Graphic学习笔记-创新互联

发现一个比较好的介绍graphic帖子， 后面会跟着帖子来梳理下graphic相关知识点
http://blog.csdn.net/u014409795/article/details/51276468

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1. BufferQueue

      class BufferQueue {
             class ProxyConsumerListener : public BnConsumerListener;
             static void createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
                       sp<IGraphicBufferConsumer>* outConsumer,
                        const sp<IGraphicBufferAlloc>& allocator = NULL);
        private:
            BufferQueue(); // Create through createBufferQueue

    }

    //看起来只有consumer一个角色？

   void BufferQueue::createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
       sp<IGraphicBufferConsumer>* outConsumer,
       const sp<IGraphicBufferAlloc>& allocator) {

       sp<BufferQueueCore> core(new BufferQueueCore(allocator));
       sp<IGraphicBufferProducer> producer(new BufferQueueProducer(core));

       sp<IGraphicBufferConsumer> consumer(new BufferQueueConsumer(core));

 BufferQueue核心是BufferQueueCore,

  看BufferQueueCore里面是管理什么的

 class BufferQueueCore : public virtual RefBase {

          friend class BufferQueueProducer;
          friend class BufferQueueConsumer;

          typedef Vector<BufferItem> Fifo; //一个BufferItem Vector

        private:

        // mAllocator is the connection to SurfaceFlinger that is used to allocate
        // new GraphicBuffer objects.
       sp<IGraphicBufferAlloc> mAllocator;
        // mSlots is an array of buffer slots that must be mirrored on the producer
       // side. This allows buffer ownership to be transferred between the producer
       // and consumer without sending a GraphicBuffer over Binder. The entire
      // array is initialized to NULL at construction time, and buffers are
      // allocated for a slot when requestBuffer is called with that slot's index.
       BufferQueueDefs::SlotsType mSlots;  //

       BufferSlot()
   : mEglDisplay(EGL_NO_DISPLAY),
     mBufferState(BufferSlot::FREE),   //state
     mRequestBufferCalled(false),
     mFrameNumber(0),
     mEglFence(EGL_NO_SYNC_KHR),
     mAcquireCalled(false),
     mNeedsCleanupOnRelease(false),
     mAttachedByConsumer(false) {
   }

   // mGraphicBuffer points to the buffer allocated for this slot or is NULL
   // if no buffer has been allocated.
   sp<GraphicBuffer> mGraphicBuffer;  //bufferslot中指向GraphicBuffer

   enum BufferState { // state 表示buffer state

    FREE = 0,  //FREE indicates that the buffer is available to be dequeued by the producer.
     // 允许produce获取该buffer，填充数据，状态变为dequeue   free 时表示该buffer还被bufferqueue 所有

  DEQUEUED = 1,// DEQUEUED indicates that the buffer has been dequeued by the  producer, but has not yet been queued or canceled. The slot is "owned" by the producer. 处于待填充数据状态,被producer所有

 QUEUED = 2,//QUEUED indicates that the buffer has been filled by the producer and queued for use by the consumer; producer填充完数据，准备提供给consumer消费，被bufferqueue所有

  ACQUIRED = 3//ACQUIRED indicates that the buffer has been acquired by the  consumer.

  buffer被consumer获取到，消费完后转为free

  在bufferqueuecore中bufferItem又是什么
  class BufferItem : public Flattenable<BufferItem> {

  // mGraphicBuffer points to the buffer allocated for this slot, or is NULL
   // if the buffer in this slot has been acquired in the past (see
   // BufferSlot.mAcquireCalled).
   sp<GraphicBuffer> mGraphicBuffer; //也有GraphicBuffer指针

    union {
       // mSlot is the slot index of this buffer (default INVALID_BUFFER_SLOT).
       int mSlot; // slot数组中索引

       // mBuf is the former name for mSlot
       int mBuf; // 旧名字
   };

  BufferSlot 与 BufferItem 都指向GraphicBuffer,然后又 通过mSlot下标关联起来，至于两者使用场景再看

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