1/*
2 * Copyright (C) 2008 Apple Inc. All rights reserved.
3 * Copyright (C) 2009 Google Inc. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1.  Redistributions of source code must retain the above copyright
10 *     notice, this list of conditions and the following disclaimer.
11 * 2.  Redistributions in binary form must reproduce the above copyright
12 *     notice, this list of conditions and the following disclaimer in the
13 *     documentation and/or other materials provided with the distribution.
14 * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
15 *     its contributors may be used to endorse or promote products derived
16 *     from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#ifndef MessageQueue_h
31#define MessageQueue_h
32
33#include <limits>
34#include <wtf/Assertions.h>
35#include <wtf/Deque.h>
36#include <wtf/Noncopyable.h>
37#include <wtf/Threading.h>
38
39namespace WTF {
40
41    enum MessageQueueWaitResult {
42        MessageQueueTerminated,       // Queue was destroyed while waiting for message.
43        MessageQueueTimeout,          // Timeout was specified and it expired.
44        MessageQueueMessageReceived   // A message was successfully received and returned.
45    };
46
47    // The queue takes ownership of messages and transfer it to the new owner
48    // when messages are fetched from the queue.
49    // Essentially, MessageQueue acts as a queue of std::unique_ptr<DataType>.
50    template<typename DataType>
51    class MessageQueue {
52        WTF_MAKE_NONCOPYABLE(MessageQueue);
53    public:
54        MessageQueue() : m_killed(false) { }
55        ~MessageQueue();
56
57        void append(std::unique_ptr<DataType>);
58        void appendAndKill(std::unique_ptr<DataType>);
59        bool appendAndCheckEmpty(std::unique_ptr<DataType>);
60        void prepend(std::unique_ptr<DataType>);
61
62        std::unique_ptr<DataType> waitForMessage();
63        std::unique_ptr<DataType> tryGetMessage();
64        std::unique_ptr<DataType> tryGetMessageIgnoringKilled();
65        template<typename Predicate>
66        std::unique_ptr<DataType> waitForMessageFilteredWithTimeout(MessageQueueWaitResult&, Predicate&&, double absoluteTime);
67
68        template<typename Predicate>
69        void removeIf(Predicate&&);
70
71        void kill();
72        bool killed() const;
73
74        // The result of isEmpty() is only valid if no other thread is manipulating the queue at the same time.
75        bool isEmpty();
76
77        static double infiniteTime() { return std::numeric_limits<double>::max(); }
78
79    private:
80        mutable Mutex m_mutex;
81        ThreadCondition m_condition;
82        Deque<std::unique_ptr<DataType>> m_queue;
83        bool m_killed;
84    };
85
86    template<typename DataType>
87    MessageQueue<DataType>::~MessageQueue()
88    {
89    }
90
91    template<typename DataType>
92    inline void MessageQueue<DataType>::append(std::unique_ptr<DataType> message)
93    {
94        MutexLocker lock(m_mutex);
95        m_queue.append(WTF::move(message));
96        m_condition.signal();
97    }
98
99    template<typename DataType>
100    inline void MessageQueue<DataType>::appendAndKill(std::unique_ptr<DataType> message)
101    {
102        MutexLocker lock(m_mutex);
103        m_queue.append(WTF::move(message));
104        m_killed = true;
105        m_condition.broadcast();
106    }
107
108    // Returns true if the queue was empty before the item was added.
