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/*
* Copyright (C) 2011 Google Inc. All rights reserved.
*
* 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.
* 3. Neither the name of Apple Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE 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 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 "ScriptExecutionContext.h"
#include <wtf/Lock.h>
namespace WebCore {
// A helper class to safely dereference the callback objects held by
// SQLStatement and SQLTransaction on the proper thread. The 'wrapped'
// callback is dereferenced:
// - by destructing the enclosing wrapper - on any thread
// - by calling clear() - on any thread
// - by unwrapping and then dereferencing normally - on context thread only
template<typename T> class SQLCallbackWrapper {
public:
SQLCallbackWrapper(RefPtr<T>&& callback, ScriptExecutionContext* scriptExecutionContext)
: m_callback(WTFMove(callback))
, m_scriptExecutionContext(m_callback ? scriptExecutionContext : 0)
{
ASSERT(!m_callback || (m_scriptExecutionContext.get() && m_scriptExecutionContext->isContextThread()));
}
~SQLCallbackWrapper()
{
clear();
}
void clear()
{
ScriptExecutionContext* scriptExecutionContextPtr;
T* callback;
{
Locker locker { m_lock };
if (!m_callback) {
ASSERT(!m_scriptExecutionContext);
return;
}
if (m_scriptExecutionContext->isContextThread()) {
m_callback = nullptr;
m_scriptExecutionContext = nullptr;
return;
}
scriptExecutionContextPtr = m_scriptExecutionContext.leakRef();
callback = m_callback.leakRef();
}
scriptExecutionContextPtr->postTask({
ScriptExecutionContext::Task::CleanupTask,
[callback, scriptExecutionContextPtr] (ScriptExecutionContext& context) {
ASSERT_UNUSED(context, &context == scriptExecutionContextPtr && context.isContextThread());
callback->deref();
scriptExecutionContextPtr->deref();
}
});
}
RefPtr<T> unwrap()
{
Locker locker { m_lock };
ASSERT(!m_callback || m_scriptExecutionContext->isContextThread());
m_scriptExecutionContext = nullptr;
return WTFMove(m_callback);
}
// Useful for optimizations only, please test the return value of unwrap to be sure.
// FIXME: This is not thread-safe.
bool hasCallback() const WTF_IGNORES_THREAD_SAFETY_ANALYSIS { return m_callback; }
private:
Lock m_lock;
RefPtr<T> m_callback WTF_GUARDED_BY_LOCK(m_lock);
RefPtr<ScriptExecutionContext> m_scriptExecutionContext WTF_GUARDED_BY_LOCK(m_lock);
};
} // namespace WebCore
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