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poll.c
/* This file is part of the Sofia-SIP package.

   Copyright (C) 2005 Nokia Corporation.

   Contact: Pekka Pessi <pekka.pessi@nokia.com>

   This file is originally from GNU C library.

   Copyright (C) 1994,1996,1997,1998,1999,2001,2002
   Free Software Foundation, Inc.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include "config.h"

#if HAVE_SELECT

#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#include "sofia-sip/su.h"

#if HAVE_ALLOCA_H
#include <alloca.h>
#endif

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

#include <string.h>

#include "sofia-sip/su_wait.h"

#undef NBBY
#undef NFDBITS
#undef FDSETSIZE
#undef roundup

#define     NBBY  8                             /* bits in a byte */
#define NFDBITS   (sizeof(long) * NBBY)         /* bits per mask */

#define FDSETSIZE(n) (((n) + NFDBITS - 1) / NFDBITS * (NFDBITS / NBBY))
#define roundup(n, x) (((n) + (x) - 1) / (x) * (x))

/* Emulated poll() using select().

This is used by su_wait().

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(struct pollfd *fds, nfds_t nfds, int timeout)
{
  struct timeval tv;
  struct pollfd *f;
  int ready;
  int maxfd = 0;

#if HAVE_ALLOCA_H
  static int max_fd_size;
  int bytes;
  fd_set *rset, *wset, *xset;

  if (!max_fd_size)
    max_fd_size = getdtablesize ();

  bytes = FDSETSIZE (max_fd_size);

  rset = alloca (bytes);
  wset = alloca (bytes);
  xset = alloca (bytes);

  /* We can't call FD_ZERO, since FD_ZERO only works with sets
     of exactly __FD_SETSIZE size.  */
  memset (rset, 0, bytes);
  memset (wset, 0, bytes);
  memset (xset, 0, bytes);
#else
  fd_set rset[1], wset[1], xset[1];

  FD_ZERO(rset);
  FD_ZERO(wset);
  FD_ZERO(xset);
#endif

  for (f = fds; f < &fds[nfds]; ++f)
    {
      f->revents = 0;
      if (f->fd >= 0)
      {
#if HAVE_ALLOCA_H
        if (f->fd >= max_fd_size)
          {
            /* The user provides a file descriptor number which is higher
             than the maximum we got from the `getdtablesize' call.
             Maybe this is ok so enlarge the arrays.  */
            fd_set *nrset, *nwset, *nxset;
            int nbytes;

            max_fd_size = roundup (f->fd, NFDBITS);
            nbytes = FDSETSIZE (max_fd_size);

            nrset = alloca (nbytes);
            nwset = alloca (nbytes);
            nxset = alloca (nbytes);

            memset ((char *) nrset + bytes, 0, nbytes - bytes);
            memset ((char *) nwset + bytes, 0, nbytes - bytes);
            memset ((char *) nxset + bytes, 0, nbytes - bytes);

            rset = memcpy (nrset, rset, bytes);
            wset = memcpy (nwset, wset, bytes);
            xset = memcpy (nxset, xset, bytes);

            bytes = nbytes;
          }
#else
        if (f->fd >= FD_SETSIZE) {
          errno = EBADF;
          return -1;
        }
#endif /* HAVE_ALLOCA_H */

        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 % 1000) * 1000;

  while (1)
    {
      ready = select (maxfd + 1, rset, wset, xset,
                  timeout == -1 ? NULL : &tv);

      /* It might be that one or more of the file descriptors is invalid.
       We now try to find and mark them and then try again.  */
      if (ready == -1 && errno == EBADF)
      {
        struct timeval sngl_tv;
#if HAVE_ALLOCA_H
        fd_set *sngl_rset = alloca (bytes);
        fd_set *sngl_wset = alloca (bytes);
        fd_set *sngl_xset = alloca (bytes);

        /* Clear the original set.  */
        memset (rset, 0, bytes);
        memset (wset, 0, bytes);
        memset (xset, 0, bytes);
#else
        fd_set sngl_rset[1];
        fd_set sngl_wset[1];
        fd_set sngl_xset[1];

        FD_ZERO(rset);
        FD_ZERO(wset);
        FD_ZERO(xset);
#endif

        /* This means we don't wait for input.  */
        sngl_tv.tv_sec = 0;
        sngl_tv.tv_usec = 0;

        maxfd = -1;

        /* Reset the return value.  */
        ready = 0;

        for (f = fds; f < &fds[nfds]; ++f)
          if (f->fd != -1 && (f->events & (POLLIN|POLLOUT|POLLPRI))
            && (f->revents & POLLNVAL) == 0)
            {
            int n;

#if HAVE_ALLOCA_H
            memset (sngl_rset, 0, bytes);
            memset (sngl_wset, 0, bytes);
            memset (sngl_xset, 0, bytes);
#else
            FD_ZERO(rset);
            FD_ZERO(wset);
            FD_ZERO(xset);
#endif

            if (f->events & POLLIN)
              FD_SET (f->fd, sngl_rset);
            if (f->events & POLLOUT)
              FD_SET (f->fd, sngl_wset);
            if (f->events & POLLPRI)
              FD_SET (f->fd, sngl_xset);

            n = select (f->fd + 1, sngl_rset, sngl_wset, sngl_xset,
                      &sngl_tv);
            if (n != -1)
              {
                /* This descriptor is ok.  */
                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)
                  maxfd = f->fd;
                if (n > 0)
                  /* Count it as being available.  */
                  ++ready;
              }
            else if (errno == EBADF)
              f->revents |= POLLNVAL;
            }
        /* Try again.  */
        continue;
      }

      break;
    }

  if (ready > 0)
    for (f = fds; f < &fds[nfds]; ++f)
      {
      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;
}

#endif

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