1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_HIDL_SYNCHRONIZED_QUEUE_H
18#define ANDROID_HIDL_SYNCHRONIZED_QUEUE_H
19
20#include <condition_variable>
21#include <mutex>
22#include <queue>
23#include <thread>
24
25namespace android {
26namespace hardware {
27namespace details {
28/* Threadsafe queue.
29 */
30template <typename T>
31struct SynchronizedQueue {
32    SynchronizedQueue(size_t limit);
33
34    /* Gets an item from the front of the queue.
35     *
36     * Blocks until the item is available.
37     */
38    T wait_pop();
39
40    /* Puts an item onto the end of the queue.
41     */
42    bool push(const T& item);
43
44    /* Gets the size of the array.
45     */
46    size_t size();
47
48private:
49    std::condition_variable mCondition;
50    std::mutex mMutex;
51    std::queue<T> mQueue;
52    const size_t mQueueLimit;
53};
54
55template <typename T>
56SynchronizedQueue<T>::SynchronizedQueue(size_t limit) : mQueueLimit(limit) {
57}
58
59template <typename T>
60T SynchronizedQueue<T>::wait_pop() {
61    std::unique_lock<std::mutex> lock(mMutex);
62
63    mCondition.wait(lock, [this]{
64        return !this->mQueue.empty();
65    });
66
67    T item = mQueue.front();
68    mQueue.pop();
69
70    return item;
71}
72
73template <typename T>
74bool SynchronizedQueue<T>::push(const T &item) {
75    bool success;
76    {
77        std::unique_lock<std::mutex> lock(mMutex);
78        if (mQueue.size() < mQueueLimit) {
79            mQueue.push(item);
80            success = true;
81        } else {
82            success = false;
83        }
84    }
85
86    mCondition.notify_one();
87    return success;
88}
89
90template <typename T>
91size_t SynchronizedQueue<T>::size() {
92    std::unique_lock<std::mutex> lock(mMutex);
93
94    return mQueue.size();
95}
96
97} // namespace details
98} // namespace hardware
99} // namespace android
100
101#endif // ANDROID_HIDL_SYNCHRONIZED_QUEUE_H
102