poll.c

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/* Copyright (C) 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <sys/poll.h>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>

/* Poll the file descriptors described by the NFDS structures starting at
   FDS.  If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
   an event to occur; if TIMEOUT is -1, block until an event occurs.
   Returns the number of file descriptors with events, zero if timed out,
   or -1 for errors.  */

int
poll (fds, nfds, timeout)
     struct pollfd *fds;
     unsigned long int nfds;
     int timeout;
{
  struct timeval tv;
  fd_set rset, wset, xset;
  struct pollfd *f;
  int ready;
  int maxfd = 0;

  FD_ZERO (&rset);
  FD_ZERO (&wset);
  FD_ZERO (&xset);

  for (f = fds; f < &fds[nfds]; ++f)
    if (f->fd >= 0)
      {
	if (f->events & POLLIN)
	  FD_SET (f->fd, &rset);
	if (f->events & POLLOUT)
	  FD_SET (f->fd, &wset);
	if (f->events & POLLPRI)
	  FD_SET (f->fd, &xset);
	if (f->fd > maxfd && (f->events & (POLLIN|POLLOUT|POLLPRI)))
	  maxfd = f->fd;
      }

  tv.tv_sec = timeout / 1000;
  tv.tv_usec = (timeout + 999) / 1000;

  ready = __select (maxfd + 1, &rset, &wset, &xset,
		    timeout == -1 ? NULL : &tv);
  if (ready > 0)
    for (f = fds; f < &fds[nfds]; ++f)
      {
	f->revents = 0;
	if (f->fd >= 0)
	  {
	    if (FD_ISSET (f->fd, &rset))
	      f->revents |= POLLIN;
	    if (FD_ISSET (f->fd, &wset))
	      f->revents |= POLLOUT;
	    if (FD_ISSET (f->fd, &xset))
	      f->revents |= POLLPRI;
	  }
      }

  return ready;
}