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-rw-r--r--lib/fd-hook.c116
1 files changed, 116 insertions, 0 deletions
diff --git a/lib/fd-hook.c b/lib/fd-hook.c
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+++ b/lib/fd-hook.c
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+/* 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