/*
 * 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 1.29 2005/11/02 23:26:50 dkf Exp $
 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.30 2005/11/27 02:33:50 das Exp $
 */

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

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

				 * 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;

    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
				 * 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

 * initializing the triggerPipe and right before the notifier thread
 * terminates.
 */

static Tcl_Condition notifierCV;

/*
 * The pollState bits:
 * The pollState bits
 *	POLL_WANT is set by each thread before it waits on its condition
 *		variable. It is checked by the notifier before it does 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.
 */

    /*
     * 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");
	    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);
	while(triggerPipe >= 0) {
	    Tcl_ConditionWait(&notifierCV, &notifierMutex, NULL);
	}

	result = Tcl_JoinThread(notifierThread, NULL);
	if (result) {
	    Tcl_Panic("Tcl_FinalizeNotifier: unable to join notifier thread");
	    Tcl_Panic("Tcl_FinalizeNotifier: unable to join notifier thread.");
	}
    }

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

    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) {
    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) {

    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) {
    if (tclStubs.tcl_DeleteFileHandler !=
	    tclOriginalNotifier.deleteFileHandlerProc) {
	tclStubs.tcl_DeleteFileHandler(fd);
	return;
    }

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

    for (prevPtr = NULL, filePtr = tsdPtr->firstFileHandlerPtr; ;
	    prevPtr = filePtr, filePtr = filePtr->nextPtr) {
	 prevPtr = filePtr, filePtr = filePtr->nextPtr) {
	if (filePtr == NULL) {
	    return;
	}
	if (filePtr->fd == fd) {
	    break;
	}
    }