107 lines
3.3 KiB
C++
107 lines
3.3 KiB
C++
/*
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* Copyright 2017 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef API_REF_COUNTED_BASE_H_
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#define API_REF_COUNTED_BASE_H_
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#include <type_traits>
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#include "rtc_base/ref_counter.h"
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namespace webrtc {
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class RefCountedBase {
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public:
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RefCountedBase() = default;
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RefCountedBase(const RefCountedBase&) = delete;
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RefCountedBase& operator=(const RefCountedBase&) = delete;
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void AddRef() const { ref_count_.IncRef(); }
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RefCountReleaseStatus Release() const {
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const auto status = ref_count_.DecRef();
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if (status == RefCountReleaseStatus::kDroppedLastRef) {
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delete this;
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}
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return status;
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}
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protected:
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// Provided for internal webrtc subclasses for corner cases where it's
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// necessary to know whether or not a reference is exclusively held.
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bool HasOneRef() const { return ref_count_.HasOneRef(); }
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virtual ~RefCountedBase() = default;
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private:
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mutable webrtc::webrtc_impl::RefCounter ref_count_{0};
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};
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// Template based version of `RefCountedBase` for simple implementations that do
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// not need (or want) destruction via virtual destructor or the overhead of a
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// vtable.
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//
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// To use:
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// struct MyInt : public rtc::RefCountedNonVirtual<MyInt> {
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// int foo_ = 0;
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// };
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//
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// rtc::scoped_refptr<MyInt> my_int(new MyInt());
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//
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// sizeof(MyInt) on a 32 bit system would then be 8, int + refcount and no
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// vtable generated.
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template <typename T>
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class RefCountedNonVirtual {
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public:
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RefCountedNonVirtual() = default;
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RefCountedNonVirtual(const RefCountedNonVirtual&) = delete;
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RefCountedNonVirtual& operator=(const RefCountedNonVirtual&) = delete;
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void AddRef() const { ref_count_.IncRef(); }
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RefCountReleaseStatus Release() const {
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// If you run into this assert, T has virtual methods. There are two
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// options:
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// 1) The class doesn't actually need virtual methods, the type is complete
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// so the virtual attribute(s) can be removed.
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// 2) The virtual methods are a part of the design of the class. In this
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// case you can consider using `RefCountedBase` instead or alternatively
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// use `rtc::RefCountedObject`.
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static_assert(!std::is_polymorphic<T>::value,
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"T has virtual methods. RefCountedBase is a better fit.");
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const auto status = ref_count_.DecRef();
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if (status == RefCountReleaseStatus::kDroppedLastRef) {
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delete static_cast<const T*>(this);
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}
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return status;
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}
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protected:
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// Provided for internal webrtc subclasses for corner cases where it's
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// necessary to know whether or not a reference is exclusively held.
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bool HasOneRef() const { return ref_count_.HasOneRef(); }
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~RefCountedNonVirtual() = default;
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private:
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mutable webrtc::webrtc_impl::RefCounter ref_count_{0};
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};
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} // namespace webrtc
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// Backwards compatibe aliases.
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// TODO: https://issues.webrtc.org/42225969 - deprecate and remove.
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namespace rtc {
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using RefCountedBase = webrtc::RefCountedBase;
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template <typename T>
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using RefCountedNonVirtual = webrtc::RefCountedNonVirtual<T>;
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} // namespace rtc
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#endif // API_REF_COUNTED_BASE_H_
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