glib/glib-unix.c

   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, write to the
  18  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19  * Boston, MA 02111-1307, USA.
  20  *
  21  * Authors: Colin Walters <walters@verbum.org>
  22  */
  23
  24 #include "config.h"
  25
  26 #include "glib-unix.h"
  27 #include "gmain-internal.h"
  28
  29 #include <string.h>
  30
  31 /**
  32  * SECTION:gunix
  33  * @title: UNIX-specific utilities and integration
  34  * @short_description: pipes, signal handling
  35  * @include: glib-unix.h
  36  *
  37  * Most of GLib is intended to be portable; in contrast, this set of
  38  * functions is designed for programs which explicitly target UNIX,
  39  * or are using it to build higher level abstractions which would be
  40  * conditionally compiled if the platform matches G_OS_UNIX.
  41  *
  42  * To use these functions, you must explicitly include the
  43  * "glib-unix.h" header.
  44  */
  45
  46 GQuark
  47 g_unix_error_quark (void)
  48 {
  49   return g_quark_from_static_string ("g-unix-error-quark");
  50 }
  51
  52 static gboolean
  53 g_unix_set_error_from_errno (GError **error,
  54                              gint     saved_errno)
  55 {
  56   g_set_error_literal (error,
  57                        G_UNIX_ERROR,
  58                        0,
  59                        g_strerror (saved_errno));
  60   errno = saved_errno;
  61   return FALSE;
  62 }
  63
  64 /**
  65  * g_unix_open_pipe:
  66  * @fds: Array of two integers
  67  * @flags: Bitfield of file descriptor flags, see "man 2 fcntl"
  68  * @error: a #GError
  69  *
  70  * Similar to the UNIX pipe() call, but on modern systems like Linux
  71  * uses the pipe2() system call, which atomically creates a pipe with
  72  * the configured flags.  The only supported flag currently is
  73  * <literal>FD_CLOEXEC</literal>.  If for example you want to configure
  74  * <literal>O_NONBLOCK</literal>, that must still be done separately with
  75  * fcntl().
  76  *
  77  * <note>This function does *not* take <literal>O_CLOEXEC</literal>, it takes
  78  * <literal>FD_CLOEXEC</literal> as if for fcntl(); these are
  79  * different on Linux/glibc.</note>
  80  *
  81  * Returns: %TRUE on success, %FALSE if not (and errno will be set).
  82  *
  83  * Since: 2.30
  84  */
  85 gboolean
  86 g_unix_open_pipe (int     *fds,
  87                   int      flags,
  88                   GError **error)
  89 {
  90   int ecode;
  91
  92   /* We only support FD_CLOEXEC */
  93   g_return_val_if_fail ((flags & (FD_CLOEXEC)) == flags, FALSE);
  94
  95 #ifdef HAVE_PIPE2
  96   {
  97     int pipe2_flags = 0;
  98     if (flags & FD_CLOEXEC)
  99       pipe2_flags |= O_CLOEXEC;
 100     /* Atomic */
 101     ecode = pipe2 (fds, pipe2_flags);
 102     if (ecode == -1 && errno != ENOSYS)
 103       return g_unix_set_error_from_errno (error, errno);
 104     else if (ecode == 0)
 105       return TRUE;
 106     /* Fall through on -ENOSYS, we must be running on an old kernel */
 107   }
 108 #endif
 109   ecode = pipe (fds);
 110   if (ecode == -1)
 111     return g_unix_set_error_from_errno (error, errno);
 112   ecode = fcntl (fds[0], flags);
 113   if (ecode == -1)
 114     {
 115       int saved_errno = errno;
 116       close (fds[0]);
 117       close (fds[1]);
 118       return g_unix_set_error_from_errno (error, saved_errno);
 119     }
 120   ecode = fcntl (fds[1], flags);
 121   if (ecode == -1)
 122     {
 123       int saved_errno = errno;
 124       close (fds[0]);
 125       close (fds[1]);
 126       return g_unix_set_error_from_errno (error, saved_errno);
 127     }
 128   return TRUE;
 129 }
 130
 131 /**
 132  * g_unix_set_fd_nonblocking:
 133  * @fd: A file descriptor
 134  * @nonblock: If %TRUE, set the descriptor to be non-blocking
 135  * @error: a #GError
 136  *
 137  * Control the non-blocking state of the given file descriptor,
 138  * according to @nonblock.  On most systems this uses <literal>O_NONBLOCK</literal>, but
 139  * on some older ones may use <literal>O_NDELAY</literal>.
