1/* Hook for making making file descriptor functions close(), ioctl() extensible.
2   Copyright (C) 2009-2012 Free Software Foundation, Inc.
3   Written by Bruno Haible <bruno@clisp.org>, 2009.
4
5   This program is free software: you can redistribute it and/or modify it
6   under the terms of the GNU General Public License as published
7   by the Free Software Foundation; either version 3 of the License, or
8   (at your option) any later version.
9
10   This program is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   General Public License for more details.
14
15   You should have received a copy of the GNU General Public License
16   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
17
18#include <config.h>
19
20/* Specification.  */
21#include "fd-hook.h"
22
23#include <stdlib.h>
24
25/* Currently, this entire code is only needed for the handling of sockets
26   on native Windows platforms.  */
27#if WINDOWS_SOCKETS
28
29/* The first and last link in the doubly linked list.
30   Initially the list is empty.  */
31static struct fd_hook anchor = { &anchor, &anchor, NULL, NULL };
32
33int
34execute_close_hooks (const struct fd_hook *remaining_list, gl_close_fn primary,
35                     int fd)
36{
37  if (remaining_list == &anchor)
38    /* End of list reached.  */
39    return primary (fd);
40  else
41    return remaining_list->private_close_fn (remaining_list->private_next,
42                                             primary, fd);
43}
44
45int
46execute_all_close_hooks (gl_close_fn primary, int fd)
47{
48  return execute_close_hooks (anchor.private_next, primary, fd);
49}
50
51int
52execute_ioctl_hooks (const struct fd_hook *remaining_list, gl_ioctl_fn primary,
53                     int fd, int request, void *arg)
54{
55  if (remaining_list == &anchor)
56    /* End of list reached.  */
57    return primary (fd, request, arg);
58  else
59    return remaining_list->private_ioctl_fn (remaining_list->private_next,
60                                             primary, fd, request, arg);
61}
62
63int
64execute_all_ioctl_hooks (gl_ioctl_fn primary,
65                         int fd, int request, void *arg)
66{
67  return execute_ioctl_hooks (anchor.private_next, primary, fd, request, arg);
68}
69
70void
71register_fd_hook (close_hook_fn close_hook, ioctl_hook_fn ioctl_hook, struct fd_hook *link)
72{
73  if (close_hook == NULL)
74    close_hook = execute_close_hooks;
75  if (ioctl_hook == NULL)
76    ioctl_hook = execute_ioctl_hooks;
77
78  if (link->private_next == NULL && link->private_prev == NULL)
79    {
80      /* Add the link to the doubly linked list.  */
81      link->private_next = anchor.private_next;
82      link->private_prev = &anchor;
83      link->private_close_fn = close_hook;
84      link->private_ioctl_fn = ioctl_hook;
85      anchor.private_next->private_prev = link;
86      anchor.private_next = link;
87    }
88  else
89    {
90      /* The link is already in use.  */
91      if (link->private_close_fn != close_hook
92          || link->private_ioctl_fn != ioctl_hook)
93        abort ();
94    }
95}
96
97void
98unregister_fd_hook (struct fd_hook *link)
99{
100  struct fd_hook *next = link->private_next;
101  struct fd_hook *prev = link->private_prev;
102
103  if (next != NULL && prev != NULL)
104    {
105      /* The link is in use.  Remove it from the doubly linked list.  */
106      prev->private_next = next;
107      next->private_prev = prev;
108      /* Clear the link, to mark it unused.  */
109      link->private_next = NULL;
110      link->private_prev = NULL;
111      link->private_close_fn = NULL;
112      link->private_ioctl_fn = NULL;
113    }
114}
115
116#endif
117