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      1 /*
      2  * Copyright (C) 2015 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 package com.android.camera.burst;
     18 
     19 import android.support.v4.util.LongSparseArray;
     20 
     21 import com.android.camera.async.SafeCloseable;
     22 import com.android.camera.one.v2.camera2proxy.ImageProxy;
     23 
     24 import java.util.ArrayList;
     25 import java.util.List;
     26 
     27 /**
     28  * A RingBuffer that is used during burst capture. It takes a
     29  * {@link EvictionHandler} instance and uses it to evict frames when the ring
     30  * buffer runs out of capacity.
     31  */
     32 class RingBuffer<T extends ImageProxy> implements SafeCloseable {
     33     private final int mMaxCapacity;
     34     private final EvictionHandler mEvictionHandler;
     35     private final LongSparseArray<T> mImages = new LongSparseArray<>();
     36 
     37     /**
     38      * Create a new ring buffer instance.
     39      *
     40      * @param maxCapacity the maximum number of images in the ring buffer.
     41      * @param evictionHandler
     42      */
     43     public RingBuffer(int maxCapacity, EvictionHandler evictionHandler) {
     44         mMaxCapacity = maxCapacity;
     45         mEvictionHandler = evictionHandler;
     46     }
     47 
     48     /**
     49      * Insert an image in the ring buffer, evicting any frames if necessary.
     50      *
     51      * @param image the image to be inserted.
     52      */
     53     public synchronized void insertImage(T image) {
     54         long timestamp = image.getTimestamp();
     55         if (mImages.get(timestamp) != null) {
     56             image.close();
     57             return;
     58         }
     59         // Add image to ring buffer so it can be closed in case eviction
     60         // handler throws.
     61         addImage(image);
     62         mEvictionHandler.onFrameInserted(timestamp);
     63         if (mImages.size() > mMaxCapacity) {
     64             long selectFrameToDrop = mEvictionHandler.selectFrameToDrop();
     65             removeAndCloseImage(selectFrameToDrop);
     66             mEvictionHandler.onFrameDropped(selectFrameToDrop);
     67         }
     68     }
     69 
     70     /**
     71      * Returns all images present in the ring buffer.
     72      */
     73     public synchronized List<T> getAndRemoveAllImages() {
     74         List<T> allImages = new ArrayList<>(mImages.size());
     75         for (int i = 0; i < mImages.size(); i++) {
     76             allImages.add(mImages.valueAt(i));
     77         }
     78         mImages.clear();
     79         return allImages;
     80     }
     81 
     82     /**
     83      * Closes the ring buffer and any images in the ring buffer.
     84      */
     85     @Override
     86     public synchronized void close() {
     87         for (int i = 0; i < mImages.size(); i++) {
     88             mImages.valueAt(i).close();
     89         }
     90         mImages.clear();
     91     }
     92 
     93     private synchronized void removeAndCloseImage(long timestampNs) {
     94         mImages.get(timestampNs).close();
     95         mImages.remove(timestampNs);
     96     }
     97 
     98     private synchronized void addImage(T image) {
     99         mImages.put(image.getTimestamp(), image);
    100     }
    101 }
    102