 140  *
 141  * Returns: %TRUE if successful
 142  *
 143  * Since: 2.30
 144  */
 145 gboolean
 146 g_unix_set_fd_nonblocking (gint       fd,
 147                            gboolean   nonblock,
 148                            GError   **error)
 149 {
 150 #ifdef F_GETFL
 151   glong fcntl_flags;
 152   fcntl_flags = fcntl (fd, F_GETFL);
 153
 154   if (fcntl_flags == -1)
 155     return g_unix_set_error_from_errno (error, errno);
 156
 157   if (nonblock)
 158     {
 159 #ifdef O_NONBLOCK
 160       fcntl_flags |= O_NONBLOCK;
 161 #else
 162       fcntl_flags |= O_NDELAY;
 163 #endif
 164     }
 165   else
 166     {
 167 #ifdef O_NONBLOCK
 168       fcntl_flags &= ~O_NONBLOCK;
 169 #else
 170       fcntl_flags &= ~O_NDELAY;
 171 #endif
 172     }
 173
 174   if (fcntl (fd, F_SETFL, fcntl_flags) == -1)
 175     return g_unix_set_error_from_errno (error, errno);
 176   return TRUE;
 177 #else
 178   return g_unix_set_error_from_errno (error, EINVAL);
 179 #endif
 180 }
 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.  Currently only <literal>SIGHUP</literal>,
 189  * <literal>SIGINT</literal>, and <literal>SIGTERM</literal> can
 190  * be monitored.  Note that unlike the UNIX default, all sources which
 191  * have created a watch will be dispatched, regardless of which
 192  * underlying thread invoked g_unix_signal_source_new().
 193  *
 194  * For example, an effective use of this function is to handle <literal>SIGTERM</literal>
 195  * cleanly; flushing any outstanding files, and then calling
 196  * g_main_loop_quit ().  It is not safe to do any of this a regular
 197  * UNIX signal handler; your handler may be invoked while malloc() or
 198  * another library function is running, causing reentrancy if you
 199  * attempt to use it from the handler.  None of the GLib/GObject API
 200  * is safe against this kind of reentrancy.
 201  *
 202  * The interaction of this source when combined with native UNIX
 203  * functions like sigprocmask() is not defined.
 204  *
 205  * The source will not initially be associated with any #GMainContext
 206  * and must be added to one with g_source_attach() before it will be
 207  * executed.
 208  *
 209  * Returns: A newly created #GSource
 210  *
 211  * Since: 2.30
 212  */
 213 GSource *
 214 g_unix_signal_source_new (int signum)
 215 {
 216   g_return_val_if_fail (signum == SIGHUP || signum == SIGINT || signum == SIGTERM, NULL);
 217
 218   return _g_main_create_unix_signal_watch (signum);
 219 }
 220
 221 /**
 222  * g_unix_signal_add_full:
 223  * @priority: the priority of the signal source. Typically this will be in
 224  *            the range between #G_PRIORITY_DEFAULT and #G_PRIORITY_HIGH.
 225  * @signum: Signal number
 226  * @handler: Callback
 227  * @user_data: Data for @handler
 228  * @notify: #GDestroyNotify for @handler
 229  *
 230  * A convenience function for g_unix_signal_source_new(), which
 231  * attaches to the default #GMainContext.  You can remove the watch
 232  * using g_source_remove().
 233  *
 234  * Returns: An ID (greater than 0) for the event source
 235  *
 236  * Since: 2.30
 237  */
 238 guint
 239 g_unix_signal_add_full (int            priority,
 240                         int            signum,
 241                         GSourceFunc    handler,
 242                         gpointer       user_data,
 243                         GDestroyNotify notify)
 244 {
 245   guint id;
 246   GSource *source;
 247
 248   source = g_unix_signal_source_new (signum);
 249
 250   if (priority != G_PRIORITY_DEFAULT)
 251     g_source_set_priority (source, priority);
 252
 253   g_source_set_callback (source, handler, user_data, notify);
 254   id = g_source_attach (source, NULL);
 255   g_source_unref (source);
 256
 257   return id;
 258 }
 259
 260 /**
 261  * g_unix_signal_add:
 262  * @signum: Signal number
 263  * @handler: Callback
 264  * @user_data: Data for @handler
 265  *
 266  * A convenience function for g_unix_signal_source_new(), which
 267  * attaches to the default #GMainContext.  You can remove the watch
 268  * using g_source_remove().
 269  *
 270  * Returns: An ID (greater than 0) for the event source
 271  *
 272  * Since: 2.30
 273  */
 274 guint
 275 g_unix_signal_add (int         signum,
 276                    GSourceFunc handler,
 277                    gpointer    user_data)
 278 {
 279   return g_unix_signal_add_full (G_PRIORITY_DEFAULT, signum, handler, user_data, NULL);
 280 }