зеркало из https://github.com/mozilla/gecko-dev.git
120 строки
3.7 KiB
C++
120 строки
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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// This header provides virtual, non-templated alternatives to MFBT's
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// RefCounted<T>. It intentionally uses MFBT coding style with the intention of
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// moving there should there be other use cases for it.
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#ifndef MOZILLA_GENERICREFCOUNTED_H_
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#define MOZILLA_GENERICREFCOUNTED_H_
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#include <type_traits>
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#include "mozilla/RefPtr.h"
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#include "mozilla/RefCounted.h"
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namespace mozilla {
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/**
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* Common base class for GenericRefCounted and GenericAtomicRefCounted.
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*
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* Having this shared base class, common to both the atomic and non-atomic
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* cases, allows to have RefPtr's that don't care about whether the
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* objects they're managing have atomic refcounts or not.
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*/
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class GenericRefCountedBase {
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protected:
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virtual ~GenericRefCountedBase() = default;
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public:
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// AddRef() and Release() method names are for compatibility with nsRefPtr.
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virtual void AddRef() = 0;
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virtual void Release() = 0;
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// ref() and deref() method names are for compatibility with wtf::RefPtr.
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// No virtual keywords here: if a subclass wants to override the refcounting
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// mechanism, it is welcome to do so by overriding AddRef() and Release().
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void ref() { AddRef(); }
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void deref() { Release(); }
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#ifdef MOZ_REFCOUNTED_LEAK_CHECKING
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virtual const char* typeName() const = 0;
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virtual size_t typeSize() const = 0;
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#endif
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};
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namespace detail {
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template <RefCountAtomicity Atomicity>
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class GenericRefCounted : public GenericRefCountedBase {
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protected:
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GenericRefCounted() : refCnt(0) {}
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virtual ~GenericRefCounted() { MOZ_ASSERT(refCnt == detail::DEAD); }
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public:
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virtual void AddRef() override {
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// Note: this method must be thread safe for GenericAtomicRefCounted.
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MOZ_ASSERT(int32_t(refCnt) >= 0);
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MozRefCountType cnt = ++refCnt;
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detail::RefCountLogger::logAddRef(this, cnt);
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}
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virtual void Release() override {
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// Note: this method must be thread safe for GenericAtomicRefCounted.
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MOZ_ASSERT(int32_t(refCnt) > 0);
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detail::RefCountLogger::ReleaseLogger logger{this};
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MozRefCountType cnt = --refCnt;
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// Note: it's not safe to touch |this| after decrementing the refcount,
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// except for below.
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logger.logRelease(cnt);
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if (0 == cnt) {
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// Because we have atomically decremented the refcount above, only
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// one thread can get a 0 count here, so as long as we can assume that
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// everything else in the system is accessing this object through
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// RefPtrs, it's safe to access |this| here.
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#ifdef DEBUG
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refCnt = detail::DEAD;
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#endif
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delete this;
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}
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}
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MozRefCountType refCount() const { return refCnt; }
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bool hasOneRef() const {
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MOZ_ASSERT(refCnt > 0);
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return refCnt == 1;
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}
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private:
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std::conditional_t<Atomicity == AtomicRefCount, Atomic<MozRefCountType>,
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MozRefCountType>
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refCnt;
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};
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} // namespace detail
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/**
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* This reference-counting base class is virtual instead of
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* being templated, which is useful in cases where one needs
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* genericity at binary code level, but comes at the cost
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* of a moderate performance and size overhead, like anything virtual.
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*/
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class GenericRefCounted
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: public detail::GenericRefCounted<detail::NonAtomicRefCount> {};
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/**
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* GenericAtomicRefCounted is like GenericRefCounted, with an atomically updated
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* reference counter.
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*/
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class GenericAtomicRefCounted
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: public detail::GenericRefCounted<detail::AtomicRefCount> {};
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} // namespace mozilla
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#endif
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