RingBufferConsumer.h revision 40602741ae87e6bf368c17dd28db4d2db344bded 
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(uint32_t consumerUsage,
67            int bufferCount = BufferQueue::MIN_UNDEQUEUED_BUFFERS);
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    sp<IGraphicBufferProducer> getProducerInterface() const { return getBufferQueue(); }
76
77    // setDefaultBufferSize is used to set the size of buffers returned by
78    // requestBuffers when a with and height of zero is requested.
79    status_t setDefaultBufferSize(uint32_t w, uint32_t h);
80
81    // setDefaultBufferFormat allows the BufferQueue to create
82    // GraphicBuffers of a defaultFormat if no format is specified
83    // by the producer endpoint.
84    status_t setDefaultBufferFormat(uint32_t defaultFormat);
85
86    // setConsumerUsage allows the BufferQueue consumer usage to be
87    // set at a later time after construction.
88    status_t setConsumerUsage(uint32_t usage);
89
90    // Buffer info, minus the graphics buffer/slot itself.
91    struct BufferInfo {
92        // mCrop is the current crop rectangle for this buffer slot.
93        Rect mCrop;
94
95        // mTransform is the current transform flags for this buffer slot.
96        uint32_t mTransform;
97
98        // mScalingMode is the current scaling mode for this buffer slot.
99        uint32_t mScalingMode;
100
101        // mTimestamp is the current timestamp for this buffer slot. This gets
102        // to set by queueBuffer each time this slot is queued.
103        int64_t mTimestamp;
104
105        // mFrameNumber is the number of the queued frame for this slot.
106        uint64_t mFrameNumber;
107
108        // mPinned is whether or not the buffer has been pinned already.
109        bool mPinned;
110    };
111
112    struct RingBufferComparator {
113        // Return < 0 to select i1, > 0 to select i2, 0 for neither
114        // i1 or i2 can be NULL.
115        //
116        // The comparator has to implement a total ordering. Otherwise
117        // a linear scan won't find the most preferred buffer.
118        virtual int compare(const BufferInfo* i1,
119                            const BufferInfo* i2) const = 0;
120
121        virtual ~RingBufferComparator() {}
122    };
123
124    struct PinnedBufferItem : public LightRefBase<PinnedBufferItem> {
125        PinnedBufferItem(wp<RingBufferConsumer> consumer,
126                         const BufferItem& item) :
127                mConsumer(consumer),
128                mBufferItem(item) {
129        }
130
131        ~PinnedBufferItem() {
132            sp<RingBufferConsumer> consumer = mConsumer.promote();
133            if (consumer != NULL) {
134                consumer->unpinBuffer(mBufferItem);
135            }
136        }
137
138        bool isEmpty() {
139            return mBufferItem.mBuf == BufferQueue::INVALID_BUFFER_SLOT;
140        }
141
142        BufferItem& getBufferItem() { return mBufferItem; }
143        const BufferItem& getBufferItem() const { return mBufferItem; }
144
145      private:
146        wp<RingBufferConsumer> mConsumer;
147        BufferItem             mBufferItem;
148    };
149
150    // Find a buffer using the filter, then pin it before returning it.
151    //
152    // The filter will be invoked on each buffer item in the ring buffer,
153    // passing the item that was selected from each previous iteration,
154    // as well as the current iteration's item.
155    //
156    // Pinning will ensure that the buffer will not be dropped when a new
157    // frame is available.
158    sp<PinnedBufferItem> pinSelectedBuffer(const RingBufferComparator& filter,
159                                           bool waitForFence = true);
160
161    // Release all the non-pinned buffers in the ring buffer
162    status_t clear();
163
164  private:
165
166    // Override ConsumerBase::onFrameAvailable
167    virtual void onFrameAvailable();
168
169    void pinBufferLocked(const BufferItem& item);
170    void unpinBuffer(const BufferItem& item);
171
172    // Releases oldest buffer. Returns NO_BUFFER_AVAILABLE
173    // if all the buffers were pinned.
174    // Returns NOT_ENOUGH_DATA if list was empty.
175    status_t releaseOldestBufferLocked(size_t* pinnedFrames);
176
177    struct RingBufferItem : public BufferItem {
178        RingBufferItem() : BufferItem(), mPinCount(0) {}
179        int mPinCount;
180    };
181
182    // List of acquired buffers in our ring buffer
183    List<RingBufferItem>       mBufferItemList;
184    const int                  mBufferCount;
185};
186
187} // namespace android
188
189#endif // ANDROID_GUI_CPUCONSUMER_H
190