/* dnsmasq is Copyright (c) 2000-2025 Simon Kelley

   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; version 2 dated June, 1991, or

   (at your option) version 3 dated 29 June, 2007.

   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, see <http://www.gnu.org/licenses/>.

*/

#include "dnsmasq.h"

/* Wrapper for poll(). Allocates and extends array of struct pollfds,

   keeps them in fd order so that we can set and test conditions on

   fd using a simple but efficient binary chop. */

/* poll_reset()

   poll_listen(fd, event)

   .

   .

   poll_listen(fd, event);

   hits = do_poll(timeout);

   if (poll_check(fd, event)

    .

    .

   if (poll_check(fd, event)

    .

    .

    event is OR of POLLIN, POLLOUT, POLLERR, etc

*/

static struct pollfd *pollfds = NULL;

static nfds_t nfds, arrsize = 0;

/* Binary search. Returns either the pollfd with fd, or

   if the fd doesn't match, or return equals nfds, the entry

   to the left of which a new record should be inserted. */

static nfds_t fd_search(int fd)

{

  nfds_t left, right, mid;

  if ((right = nfds) == 0)

    return 0;

  left = 0;

  while (1)

    {

      if (right == left + 1)

  return (pollfds[left].fd >= fd) ? left : right;

      mid = (left + right)/2;

      if (pollfds[mid].fd > fd)

  right = mid;

      else 

  left = mid;

    }

}

void poll_reset(void)

{

  nfds = 0;

}

int do_poll(int timeout)

{

  return poll(pollfds, nfds, timeout);

}

int poll_check(int fd, short event)

{

  nfds_t i = fd_search(fd);

  if (i < nfds && pollfds[i].fd == fd)

    return pollfds[i].revents & event;

  return 0;

}

void poll_listen(int fd, short event)

{

   nfds_t i = fd_search(fd);

   if (i < nfds && pollfds[i].fd == fd)

     pollfds[i].events |= event;

   else

     {

       if (arrsize == nfds)

   {

     /* Array too small. Extend. */

     struct pollfd *new;

     arrsize = (arrsize == 0) ? 64 : arrsize * 2;

     if (!(new = whine_realloc(pollfds, arrsize * sizeof(struct pollfd))))

       return;

     pollfds = new;

   }

       memmove(&pollfds[i+1], &pollfds[i], (nfds - i) * sizeof(struct pollfd));

       pollfds[i].fd = fd;

       pollfds[i].events = event;

       nfds++;

     }

}