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      1 /*
      2  * libjingle
      3  * Copyright 2013, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 package org.appspot.apprtc;
     29 
     30 import org.webrtc.VideoRenderer.I420Frame;
     31 
     32 import java.util.HashMap;
     33 import java.util.LinkedList;
     34 
     35 /**
     36  * This class acts as an allocation pool meant to minimize GC churn caused by
     37  * frame allocation & disposal.  The public API comprises of just two methods:
     38  * copyFrame(), which allocates as necessary and copies, and
     39  * returnFrame(), which returns frame ownership to the pool for use by a later
     40  * call to copyFrame().
     41  *
     42  * This class is thread-safe; calls to copyFrame() and returnFrame() are allowed
     43  * to happen on any thread.
     44  */
     45 class FramePool {
     46   // Maps each summary code (see summarizeFrameDimensions()) to a list of frames
     47   // of that description.
     48   private final HashMap<Long, LinkedList<I420Frame>> availableFrames =
     49       new HashMap<Long, LinkedList<I420Frame>>();
     50   // Every dimension (e.g. width, height, stride) of a frame must be less than
     51   // this value.
     52   private static final long MAX_DIMENSION = 4096;
     53 
     54   public I420Frame takeFrame(I420Frame source) {
     55     long desc = summarizeFrameDimensions(source);
     56     I420Frame dst = null;
     57     synchronized (availableFrames) {
     58       LinkedList<I420Frame> frames = availableFrames.get(desc);
     59       if (frames == null) {
     60         frames = new LinkedList<I420Frame>();
     61         availableFrames.put(desc, frames);
     62       }
     63       if (!frames.isEmpty()) {
     64         dst = frames.pop();
     65       } else {
     66         dst = new I420Frame(
     67             source.width, source.height, source.yuvStrides, null);
     68       }
     69     }
     70     return dst;
     71   }
     72 
     73   public void returnFrame(I420Frame frame) {
     74     long desc = summarizeFrameDimensions(frame);
     75     synchronized (availableFrames) {
     76       LinkedList<I420Frame> frames = availableFrames.get(desc);
     77       if (frames == null) {
     78         throw new IllegalArgumentException("Unexpected frame dimensions");
     79       }
     80       frames.add(frame);
     81     }
     82   }
     83 
     84   /** Validate that |frame| can be managed by the pool. */
     85   public static boolean validateDimensions(I420Frame frame) {
     86     return frame.width < MAX_DIMENSION && frame.height < MAX_DIMENSION &&
     87         frame.yuvStrides[0] < MAX_DIMENSION &&
     88         frame.yuvStrides[1] < MAX_DIMENSION &&
     89         frame.yuvStrides[2] < MAX_DIMENSION;
     90   }
     91 
     92   // Return a code summarizing the dimensions of |frame|.  Two frames that
     93   // return the same summary are guaranteed to be able to store each others'
     94   // contents.  Used like Object.hashCode(), but we need all the bits of a long
     95   // to do a good job, and hashCode() returns int, so we do this.
     96   private static long summarizeFrameDimensions(I420Frame frame) {
     97     long ret = frame.width;
     98     ret = ret * MAX_DIMENSION + frame.height;
     99     ret = ret * MAX_DIMENSION + frame.yuvStrides[0];
    100     ret = ret * MAX_DIMENSION + frame.yuvStrides[1];
    101     ret = ret * MAX_DIMENSION + frame.yuvStrides[2];
    102     return ret;
    103   }
    104 }
    105