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 
BytesBuffer(int capacity)35         private BytesBuffer(int capacity) {
36             this.data = new byte[capacity];
37         }
38 
39         // an helper function to read content from FileDescriptor
readFrom(JobContext jc, FileDescriptor fd)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 
BytesBufferPool(int poolSize, int bufferSize)68     public BytesBufferPool(int poolSize, int bufferSize) {
69         mList = new ArrayList<BytesBuffer>(poolSize);
70         mPoolSize = poolSize;
71         mBufferSize = bufferSize;
72     }
73 
get()74     public synchronized BytesBuffer get() {
75         int n = mList.size();
76         return n > 0 ? mList.remove(n - 1) : new BytesBuffer(mBufferSize);
77     }
78 
recycle(BytesBuffer buffer)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 
clear()88     public synchronized void clear() {
89         mList.clear();
90     }
91 }
92