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