1 /* Hook for making file descriptor functions close(), ioctl() extensible.
2 Copyright (C) 2009-2021 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 Lesser 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 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://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. */
31 static struct fd_hook anchor = { &anchor, &anchor, NULL, NULL };
32
33 int
execute_close_hooks(const struct fd_hook * remaining_list,gl_close_fn primary,int fd)34 execute_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
45 int
execute_all_close_hooks(gl_close_fn primary,int fd)46 execute_all_close_hooks (gl_close_fn primary, int fd)
47 {
48 return execute_close_hooks (anchor.private_next, primary, fd);
49 }
50
51 int
execute_ioctl_hooks(const struct fd_hook * remaining_list,gl_ioctl_fn primary,int fd,int request,void * arg)52 execute_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
63 int
execute_all_ioctl_hooks(gl_ioctl_fn primary,int fd,int request,void * arg)64 execute_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
70 void
register_fd_hook(close_hook_fn close_hook,ioctl_hook_fn ioctl_hook,struct fd_hook * link)71 register_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
97 void
unregister_fd_hook(struct fd_hook * link)98 unregister_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