newlib-cygwin/winsup/cygwin/poll.cc

/* poll.cc. Implements poll(2) via usage of select(2) call.

   Copyright 2000 Cygnus Solutions.

   This file is part of Cygwin.

   This software is a copyrighted work licensed under the terms of the
   Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   details. */

#include "winsup.h"
#include <sys/poll.h>

extern "C"
int
poll (struct pollfd *fds, unsigned int nfds, int timeout)
{
  int max_fd = 0;
  fd_set open_fds, read_fds, write_fds, except_fds;
  struct timeval tv = { timeout / 1000, (timeout % 1000) * 1000 };

  FD_ZERO (&open_fds);
  FD_ZERO (&read_fds);
  FD_ZERO (&write_fds);
  FD_ZERO (&except_fds);

  for (unsigned int i = 0; i < nfds; ++i)
    if (!dtable.not_open (fds[i].fd))
      {
        FD_SET (fds[i].fd, &open_fds);
        if (fds[i].events & POLLIN)
          FD_SET (fds[i].fd, &read_fds);
        if (fds[i].events & POLLOUT)
          FD_SET (fds[i].fd, &write_fds);
        if (fds[i].events & POLLPRI)
          FD_SET (fds[i].fd, &except_fds);
        if (fds[i].fd > max_fd)
          max_fd = fds[i].fd;
      }

  int ret = cygwin_select (max_fd + 1, &read_fds, &write_fds, &except_fds,
                           timeout < 0 ? NULL : &tv);

  if (ret >= 0)
    for (unsigned int i = 0; i < nfds; ++i)
      {
        if (!FD_ISSET (fds[i].fd, &open_fds))
	  fds[i].revents = POLLNVAL;
        else if (dtable.not_open(fds[i].fd))
	  fds[i].revents = POLLHUP;
        else
	  {
            fds[i].revents = 0;
	    if (FD_ISSET (fds[i].fd, &read_fds))
	      fds[i].revents |= POLLIN;
	    if (FD_ISSET (fds[i].fd, &write_fds))
	      fds[i].revents |= POLLOUT;
	    if (FD_ISSET (fds[i].fd, &except_fds))
	      fds[i].revents |= POLLPRI;
	  }
      }

  return ret;
}