uxwrap.c

Netscape NSPR库源码

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is the Netscape Portable Runtime (NSPR).
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1998-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s):
 * 
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
 * instead of those above.  If you wish to allow use of your 
 * version of this file only under the terms of the GPL and not to
 * allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by
 * the GPL.  If you do not delete the provisions above, a recipient
 * may use your version of this file under either the MPL or the
 * GPL.
 */

/*
 *------------------------------------------------------------------------
 * File: uxwrap.c
 *
 *     Our wrapped versions of the Unix select() and poll() system calls.
 *
 *------------------------------------------------------------------------
 */

#include "primpl.h"

#if defined(_PR_PTHREADS) || defined(_PR_GLOBAL_THREADS_ONLY) || defined(QNX)
/* Do not wrap select() and poll(). */
#else  /* defined(_PR_PTHREADS) || defined(_PR_GLOBAL_THREADS_ONLY) */
/* The include files for select() */
#ifdef IRIX
#include <unistd.h>
#include <bstring.h>
#endif

#include <string.h>
#include <sys/types.h>
#include <sys/time.h>

#define ZAP_SET(_to, _width)				      \
    PR_BEGIN_MACRO					      \
	memset(_to, 0,					      \
	       ((_width + 8*sizeof(int)-1) / (8*sizeof(int))) \
		* sizeof(int)				      \
	       );					      \
    PR_END_MACRO

/* see comments in ns/cmd/xfe/mozilla.c (look for "PR_XGetXtHackFD") */
static int _pr_xt_hack_fd = -1;
 
int PR_XGetXtHackFD(void)
{
    int fds[2];
 
    if (_pr_xt_hack_fd == -1) {
        if (!pipe(fds)) {
            _pr_xt_hack_fd = fds[0];
        }
    }
    return _pr_xt_hack_fd;
}

static int (*_pr_xt_hack_okayToReleaseXLock)(void) = 0;

void PR_SetXtHackOkayToReleaseXLockFn(int (*fn)(void))
{
    _pr_xt_hack_okayToReleaseXLock = fn; 
}


/*
 *-----------------------------------------------------------------------
 *  select() --
 *
 *    Wrap up the select system call so that we can deschedule
 *    a thread that tries to wait for i/o.
 *
 *-----------------------------------------------------------------------
 */

#if defined(HPUX9)
int select(size_t width, int *rl, int *wl, int *el, const struct timeval *tv)
#elif defined(NEXTSTEP)
int wrap_select(int width, fd_set *rd, fd_set *wr, fd_set *ex,
        const struct timeval *tv)
#elif defined(AIX_RENAME_SELECT)
int wrap_select(unsigned long width, void *rl, void *wl, void *el,
        struct timeval *tv)
#elif defined(_PR_SELECT_CONST_TIMEVAL)
int select(int width, fd_set *rd, fd_set *wr, fd_set *ex,
        const struct timeval *tv)
#else
int select(int width, fd_set *rd, fd_set *wr, fd_set *ex, struct timeval *tv)
#endif
{
    int osfd;
    _PRUnixPollDesc *unixpds, *unixpd, *eunixpd;
    PRInt32 pdcnt;
    PRIntervalTime timeout;
    int retVal;
#if defined(HPUX9) || defined(AIX_RENAME_SELECT)
    fd_set *rd = (fd_set*) rl;
    fd_set *wr = (fd_set*) wl;
    fd_set *ex = (fd_set*) el;
#endif

#if 0
    /*
     * Easy special case: zero timeout.  Simply call the native
     * select() with no fear of blocking.
     */
    if (tv != NULL && tv->tv_sec == 0 && tv->tv_usec == 0) {
#if defined(HPUX9) || defined(AIX_RENAME_SELECT)
        return _MD_SELECT(width, rl, wl, el, tv);
#else
        return _MD_SELECT(width, rd, wr, ex, tv);
#endif
    }
#endif

    if (!_pr_initialized) {
        _PR_ImplicitInitialization();
    }
		
#ifndef _PR_LOCAL_THREADS_ONLY
    if (_PR_IS_NATIVE_THREAD(_PR_MD_CURRENT_THREAD())) {
        return _MD_SELECT(width, rd, wr, ex, tv);	
    }
#endif

    if (width < 0 || width > FD_SETSIZE) {
        errno = EINVAL;
        return -1;
    }

