lib/pselect.c

   1 /* pselect - synchronous I/O multiplexing
   2
   3    Copyright 2011-2012 Free Software Foundation, Inc.
   4
   5    This file is part of gnulib.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License along
  18    with this program; if not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* written by Paul Eggert */
  21
  22 #include <config.h>
  23
  24 #include <sys/select.h>
  25
  26 #include <errno.h>
  27 #include <signal.h>
  28
  29 /* Examine the size-NFDS file descriptor sets in RFDS, WFDS, and XFDS
  30    to see whether some of their descriptors are ready for reading,
  31    ready for writing, or have exceptions pending.  Wait for at most
  32    TIMEOUT seconds, and use signal mask SIGMASK while waiting.  A null
  33    pointer parameter stands for no descriptors, an infinite timeout,
  34    or an unaffected signal mask.  */
  35
  36 int
  37 pselect (int nfds, fd_set *restrict rfds,
  38          fd_set *restrict wfds, fd_set *restrict xfds,
  39          struct timespec const *restrict timeout,
  40          sigset_t const *restrict sigmask)
  41 {
  42   int select_result;
  43   sigset_t origmask;
  44   struct timeval tv, *tvp;
  45
  46   if (timeout)
  47     {
  48       if (! (0 <= timeout->tv_nsec && timeout->tv_nsec < 1000000000))
  49         {
  50           errno = EINVAL;
  51           return -1;
  52         }
  53
  54       tv.tv_sec = timeout->tv_sec;
  55       tv.tv_usec = (timeout->tv_nsec + 999) / 1000;
  56       tvp = &tv;
  57     }
  58   else
  59     tvp = NULL;
  60
  61   /* Signal mask munging should be atomic, but this is the best we can
  62      do in this emulation.  */
  63   if (sigmask)
  64     pthread_sigmask (SIG_SETMASK, sigmask, &origmask);
  65
  66   select_result = select (nfds, rfds, wfds, xfds, tvp);
  67
  68   if (sigmask)
  69     {
  70       int select_errno = errno;
  71       pthread_sigmask (SIG_SETMASK, &origmask, NULL);
  72       errno = select_errno;
  73     }
  74
  75   return select_result;
  76 }