/* Mask of events that have been seen since the
				 * last time file handlers were invoked for
				 * this file. */
    Tcl_FileProc *proc;		/* Procedure to call, in the style of
				 * Tcl_CreateFileHandler. */
    ClientData clientData;	/* Argument to pass to proc. */
    struct FileHandler *nextPtr;/* Next in list of all files we care about. */
} FileHandler;

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

typedef struct FileHandlerEvent {
    Tcl_Event header;		/* Information that is standard for
				 * all events. */
    int fd;			/* File descriptor that is ready.  Used
				 * to find the FileHandler structure for
				 * the file (can't point directly to the
				 * FileHandler structure because it could
				 * go away while the event is queued). */
} FileHandlerEvent;

/*
 * The following 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. */
    fd_mask checkMasks[3*MASK_SIZE];
				/* This array 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. */
    fd_mask readyMasks[3*MASK_SIZE];
				/* This array reflects the readable/writable
				 * conditions that were found to exist by the
				 * last call to select. */
    int numFdBits;		/* Number of valid bits in checkMasks
				 * (one more than highest fd for which
				 * Tcl_WatchFile has been called). */
#ifdef TCL_THREADS
    int onList;			/* True if it is in this list */
    unsigned int pollState;	/* pollState is used to implement a polling 
				 * handshake between each thread and the
				 * notifier thread. Bits defined below. */
    struct ThreadSpecificData *nextPtr, *prevPtr;
                                /* All threads that are currently waiting on 
                                 * an event have their ThreadSpecificData
                                 * structure on a doubly-linked listed formed
                                 * from these pointers.  You must hold the
                                 * notifierMutex lock before accessing these
                                 * fields. */
    Tcl_Condition waitCV;     /* Any other thread alerts a notifier
				 * that an event is ready to be processed
				 * by signaling this condition variable. */
    int eventReady;           /* True if an event is ready to be processed.
                               * Used as condition flag together with
                               * waitCV above. */
#endif
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

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

static int notifierCount = 0;

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

static ThreadSpecificData *waitingListPtr = NULL;

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

static int triggerPipe = -1;

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

TCL_DECLARE_MUTEX(notifierMutex)

/*
 * The notifier thread signals the notifierCV when it has finished
 * initializing the triggerPipe and right before the notifier
 * thread terminates.
 */

static Tcl_Condition notifierCV;

/*
 * The pollState bits
 *	POLL_WANT is set by each thread before it waits on its condition
 *		variable.  It is checked by the notifier before it does
 *		select.
 *	POLL_DONE is set by the notifier if it goes into select after
 *		seeing POLL_WANT.  The idea is to ensure it tries a select
 *		with the same bits the initial thread had set.
 */
#define POLL_WANT	0x1
#define POLL_DONE	0x2

/*
 * This is the thread ID of the notifier thread that does select.
 */
static Tcl_ThreadId notifierThread;

#endif

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

#ifdef TCL_THREADS
static void	NotifierThreadProc _ANSI_ARGS_((ClientData clientData));
#endif
static int	FileHandlerEventProc _ANSI_ARGS_((Tcl_Event *evPtr,
		    int flags));

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InitNotifier --
 *
 *	Initializes the platform specific notifier state.
 *
 * Results:
 *	Returns a handle to the notifier state for this thread..
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_InitNotifier()
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

#ifdef TCL_THREADS
    tsdPtr->eventReady = 0;

    /*
     * Start the Notifier thread if necessary.
     */

    Tcl_MutexLock(&notifierMutex);
    if (notifierCount == 0) {
	if (Tcl_CreateThread(&notifierThread, NotifierThreadProc, NULL,
		     TCL_THREAD_STACK_DEFAULT, TCL_THREAD_NOFLAGS) != TCL_OK) {
	    panic("Tcl_InitNotifier: unable to start notifier thread");
	}
    }
    notifierCount++;

    /*
     * Wait for the notifier pipe to be created.
     */

    while (triggerPipe < 0) {
	Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);
    }

    Tcl_MutexUnlock(&notifierMutex);
#endif
    return (ClientData) tsdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FinalizeNotifier --
 *
 *	This function is called to cleanup the notifier state before
 *	a thread is terminated.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May terminate the background notifier thread if this is the
 *	last notifier instance.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_FinalizeNotifier(clientData)
    ClientData clientData;		/* Not used. */
{
#ifdef TCL_THREADS
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    Tcl_MutexLock(&notifierMutex);
    notifierCount--;

