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