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