FifoControllerBase.h revision c0c70e3c7dd10bc2c0caffcab1f3f5fb406b35fb 
1/*
2 * Copyright 2015 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_BASE_H
18#define FIFO_FIFO_CONTROLLER_BASE_H
19
20#include <stdint.h>
21
22namespace android {
23
24typedef int64_t fifo_counter_t;
25typedef int32_t fifo_frames_t;
26
27/**
28 * Manage the read/write indices of a circular buffer.
29 *
30 * The caller is responsible for reading and writing the actual data.
31 * Note that the span of available frames may not be contiguous. They
32 * may wrap around from the end to the beginning of the buffer. In that
33 * case the data must be read or written in at least two blocks of frames.
34 *
35 */
36class FifoControllerBase {
37
38public:
39    /**
40     * Constructor for FifoControllerBase
41     * @param capacity Total size of the circular buffer in frames.
42     * @param threshold Number of frames to fill. Must be less than capacity.
43     */
44    FifoControllerBase(fifo_frames_t capacity, fifo_frames_t threshold);
45
46    virtual ~FifoControllerBase();
47
48    // Abstract methods to be implemented in subclasses.
49    /**
50     * @return Counter used by the reader of the FIFO.
51     */
52    virtual fifo_counter_t getReadCounter() = 0;
53
54    /**
55     * This is normally only used internally.
56     * @param count Number of frames that have been read.
57     */
58    virtual void setReadCounter(fifo_counter_t count) = 0;
59
60    /**
61     * @return Counter used by the reader of the FIFO.
62     */
63    virtual fifo_counter_t getWriteCounter() = 0;
64
65    /**
66     * This is normally only used internally.
67     * @param count Number of frames that have been read.
68     */
69    virtual void setWriteCounter(fifo_counter_t count) = 0;
70
71    /**
72     * This may be negative if an unthrottled reader has read beyond the available data.
73     * @return number of valid frames available to read. Never read more than this.
74     */
75    fifo_frames_t getFullFramesAvailable();
76
77    /**
78     * The index in a circular buffer of the next frame to read.
79     */
80    fifo_frames_t getReadIndex();
81
82    /**
83     * @param numFrames number of frames to advance the read index
84     */
85    void advanceReadIndex(fifo_frames_t numFrames);
86
87    /**
88     * @return number of frames that can be written. Never write more than this.
89     */
90    fifo_frames_t getEmptyFramesAvailable();
91
92    /**
93     * The index in a circular buffer of the next frame to write.
94     */
95    fifo_frames_t getWriteIndex();
96
97    /**
98     * @param numFrames number of frames to advance the write index
99     */
100    void advanceWriteIndex(fifo_frames_t numFrames);
101
102    /**
103     * You can request that the buffer not be filled above a maximum
104     * number of frames.
105     * @param threshold effective size of the buffer
106     */
107    void setThreshold(fifo_frames_t threshold);
108
109    fifo_frames_t getThreshold() const {
110        return mThreshold;
111    }
112
113    fifo_frames_t getCapacity() const {
114        return mCapacity;
115    }
116
117
118private:
119    fifo_frames_t mCapacity;
120    fifo_frames_t mThreshold;
121};
122
123}  // android
124
125#endif // FIFO_FIFO_CONTROLLER_BASE_H
126