// Copyright 2013 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_MEMORY_REF_COUNTED_DELETE_ON_SEQUENCE_H_
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#define BASE_MEMORY_REF_COUNTED_DELETE_ON_SEQUENCE_H_
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#include <utility>
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#include "base/location.h"
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#include "base/logging.h"
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "base/sequenced_task_runner.h"
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namespace base {
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// RefCountedDeleteOnSequence is similar to RefCountedThreadSafe, and ensures
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// that the object will be deleted on a specified sequence.
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//
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// Sample usage:
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// class Foo : public RefCountedDeleteOnSequence<Foo> {
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//
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// Foo(scoped_refptr<SequencedTaskRunner> task_runner)
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// : RefCountedDeleteOnSequence<Foo>(std::move(task_runner)) {}
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// ...
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// private:
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// friend class RefCountedDeleteOnSequence<Foo>;
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// friend class DeleteHelper<Foo>;
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//
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// ~Foo();
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// };
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template <class T>
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class RefCountedDeleteOnSequence : public subtle::RefCountedThreadSafeBase {
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public:
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static constexpr subtle::StartRefCountFromZeroTag kRefCountPreference =
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subtle::kStartRefCountFromZeroTag;
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// A SequencedTaskRunner for the current sequence can be acquired by calling
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// SequencedTaskRunnerHandle::Get().
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RefCountedDeleteOnSequence(
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scoped_refptr<SequencedTaskRunner> owning_task_runner)
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: subtle::RefCountedThreadSafeBase(T::kRefCountPreference),
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owning_task_runner_(std::move(owning_task_runner)) {
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DCHECK(owning_task_runner_);
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}
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void AddRef() const { subtle::RefCountedThreadSafeBase::AddRef(); }
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void Release() const {
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if (subtle::RefCountedThreadSafeBase::Release())
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DestructOnSequence();
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}
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protected:
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friend class DeleteHelper<RefCountedDeleteOnSequence>;
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~RefCountedDeleteOnSequence() = default;
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SequencedTaskRunner* owning_task_runner() {
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return owning_task_runner_.get();
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}
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const SequencedTaskRunner* owning_task_runner() const {
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return owning_task_runner_.get();
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}
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private:
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void DestructOnSequence() const {
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const T* t = static_cast<const T*>(this);
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if (owning_task_runner_->RunsTasksInCurrentSequence())
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delete t;
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else
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owning_task_runner_->DeleteSoon(FROM_HERE, t);
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}
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const scoped_refptr<SequencedTaskRunner> owning_task_runner_;
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DISALLOW_COPY_AND_ASSIGN(RefCountedDeleteOnSequence);
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};
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} // namespace base
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#endif // BASE_MEMORY_REF_COUNTED_DELETE_ON_SEQUENCE_H_
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