sysdeps/unix/bsd/poll.c

   1 /* Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <sys/poll.h>
  20 #include <sys/types.h>
  21 #include <errno.h>
  22 #include <string.h>
  23 #include <sys/time.h>
  24
  25 /* Poll the file descriptors described by the NFDS structures starting at
  26    FDS.  If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
  27    an event to occur; if TIMEOUT is -1, block until an event occurs.
  28    Returns the number of file descriptors with events, zero if timed out,
  29    or -1 for errors.  */
  30
  31 int
  32 poll (fds, nfds, timeout)
  33      struct pollfd *fds;
  34      unsigned long int nfds;
  35      int timeout;
  36 {
  37   struct timeval tv;
  38   fd_set rset, wset, xset;
  39   struct pollfd *f;
  40   int ready;
  41   int maxfd = 0;
  42
  43   FD_ZERO (&rset);
  44   FD_ZERO (&wset);
  45   FD_ZERO (&xset);
  46
  47   for (f = fds; f < &fds[nfds]; ++f)
  48     if (f->fd >= 0)
  49       {
  50         if (f->events & POLLIN)
  51           FD_SET (f->fd, &rset);
  52         if (f->events & POLLOUT)
  53           FD_SET (f->fd, &wset);
  54         if (f->events & POLLPRI)
  55           FD_SET (f->fd, &xset);
  56         if (f->fd > maxfd && (f->events & (POLLIN|POLLOUT|POLLPRI)))
  57           maxfd = f->fd;
  58       }
  59
  60   tv.tv_sec = timeout / 1000;
  61   tv.tv_usec = (timeout % 1000) * 1000;
  62
  63   ready = __select (maxfd + 1, &rset, &wset, &xset,
  64                     timeout == -1 ? NULL : &tv);
  65   if (ready > 0)
  66     for (f = fds; f < &fds[nfds]; ++f)
  67       {
  68         f->revents = 0;
  69         if (f->fd >= 0)
  70           {
  71             if (FD_ISSET (f->fd, &rset))
  72               f->revents |= POLLIN;
  73             if (FD_ISSET (f->fd, &wset))
  74               f->revents |= POLLOUT;
  75             if (FD_ISSET (f->fd, &xset))
  76               f->revents |= POLLPRI;
  77           }
  78       }
  79
  80   return ready;
  81 }