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 | |
34 | namespace 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 |
42 | template<typename T> class SQLCallbackWrapper { |
43 | public: |
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 | |
95 | private: |
96 | Lock m_mutex; |
97 | RefPtr<T> m_callback; |
98 | RefPtr<ScriptExecutionContext> m_scriptExecutionContext; |
99 | }; |
100 | |
101 | } // namespace WebCore |
102 | |