[glib] Add GMutexLocker

[Ryan Lortie <desrt src gnome org>]

commit 1404d3e12819b342fda74d082dcb067a029141b1
Author: Xavier Claessens <xavier claessens collabora com>
Date:   Thu Feb 5 10:35:42 2015 -0500

    Add GMutexLocker
    
    https://bugzilla.gnome.org/show_bug.cgi?id=744012

 docs/reference/glib/glib-sections.txt |    5 ++
 glib/glib-autocleanups.h              |    1 +
 glib/gthread.h                        |   69 +++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/glib/glib-sections.txt b/docs/reference/glib/glib-sections.txt
index f48c2f0..45827d6 100644
--- a/docs/reference/glib/glib-sections.txt
+++ b/docs/reference/glib/glib-sections.txt
@@ -649,6 +649,11 @@ g_mutex_trylock
 g_mutex_unlock
 
 <SUBSECTION>
+GMutexLocker
+g_mutex_locker_new
+g_mutex_locker_free
+
+<SUBSECTION>
 G_LOCK_DEFINE
 G_LOCK_DEFINE_STATIC
 G_LOCK_EXTERN
diff --git a/glib/glib-autocleanups.h b/glib/glib-autocleanups.h
index 4d9f7ee..a3c059a 100644
--- a/glib/glib-autocleanups.h
+++ b/glib/glib-autocleanups.h
@@ -54,6 +54,7 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC(GSList, g_slist_free)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GStringChunk, g_string_chunk_free)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GThread, g_thread_unref)
 G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(GMutex, g_mutex_clear)
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GMutexLocker, g_mutex_locker_free)
 G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(GCond, g_cond_clear)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GTimer, g_timer_destroy)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GTimeZone, g_time_zone_unref)
diff --git a/glib/gthread.h b/glib/gthread.h
index 3f026f6..d7b1f58 100644
--- a/glib/gthread.h
+++ b/glib/gthread.h
@@ -266,6 +266,75 @@ void            g_once_init_leave               (volatile void  *location,
 GLIB_AVAILABLE_IN_2_36
 guint          g_get_num_processors (void);
 
+/**
+ * GMutexLocker:
+ *
+ * Opaque type. See g_mutex_locker_new() for details.
+ * Since: 2.44
+ */
+typedef void GMutexLocker;
+
+/**
+ * g_mutex_locker_new:
+ * @mutex: a mutex to lock
+ *
+ * Lock @mutex and return a new #GMutexLocker. Unlock with
+ * g_mutex_locker_free(). Using g_mutex_unlock() on @mutex
+ * while a #GMutexLocker exists can lead to undefined behaviour.
+ *
+ * This is intended to be used with g_autoptr().  Note that g_autoptr()
+ * is only available when using GCC or clang, so the following example
+ * will only work with those compilers:
+ * |[
+ * typedef struct
+ * {
+ *   ...
+ *   GMutex mutex;
+ *   ...
+ * } MyObject;
+ *
+ * static void
+ * my_object_do_stuff (MyObject *self)
+ * {
+ *   g_autoptr(GMutexLocker) locker = g_mutex_locker_new (&self->mutex);
+ *
+ *   // Code with mutex locked here
+ *
+ *   if (cond)
+ *     // No need to unlock
+ *     return;
+ *
+ *   // Optionally early unlock
+ *   g_clear_pointer (&locker, g_mutex_locker_free);
+ *
+ *   // Code with mutex unlocked here
+ * }
+ * ]|
+ *
+ * Returns: a #GMutexLocker
+ * Since: 2.44
+ */
+static inline GMutexLocker *
+g_mutex_locker_new (GMutex *mutex)
+{
+  g_mutex_lock (mutex);
+  return (GMutexLocker *) mutex;
+}
+
+/**
+ * g_mutex_locker_free:
+ * @locker: a GMutexLocker
+ *
+ * Unlock @locker's mutex. See g_mutex_locker_new() for details.
+ *
+ * Since: 2.44
+ */
+static inline void
+g_mutex_locker_free (GMutexLocker *locker)
+{
+  g_mutex_unlock ((GMutex *) locker);
+}
+
 G_END_DECLS
 
 #endif /* __G_THREAD_H__ */