/* * 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; { LockHolder locker(m_mutex); 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() { LockHolder locker(m_mutex); 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. bool hasCallback() const { return m_callback; } private: Lock m_mutex; RefPtr<T> m_callback; RefPtr<ScriptExecutionContext> m_scriptExecutionContext; }; } // namespace WebCore