| /* |
| * 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 Computer, 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. |
| */ |
| #ifndef SQLCallbackWrapper_h |
| #define SQLCallbackWrapper_h |
| |
| #if ENABLE(DATABASE) |
| |
| #include "CrossThreadTask.h" |
| #include "ScriptExecutionContext.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(PassRefPtr<T> callback, ScriptExecutionContext* scriptExecutionContext) |
| : m_callback(callback) |
| , m_scriptExecutionContext(m_callback ? scriptExecutionContext : 0) |
| { |
| ASSERT(!m_callback || (m_scriptExecutionContext.get() && m_scriptExecutionContext->isContextThread())); |
| } |
| |
| ~SQLCallbackWrapper() |
| { |
| clear(); |
| } |
| |
| void clear() |
| { |
| ScriptExecutionContext* context; |
| T* callback; |
| { |
| MutexLocker locker(m_mutex); |
| if (!m_callback) { |
| ASSERT(!m_scriptExecutionContext); |
| return; |
| } |
| if (m_scriptExecutionContext->isContextThread()) { |
| m_callback = 0; |
| m_scriptExecutionContext = 0; |
| return; |
| } |
| context = m_scriptExecutionContext.release().leakRef(); |
| callback = m_callback.release().leakRef(); |
| } |
| context->postTask(createCallbackTask(&safeRelease, callback)); |
| } |
| |
| PassRefPtr<T> unwrap() |
| { |
| MutexLocker locker(m_mutex); |
| ASSERT(!m_callback || m_scriptExecutionContext->isContextThread()); |
| m_scriptExecutionContext = 0; |
| 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: |
| static void safeRelease(ScriptExecutionContext* context, T* callback) |
| { |
| ASSERT(callback && context && context->isContextThread()); |
| callback->deref(); |
| context->deref(); |
| } |
| |
| Mutex m_mutex; |
| RefPtr<T> m_callback; |
| RefPtr<ScriptExecutionContext> m_scriptExecutionContext; |
| }; |
| |
| } // namespace WebCore |
| |
| #endif // ENABLE(DATABASE) |
| |
| #endif // SQLCallbackWrapper_h |