1/* 2 * Copyright (C) 2011 Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of Apple Inc. ("Apple") nor the names of 14 * its contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28#ifndef SQLCallbackWrapper_h 29#define SQLCallbackWrapper_h 30 31#if ENABLE(SQL_DATABASE) 32 33#include "ScriptExecutionContext.h" 34#include <wtf/ThreadingPrimitives.h> 35 36namespace WebCore { 37 38// A helper class to safely dereference the callback objects held by 39// SQLStatement and SQLTransaction on the proper thread. The 'wrapped' 40// callback is dereferenced: 41// - by destructing the enclosing wrapper - on any thread 42// - by calling clear() - on any thread 43// - by unwrapping and then dereferencing normally - on context thread only 44template<typename T> class SQLCallbackWrapper { 45public: 46 SQLCallbackWrapper(PassRefPtr<T> callback, ScriptExecutionContext* scriptExecutionContext) 47 : m_callback(callback) 48 , m_scriptExecutionContext(m_callback ? scriptExecutionContext : 0) 49 { 50 ASSERT(!m_callback || (m_scriptExecutionContext.get() && m_scriptExecutionContext->isContextThread())); 51 } 52 53 ~SQLCallbackWrapper() 54 { 55 clear(); 56 } 57 58 void clear() 59 { 60 ScriptExecutionContext* scriptExecutionContextPtr; 61 T* callback; 62 { 63 MutexLocker locker(m_mutex); 64 if (!m_callback) { 65 ASSERT(!m_scriptExecutionContext); 66 return; 67 } 68 if (m_scriptExecutionContext->isContextThread()) { 69 m_callback = 0; 70 m_scriptExecutionContext = 0; 71 return; 72 } 73 scriptExecutionContextPtr = m_scriptExecutionContext.release().leakRef(); 74 callback = m_callback.release().leakRef(); 75 } 76 scriptExecutionContextPtr->postTask({ ScriptExecutionContext::Task::CleanupTask, [=] (ScriptExecutionContext& context) { 77 ASSERT_UNUSED(context, &context == scriptExecutionContextPtr && context.isContextThread()); 78 callback->deref(); 79 scriptExecutionContextPtr->deref(); 80 } }); 81 } 82 83 PassRefPtr<T> unwrap() 84 { 85 MutexLocker locker(m_mutex); 86 ASSERT(!m_callback || m_scriptExecutionContext->isContextThread()); 87 m_scriptExecutionContext = 0; 88 return m_callback.release(); 89 } 90 91 // Useful for optimizations only, please test the return value of unwrap to be sure. 92 bool hasCallback() const { return m_callback; } 93 94private: 95 Mutex m_mutex; 96 RefPtr<T> m_callback; 97 RefPtr<ScriptExecutionContext> m_scriptExecutionContext; 98}; 99 100} // namespace WebCore 101 102#endif // ENABLE(SQL_DATABASE) 103 104#endif // SQLCallbackWrapper_h 105