[glibutil] Added gutil_weakref module

Ref-countable weak reference can be used to avoid calling g_weak_ref_set()
too often because it grabs global weak_locations_lock for exclusive access.
Note that g_weak_ref_set() is also invoked internally by g_weak_ref_init()
and g_weak_ref_clear().

g_weak_ref_get() on the other hand only acquires weak_locations_lock
for read-only access which is less of a bottleneck in a multi-threaded
environment. And it's generally significantly simpler and faster than
g_weak_ref_set().

Makefile

@@ -53,7 +53,8 @@ SRC = \
   gutil_misc.c \
   gutil_ring.c \
   gutil_strv.c \
-  gutil_timenotify.c
+  gutil_timenotify.c \
+  gutil_weakref.c
 
 #
 # Directories

include/gutil_types.h

@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2014-2021 Jolla Ltd.
- * Copyright (C) 2014-2021 Slava Monich <slava.monich@jolla.com>
+ * Copyright (C) 2023 Slava Monich <slava@monich.com>
  *
  * You may use this file under the terms of BSD license as follows:
  *
@@ -48,6 +48,7 @@ typedef struct gutil_int_history GUtilIntHistory;
 typedef struct gutil_inotify_watch GUtilInotifyWatch;
 typedef struct gutil_ring GUtilRing;
 typedef struct gutil_time_notify GUtilTimeNotify;
+typedef struct gutil_weakref GUtilWeakRef; /* Since 1.0.68 */
 
 typedef struct gutil_data {
     const guint8* bytes;

include/gutil_weakref.h

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2023 Slava Monich <slava@monich.com>
+ *
+ * You may use this file under the terms of BSD license as follows:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *   3. Neither the names of the copyright holders nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GUTIL_WEAKREF_H
+#define GUTIL_WEAKREF_H
+
+#include "gutil_types.h"
+
+/*
+ * Ref-countable weak reference can be used to avoid calling g_weak_ref_set()
+ * too often because it grabs global weak_locations_lock for exclusive access.
+ * Note that g_weak_ref_set() is also invoked internally by g_weak_ref_init()
+ * and g_weak_ref_clear().
+ *
+ * g_weak_ref_get() on the other hand only acquires weak_locations_lock
+ * for read-only access which is less of a bottleneck in a multi-threaded
+ * environment. And it's generally significantly simpler and faster than
+ * g_weak_ref_set().
+ *
+ * Since 1.0.68
+ */
+
+G_BEGIN_DECLS
+
+GUtilWeakRef*
+gutil_weakref_new(
+    gpointer obj);
+
+GUtilWeakRef*
+gutil_weakref_ref(
+    GUtilWeakRef* ref);
+
+void
+gutil_weakref_unref(
+    GUtilWeakRef* ref);
+
+gpointer
+gutil_weakref_get(
+    GUtilWeakRef* ref);
+
+void
+gutil_weakref_set(
+    GUtilWeakRef* ref,
+    gpointer obj);
+
+G_END_DECLS
+
+#endif /* GUTIL_WEAKREF_H */
+
+/*
+ * Local Variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

