root/lib/pselect.c

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DEFINITIONS

This source file includes following definitions.
  1. pselect
  2. rpl_pselect

     1 /* pselect - synchronous I/O multiplexing
     2 
     3    Copyright 2011-2023 Free Software Foundation, Inc.
     4 
     5    This file is part of gnulib.
     6 
     7    This file is free software: you can redistribute it and/or modify
     8    it under the terms of the GNU Lesser General Public License as
     9    published by the Free Software Foundation; either version 2.1 of the
    10    License, or (at your option) any later version.
    11 
    12    This file 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 Lesser General Public License for more details.
    16 
    17    You should have received a copy of the GNU Lesser General Public License
    18    along with this program.  If not, see <https://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 #if !HAVE_PSELECT
    37 
    38 int
    39 pselect (int nfds, fd_set *restrict rfds,
    40          fd_set *restrict wfds, fd_set *restrict xfds,
    41          struct timespec const *restrict timeout,
    42          sigset_t const *restrict sigmask)
    43 {
    44   int select_result;
    45   sigset_t origmask;
    46   struct timeval tv, *tvp;
    47 
    48   if (nfds < 0 || nfds > FD_SETSIZE)
    49     {
    50       errno = EINVAL;
    51       return -1;
    52     }
    53 
    54   if (timeout)
    55     {
    56       if (! (0 <= timeout->tv_nsec && timeout->tv_nsec < 1000000000))
    57         {
    58           errno = EINVAL;
    59           return -1;
    60         }
    61 
    62       tv = (struct timeval) {
    63         .tv_sec = timeout->tv_sec,
    64         .tv_usec = (timeout->tv_nsec + 999) / 1000
    65       };
    66       tvp = &tv;
    67     }
    68   else
    69     tvp = NULL;
    70 
    71   /* Signal mask munging should be atomic, but this is the best we can
    72      do in this emulation.  */
    73   if (sigmask)
    74     pthread_sigmask (SIG_SETMASK, sigmask, &origmask);
    75 
    76   select_result = select (nfds, rfds, wfds, xfds, tvp);
    77 
    78   if (sigmask)
    79     {
    80       int select_errno = errno;
    81       pthread_sigmask (SIG_SETMASK, &origmask, NULL);
    82       errno = select_errno;
    83     }
    84 
    85   return select_result;
    86 }
    87 
    88 #else /* HAVE_PSELECT */
    89 # include <unistd.h>
    90 # undef pselect
    91 
    92 int
    93 rpl_pselect (int nfds, fd_set *restrict rfds,
    94              fd_set *restrict wfds, fd_set *restrict xfds,
    95              struct timespec const *restrict timeout,
    96              sigset_t const *restrict sigmask)
    97 {
    98   int i;
    99 
   100   /* FreeBSD 8.2 has a bug: it does not always detect invalid fds.  */
   101   if (nfds < 0 || nfds > FD_SETSIZE)
   102     {
   103       errno = EINVAL;
   104       return -1;
   105     }
   106   for (i = 0; i < nfds; i++)
   107     {
   108       if (((rfds && FD_ISSET (i, rfds))
   109            || (wfds && FD_ISSET (i, wfds))
   110            || (xfds && FD_ISSET (i, xfds)))
   111           && dup2 (i, i) != i)
   112         return -1;
   113     }
   114 
   115   return pselect (nfds, rfds, wfds, xfds, timeout, sigmask);
   116 }
   117 
   118 #endif

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