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 #include <gui/BufferQueue.h>
23 
24 #include <utils/List.h>
25 
26 #define ANDROID_GRAPHICS_RINGBUFFERCONSUMER_JNI_ID "mRingBufferConsumer"
27 
28 namespace android {
29 
30 class String8;
31 
32 /**
33  * The RingBufferConsumer maintains a ring buffer of BufferItem objects,
34  * (which are 'acquired' as long as they are part of the ring buffer, and
35  *  'released' when they leave the ring buffer).
36  *
37  * When new buffers are produced, the oldest non-pinned buffer item is immediately
38  * dropped from the ring buffer, and overridden with the newest buffer.
39  *
40  * Users can only access a buffer item after pinning it (which also guarantees
41  * that during its duration it will not be released back into the BufferQueue).
42  *
43  * Note that the 'oldest' buffer is the one with the smallest timestamp.
44  *
45  * Edge cases:
46  *  - If ringbuffer is not full, no drops occur when a buffer is produced.
47  *  - If all the buffers get filled or pinned then there will be no empty
48  *    buffers left, so the producer will block on dequeue.
49  */
50 class RingBufferConsumer : public ConsumerBase,
51                            public ConsumerBase::FrameAvailableListener
52 {
53   public:
54     typedef ConsumerBase::FrameAvailableListener FrameAvailableListener;
55 
56     enum { INVALID_BUFFER_SLOT = BufferQueue::INVALID_BUFFER_SLOT };
57     enum { NO_BUFFER_AVAILABLE = BufferQueue::NO_BUFFER_AVAILABLE };
58 
59     // Create a new ring buffer consumer. The consumerUsage parameter determines
60     // the consumer usage flags passed to the graphics allocator. The
61     // bufferCount parameter specifies how many buffers can be pinned for user
62     // access at the same time.
63     RingBufferConsumer(const sp<IGraphicBufferConsumer>& consumer, uint64_t consumerUsage,
64             int bufferCount);
65 
66     virtual ~RingBufferConsumer();
67 
68     // set the name of the RingBufferConsumer that will be used to identify it in
69     // log messages.
70     void setName(const String8& name);
71 
72     // setDefaultBufferSize is used to set the size of buffers returned by
73     // requestBuffers when a with and height of zero is requested.
74     status_t setDefaultBufferSize(uint32_t w, uint32_t h);
75 
76     // setDefaultBufferFormat allows the BufferQueue to create
77     // GraphicBuffers of a defaultFormat if no format is specified
78     // by the producer endpoint.
79     status_t setDefaultBufferFormat(uint32_t defaultFormat);
80 
81     // setConsumerUsage allows the BufferQueue consumer usage to be
82     // set at a later time after construction.
83     status_t setConsumerUsage(uint64_t usage);
84 
85     // Buffer info, minus the graphics buffer/slot itself.
86     struct BufferInfo {
87         // mCrop is the current crop rectangle for this buffer slot.
88         Rect mCrop;
89 
90         // mTransform is the current transform flags for this buffer slot.
91         uint32_t mTransform;
92 
93         // mScalingMode is the current scaling mode for this buffer slot.
94         uint32_t mScalingMode;
95 
96         // mTimestamp is the current timestamp for this buffer slot. This gets
97         // to set by queueBuffer each time this slot is queued.
98         int64_t mTimestamp;
99 
100         // mFrameNumber is the number of the queued frame for this slot.
101         uint64_t mFrameNumber;
102 
103         // mPinned is whether or not the buffer has been pinned already.
104         bool mPinned;
105     };
106 
107     struct RingBufferComparator {
108         // Return < 0 to select i1, > 0 to select i2, 0 for neither
109         // i1 or i2 can be NULL.
110         //
111         // The comparator has to implement a total ordering. Otherwise
112         // a linear scan won't find the most preferred buffer.
113         virtual int compare(const BufferInfo* i1,
114                             const BufferInfo* i2) const = 0;
115 
~RingBufferComparatorRingBufferComparator116         virtual ~RingBufferComparator() {}
117     };
118 
119     struct PinnedBufferItem : public LightRefBase<PinnedBufferItem> {
PinnedBufferItemPinnedBufferItem120         PinnedBufferItem(wp<RingBufferConsumer> consumer,
121                          const BufferItem& item) :
122                 mConsumer(consumer),
123                 mBufferItem(item) {
124         }
125 
~PinnedBufferItemPinnedBufferItem126         ~PinnedBufferItem() {
127             sp<RingBufferConsumer> consumer = mConsumer.promote();
128             if (consumer != NULL) {
129                 consumer->unpinBuffer(mBufferItem);
130             }
131         }
132 
isEmptyPinnedBufferItem133         bool isEmpty() {
134             return mBufferItem.mSlot == BufferQueue::INVALID_BUFFER_SLOT;
135         }
136 
getBufferItemPinnedBufferItem137         BufferItem& getBufferItem() { return mBufferItem; }
getBufferItemPinnedBufferItem138         const BufferItem& getBufferItem() const { return mBufferItem; }
139 
140       private:
141         wp<RingBufferConsumer> mConsumer;
142         BufferItem             mBufferItem;
143     };
144 
145     // Find a buffer using the filter, then pin it before returning it.
146     //
147     // The filter will be invoked on each buffer item in the ring buffer,
148     // passing the item that was selected from each previous iteration,
149     // as well as the current iteration's item.
150     //
151     // Pinning will ensure that the buffer will not be dropped when a new
152     // frame is available.
153     sp<PinnedBufferItem> pinSelectedBuffer(const RingBufferComparator& filter,
154                                            bool waitForFence = true);
155 
156     // Release all the non-pinned buffers in the ring buffer
157     status_t clear();
158 
159     // Return 0 if RingBuffer is empty, otherwise return timestamp of latest buffer.
160     nsecs_t getLatestTimestamp();
161 
162   private:
163 
164     // Override ConsumerBase::onFrameAvailable
165     virtual void onFrameAvailable(const BufferItem& item);
166 
167     void pinBufferLocked(const BufferItem& item);
168     void unpinBuffer(const BufferItem& item);
169 
170     // Releases oldest buffer. Returns NO_BUFFER_AVAILABLE
171     // if all the buffers were pinned.
172     // Returns NOT_ENOUGH_DATA if list was empty.
173     status_t releaseOldestBufferLocked(size_t* pinnedFrames);
174 
175     struct RingBufferItem : public BufferItem {
RingBufferItemRingBufferItem176         RingBufferItem() : BufferItem(), mPinCount(0) {}
177         int mPinCount;
178     };
179 
180     // List of acquired buffers in our ring buffer
181     List<RingBufferItem>       mBufferItemList;
182     const int                  mBufferCount;
183 
184     // Timestamp of latest buffer
185     nsecs_t mLatestTimestamp;
186 };
187 
188 } // namespace android
189 
190 #endif // ANDROID_GUI_RINGBUFFERCONSUMER_H
191