src/gutil_weakref.c

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2023 Slava Monich <slava@monich.com>
+ *
+ * You may use this file under the terms of BSD license as follows:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *   3. Neither the names of the copyright holders nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "gutil_weakref.h"
+#include "gutil_log.h"
+#include "gutil_macros.h"
+
+#include <glib-object.h>
+
+/*
+ * Ref-countable weak reference can be used to avoid calling g_weak_ref_set()
+ * too often because it grabs global weak_locations_lock for exclusive access.
+ * Note that g_weak_ref_set() is also invoked internally by g_weak_ref_init()
+ * and g_weak_ref_clear().
+ *
+ * g_weak_ref_get() on the other hand only acquires weak_locations_lock
+ * for read-only access which is less of a bottleneck in a multi-threaded
+ * environment. And it's generally significantly simpler and faster than
+ * g_weak_ref_set().
+ *
+ * Since 1.0.68
+ */
+
+struct gutil_weakref {
+    gint ref_count;
+    GWeakRef weak_ref;
+};
+
+GUtilWeakRef*
+gutil_weakref_new(
+    gpointer obj)
+{
+    GUtilWeakRef* self = g_slice_new(GUtilWeakRef);
+
+    g_atomic_int_set(&self->ref_count, 1);
+    g_weak_ref_init(&self->weak_ref, obj);
+    return self;
+}
+
+GUtilWeakRef*
+gutil_weakref_ref(
+    GUtilWeakRef* self)
+{
+    if (G_LIKELY(self)) {
+        GASSERT(self->ref_count > 0);
+        g_atomic_int_inc(&self->ref_count);
+    }
+    return self;
+}
+
+void
+gutil_weakref_unref(
+    GUtilWeakRef* self)
+{
+    if (G_LIKELY(self)) {
+        GASSERT(self->ref_count > 0);
+        if (g_atomic_int_dec_and_test(&self->ref_count)) {
+            g_weak_ref_clear(&self->weak_ref);
+            gutil_slice_free(self);
+        }
+    }
+}
+
+gpointer
+gutil_weakref_get(
+    GUtilWeakRef* self)
+{
+    return G_LIKELY(self) ? g_weak_ref_get(&self->weak_ref) : NULL;
+}
+
+void
+gutil_weakref_set(
+    GUtilWeakRef* self,
+    gpointer obj)
+{
+    if (G_LIKELY(self)) {
+        g_weak_ref_set(&self->weak_ref, obj);
+    }
+}
+
+/*
+ * Local Variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

test/Makefile

@@ -12,3 +12,4 @@ all:
 	@$(MAKE) -C test_misc $*
 	@$(MAKE) -C test_ring $*
 	@$(MAKE) -C test_strv $*
+	@$(MAKE) -C test_weakref $*

test/coverage/run

@@ -13,7 +13,8 @@ test_ints \
 test_log \
 test_misc \
 test_ring \
-test_strv"
+test_strv \
+test_weakref"
 
 FLAVOR="coverage"
 

test/test_weakref/Makefile

@@ -0,0 +1,5 @@
+# -*- Mode: makefile-gmake -*-
+
+EXE = test_weakref
+
+include ../common/Makefile

test/test_weakref/test_weakref.c

@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2023 Slava Monich <slava@monich.com>
+ *
+ * You may use this file under the terms of BSD license as follows:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *   3. Neither the names of the copyright holders nor the names of its
+ *      contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "test_common.h"
+
+#include "gutil_weakref.h"
+
+#include <glib-object.h>
+
+static TestOpt test_opt;
+
+/*==========================================================================*
+ * null
+ *==========================================================================*/
+
+static
+void
+test_null()
+{
+    gutil_weakref_unref(NULL);
+    gutil_weakref_set(NULL, NULL);
+    g_assert(!gutil_weakref_ref(NULL));
+    g_assert(!gutil_weakref_get(NULL));
+}
+
+/*==========================================================================*
+ * basic
+ *==========================================================================*/
+
+static
+void
+test_basic()
+{
+    GObject* obj = g_object_new(TEST_OBJECT_TYPE, NULL);
+    GUtilWeakRef* ref = gutil_weakref_new(obj);
+
+    g_assert(gutil_weakref_ref(ref) == ref);
+    gutil_weakref_unref(ref);
+    g_assert(gutil_weakref_get(ref) == obj);
+    g_object_unref(obj);
+    gutil_weakref_unref(ref);
+
+    ref = gutil_weakref_new(NULL);
+    g_assert(!gutil_weakref_get(ref));
+    gutil_weakref_set(ref, obj);
+    g_assert(gutil_weakref_get(ref) == obj);
+    g_object_unref(obj);
+    g_object_unref(obj); /* This actually deallocates the object */
+    g_assert(!gutil_weakref_get(ref));
+    gutil_weakref_unref(ref);
+}
+
+/*==========================================================================*
+ * Common
+ *==========================================================================*/
+
+#define TEST_(name) "/weakref/" name
+
+int main(int argc, char* argv[])
+{
+    G_GNUC_BEGIN_IGNORE_DEPRECATIONS;
+    g_type_init();
+    G_GNUC_END_IGNORE_DEPRECATIONS;
+    g_test_init(&argc, &argv, NULL);
+    test_init(&test_opt, argc, argv);
+    g_test_add_func(TEST_("null"), test_null);
+    g_test_add_func(TEST_("basic"), test_basic);
+    return g_test_run();
+}
+
+/*
+ * Local Variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */