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 #include "core/dom/ExecutionContext.h" 32 #include "core/dom/ExecutionContextTask.h" 33 #include "wtf/ThreadingPrimitives.h" 34 35 namespace WebCore { 36 37 // A helper class to safely dereference the callback objects held by 38 // SQLStatement and SQLTransaction on the proper thread. The 'wrapped' 39 // callback is dereferenced: 40 // - by destructing the enclosing wrapper - on any thread 41 // - by calling clear() - on any thread 42 // - by unwrapping and then dereferencing normally - on context thread only 43 template<typename T> class SQLCallbackWrapper { 44 public: SQLCallbackWrapper(PassOwnPtr<T> callback,ExecutionContext * executionContext)45 SQLCallbackWrapper(PassOwnPtr<T> callback, ExecutionContext* executionContext) 46 : m_callback(callback) 47 , m_executionContext(m_callback ? executionContext : 0) 48 { 49 ASSERT(!m_callback || (m_executionContext.get() && m_executionContext->isContextThread())); 50 } 51 ~SQLCallbackWrapper()52 ~SQLCallbackWrapper() 53 { 54 clear(); 55 } 56 clear()57 void clear() 58 { 59 ExecutionContext* context; 60 OwnPtr<T> callback; 61 { 62 MutexLocker locker(m_mutex); 63 if (!m_callback) { 64 ASSERT(!m_executionContext); 65 return; 66 } 67 if (m_executionContext->isContextThread()) { 68 m_callback.clear(); 69 m_executionContext.clear(); 70 return; 71 } 72 context = m_executionContext.release().leakRef(); 73 callback = m_callback.release(); 74 } 75 context->postTask(SafeReleaseTask::create(callback.release())); 76 } 77 unwrap()78 PassOwnPtr<T> unwrap() 79 { 80 MutexLocker locker(m_mutex); 81 ASSERT(!m_callback || m_executionContext->isContextThread()); 82 m_executionContext.clear(); 83 return m_callback.release(); 84 } 85 86 // Useful for optimizations only, please test the return value of unwrap to be sure. hasCallback()87 bool hasCallback() const { return m_callback; } 88 89 private: 90 class SafeReleaseTask : public ExecutionContextTask { 91 public: create(PassOwnPtr<T> callbackToRelease)92 static PassOwnPtr<SafeReleaseTask> create(PassOwnPtr<T> callbackToRelease) 93 { 94 return adoptPtr(new SafeReleaseTask(callbackToRelease)); 95 } 96 performTask(ExecutionContext * context)97 virtual void performTask(ExecutionContext* context) 98 { 99 ASSERT(m_callbackToRelease && context && context->isContextThread()); 100 m_callbackToRelease.clear(); 101 context->deref(); 102 } 103 isCleanupTask()104 virtual bool isCleanupTask() const { return true; } 105 106 private: SafeReleaseTask(PassOwnPtr<T> callbackToRelease)107 explicit SafeReleaseTask(PassOwnPtr<T> callbackToRelease) 108 : m_callbackToRelease(callbackToRelease) 109 { 110 } 111 112 OwnPtr<T> m_callbackToRelease; 113 }; 114 115 Mutex m_mutex; 116 OwnPtr<T> m_callback; 117 RefPtr<ExecutionContext> m_executionContext; 118 }; 119 120 } // namespace WebCore 121 122 #endif // SQLCallbackWrapper_h 123