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https://github.com/RGBCube/serenity
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5c1b3ce42e
We allow the ref-counting parts of an object to be mutated even when the object itself is a const. An important detail is that we allow invoking 'will_be_destroyed' and 'one_ref_left', which are not required to be const qualified, on const objects.
104 lines
2.8 KiB
C++
104 lines
2.8 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/StdLibExtras.h>
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namespace AK {
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template<class T>
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constexpr auto call_will_be_destroyed_if_present(const T* object) -> decltype(object->will_be_destroyed(), TrueType {})
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{
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const_cast<T*>(object)->will_be_destroyed();
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return {};
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}
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constexpr auto call_will_be_destroyed_if_present(...) -> FalseType
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{
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return {};
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}
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template<class T>
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constexpr auto call_one_ref_left_if_present(const T* object) -> decltype(object->one_ref_left(), TrueType {})
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{
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const_cast<T*>(object)->one_ref_left();
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return {};
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}
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constexpr auto call_one_ref_left_if_present(...) -> FalseType
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{
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return {};
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}
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class RefCountedBase {
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public:
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void ref() const
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{
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ASSERT(m_ref_count);
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++m_ref_count;
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}
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int ref_count() const
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{
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return m_ref_count;
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}
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protected:
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RefCountedBase() {}
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~RefCountedBase()
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{
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ASSERT(!m_ref_count);
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}
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void deref_base() const
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{
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ASSERT(m_ref_count);
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--m_ref_count;
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}
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mutable int m_ref_count { 1 };
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};
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template<typename T>
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class RefCounted : public RefCountedBase {
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public:
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void unref() const
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{
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deref_base();
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if (m_ref_count == 0) {
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call_will_be_destroyed_if_present(static_cast<const T*>(this));
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delete static_cast<const T*>(this);
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} else if (m_ref_count == 1) {
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call_one_ref_left_if_present(static_cast<const T*>(this));
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}
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}
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};
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}
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using AK::RefCounted;
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