src/network/poll.c

   1 /*****************************************************************************
   2  * poll.c: I/O event multiplexing
   3  *****************************************************************************
   4  * Copyright © 2007 Rémi Denis-Courmont
   5  * $Id$
   6  *
   7  * Author: Rémi Denis-Courmont
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 #ifdef HAVE_CONFIG_H
  25 # include "config.h"
  26 #endif
  27
  28 #include <vlc_common.h>
  29 #include <stdlib.h>
  30 #include <vlc_network.h>
  31
  32
  33 #ifdef HAVE_MAEMO
  34 # include <signal.h>
  35 # include <errno.h>
  36 # include <poll.h>
  37
  38 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
  39 {
  40     struct timespec tsbuf, *ts;
  41     sigset_t set;
  42     int canc, ret;
  43
  44     if (timeout != -1)
  45     {
  46         div_t d = div (timeout, 1000);
  47         tsbuf.tv_sec = d.quot;
  48         tsbuf.tv_nsec = d.rem * 1000000;
  49         ts = &tsbuf;
  50     }
  51     else
  52         ts = NULL;
  53
  54     pthread_sigmask (SIG_BLOCK, NULL, &set);
  55     sigdelset (&set, SIGRTMIN);
  56
  57     canc = vlc_savecancel ();
  58     ret = ppoll (fds, nfds, ts, &set);
  59     vlc_restorecancel (canc);
  60
  61     vlc_testcancel ();
  62     return ret;
  63 }
  64
  65 #elif defined (HAVE_POLL)
  66 struct pollfd;
  67
  68 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
  69 {
  70     (void)fds; (void)nfds; (void)timeout;
  71     abort ();
  72 }
  73 #else /* !HAVE_POLL */
  74
  75 #include <string.h>
  76
  77 int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
  78 {
  79     fd_set rdset, wrset, exset;
  80     struct timeval tv = { 0, 0 };
  81     int val;
  82
  83 resume:
  84     val = -1;
  85     vlc_testcancel ();
  86
  87     FD_ZERO (&rdset);
  88     FD_ZERO (&wrset);
  89     FD_ZERO (&exset);
  90     for (unsigned i = 0; i < nfds; i++)
  91     {
  92         int fd = fds[i].fd;
  93         if (val < fd)
  94             val = fd;
  95
  96         /* With POSIX, FD_SET & FD_ISSET are not defined if fd is negative or
  97          * bigger or equal than FD_SETSIZE. That is one of the reasons why VLC
  98          * uses poll() rather than select(). Most POSIX systems implement
  99          * fd_set has a bit field with no sanity checks. This is especially bad
 100          * on systems (such as BSD) that have no process open files limit by
 101          * default, such that it is quite feasible to get fd >= FD_SETSIZE.
 102          * The next instructions will result in a buffer overflow if run on
 103          * a POSIX system, and the later FD_ISSET will do undefined memory
 104          * access.
 105          *
 106          * With Winsock, fd_set is a table of integers. This is awfully slow.
 107          * However, FD_SET and FD_ISSET silently and safely discard
 108          * overflows. If it happens we will loose socket events. Note that
 109          * most (if not all) Winsock SOCKET handles are actually bigger than
 110          * FD_SETSIZE in terms of absolute value - they are not POSIX file
 111          * descriptors. From Vista, there is a much nicer WSAPoll(), but Mingw
 112          * is yet to support it.
 113          *
 114          * With BeOS, the situation is unknown (FIXME: document).
 115          */
 116         if (fds[i].events & POLLIN)
 117             FD_SET (fd, &rdset);
 118         if (fds[i].events & POLLOUT)
 119             FD_SET (fd, &wrset);
 120         if (fds[i].events & POLLPRI)
 121             FD_SET (fd, &exset);
 122     }
 123
 124 #ifndef HAVE_ALERTABLE_SELECT
 125 # warning FIXME! Fix cancellation and remove this crap.
 126     if ((timeout < 0) || (timeout > 50))
 127     {
 128         tv.tv_sec = 0;
 129         tv.tv_usec = 50000;
 130     }
 131     else
 132 #endif
 133     if (timeout >= 0)
 134     {
 135         div_t d = div (timeout, 1000);
 136         tv.tv_sec = d.quot;
 137         tv.tv_usec = d.rem * 1000;
 138     }
 139
 140     val = select (val + 1, &rdset, &wrset, &exset,
 141                   /*(timeout >= 0) ?*/ &tv /*: NULL*/);
 142
 143 #ifndef HAVE_ALERTABLE_SELECT
 144     if (val == 0)
 145     {
 146         if (timeout > 0)
 147             timeout -= (timeout > 50) ? 50 : timeout;
 148         if (timeout != 0)
 149             goto resume;
 150     }
 151 #endif
 152
 153     if (val == -1)
 154         return -1;
 155
 156     for (unsigned i = 0; i < nfds; i++)
 157     {
 158         int fd = fds[i].fd;
 159         fds[i].revents = (FD_ISSET (fd, &rdset) ? POLLIN : 0)
 160                        | (FD_ISSET (fd, &wrset) ? POLLOUT : 0)
 161                        | (FD_ISSET (fd, &exset) ? POLLPRI : 0);
 162     }
 163     return val;
 164 }
 165 #endif /* !HAVE_POLL */