sysdeps/unix/sysv/linux/poll.c

   1 /* Poll system call, with emulation if it is not available.
   2    Copyright (C) 1997, 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <sys/poll.h>
  22
  23 #include <sys/syscall.h>
  24 #ifdef __NR_poll
  25
  26 extern int __syscall_poll __P ((struct pollfd *fds, unsigned int nfds,
  27                                 int timeout));
  28 weak_extern (__syscall_poll)
  29
  30 static int __emulate_poll __P ((struct pollfd *fds, unsigned long int nfds,
  31                                 int timeout)) internal_function;
  32
  33 /* The real implementation.  */
  34 int
  35 __poll (fds, nfds, timeout)
  36      struct pollfd *fds;
  37      unsigned long int nfds;
  38      int timeout;
  39 {
  40   static int must_emulate = 0;
  41   int (*syscall) __P ((struct pollfd *, unsigned int, int)) = __syscall_poll;
  42
  43   if (!must_emulate)
  44     {
  45       if (syscall)
  46         {
  47           int errno_saved = errno;
  48           int retval = __syscall_poll (fds, nfds, timeout);
  49
  50           if (retval >= 0 || errno != ENOSYS)
  51             return retval;
  52
  53           __set_errno (errno_saved);
  54         }
  55
  56       must_emulate = 1;
  57     }
  58
  59   return __emulate_poll (fds, nfds, timeout);
  60 }
  61 weak_alias (__poll, poll)
  62
  63 /* Get the emulation code.  */
  64 # define __poll(fds, nfds, timeout) \
  65   static internal_function __emulate_poll (fds, nfds, timeout)
  66 #endif
  67 #include <sysdeps/unix/bsd/poll.c>