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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 package com.android.gallery3d.data;
     18 
     19 import com.android.gallery3d.util.ThreadPool.JobContext;
     20 
     21 import java.io.FileDescriptor;
     22 import java.io.FileInputStream;
     23 import java.io.IOException;
     24 import java.util.ArrayList;
     25 
     26 public class BytesBufferPool {
     27 
     28     private static final int READ_STEP = 4096;
     29 
     30     public static class BytesBuffer {
     31         public byte[] data;
     32         public int offset;
     33         public int length;
     34 
     35         private BytesBuffer(int capacity) {
     36             this.data = new byte[capacity];
     37         }
     38 
     39         // an helper function to read content from FileDescriptor
     40         public void readFrom(JobContext jc, FileDescriptor fd) throws IOException {
     41             FileInputStream fis = new FileInputStream(fd);
     42             length = 0;
     43             try {
     44                 int capacity = data.length;
     45                 while (true) {
     46                     int step = Math.min(READ_STEP, capacity - length);
     47                     int rc = fis.read(data, length, step);
     48                     if (rc < 0 || jc.isCancelled()) return;
     49                     length += rc;
     50 
     51                     if (length == capacity) {
     52                         byte[] newData = new byte[data.length * 2];
     53                         System.arraycopy(data, 0, newData, 0, data.length);
     54                         data = newData;
     55                         capacity = data.length;
     56                     }
     57                 }
     58             } finally {
     59                 fis.close();
     60             }
     61         }
     62     }
     63 
     64     private final int mPoolSize;
     65     private final int mBufferSize;
     66     private final ArrayList<BytesBuffer> mList;
     67 
     68     public BytesBufferPool(int poolSize, int bufferSize) {
     69         mList = new ArrayList<BytesBuffer>(poolSize);
     70         mPoolSize = poolSize;
     71         mBufferSize = bufferSize;
     72     }
     73 
     74     public synchronized BytesBuffer get() {
     75         int n = mList.size();
     76         return n > 0 ? mList.remove(n - 1) : new BytesBuffer(mBufferSize);
     77     }
     78 
     79     public synchronized void recycle(BytesBuffer buffer) {
     80         if (buffer.data.length != mBufferSize) return;
     81         if (mList.size() < mPoolSize) {
     82             buffer.offset = 0;
     83             buffer.length = 0;
     84             mList.add(buffer);
     85         }
     86     }
     87 
     88     public synchronized void clear() {
     89         mList.clear();
     90     }
     91 }
     92