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 Computer, 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(DATABASE) 32 33 #include "CrossThreadTask.h" 34 #include "ScriptExecutionContext.h" 35 #include <wtf/ThreadingPrimitives.h> 36 37 namespace WebCore { 38 39 // A helper class to safely dereference the callback objects held by 40 // SQLStatement and SQLTransaction on the proper thread. The 'wrapped' 41 // callback is dereferenced: 42 // - by destructing the enclosing wrapper - on any thread 43 // - by calling clear() - on any thread 44 // - by unwrapping and then dereferencing normally - on context thread only 45 template<typename T> class SQLCallbackWrapper { 46 public: SQLCallbackWrapper(PassRefPtr<T> callback,ScriptExecutionContext * scriptExecutionContext)47 SQLCallbackWrapper(PassRefPtr<T> callback, ScriptExecutionContext* scriptExecutionContext) 48 : m_callback(callback) 49 , m_scriptExecutionContext(m_callback ? scriptExecutionContext : 0) 50 { 51 ASSERT(!m_callback || (m_scriptExecutionContext.get() && m_scriptExecutionContext->isContextThread())); 52 } 53 ~SQLCallbackWrapper()54 ~SQLCallbackWrapper() 55 { 56 clear(); 57 } 58 clear()59 void clear() 60 { 61 ScriptExecutionContext* context; 62 T* callback; 63 { 64 MutexLocker locker(m_mutex); 65 if (!m_callback) { 66 ASSERT(!m_scriptExecutionContext); 67 return; 68 } 69 if (m_scriptExecutionContext->isContextThread()) { 70 m_callback = 0; 71 m_scriptExecutionContext = 0; 72 return; 73 } 74 context = m_scriptExecutionContext.release().leakRef(); 75 callback = m_callback.release().leakRef(); 76 } 77 context->postTask(createCallbackTask(&safeRelease, callback)); 78 } 79 unwrap()80 PassRefPtr<T> unwrap() 81 { 82 MutexLocker locker(m_mutex); 83 ASSERT(!m_callback || m_scriptExecutionContext->isContextThread()); 84 m_scriptExecutionContext = 0; 85 return m_callback.release(); 86 } 87 88 // Useful for optimizations only, please test the return value of unwrap to be sure. hasCallback()89 bool hasCallback() const { return m_callback; } 90 91 private: safeRelease(ScriptExecutionContext * context,T * callback)92 static void safeRelease(ScriptExecutionContext* context, T* callback) 93 { 94 ASSERT(callback && context && context->isContextThread()); 95 callback->deref(); 96 context->deref(); 97 } 98 99 Mutex m_mutex; 100 RefPtr<T> m_callback; 101 RefPtr<ScriptExecutionContext> m_scriptExecutionContext; 102 }; 103 104 } // namespace WebCore 105 106 #endif // ENABLE(DATABASE) 107 108 #endif // SQLCallbackWrapper_h 109