event_ref_queue.h revision 5d9b2d68940f7dac47bf2fbad6f6069ed3b2faaa 
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 CHRE_EVENT_REF_QUEUE_H
18#define CHRE_EVENT_REF_QUEUE_H
19
20#include "chre/core/event.h"
21#include "chre/util/array_queue.h"
22
23namespace chre {
24
25/**
26 * A non-thread-safe, non-blocking wrapper around ArrayQueue that stores Event*
27 * and manages the Event reference counter.
28 * TODO: make this a template specialization? Or rework the ref count design?
29 */
30class EventRefQueue {
31 public:
32  ~EventRefQueue();
33
34  /**
35   * @return true if there are no events in the queue
36   */
37  bool empty() const;
38
39  /**
40   * Adds an event to the queue, and increments its reference counter
41   *
42   * @param event The event to add
43   * @return true on success
44   */
45  bool push(Event *event);
46
47  /**
48   * Removes the oldest event from the queue, and decrements its reference
49   * counter. Does not trigger freeing of the event if the reference count
50   * reaches 0 as a result of this function call. The queue must be non-empty as
51   * a precondition to calling this function, or undefined behavior will result.
52   *
53   * @return Pointer to the next event in the queue
54   */
55  Event *pop();
56
57 private:
58  //! The maximum number of events that can be outstanding for an app.
59  static constexpr size_t kMaxPendingEvents = 16;
60
61  //! The queue of incoming events.
62  ArrayQueue<Event *, kMaxPendingEvents> mQueue;
63};
64
65}  // namespace chre
66
67#endif  // CHRE_EVENT_REF_QUEUE_H
68