1/*
2 * Copyright 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 FIFO_FIFO_CONTROLLER_INDIRECT_H
18#define FIFO_FIFO_CONTROLLER_INDIRECT_H
19
20#include <stdint.h>
21#include <atomic>
22
23#include "FifoControllerBase.h"
24
25namespace android {
26
27/**
28 * A FifoControllerBase with counters external to the class.
29 *
30 * The actual copunters may be stored in separate regions of shared memory
31 * with different access rights.
32 */
33class FifoControllerIndirect : public FifoControllerBase {
34
35public:
36    FifoControllerIndirect(fifo_frames_t capacity,
37                           fifo_frames_t threshold,
38                           fifo_counter_t * readCounterAddress,
39                           fifo_counter_t * writeCounterAddress)
40        : FifoControllerBase(capacity, threshold)
41        , mReadCounterAddress((std::atomic<fifo_counter_t> *) readCounterAddress)
42        , mWriteCounterAddress((std::atomic<fifo_counter_t> *) writeCounterAddress)
43    {
44        setReadCounter(0);
45        setWriteCounter(0);
46    }
47    virtual ~FifoControllerIndirect() {};
48
49    // TODO review use of memory barriers, probably incorrect
50    virtual fifo_counter_t getReadCounter() override {
51        return mReadCounterAddress->load(std::memory_order_acquire);
52    }
53
54    virtual void setReadCounter(fifo_counter_t count) override {
55        mReadCounterAddress->store(count, std::memory_order_release);
56    }
57
58    virtual fifo_counter_t getWriteCounter() override {
59        return mWriteCounterAddress->load(std::memory_order_acquire);
60    }
61
62    virtual void setWriteCounter(fifo_counter_t count) override {
63        mWriteCounterAddress->store(count, std::memory_order_release);
64    }
65
66private:
67    std::atomic<fifo_counter_t> * mReadCounterAddress;
68    std::atomic<fifo_counter_t> * mWriteCounterAddress;
69};
70
71}  // android
72
73#endif //FIFO_FIFO_CONTROLLER_INDIRECT_H
74