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/*
* Copyright (C) 2007, 2008, 2010, 2013, 2014 Apple Inc. All rights reserved.
* Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <atomic>
#include <wtf/FastMalloc.h>
#include <wtf/MainThread.h>
#include <wtf/Noncopyable.h>
namespace WTF {
#if defined(NDEBUG) && !ENABLE(SECURITY_ASSERTIONS)
#define CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE 0
#else
#define CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE 1
#endif
class ThreadSafeRefCountedBase {
WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
WTF_MAKE_FAST_ALLOCATED;
public:
ThreadSafeRefCountedBase() = default;
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
~ThreadSafeRefCountedBase()
{
// When this ThreadSafeRefCounted object is a part of another object, derefBase() is never called on this object.
m_deletionHasBegun = true;
}
#endif
void ref() const
{
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
#endif
++m_refCount;
}
bool hasOneRef() const
{
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
ASSERT(!m_deletionHasBegun);
#endif
return refCount() == 1;
}
unsigned refCount() const
{
return m_refCount;
}
protected:
// Returns whether the pointer should be freed or not.
bool derefBase() const
{
ASSERT(m_refCount);
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
#endif
if (UNLIKELY(!--m_refCount)) {
// Setting m_refCount to 1 here prevents double delete within the destructor but not from another thread
// since such a thread could have ref'ed this object long after it had been deleted. See webkit.org/b/201576.
m_refCount = 1;
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
m_deletionHasBegun = true;
#endif
return true;
}
return false;
}
private:
mutable std::atomic<unsigned> m_refCount { 1 };
#if CHECK_THREAD_SAFE_REF_COUNTED_LIFECYCLE
mutable std::atomic<bool> m_deletionHasBegun { false };
#endif
};
enum class DestructionThread { Any, Main, MainRunLoop };
template<class T, DestructionThread destructionThread = DestructionThread::Any> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
public:
void deref() const
{
if (!derefBase())
return;
auto deleteThis = [this] {
delete static_cast<const T*>(this);
};
switch (destructionThread) {
case DestructionThread::Any:
break;
case DestructionThread::Main:
ensureOnMainThread(WTFMove(deleteThis));
return;
case DestructionThread::MainRunLoop:
ensureOnMainRunLoop(WTFMove(deleteThis));
return;
}
deleteThis();
}
protected:
ThreadSafeRefCounted() = default;
};
} // namespace WTF
using WTF::ThreadSafeRefCounted;
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