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1 office 1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 2011 Red Hat, Inc.
3 *
4 * glib-unix.c: UNIX specific API wrappers and convenience functions
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 *
19 * Authors: Colin Walters <walters@verbum.org>
20 */
21  
22 #include "config.h"
23  
24 /* To make bionic export pipe2() */
25 #ifndef _GNU_SOURCE
26 #define _GNU_SOURCE 1
27 #endif
28  
29 #include "glib-unix.h"
30 #include "gmain-internal.h"
31  
32 #include <string.h>
33  
34 /**
35 * SECTION:gunix
36 * @title: UNIX-specific utilities and integration
37 * @short_description: pipes, signal handling
38 * @include: glib-unix.h
39 *
40 * Most of GLib is intended to be portable; in contrast, this set of
41 * functions is designed for programs which explicitly target UNIX,
42 * or are using it to build higher level abstractions which would be
43 * conditionally compiled if the platform matches G_OS_UNIX.
44 *
45 * To use these functions, you must explicitly include the
46 * "glib-unix.h" header.
47 */
48  
49 G_DEFINE_QUARK (g-unix-error-quark, g_unix_error)
50  
51 static gboolean
52 g_unix_set_error_from_errno (GError **error,
53 gint saved_errno)
54 {
55 g_set_error_literal (error,
56 G_UNIX_ERROR,
57 0,
58 g_strerror (saved_errno));
59 errno = saved_errno;
60 return FALSE;
61 }
62  
63 /**
64 * g_unix_open_pipe:
65 * @fds: Array of two integers
66 * @flags: Bitfield of file descriptor flags, as for fcntl()
67 * @error: a #GError
68 *
69 * Similar to the UNIX pipe() call, but on modern systems like Linux
70 * uses the pipe2() system call, which atomically creates a pipe with
71 * the configured flags. The only supported flag currently is
72 * %FD_CLOEXEC. If for example you want to configure %O_NONBLOCK, that
73 * must still be done separately with fcntl().
74 *
75 * This function does not take %O_CLOEXEC, it takes %FD_CLOEXEC as if
76 * for fcntl(); these are different on Linux/glibc.
77 *
78 * Returns: %TRUE on success, %FALSE if not (and errno will be set).
79 *
80 * Since: 2.30
81 */
82 gboolean
83 g_unix_open_pipe (int *fds,
84 int flags,
85 GError **error)
86 {
87 int ecode;
88  
89 /* We only support FD_CLOEXEC */
90 g_return_val_if_fail ((flags & (FD_CLOEXEC)) == flags, FALSE);
91  
92 #ifdef HAVE_PIPE2
93 {
94 int pipe2_flags = 0;
95 if (flags & FD_CLOEXEC)
96 pipe2_flags |= O_CLOEXEC;
97 /* Atomic */
98 ecode = pipe2 (fds, pipe2_flags);
99 if (ecode == -1 && errno != ENOSYS)
100 return g_unix_set_error_from_errno (error, errno);
101 else if (ecode == 0)
102 return TRUE;
103 /* Fall through on -ENOSYS, we must be running on an old kernel */
104 }
105 #endif
106 ecode = pipe (fds);
107 if (ecode == -1)
108 return g_unix_set_error_from_errno (error, errno);
109  
110 if (flags == 0)
111 return TRUE;
112  
113 ecode = fcntl (fds[0], F_SETFD, flags);
114 if (ecode == -1)
115 {
116 int saved_errno = errno;
117 close (fds[0]);
118 close (fds[1]);
119 return g_unix_set_error_from_errno (error, saved_errno);
120 }
121 ecode = fcntl (fds[1], F_SETFD, flags);
122 if (ecode == -1)
123 {
124 int saved_errno = errno;
125 close (fds[0]);
126 close (fds[1]);
127 return g_unix_set_error_from_errno (error, saved_errno);
128 }
129 return TRUE;
130 }
131  
132 /**
133 * g_unix_set_fd_nonblocking:
134 * @fd: A file descriptor
135 * @nonblock: If %TRUE, set the descriptor to be non-blocking
136 * @error: a #GError
137 *
138 * Control the non-blocking state of the given file descriptor,
139 * according to @nonblock. On most systems this uses %O_NONBLOCK, but
140 * on some older ones may use %O_NDELAY.
