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 | |
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19 | package org.apache.hadoop.io.compress; |
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20 | |
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21 | import java.io.IOException; |
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22 | |
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23 | /** |
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24 | * Specification of a stream-based 'compressor' which can be |
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25 | * plugged into a {@link CompressionOutputStream} to compress data. |
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26 | * This is modelled after {@link java.util.zip.Deflater} |
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27 | * |
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28 | */ |
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29 | public interface Compressor { |
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30 | /** |
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31 | * Sets input data for compression. |
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32 | * This should be called whenever #needsInput() returns |
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33 | * <code>true</code> indicating that more input data is required. |
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34 | * |
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35 | * @param b Input data |
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36 | * @param off Start offset |
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37 | * @param len Length |
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38 | */ |
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39 | public void setInput(byte[] b, int off, int len); |
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40 | |
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41 | /** |
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42 | * Returns true if the input data buffer is empty and |
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43 | * #setInput() should be called to provide more input. |
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44 | * |
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45 | * @return <code>true</code> if the input data buffer is empty and |
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46 | * #setInput() should be called in order to provide more input. |
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47 | */ |
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48 | public boolean needsInput(); |
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49 | |
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50 | /** |
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51 | * Sets preset dictionary for compression. A preset dictionary |
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52 | * is used when the history buffer can be predetermined. |
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53 | * |
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54 | * @param b Dictionary data bytes |
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55 | * @param off Start offset |
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56 | * @param len Length |
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57 | */ |
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58 | public void setDictionary(byte[] b, int off, int len); |
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59 | |
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60 | /** |
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61 | * Return number of uncompressed bytes input so far. |
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62 | */ |
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63 | public long getBytesRead(); |
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64 | |
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65 | /** |
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66 | * Return number of compressed bytes output so far. |
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67 | */ |
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68 | public long getBytesWritten(); |
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69 | |
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70 | /** |
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71 | * When called, indicates that compression should end |
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72 | * with the current contents of the input buffer. |
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73 | */ |
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74 | public void finish(); |
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75 | |
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76 | /** |
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77 | * Returns true if the end of the compressed |
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78 | * data output stream has been reached. |
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79 | * @return <code>true</code> if the end of the compressed |
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80 | * data output stream has been reached. |
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81 | */ |
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82 | public boolean finished(); |
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83 | |
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84 | /** |
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85 | * Fills specified buffer with compressed data. Returns actual number |
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86 | * of bytes of compressed data. A return value of 0 indicates that |
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87 | * needsInput() should be called in order to determine if more input |
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88 | * data is required. |
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89 | * |
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90 | * @param b Buffer for the compressed data |
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91 | * @param off Start offset of the data |
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92 | * @param len Size of the buffer |
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93 | * @return The actual number of bytes of compressed data. |
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94 | */ |
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95 | public int compress(byte[] b, int off, int len) throws IOException; |
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96 | |
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97 | /** |
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98 | * Resets compressor so that a new set of input data can be processed. |
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99 | */ |
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100 | public void reset(); |
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101 | |
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102 | /** |
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103 | * Closes the compressor and discards any unprocessed input. |
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104 | */ |
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105 | public void end(); |
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106 | } |
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