1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one |
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3 | * or more contributor license agreements. See the NOTICE file |
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4 | * distributed with this work for additional information |
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5 | * regarding copyright ownership. The ASF licenses this file |
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6 | * to you under the Apache License, Version 2.0 (the |
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7 | * "License"); you may not use this file except in compliance |
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8 | * with the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | package org.apache.hadoop.fs; |
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19 | |
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20 | import java.io.BufferedInputStream; |
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21 | import java.io.IOException; |
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22 | |
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23 | |
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24 | /** |
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25 | * A class optimizes reading from FSInputStream by bufferring |
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26 | */ |
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27 | |
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28 | |
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29 | public class BufferedFSInputStream extends BufferedInputStream |
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30 | implements Seekable, PositionedReadable { |
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31 | /** |
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32 | * Creates a <code>BufferedFSInputStream</code> |
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33 | * with the specified buffer size, |
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34 | * and saves its argument, the input stream |
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35 | * <code>in</code>, for later use. An internal |
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36 | * buffer array of length <code>size</code> |
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37 | * is created and stored in <code>buf</code>. |
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38 | * |
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39 | * @param in the underlying input stream. |
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40 | * @param size the buffer size. |
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41 | * @exception IllegalArgumentException if size <= 0. |
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42 | */ |
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43 | public BufferedFSInputStream(FSInputStream in, int size) { |
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44 | super(in, size); |
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45 | } |
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46 | |
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47 | public long getPos() throws IOException { |
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48 | return ((FSInputStream)in).getPos()-(count-pos); |
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49 | } |
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50 | |
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51 | public long skip(long n) throws IOException { |
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52 | if (n <= 0) { |
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53 | return 0; |
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54 | } |
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55 | |
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56 | seek(getPos()+n); |
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57 | return n; |
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58 | } |
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59 | |
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60 | public void seek(long pos) throws IOException { |
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61 | if( pos<0 ) { |
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62 | return; |
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63 | } |
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64 | // optimize: check if the pos is in the buffer |
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65 | long end = ((FSInputStream)in).getPos(); |
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66 | long start = end - count; |
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67 | if( pos>=start && pos<end) { |
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68 | this.pos = (int)(pos-start); |
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69 | return; |
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70 | } |
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71 | |
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72 | // invalidate buffer |
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73 | this.pos = 0; |
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74 | this.count = 0; |
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75 | |
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76 | ((FSInputStream)in).seek(pos); |
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77 | } |
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78 | |
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79 | public boolean seekToNewSource(long targetPos) throws IOException { |
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80 | pos = 0; |
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81 | count = 0; |
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82 | return ((FSInputStream)in).seekToNewSource(targetPos); |
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83 | } |
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84 | |
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85 | public int read(long position, byte[] buffer, int offset, int length) throws IOException { |
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86 | return ((FSInputStream)in).read(position, buffer, offset, length) ; |
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87 | } |
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88 | |
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89 | public void readFully(long position, byte[] buffer, int offset, int length) throws IOException { |
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90 | ((FSInputStream)in).readFully(position, buffer, offset, length); |
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91 | } |
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92 | |
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93 | public void readFully(long position, byte[] buffer) throws IOException { |
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94 | ((FSInputStream)in).readFully(position, buffer); |
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95 | } |
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96 | } |
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