/*
* Copyright (C) 2011 Google Inc. All rights reserved.
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*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
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* its contributors may be used to endorse or promote products derived
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*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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*/
#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