141 *
142 * Returns: %TRUE if successful
143 *
144 * Since: 2.30
145 */
146 gboolean
147 g_unix_set_fd_nonblocking (gint fd,
148 gboolean nonblock,
149 GError **error)
150 {
151 #ifdef F_GETFL
152 glong fcntl_flags;
153 fcntl_flags = fcntl (fd, F_GETFL);
154  
155 if (fcntl_flags == -1)
156 return g_unix_set_error_from_errno (error, errno);
157  
158 if (nonblock)
159 {
160 #ifdef O_NONBLOCK
161 fcntl_flags |= O_NONBLOCK;
162 #else
163 fcntl_flags |= O_NDELAY;
164 #endif
165 }
166 else
167 {
168 #ifdef O_NONBLOCK
169 fcntl_flags &= ~O_NONBLOCK;
170 #else
171 fcntl_flags &= ~O_NDELAY;
172 #endif
173 }
174  
175 if (fcntl (fd, F_SETFL, fcntl_flags) == -1)
176 return g_unix_set_error_from_errno (error, errno);
177 return TRUE;
178 #else
179 return g_unix_set_error_from_errno (error, EINVAL);
180 #endif
181 }
182  
183 /**
184 * g_unix_signal_source_new:
185 * @signum: A signal number
186 *
187 * Create a #GSource that will be dispatched upon delivery of the UNIX
188 * signal @signum. In GLib versions before 2.36, only `SIGHUP`, `SIGINT`,
189 * `SIGTERM` can be monitored. In GLib 2.36, `SIGUSR1` and `SIGUSR2`
190 * were added.
191 *
192 * Note that unlike the UNIX default, all sources which have created a
193 * watch will be dispatched, regardless of which underlying thread
194 * invoked g_unix_signal_source_new().
195 *
196 * For example, an effective use of this function is to handle `SIGTERM`
197 * cleanly; flushing any outstanding files, and then calling
198 * g_main_loop_quit (). It is not safe to do any of this a regular
199 * UNIX signal handler; your handler may be invoked while malloc() or
200 * another library function is running, causing reentrancy if you
201 * attempt to use it from the handler. None of the GLib/GObject API
202 * is safe against this kind of reentrancy.
203 *
204 * The interaction of this source when combined with native UNIX
205 * functions like sigprocmask() is not defined.
206 *
207 * The source will not initially be associated with any #GMainContext
208 * and must be added to one with g_source_attach() before it will be
209 * executed.
210 *
211 * Returns: A newly created #GSource
212 *
213 * Since: 2.30
214 */
215 GSource *
216 g_unix_signal_source_new (int signum)
217 {
218 g_return_val_if_fail (signum == SIGHUP || signum == SIGINT || signum == SIGTERM ||
219 signum == SIGUSR1 || signum == SIGUSR2, NULL);
220  
221 return _g_main_create_unix_signal_watch (signum);
222 }
223  
224 /**
225 * g_unix_signal_add_full: (rename-to g_unix_signal_add)
226 * @priority: the priority of the signal source. Typically this will be in
227 * the range between #G_PRIORITY_DEFAULT and #G_PRIORITY_HIGH.
228 * @signum: Signal number
229 * @handler: Callback
230 * @user_data: Data for @handler
231 * @notify: #GDestroyNotify for @handler
232 *
233 * A convenience function for g_unix_signal_source_new(), which
234 * attaches to the default #GMainContext. You can remove the watch
235 * using g_source_remove().
236 *
237 * Returns: An ID (greater than 0) for the event source
238 *
239 * Since: 2.30
240 */
241 guint
242 g_unix_signal_add_full (int priority,
243 int signum,
244 GSourceFunc handler,
245 gpointer user_data,
246 GDestroyNotify notify)
247 {
248 guint id;
249 GSource *source;
250  
251 source = g_unix_signal_source_new (signum);
252  
253 if (priority != G_PRIORITY_DEFAULT)
254 g_source_set_priority (source, priority);
255  
256 g_source_set_callback (source, handler, user_data, notify);
257 id = g_source_attach (source, NULL);
258 g_source_unref (source);
259  
260 return id;
261 }
262  
263 /**
264 * g_unix_signal_add:
265 * @signum: Signal number
266 * @handler: Callback
267 * @user_data: Data for @handler
268 *
269 * A convenience function for g_unix_signal_source_new(), which
270 * attaches to the default #GMainContext. You can remove the watch
271 * using g_source_remove().
