| /* grefcount.c: Reference counting |
| * |
| * Copyright 2018 Emmanuele Bassi |
| * |
| * SPDX-License-Identifier: LGPL-2.1-or-later |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * This library 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 |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with this library; if not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #include "config.h" |
| |
| #include "grefcount.h" |
| |
| #include "gatomic.h" |
| #include "gmessages.h" |
| |
| /** |
| * grefcount: |
| * |
| * A type for implementing non-atomic reference count semantics. |
| * |
| * Use g_ref_count_init() to initialize it; g_ref_count_inc() to |
| * increase the counter, and g_ref_count_dec() to decrease it. |
| * |
| * It is safe to use #grefcount only if you're expecting to operate |
| * on the reference counter from a single thread. It is entirely up |
| * to you to ensure that all reference count changes happen in the |
| * same thread. |
| * |
| * See also: #gatomicrefcount |
| * |
| * Since: 2.58 |
| */ |
| |
| /** |
| * gatomicrefcount: |
| * |
| * A type for implementing atomic reference count semantics. |
| * |
| * Use g_atomic_ref_count_init() to initialize it; g_atomic_ref_count_inc() |
| * to increase the counter, and g_atomic_ref_count_dec() to decrease it. |
| * |
| * It is safe to use #gatomicrefcount if you're expecting to operate on the |
| * reference counter from multiple threads. |
| * |
| * See also: #grefcount |
| * |
| * Since: 2.58 |
| */ |
| |
| /** |
| * g_ref_count_init: |
| * @rc: the address of a reference count variable |
| * |
| * Initializes a reference count variable to 1. |
| * |
| * Since: 2.58 |
| */ |
| void |
| (g_ref_count_init) (grefcount *rc) |
| { |
| g_return_if_fail (rc != NULL); |
| |
| /* Non-atomic refcounting is implemented using the negative range |
| * of signed integers: |
| * |
| * G_MININT Z¯< 0 > Z⁺ G_MAXINT |
| * |----------------------------|----------------------------| |
| * |
| * Acquiring a reference moves us towards MININT, and releasing a |
| * reference moves us towards 0. |
| */ |
| *rc = -1; |
| } |
| |
| /** |
| * g_ref_count_inc: |
| * @rc: the address of a reference count variable |
| * |
| * Increases the reference count. |
| * |
| * Since: 2.58 |
| */ |
| void |
| (g_ref_count_inc) (grefcount *rc) |
| { |
| grefcount rrc; |
| |
| g_return_if_fail (rc != NULL); |
| |
| rrc = *rc; |
| |
| g_return_if_fail (rrc < 0); |
| |
| /* Check for saturation */ |
| if (rrc == G_MININT) |
| { |
| g_critical ("Reference count %p has reached saturation", rc); |
| return; |
| } |
| |
| rrc -= 1; |
| |
| *rc = rrc; |
| } |
| |
| /** |
| * g_ref_count_dec: |
| * @rc: the address of a reference count variable |
| * |
| * Decreases the reference count. |
| * |
| * If %TRUE is returned, the reference count reached 0. After this point, @rc |
| * is an undefined state and must be reinitialized with |
| * g_ref_count_init() to be used again. |
| * |
| * Returns: %TRUE if the reference count reached 0, and %FALSE otherwise |
| * |
| * Since: 2.58 |
| */ |
| gboolean |
| (g_ref_count_dec) (grefcount *rc) |
| { |
| grefcount rrc; |
| |
| g_return_val_if_fail (rc != NULL, FALSE); |
| |
| rrc = *rc; |
| |
| g_return_val_if_fail (rrc < 0, FALSE); |
| |
| rrc += 1; |
| if (rrc == 0) |
| return TRUE; |
| |
| *rc = rrc; |
| |
| return FALSE; |
| } |
| |
| /** |
| * g_ref_count_compare: |
| * @rc: the address of a reference count variable |
| * @val: the value to compare |
| * |
| * Compares the current value of @rc with @val. |
| * |
| * Returns: %TRUE if the reference count is the same |
| * as the given value |
| * |
| * Since: 2.58 |
| */ |
| gboolean |
| (g_ref_count_compare) (grefcount *rc, |
| gint val) |
| { |
| grefcount rrc; |
| |
| g_return_val_if_fail (rc != NULL, FALSE); |
| g_return_val_if_fail (val >= 0, FALSE); |
| |
| rrc = *rc; |
| |
| if (val == G_MAXINT) |
| return rrc == G_MININT; |
| |
| return rrc == -val; |
| } |
| |
| /** |
| * g_atomic_ref_count_init: |
| * @arc: the address of an atomic reference count variable |
| * |
| * Initializes a reference count variable to 1. |
| * |
| * Since: 2.58 |
| */ |
| void |
| (g_atomic_ref_count_init) (gatomicrefcount *arc) |
| { |
| g_return_if_fail (arc != NULL); |
| |
| /* Atomic refcounting is implemented using the positive range |
| * of signed integers: |
| * |
| * G_MININT Z¯< 0 > Z⁺ G_MAXINT |
| * |----------------------------|----------------------------| |
| * |
| * Acquiring a reference moves us towards MAXINT, and releasing a |
| * reference moves us towards 0. |
| */ |
| *arc = 1; |
| } |
| |
| /** |
| * g_atomic_ref_count_inc: |
| * @arc: the address of an atomic reference count variable |
| * |
| * Atomically increases the reference count. |
| * |
| * Since: 2.58 |
| */ |
| void |
| (g_atomic_ref_count_inc) (gatomicrefcount *arc) |
| { |
| gint old_value; |
| |
| g_return_if_fail (arc != NULL); |
| old_value = g_atomic_int_add (arc, 1); |
| g_return_if_fail (old_value > 0); |
| |
| if (old_value == G_MAXINT) |
| g_critical ("Reference count has reached saturation"); |
| } |
| |
| /** |
| * g_atomic_ref_count_dec: |
| * @arc: the address of an atomic reference count variable |
| * |
| * Atomically decreases the reference count. |
| * |
| * If %TRUE is returned, the reference count reached 0. After this point, @arc |
| * is an undefined state and must be reinitialized with |
| * g_atomic_ref_count_init() to be used again. |
| * |
| * Returns: %TRUE if the reference count reached 0, and %FALSE otherwise |
| * |
| * Since: 2.58 |
| */ |
| gboolean |
| (g_atomic_ref_count_dec) (gatomicrefcount *arc) |
| { |
| gint old_value; |
| |
| g_return_val_if_fail (arc != NULL, FALSE); |
| old_value = g_atomic_int_add (arc, -1); |
| g_return_val_if_fail (old_value > 0, FALSE); |
| |
| return old_value == 1; |
| } |
| |
| /** |
| * g_atomic_ref_count_compare: |
| * @arc: the address of an atomic reference count variable |
| * @val: the value to compare |
| * |
| * Atomically compares the current value of @arc with @val. |
| * |
| * Returns: %TRUE if the reference count is the same |
| * as the given value |
| * |
| * Since: 2.58 |
| */ |
| gboolean |
| (g_atomic_ref_count_compare) (gatomicrefcount *arc, |
| gint val) |
| { |
| g_return_val_if_fail (arc != NULL, FALSE); |
| g_return_val_if_fail (val >= 0, FALSE); |
| |
| return g_atomic_int_get (arc) == val; |
| } |