/* Hook for making file descriptor functions close(), ioctl() extensible.

   Copyright (C) 2009-2020 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2009.

   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 3 of the License, 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, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include "fd-hook.h"

#include <stdlib.h>

/* Currently, this entire code is only needed for the handling of sockets

   on native Windows platforms.  */

#if WINDOWS_SOCKETS

/* The first and last link in the doubly linked list.

   Initially the list is empty.  */

static struct fd_hook anchor = { &anchor, &anchor, NULL, NULL };

int

execute_close_hooks (const struct fd_hook *remaining_list, gl_close_fn primary,

                     int fd)

{

  if (remaining_list == &anchor)

    /* End of list reached.  */

    return primary (fd);

  else

    return remaining_list->private_close_fn (remaining_list->private_next,

                                             primary, fd);

}

int

execute_all_close_hooks (gl_close_fn primary, int fd)

{

  return execute_close_hooks (anchor.private_next, primary, fd);

}

int

execute_ioctl_hooks (const struct fd_hook *remaining_list, gl_ioctl_fn primary,

                     int fd, int request, void *arg)

{

  if (remaining_list == &anchor)

    /* End of list reached.  */

    return primary (fd, request, arg);

  else

    return remaining_list->private_ioctl_fn (remaining_list->private_next,

                                             primary, fd, request, arg);

}

int

execute_all_ioctl_hooks (gl_ioctl_fn primary,

                         int fd, int request, void *arg)

{

  return execute_ioctl_hooks (anchor.private_next, primary, fd, request, arg);

}

void

register_fd_hook (close_hook_fn close_hook, ioctl_hook_fn ioctl_hook, struct fd_hook *link)

{

  if (close_hook == NULL)

    close_hook = execute_close_hooks;

  if (ioctl_hook == NULL)

    ioctl_hook = execute_ioctl_hooks;

  if (link->private_next == NULL && link->private_prev == NULL)

    {

      /* Add the link to the doubly linked list.  */

      link->private_next = anchor.private_next;

      link->private_prev = &anchor;

      link->private_close_fn = close_hook;

      link->private_ioctl_fn = ioctl_hook;

      anchor.private_next->private_prev = link;

      anchor.private_next = link;

    }

  else

    {

      /* The link is already in use.  */

      if (link->private_close_fn != close_hook

          || link->private_ioctl_fn != ioctl_hook)

        abort ();

    }

}

void

unregister_fd_hook (struct fd_hook *link)

{

  struct fd_hook *next = link->private_next;

  struct fd_hook *prev = link->private_prev;

  if (next != NULL && prev != NULL)

    {

      /* The link is in use.  Remove it from the doubly linked list.  */

      prev->private_next = next;

      next->private_prev = prev;

      /* Clear the link, to mark it unused.  */

      link->private_next = NULL;

      link->private_prev = NULL;

      link->private_close_fn = NULL;

      link->private_ioctl_fn = NULL;

    }

}

#endif