newlib/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>
#include <errno.h>
#include "fhandler.h"
#include "dtable.h"
#include "cygerrno.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 };

  for (unsigned int i = 0; i < nfds; ++i)
    if (fds[i].fd > max_fd)
      max_fd = fds[i].fd;

  size_t fds_size = howmany(max_fd + 1, NFDBITS) * sizeof (fd_mask);

  open_fds = (fd_set *) alloca (fds_size);
  read_fds = (fd_set *) alloca (fds_size);
  write_fds = (fd_set *) alloca (fds_size);
  except_fds = (fd_set *) alloca (fds_size);

  if (!open_fds || !read_fds || !write_fds || !except_fds)
    {
      set_errno (ENOMEM);
      return -1;
    }

  memset (open_fds, 0, fds_size);
  memset (read_fds, 0, fds_size);
  memset (write_fds, 0, fds_size);
  memset (except_fds, 0, fds_size);

  for (unsigned int i = 0; i < nfds; ++i)
    if (!fdtab.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);
      }

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

  for (unsigned int i = 0; i < nfds; ++i)
    {
      if (!FD_ISSET (fds[i].fd, open_fds))
        fds[i].revents = POLLNVAL;
      else if (fdtab.not_open(fds[i].fd))
        fds[i].revents = POLLHUP;
      else if (ret < 0)
        fds[i].revents = POLLERR;
      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;
}