gnulib/lib/poll.c

/* Emulation for poll(2)
   Contributed by Paolo Bonzini.

   Copyright 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

   This file is part of gnulib.

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

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

#include "config.h"

#include <sys/types.h>
#include "poll.h"
#include <errno.h>
#include <limits.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <unistd.h>

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#ifdef HAVE_SYS_FILIO_H
#include <sys/filio.h>
#endif

#if TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif

#ifndef INFTIM
#define INFTIM (-1)
#endif

#ifndef EOVERFLOW
#define EOVERFLOW EINVAL
#endif

int
poll (pfd, nfd, timeout)
     struct pollfd *pfd;
     nfds_t nfd;
     int timeout;
{
  fd_set rfds, wfds, efds;
  struct timeval tv, *ptv;
  int maxfd, rc, happened;
  nfds_t i;

#ifdef _SC_OPEN_MAX
  if (nfd > sysconf (_SC_OPEN_MAX))
    {
      errno = EINVAL;
      return -1;
    }
#else /* !_SC_OPEN_MAX */
#ifdef OPEN_MAX
  if (nfd > OPEN_MAX)
    {
      errno = EINVAL;
      return -1;
    }
#endif /* OPEN_MAX -- else, no check is needed */
#endif /* !_SC_OPEN_MAX */

  /* EFAULT is not necessary to implement, but let's do it in the
     simplest case. */
  if (!pfd)
    {
      errno = EFAULT;
      return -1;
    }

  /* convert timeout number into a timeval structure */
  ptv = &tv;
  if (timeout >= 0)
    {
      /* return immediately or after timeout */
      ptv->tv_sec = timeout / 1000;
      ptv->tv_usec = (timeout % 1000) * 1000;
    }
  else if (timeout == INFTIM)
    /* wait forever */
    ptv = NULL;
  else
    {
      errno = EINVAL;
      return -1;
    }

  /* create fd sets and determine max fd */
  maxfd = -1;
  FD_ZERO (&rfds);
  FD_ZERO (&wfds);
  FD_ZERO (&efds);
  for (i = 0; i < nfd; i++)
    {
      if (pfd[i].fd < 0)
	continue;

      if (pfd[i].events & (POLLIN | POLLRDNORM))
	FD_SET (pfd[i].fd, &rfds);

      /* see select(2): "the only exceptional condition detectable
         is out-of-band data received on a socket", hence we push
         POLLWRBAND events onto wfds instead of efds. */
      if (pfd[i].events & (POLLOUT | POLLWRNORM | POLLWRBAND))
	FD_SET (pfd[i].fd, &wfds);
      if (pfd[i].events & (POLLPRI | POLLRDBAND))
	FD_SET (pfd[i].fd, &efds);
      if (pfd[i].fd >= maxfd
	  && (pfd[i].events & (POLLIN | POLLOUT | POLLPRI
			       | POLLRDNORM | POLLRDBAND
			       | POLLWRNORM | POLLWRBAND)))
	{
	  maxfd = pfd[i].fd;
	  if (maxfd > FD_SETSIZE)
	    {
	      errno = EOVERFLOW;
	      return -1;
	    }
	}
    }

  /* examine fd sets */
  rc = select (maxfd + 1, &rfds, &wfds, &efds, ptv);

  /* establish results */
  if (rc > 0)
    {
      rc = 0;
      for (i = 0; i < nfd; i++)
	{
	  pfd[i].revents = 0;
	  if (pfd[i].fd < 0)
	    continue;

	  happened = 0;
	  if (FD_ISSET (pfd[i].fd, &rfds))
	    {
	      int r;
	      long avail = -1;
	      /* support for POLLHUP.  */
#if defined __MACH__ && defined __APPLE__
	      /* There is a bug in Mac OS X that causes it to ignore MSG_PEEK for
		 some kinds of descriptors.  Use FIONREAD to emulate POLLHUP.
		 It is still not completely POSIX compliant (it does not fully
		 work on TTYs), but at least it does not delete data!  For other
		 platforms, we still use MSG_PEEK because it was proved to be
		 reliable, and I a leery of changing it.  */
	      do
		r = ioctl (pfd[i].fd, FIONREAD, &avail);
	      while (r == -1 && (errno == EAGAIN || errno == EINTR));
	      if (avail < 0)
	        avail = 0;
#else
	      char data[64];
	      r = recv (pfd[i].fd, data, 64, MSG_PEEK);
	      if (r == -1)
		{
		  avail = (errno == ESHUTDOWN || errno == ECONNRESET ||
	                   errno == ECONNABORTED || errno == ENETRESET) ? 0 : -1;
		  errno = 0;
		}
	      else
	        avail = r;
#endif

	      /* An hung up descriptor does not increase the return value! */
	      if (avail == 0)
		pfd[i].revents |= POLLHUP;
	      else if (avail == -1)
		pfd[i].revents |= POLLERR;
	      else
		happened |= POLLIN | POLLRDNORM;
	    }

	  if (FD_ISSET (pfd[i].fd, &wfds))
	    happened |= POLLOUT | POLLWRNORM | POLLWRBAND;

	  if (FD_ISSET (pfd[i].fd, &efds))
	    happened |= POLLPRI | POLLRDBAND;

	  pfd[i].revents |= pfd[i].events & happened;
	  rc += (happened > 0);
	}
    }

  return rc;
}