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diff --git a/services/camera/libcameraservice/gui/RingBufferConsumer.h b/services/camera/libcameraservice/gui/RingBufferConsumer.h
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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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_RINGBUFFERCONSUMER_H
+#define ANDROID_GUI_RINGBUFFERCONSUMER_H
+
+#include <gui/ConsumerBase.h>
+
+#include <ui/GraphicBuffer.h>
+
+#include <utils/String8.h>
+#include <utils/Vector.h>
+#include <utils/threads.h>
+#include <utils/List.h>
+
+#define ANDROID_GRAPHICS_RINGBUFFERCONSUMER_JNI_ID "mRingBufferConsumer"
+
+namespace android {
+
+/**
+ * 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
+{
+  public:
+    typedef ConsumerBase::FrameAvailableListener FrameAvailableListener;
+
+    typedef BufferQueue::BufferItem BufferItem;
+
+    enum { INVALID_BUFFER_SLOT = BufferQueue::INVALID_BUFFER_SLOT };
+    enum { NO_BUFFER_AVAILABLE = BufferQueue::NO_BUFFER_AVAILABLE };
+
+    // 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 = BufferQueue::MIN_UNDEQUEUED_BUFFERS);
+
+    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) :
+                mConsumer(consumer),
+                mBufferItem(item) {
+        }
+
+        ~PinnedBufferItem() {
+            sp<RingBufferConsumer> consumer = mConsumer.promote();
+            if (consumer != NULL) {
+                consumer->unpinBuffer(mBufferItem);
+            }
+        }
+
+        bool isEmpty() {
+            return mBufferItem.mBuf == BufferQueue::INVALID_BUFFER_SLOT;
+        }
+
+        BufferItem& getBufferItem() { return mBufferItem; }
+        const BufferItem& getBufferItem() const { return mBufferItem; }
+
+      private:
+        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();
+
+  private:
+
+    // Override ConsumerBase::onFrameAvailable
+    virtual void onFrameAvailable();
+
+    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;
+};
+
+} // namespace android
+
+#endif // ANDROID_GUI_CPUCONSUMER_H