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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 Computer, 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.
*/
#ifndef SQLCallbackWrapper_h
#define SQLCallbackWrapper_h
#include "core/dom/ExecutionContext.h"
#include "core/dom/ExecutionContextTask.h"
#include "wtf/ThreadingPrimitives.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(PassOwnPtr<T> callback, ExecutionContext* executionContext)
: m_callback(callback)
, m_executionContext(m_callback ? executionContext : 0)
{
ASSERT(!m_callback || (m_executionContext.get() && m_executionContext->isContextThread()));
}
~SQLCallbackWrapper()
{
clear();
}
void clear()
{
ExecutionContext* context;
OwnPtr<T> callback;
{
MutexLocker locker(m_mutex);
if (!m_callback) {
ASSERT(!m_executionContext);
return;
}
if (m_executionContext->isContextThread()) {
m_callback.clear();
m_executionContext.clear();
return;
}
context = m_executionContext.release().leakRef();
callback = m_callback.release();
}
context->postTask(SafeReleaseTask::create(callback.release()));
}
PassOwnPtr<T> unwrap()
{
MutexLocker locker(m_mutex);
ASSERT(!m_callback || m_executionContext->isContextThread());
m_executionContext.clear();
return m_callback.release();
}
// Useful for optimizations only, please test the return value of unwrap to be sure.
bool hasCallback() const { return m_callback; }
private:
class SafeReleaseTask : public ExecutionContextTask {
public:
static PassOwnPtr<SafeReleaseTask> create(PassOwnPtr<T> callbackToRelease)
{
return adoptPtr(new SafeReleaseTask(callbackToRelease));
}
virtual void performTask(ExecutionContext* context)
{
ASSERT(m_callbackToRelease && context && context->isContextThread());
m_callbackToRelease.clear();
context->deref();
}
virtual bool isCleanupTask() const { return true; }
private:
explicit SafeReleaseTask(PassOwnPtr<T> callbackToRelease)
: m_callbackToRelease(callbackToRelease)
{
}
OwnPtr<T> m_callbackToRelease;
};
Mutex m_mutex;
OwnPtr<T> m_callback;
RefPtr<ExecutionContext> m_executionContext;
};
} // namespace WebCore
#endif // SQLCallbackWrapper_h
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