    /*
     * If this is the last thread to use the notifier, close the notifier
     * pipe and wait for the background thread to terminate.
     */

    if (notifierCount == 0) {
	if (triggerPipe < 0) {
	    panic("Tcl_FinalizeNotifier: notifier pipe not initialized");
	}

        /*
	 * Send "q" message to the notifier thread so that it will
	 * terminate.  The notifier will return from its call to select()
	 * and notice that a "q" message has arrived, it will then close
	 * its side of the pipe and terminate its thread.  Note the we can
	 * not just close the pipe and check for EOF in the notifier
	 * thread because if a background child process was created with
	 * exec, select() would not register the EOF on the pipe until the
	 * child processes had terminated. [Bug: 4139]
	 */
	write(triggerPipe, "q", 1);
	close(triggerPipe);

	Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);
    }

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

    Tcl_ConditionFinalize(&(tsdPtr->waitCV));

    Tcl_MutexUnlock(&notifierMutex);
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AlertNotifier --
 *
 *	Wake up the specified notifier from any thread. This routine
 *	is called by the platform independent notifier code whenever
 *	the Tcl_ThreadAlert routine is called.  This routine is
 *	guaranteed not to be called on a given notifier after
 *	Tcl_FinalizeNotifier is called for that notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Signals the notifier condition variable for the specified
 *	notifier.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AlertNotifier(clientData)
    ClientData clientData;
{
#ifdef TCL_THREADS
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) clientData;
    Tcl_MutexLock(&notifierMutex);
    tsdPtr->eventReady = 1;
    Tcl_ConditionNotify(&tsdPtr->waitCV);
    Tcl_MutexUnlock(&notifierMutex);
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetTimer --
 *
 *	This procedure sets the current notifier timer value.  This
 *	interface is not implemented in this notifier because we are
 *	always running inside of Tcl_DoOneEvent.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetTimer(timePtr)
    Tcl_Time *timePtr;		/* Timeout value, may be NULL. */
{
    /*
     * The interval timer doesn't do anything in this implementation,
     * because the only event loop is via Tcl_DoOneEvent, which passes
     * timeout values to Tcl_WaitForEvent.
     */

    if (tclStubs.tcl_SetTimer != Tcl_SetTimer) {
	tclStubs.tcl_SetTimer(timePtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ServiceModeHook --
 *
 *	This function is invoked whenever the service mode changes.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ServiceModeHook(mode)
    int mode;			/* Either TCL_SERVICE_ALL, or
				 * TCL_SERVICE_NONE. */
{
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateFileHandler --
 *
 *	This procedure registers a file handler with the select notifier.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new file handler structure.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateFileHandler(fd, mask, proc, clientData)
    int fd;			/* Handle of stream to watch. */
    int mask;			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, and TCL_EXCEPTION:
				 * indicates conditions under which
				 * proc should be called. */
    Tcl_FileProc *proc;		/* Procedure to call for each
				 * selected event. */
    ClientData clientData;	/* Arbitrary data to pass to proc. */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    FileHandler *filePtr;
    int index, bit;

    if (tclStubs.tcl_CreateFileHandler != Tcl_CreateFileHandler) {
	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.
     */

    index = fd/(NBBY*sizeof(fd_mask));
    bit = 1 << (fd%(NBBY*sizeof(fd_mask)));
    if (mask & TCL_READABLE) {
	tsdPtr->checkMasks[index] |= bit;
    } else {
	tsdPtr->checkMasks[index] &= ~bit;
    } 
    if (mask & TCL_WRITABLE) {
	(tsdPtr->checkMasks+MASK_SIZE)[index] |= bit;
    } else {
	(tsdPtr->checkMasks+MASK_SIZE)[index] &= ~bit;
    }
    if (mask & TCL_EXCEPTION) {
	(tsdPtr->checkMasks+2*(MASK_SIZE))[index] |= bit;
    } else {
	(tsdPtr->checkMasks+2*(MASK_SIZE))[index] &= ~bit;
    }
    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(fd)
    int fd;		/* Stream id for which to remove callback procedure. */
{
    FileHandler *filePtr, *prevPtr;
    int index, bit, i;
    unsigned long flags;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_DeleteFileHandler != Tcl_DeleteFileHandler) {
	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.
     */

    index = fd/(NBBY*sizeof(fd_mask));
    bit = 1 << (fd%(NBBY*sizeof(fd_mask)));

    if (filePtr->mask & TCL_READABLE) {
	tsdPtr->checkMasks[index] &= ~bit;
    }