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
29#pragma once
30
31#include "ScriptExecutionContext.h"
32#include <wtf/Lock.h>
33
34namespace WebCore {
35
36// A helper class to safely dereference the callback objects held by
37// SQLStatement and SQLTransaction on the proper thread. The 'wrapped'
38// callback is dereferenced:
39// - by destructing the enclosing wrapper - on any thread
40// - by calling clear() - on any thread
41// - by unwrapping and then dereferencing normally - on context thread only
42template<typename T> class SQLCallbackWrapper {
43public:
44 SQLCallbackWrapper(RefPtr<T>&& callback, ScriptExecutionContext* scriptExecutionContext)
45 : m_callback(WTFMove(callback))
46 , m_scriptExecutionContext(m_callback ? scriptExecutionContext : 0)
47 {
48 ASSERT(!m_callback || (m_scriptExecutionContext.get() && m_scriptExecutionContext->isContextThread()));
49 }
50
51 ~SQLCallbackWrapper()
52 {
53 clear();
54 }
55
56 void clear()
57 {
58 ScriptExecutionContext* scriptExecutionContextPtr;
59 T* callback;
60 {
61 LockHolder locker(m_mutex);
62 if (!m_callback) {
63 ASSERT(!m_scriptExecutionContext);
64 return;
65 }
66 if (m_scriptExecutionContext->isContextThread()) {
67 m_callback = nullptr;
68 m_scriptExecutionContext = nullptr;
69 return;
70 }
71 scriptExecutionContextPtr = m_scriptExecutionContext.leakRef();
72 callback = m_callback.leakRef();
73 }
74 scriptExecutionContextPtr->postTask({
75 ScriptExecutionContext::Task::CleanupTask,
76 [callback, scriptExecutionContextPtr] (ScriptExecutionContext& context) {
77 ASSERT_UNUSED(context, &context == scriptExecutionContextPtr && context.isContextThread());
78 callback->deref();
79 scriptExecutionContextPtr->deref();
80 }
81 });
82 }
83
84 RefPtr<T> unwrap()
85 {
86 LockHolder locker(m_mutex);
87 ASSERT(!m_callback || m_scriptExecutionContext->isContextThread());
88 m_scriptExecutionContext = nullptr;
89 return WTFMove(m_callback);
90 }
91
92 // Useful for optimizations only, please test the return value of unwrap to be sure.
93 bool hasCallback() const { return m_callback; }
94
95private:
96 Lock m_mutex;
97 RefPtr<T> m_callback;
98 RefPtr<ScriptExecutionContext> m_scriptExecutionContext;
99};
100
101} // namespace WebCore
102