272 *
273 * Returns: An ID (greater than 0) for the event source
274 *
275 * Since: 2.30
276 */
277 guint
278 g_unix_signal_add (int signum,
279 GSourceFunc handler,
280 gpointer user_data)
281 {
282 return g_unix_signal_add_full (G_PRIORITY_DEFAULT, signum, handler, user_data, NULL);
283 }
284  
285 typedef struct
286 {
287 GSource source;
288  
289 gint fd;
290 gpointer tag;
291 } GUnixFDSource;
292  
293 static gboolean
294 g_unix_fd_source_dispatch (GSource *source,
295 GSourceFunc callback,
296 gpointer user_data)
297 {
298 GUnixFDSource *fd_source = (GUnixFDSource *) source;
299 GUnixFDSourceFunc func = (GUnixFDSourceFunc) callback;
300  
301 if (!callback)
302 {
303 g_warning ("GUnixFDSource dispatched without callback\n"
304 "You must call g_source_set_callback().");
305 return FALSE;
306 }
307  
308 return (* func) (fd_source->fd, g_source_query_unix_fd (source, fd_source->tag), user_data);
309 }
310  
311 GSourceFuncs g_unix_fd_source_funcs = {
312 NULL, NULL, g_unix_fd_source_dispatch, NULL
313 };
314  
315 /**
316 * g_unix_fd_source_new:
317 * @fd: a file descriptor
318 * @condition: IO conditions to watch for on @fd
319 *
320 * Creates a #GSource to watch for a particular IO condition on a file
321 * descriptor.
322 *
323 * The source will never close the fd -- you must do it yourself.
324 *
325 * Returns: the newly created #GSource
326 *
327 * Since: 2.36
328 **/
329 GSource *
330 g_unix_fd_source_new (gint fd,
331 GIOCondition condition)
332 {
333 GUnixFDSource *fd_source;
334 GSource *source;
335  
336 source = g_source_new (&g_unix_fd_source_funcs, sizeof (GUnixFDSource));
337 fd_source = (GUnixFDSource *) source;
338  
339 fd_source->fd = fd;
340 fd_source->tag = g_source_add_unix_fd (source, fd, condition);
341  
342 return source;
343 }
344  
345 /**
346 * g_unix_fd_add_full:
347 * @priority: the priority of the source
348 * @fd: a file descriptor
349 * @condition: IO conditions to watch for on @fd
350 * @function: a #GUnixFDSourceFunc
351 * @user_data: data to pass to @function
352 * @notify: function to call when the idle is removed, or %NULL
353 *
354 * Sets a function to be called when the IO condition, as specified by
355 * @condition becomes true for @fd.
356 *
357 * This is the same as g_unix_fd_add(), except that it allows you to
358 * specify a non-default priority and a provide a #GDestroyNotify for
359 * @user_data.
360 *
361 * Returns: the ID (greater than 0) of the event source
362 *
363 * Since: 2.36
364 **/
365 guint
366 g_unix_fd_add_full (gint priority,
367 gint fd,
368 GIOCondition condition,
369 GUnixFDSourceFunc function,
370 gpointer user_data,
371 GDestroyNotify notify)
372 {
373 GSource *source;
374 guint id;
375  
376 g_return_val_if_fail (function != NULL, 0);
377  
378 source = g_unix_fd_source_new (fd, condition);
379  
380 if (priority != G_PRIORITY_DEFAULT)
381 g_source_set_priority (source, priority);
382  
383 g_source_set_callback (source, (GSourceFunc) function, user_data, notify);
384 id = g_source_attach (source, NULL);
385 g_source_unref (source);
386  
387 return id;
388 }
389  
390 /**
391 * g_unix_fd_add:
392 * @fd: a file descriptor
393 * @condition: IO conditions to watch for on @fd
394 * @function: a #GPollFDFunc
395 * @user_data: data to pass to @function
396 *
397 * Sets a function to be called when the IO condition, as specified by
398 * @condition becomes true for @fd.
399 *
400 * @function will be called when the specified IO condition becomes
401 * %TRUE. The function is expected to clear whatever event caused the
402 * IO condition to become true and return %TRUE in order to be notified
403 * when it happens again. If @function returns %FALSE then the watch
404 * will be cancelled.
405 *
406 * The return value of this function can be passed to g_source_remove()
407 * to cancel the watch at any time that it exists.
408 *
409 * The source will never close the fd -- you must do it yourself.
410 *
411 * Returns: the ID (greater than 0) of the event source
412 *
413 * Since: 2.36
414 **/
415 guint
416 g_unix_fd_add (gint fd,
417 GIOCondition condition,
418 GUnixFDSourceFunc function,
419 gpointer user_data)
420 {
421 return g_unix_fd_add_full (G_PRIORITY_DEFAULT, fd, condition, function, user_data, NULL);
422 }