    /* Compute timeout */
    if (tv) {
        /*
         * These acceptable ranges for t_sec and t_usec are taken
         * from the select() man pages.
         */
        if (tv->tv_sec < 0 || tv->tv_sec > 100000000
                || tv->tv_usec < 0 || tv->tv_usec >= 1000000) {
            errno = EINVAL;
            return -1;
        }

        /* Convert microseconds to ticks */
        timeout = PR_MicrosecondsToInterval(1000000*tv->tv_sec + tv->tv_usec);
    } else {
        /* tv being a NULL pointer means blocking indefinitely */
        timeout = PR_INTERVAL_NO_TIMEOUT;
    }

    /* Check for no descriptors case (just doing a timeout) */
    if ((!rd && !wr && !ex) || !width) {
        PR_Sleep(timeout);
        return 0;
    }

    /*
     * Set up for PR_Poll().  The PRPollDesc array is allocated
     * dynamically.  If this turns out to have high performance
     * penalty, one can change to use a large PRPollDesc array
     * on the stack, and allocate dynamically only when it turns
     * out to be not large enough.
     *
     * I allocate an array of size 'width', which is the maximum
     * number of fds we may need to poll.
     */
    unixpds = (_PRUnixPollDesc *) PR_CALLOC(width * sizeof(_PRUnixPollDesc));
    if (!unixpds) {
        errno = ENOMEM;
        return -1;
    }

    pdcnt = 0;
    unixpd = unixpds;
    for (osfd = 0; osfd < width; osfd++) {
        int in_flags = 0;
        if (rd && FD_ISSET(osfd, rd)) {
            in_flags |= _PR_UNIX_POLL_READ;
        }
        if (wr && FD_ISSET(osfd, wr)) {
            in_flags |= _PR_UNIX_POLL_WRITE;
        }
        if (ex && FD_ISSET(osfd, ex)) {
            in_flags |= _PR_UNIX_POLL_EXCEPT;
        }
        if (in_flags) {
            unixpd->osfd = osfd;
            unixpd->in_flags = in_flags;
            unixpd->out_flags = 0;
            unixpd++;
            pdcnt++;
        }
    }

    /*
     * see comments in mozilla/cmd/xfe/mozilla.c (look for
     * "PR_XGetXtHackFD")
     */
   {
     int needToLockXAgain;
 
     needToLockXAgain = 0;
     if (rd && (_pr_xt_hack_fd != -1)
             && FD_ISSET(_pr_xt_hack_fd, rd) && PR_XIsLocked()
             && (!_pr_xt_hack_okayToReleaseXLock
             || _pr_xt_hack_okayToReleaseXLock())) {
         PR_XUnlock();
         needToLockXAgain = 1;
     }

    /* This is the potentially blocking step */
    retVal = _PR_WaitForMultipleFDs(unixpds, pdcnt, timeout);

     if (needToLockXAgain) {
         PR_XLock();
     }
   }

    if (retVal > 0) {
        /* Compute select results */
        if (rd) ZAP_SET(rd, width);
        if (wr) ZAP_SET(wr, width);
        if (ex) ZAP_SET(ex, width);

        /*
         * The return value can be either the number of ready file
         * descriptors or the number of set bits in the three fd_set's.
         */
        retVal = 0;  /* we're going to recompute */
        eunixpd = unixpds + pdcnt;
        for (unixpd = unixpds; unixpd < eunixpd; unixpd++) {
            if (unixpd->out_flags) {
                int nbits = 0;  /* The number of set bits on for this fd */

                if (unixpd->out_flags & _PR_UNIX_POLL_NVAL) {
                    errno = EBADF;
                    PR_LOG(_pr_io_lm, PR_LOG_ERROR,
                            ("select returns EBADF for %d", unixpd->osfd));
                    retVal = -1;
                    break;
                }
                /*
                 * If a socket has a pending error, it is considered
                 * both readable and writable.  (See W. Richard Stevens,
                 * Unix Network Programming, Vol. 1, 2nd Ed., Section 6.3,
                 * pp. 153-154.)  We also consider a socket readable if
                 * it has a hangup condition.
                 */
                if (rd && (unixpd->in_flags & _PR_UNIX_POLL_READ)
                        && (unixpd->out_flags & (_PR_UNIX_POLL_READ