109    template<typename DataType>
110    inline bool MessageQueue<DataType>::appendAndCheckEmpty(std::unique_ptr<DataType> message)
111    {
112        MutexLocker lock(m_mutex);
113        bool wasEmpty = m_queue.isEmpty();
114        m_queue.append(WTF::move(message));
115        m_condition.signal();
116        return wasEmpty;
117    }
118
119    template<typename DataType>
120    inline void MessageQueue<DataType>::prepend(std::unique_ptr<DataType> message)
121    {
122        MutexLocker lock(m_mutex);
123        m_queue.prepend(WTF::move(message));
124        m_condition.signal();
125    }
126
127    template<typename DataType>
128    inline auto MessageQueue<DataType>::waitForMessage() -> std::unique_ptr<DataType>
129    {
130        MessageQueueWaitResult exitReason;
131        std::unique_ptr<DataType> result = waitForMessageFilteredWithTimeout(exitReason, [](const DataType&) { return true; }, infiniteTime());
132        ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);
133        return result;
134    }
135
136    template<typename DataType>
137    template<typename Predicate>
138    inline auto MessageQueue<DataType>::waitForMessageFilteredWithTimeout(MessageQueueWaitResult& result, Predicate&& predicate, double absoluteTime) -> std::unique_ptr<DataType>
139    {
140        MutexLocker lock(m_mutex);
141        bool timedOut = false;
142
143        auto found = m_queue.end();
144        while (!m_killed && !timedOut) {
145            found = m_queue.findIf([&predicate](const std::unique_ptr<DataType>& ptr) -> bool {
146                ASSERT(ptr);
147                return predicate(*ptr);
148            });
149            if (found != m_queue.end())
150                break;
151
152            timedOut = !m_condition.timedWait(m_mutex, absoluteTime);
153        }
154
155        ASSERT(!timedOut || absoluteTime != infiniteTime());
156
157        if (m_killed) {
158            result = MessageQueueTerminated;
159            return nullptr;
160        }
161
162        if (timedOut) {
163            result = MessageQueueTimeout;
164            return nullptr;
165        }
166
167        ASSERT(found != m_queue.end());
168        std::unique_ptr<DataType> message = WTF::move(*found);
169        m_queue.remove(found);
170        result = MessageQueueMessageReceived;
171        return message;
172    }
173
174    template<typename DataType>
175    inline auto MessageQueue<DataType>::tryGetMessage() -> std::unique_ptr<DataType>
176    {
177        MutexLocker lock(m_mutex);
178        if (m_killed)
179            return nullptr;
180        if (m_queue.isEmpty())
181            return nullptr;
182
183        return m_queue.takeFirst();
184    }
185
186    template<typename DataType>
187    inline auto MessageQueue<DataType>::tryGetMessageIgnoringKilled() -> std::unique_ptr<DataType>
188    {
189        MutexLocker lock(m_mutex);
190        if (m_queue.isEmpty())
191            return nullptr;
192
193        return m_queue.takeFirst();
194    }
195
196    template<typename DataType>
197    template<typename Predicate>
198    inline void MessageQueue<DataType>::removeIf(Predicate&& predicate)
199    {
200        MutexLocker lock(m_mutex);
201        while (true) {
202            auto found = m_queue.findIf([&predicate](const std::unique_ptr<DataType>& ptr) -> bool {
203                ASSERT(ptr);
204                return predicate(*ptr);
205            });
206
207            if (found == m_queue.end())
208                break;
209
210            m_queue.remove(found);
211        }
212    }
213
214    template<typename DataType>
215    inline bool MessageQueue<DataType>::isEmpty()
216    {
217        MutexLocker lock(m_mutex);
218        if (m_killed)
219            return true;
220        return m_queue.isEmpty();
221    }
222
223    template<typename DataType>
224    inline void MessageQueue<DataType>::kill()
225    {
226        MutexLocker lock(m_mutex);
227        m_killed = true;
228        m_condition.broadcast();
229    }
230
231    template<typename DataType>
232    inline bool MessageQueue<DataType>::killed() const
233    {
234        MutexLocker lock(m_mutex);
235        return m_killed;
236    }
237} // namespace WTF
238
239using WTF::MessageQueue;
240// MessageQueueWaitResult enum and all its values.
241using WTF::MessageQueueWaitResult;
242using WTF::MessageQueueTerminated;
243using WTF::MessageQueueTimeout;
244using WTF::MessageQueueMessageReceived;
245
246#endif // MessageQueue_h
247