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* Copyright (C) 2013 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <gui/BufferItem.h>
#include <gui/ConsumerBase.h>
#include <gui/BufferQueue.h>
#include <utils/List.h>
namespace android {
class String8;
* The RingBufferConsumer maintains a ring buffer of BufferItem objects,
* (which are 'acquired' as long as they are part of the ring buffer, and
* 'released' when they leave the ring buffer).
* When new buffers are produced, the oldest non-pinned buffer item is immediately
* dropped from the ring buffer, and overridden with the newest buffer.
* Users can only access a buffer item after pinning it (which also guarantees
* that during its duration it will not be released back into the BufferQueue).
* Note that the 'oldest' buffer is the one with the smallest timestamp.
* Edge cases:
* - If ringbuffer is not full, no drops occur when a buffer is produced.
* - If all the buffers get filled or pinned then there will be no empty
* buffers left, so the producer will block on dequeue.
class RingBufferConsumer : public ConsumerBase,
public ConsumerBase::FrameAvailableListener
typedef ConsumerBase::FrameAvailableListener FrameAvailableListener;
// Create a new ring buffer consumer. The consumerUsage parameter determines
// the consumer usage flags passed to the graphics allocator. The
// bufferCount parameter specifies how many buffers can be pinned for user
// access at the same time.
RingBufferConsumer(const sp<IGraphicBufferConsumer>& consumer, uint32_t consumerUsage,
int bufferCount);
virtual ~RingBufferConsumer();
// set the name of the RingBufferConsumer that will be used to identify it in
// log messages.
void setName(const String8& name);
// setDefaultBufferSize is used to set the size of buffers returned by
// requestBuffers when a with and height of zero is requested.
status_t setDefaultBufferSize(uint32_t w, uint32_t h);
// setDefaultBufferFormat allows the BufferQueue to create
// GraphicBuffers of a defaultFormat if no format is specified
// by the producer endpoint.
status_t setDefaultBufferFormat(uint32_t defaultFormat);
// setConsumerUsage allows the BufferQueue consumer usage to be
// set at a later time after construction.
status_t setConsumerUsage(uint32_t usage);
// Buffer info, minus the graphics buffer/slot itself.
struct BufferInfo {
// mCrop is the current crop rectangle for this buffer slot.
Rect mCrop;
// mTransform is the current transform flags for this buffer slot.
uint32_t mTransform;
// mScalingMode is the current scaling mode for this buffer slot.
uint32_t mScalingMode;
// mTimestamp is the current timestamp for this buffer slot. This gets
// to set by queueBuffer each time this slot is queued.
int64_t mTimestamp;
// mFrameNumber is the number of the queued frame for this slot.
uint64_t mFrameNumber;
// mPinned is whether or not the buffer has been pinned already.
bool mPinned;
struct RingBufferComparator {
// Return < 0 to select i1, > 0 to select i2, 0 for neither
// i1 or i2 can be NULL.
// The comparator has to implement a total ordering. Otherwise
// a linear scan won't find the most preferred buffer.
virtual int compare(const BufferInfo* i1,
const BufferInfo* i2) const = 0;
virtual ~RingBufferComparator() {}
struct PinnedBufferItem : public LightRefBase<PinnedBufferItem> {
PinnedBufferItem(wp<RingBufferConsumer> consumer,
const BufferItem& item) :
mBufferItem(item) {
~PinnedBufferItem() {
sp<RingBufferConsumer> consumer = mConsumer.promote();
if (consumer != NULL) {
bool isEmpty() {
return mBufferItem.mSlot == BufferQueue::INVALID_BUFFER_SLOT;
BufferItem& getBufferItem() { return mBufferItem; }
const BufferItem& getBufferItem() const { return mBufferItem; }
wp<RingBufferConsumer> mConsumer;
BufferItem mBufferItem;
// Find a buffer using the filter, then pin it before returning it.
// The filter will be invoked on each buffer item in the ring buffer,
// passing the item that was selected from each previous iteration,
// as well as the current iteration's item.
// Pinning will ensure that the buffer will not be dropped when a new
// frame is available.
sp<PinnedBufferItem> pinSelectedBuffer(const RingBufferComparator& filter,
bool waitForFence = true);
// Release all the non-pinned buffers in the ring buffer
status_t clear();
// Return 0 if RingBuffer is empty, otherwise return timestamp of latest buffer.
nsecs_t getLatestTimestamp();
// Override ConsumerBase::onFrameAvailable
virtual void onFrameAvailable(const BufferItem& item);
void pinBufferLocked(const BufferItem& item);
void unpinBuffer(const BufferItem& item);
// Releases oldest buffer. Returns NO_BUFFER_AVAILABLE
// if all the buffers were pinned.
// Returns NOT_ENOUGH_DATA if list was empty.
status_t releaseOldestBufferLocked(size_t* pinnedFrames);
struct RingBufferItem : public BufferItem {
RingBufferItem() : BufferItem(), mPinCount(0) {}
int mPinCount;
// List of acquired buffers in our ring buffer
List<RingBufferItem> mBufferItemList;
const int mBufferCount;
// Timestamp of latest buffer
nsecs_t mLatestTimestamp;
} // namespace android