RingBufferConsumer.h revision 6b7a2294b9e4da784cfe4b562ee1720ad606c852 
1/*
2 * Copyright (C) 2013 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 ANDROID_GUI_RINGBUFFERCONSUMER_H
18#define ANDROID_GUI_RINGBUFFERCONSUMER_H
19
20#include <gui/ConsumerBase.h>
21
22#include <ui/GraphicBuffer.h>
23
24#include <utils/String8.h>
25#include <utils/Vector.h>
26#include <utils/threads.h>
27#include <utils/List.h>
28
29#define ANDROID_GRAPHICS_RINGBUFFERCONSUMER_JNI_ID "mRingBufferConsumer"
30
31namespace android {
32
33/**
34 * The RingBufferConsumer maintains a ring buffer of BufferItem objects,
35 * (which are 'acquired' as long as they are part of the ring buffer, and
36 *  'released' when they leave the ring buffer).
37 *
38 * When new buffers are produced, the oldest non-pinned buffer item is immediately
39 * dropped from the ring buffer, and overridden with the newest buffer.
40 *
41 * Users can only access a buffer item after pinning it (which also guarantees
42 * that during its duration it will not be released back into the BufferQueue).
43 *
44 * Note that the 'oldest' buffer is the one with the smallest timestamp.
45 *
46 * Edge cases:
47 *  - If ringbuffer is not full, no drops occur when a buffer is produced.
48 *  - If all the buffers get filled or pinned then there will be no empty
49 *    buffers left, so the producer will block on dequeue.
50 */
51class RingBufferConsumer : public ConsumerBase,
52                           public ConsumerBase::FrameAvailableListener
53{
54  public:
55    typedef ConsumerBase::FrameAvailableListener FrameAvailableListener;
56
57    typedef BufferQueue::BufferItem BufferItem;
58
59    enum { INVALID_BUFFER_SLOT = BufferQueue::INVALID_BUFFER_SLOT };
60    enum { NO_BUFFER_AVAILABLE = BufferQueue::NO_BUFFER_AVAILABLE };
61
62    // Create a new ring buffer consumer. The consumerUsage parameter determines
63    // the consumer usage flags passed to the graphics allocator. The
64    // bufferCount parameter specifies how many buffers can be pinned for user
65    // access at the same time.
66    RingBufferConsumer(const sp<IGraphicBufferConsumer>& consumer, uint32_t consumerUsage,
67            int bufferCount);
68
69    virtual ~RingBufferConsumer();
70
71    // set the name of the RingBufferConsumer that will be used to identify it in
72    // log messages.
73    void setName(const String8& name);
74
75    // setDefaultBufferSize is used to set the size of buffers returned by
76    // requestBuffers when a with and height of zero is requested.
77    status_t setDefaultBufferSize(uint32_t w, uint32_t h);
78
79    // setDefaultBufferFormat allows the BufferQueue to create
80    // GraphicBuffers of a defaultFormat if no format is specified
81    // by the producer endpoint.
82    status_t setDefaultBufferFormat(uint32_t defaultFormat);
83
84    // setConsumerUsage allows the BufferQueue consumer usage to be
85    // set at a later time after construction.
86    status_t setConsumerUsage(uint32_t usage);
87
88    // Buffer info, minus the graphics buffer/slot itself.
89    struct BufferInfo {
90        // mCrop is the current crop rectangle for this buffer slot.
91        Rect mCrop;
92
93        // mTransform is the current transform flags for this buffer slot.
94        uint32_t mTransform;
95
96        // mScalingMode is the current scaling mode for this buffer slot.
97        uint32_t mScalingMode;
98
99        // mTimestamp is the current timestamp for this buffer slot. This gets
100        // to set by queueBuffer each time this slot is queued.
101        int64_t mTimestamp;
102
103        // mFrameNumber is the number of the queued frame for this slot.
104        uint64_t mFrameNumber;
105
106        // mPinned is whether or not the buffer has been pinned already.
107        bool mPinned;
108    };
109
110    struct RingBufferComparator {
111        // Return < 0 to select i1, > 0 to select i2, 0 for neither
112        // i1 or i2 can be NULL.
113        //
114        // The comparator has to implement a total ordering. Otherwise
115        // a linear scan won't find the most preferred buffer.
116        virtual int compare(const BufferInfo* i1,
117                            const BufferInfo* i2) const = 0;
118
119        virtual ~RingBufferComparator() {}
120    };
121
122    struct PinnedBufferItem : public LightRefBase<PinnedBufferItem> {
123        PinnedBufferItem(wp<RingBufferConsumer> consumer,
124                         const BufferItem& item) :
125                mConsumer(consumer),
126                mBufferItem(item) {
127        }
128
129        ~PinnedBufferItem() {
130            sp<RingBufferConsumer> consumer = mConsumer.promote();
131            if (consumer != NULL) {
132                consumer->unpinBuffer(mBufferItem);
133            }
134        }
135
136        bool isEmpty() {
137            return mBufferItem.mBuf == BufferQueue::INVALID_BUFFER_SLOT;
138        }
139
140        BufferItem& getBufferItem() { return mBufferItem; }
141        const BufferItem& getBufferItem() const { return mBufferItem; }
142
143      private:
144        wp<RingBufferConsumer> mConsumer;
145        BufferItem             mBufferItem;
146    };
147
148    // Find a buffer using the filter, then pin it before returning it.
149    //
150    // The filter will be invoked on each buffer item in the ring buffer,
151    // passing the item that was selected from each previous iteration,
152    // as well as the current iteration's item.
153    //
154    // Pinning will ensure that the buffer will not be dropped when a new
155    // frame is available.
156    sp<PinnedBufferItem> pinSelectedBuffer(const RingBufferComparator& filter,
157                                           bool waitForFence = true);
158
159    // Release all the non-pinned buffers in the ring buffer
160    status_t clear();
161
162    // Return 0 if RingBuffer is empty, otherwise return timestamp of latest buffer.
163    nsecs_t getLatestTimestamp();
164
165  private:
166
167    // Override ConsumerBase::onFrameAvailable
168    virtual void onFrameAvailable();
169
170    void pinBufferLocked(const BufferItem& item);
171    void unpinBuffer(const BufferItem& item);
172
173    // Releases oldest buffer. Returns NO_BUFFER_AVAILABLE
174    // if all the buffers were pinned.
175    // Returns NOT_ENOUGH_DATA if list was empty.
176    status_t releaseOldestBufferLocked(size_t* pinnedFrames);
177
178    struct RingBufferItem : public BufferItem {
179        RingBufferItem() : BufferItem(), mPinCount(0) {}
180        int mPinCount;
181    };
182
183    // List of acquired buffers in our ring buffer
184    List<RingBufferItem>       mBufferItemList;
185    const int                  mBufferCount;
186
187    // Timestamp of latest buffer
188    nsecs_t mLatestTimestamp;
189};
190
191} // namespace android
192
193#endif // ANDROID_GUI_CPUCONSUMER_H
194