1 /*
2  * Copyright (C) 2019 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 #pragma once
18 
19 #include "LogEvent.h"
20 
21 #include <condition_variable>
22 #include <memory>
23 #include <mutex>
24 #include <queue>
25 #include <thread>
26 
27 namespace android {
28 namespace os {
29 namespace statsd {
30 
31 /**
32  * A zero copy thread safe queue buffer for producing and consuming LogEvent.
33  */
34 class LogEventQueue {
35 public:
LogEventQueue(size_t maxSize)36     explicit LogEventQueue(size_t maxSize) : mQueueLimit(maxSize){};
37 
38     /**
39      * Blocking read one event from the queue.
40      */
41     std::unique_ptr<LogEvent> waitPop();
42 
43     /**
44      * Puts a LogEvent ptr to the end of the queue.
45      * Returns false on failure when the queue is full, and output the oldest event timestamp
46      * in the queue.
47      */
48     bool push(std::unique_ptr<LogEvent> event, int64_t* oldestTimestampNs);
49 
50 private:
51     const size_t mQueueLimit;
52     std::condition_variable mCondition;
53     std::mutex mMutex;
54     std::queue<std::unique_ptr<LogEvent>> mQueue;
55 };
56 
57 }  // namespace statsd
58 }  // namespace os
59 }  // namespace android
60