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      1 /*
      2  * Copyright (C) 2012 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_BUFFERQUEUE_H
     18 #define ANDROID_GUI_BUFFERQUEUE_H
     19 
     20 #include <gui/BufferItem.h>
     21 #include <gui/BufferQueueDefs.h>
     22 #include <gui/IGraphicBufferConsumer.h>
     23 #include <gui/IGraphicBufferProducer.h>
     24 #include <gui/IConsumerListener.h>
     25 
     26 // These are only required to keep other parts of the framework with incomplete
     27 // dependencies building successfully
     28 #include <gui/IGraphicBufferAlloc.h>
     29 
     30 namespace android {
     31 
     32 class BufferQueue {
     33 public:
     34     // BufferQueue will keep track of at most this value of buffers.
     35     // Attempts at runtime to increase the number of buffers past this will fail.
     36     enum { NUM_BUFFER_SLOTS = BufferQueueDefs::NUM_BUFFER_SLOTS };
     37     // Used as a placeholder slot# when the value isn't pointing to an existing buffer.
     38     enum { INVALID_BUFFER_SLOT = BufferItem::INVALID_BUFFER_SLOT };
     39     // Alias to <IGraphicBufferConsumer.h> -- please scope from there in future code!
     40     enum {
     41         NO_BUFFER_AVAILABLE = IGraphicBufferConsumer::NO_BUFFER_AVAILABLE,
     42         PRESENT_LATER = IGraphicBufferConsumer::PRESENT_LATER,
     43     };
     44 
     45     // When in async mode we reserve two slots in order to guarantee that the
     46     // producer and consumer can run asynchronously.
     47     enum { MAX_MAX_ACQUIRED_BUFFERS = NUM_BUFFER_SLOTS - 2 };
     48 
     49     // for backward source compatibility
     50     typedef ::android::ConsumerListener ConsumerListener;
     51 
     52     // ProxyConsumerListener is a ConsumerListener implementation that keeps a weak
     53     // reference to the actual consumer object.  It forwards all calls to that
     54     // consumer object so long as it exists.
     55     //
     56     // This class exists to avoid having a circular reference between the
     57     // BufferQueue object and the consumer object.  The reason this can't be a weak
     58     // reference in the BufferQueue class is because we're planning to expose the
     59     // consumer side of a BufferQueue as a binder interface, which doesn't support
     60     // weak references.
     61     class ProxyConsumerListener : public BnConsumerListener {
     62     public:
     63         ProxyConsumerListener(const wp<ConsumerListener>& consumerListener);
     64         virtual ~ProxyConsumerListener();
     65         virtual void onFrameAvailable(const BufferItem& item) override;
     66         virtual void onFrameReplaced(const BufferItem& item) override;
     67         virtual void onBuffersReleased() override;
     68         virtual void onSidebandStreamChanged() override;
     69     private:
     70         // mConsumerListener is a weak reference to the IConsumerListener.  This is
     71         // the raison d'etre of ProxyConsumerListener.
     72         wp<ConsumerListener> mConsumerListener;
     73     };
     74 
     75     // BufferQueue manages a pool of gralloc memory slots to be used by
     76     // producers and consumers. allocator is used to allocate all the
     77     // needed gralloc buffers.
     78     static void createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
     79             sp<IGraphicBufferConsumer>* outConsumer,
     80             const sp<IGraphicBufferAlloc>& allocator = NULL);
     81 
     82 private:
     83     BufferQueue(); // Create through createBufferQueue
     84 };
     85 
     86 // ----------------------------------------------------------------------------
     87 }; // namespace android
     88 
     89 #endif // ANDROID_GUI_BUFFERQUEUE_H
     90