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annotate hg4j/src/main/java/org/tmatesoft/hg/internal/FilterDataAccess.java @ 213:6ec4af642ba8 gradle

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Project uses Gradle for build - actual changes
author Alexander Kitaev <kitaev@gmail.com>
date Tue, 10 May 2011 10:52:53 +0200
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6ec4af642ba8 Project uses Gradle for build - actual changes
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1 /*
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2 * Copyright (c) 2011 TMate Software Ltd
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3 *
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4 * This program is free software; you can redistribute it and/or modify
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5 * it under the terms of the GNU General Public License as published by
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6 * the Free Software Foundation; version 2 of the License.
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7 *
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8 * This program is distributed in the hope that it will be useful,
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9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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11 * GNU General Public License for more details.
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12 *
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13 * For information on how to redistribute this software under
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14 * the terms of a license other than GNU General Public License
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15 * contact TMate Software at support@hg4j.com
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16 */
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17 package org.tmatesoft.hg.internal;
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18
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19 import java.io.IOException;
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20
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21
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22 /**
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23 * XXX Perhaps, DataAccessSlice? Unlike FilterInputStream, we limit amount of data read from DataAccess being filtered.
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24 *
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25 *
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26 * @author Artem Tikhomirov
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27 * @author TMate Software Ltd.
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28 */
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29 public class FilterDataAccess extends DataAccess {
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30 private final DataAccess dataAccess;
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31 private final int offset;
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32 private final int length;
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33 private int count;
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34
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35 public FilterDataAccess(DataAccess dataAccess, int offset, int length) {
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36 this.dataAccess = dataAccess;
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37 this.offset = offset;
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38 this.length = length;
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39 count = length;
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40 }
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41
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42 protected int available() {
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43 return count;
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44 }
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45
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46 @Override
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47 public FilterDataAccess reset() throws IOException {
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48 count = length;
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49 return this;
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50 }
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51
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52 @Override
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53 public boolean isEmpty() {
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54 return count <= 0;
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55 }
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56
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57 @Override
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58 public int length() {
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59 return length;
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60 }
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61
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62 @Override
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63 public void seek(int localOffset) throws IOException {
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64 if (localOffset < 0 || localOffset > length) {
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65 throw new IllegalArgumentException();
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66 }
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67 dataAccess.seek(offset + localOffset);
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68 count = (int) (length - localOffset);
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69 }
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70
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71 @Override
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72 public void skip(int bytes) throws IOException {
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73 int newCount = count - bytes;
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74 if (newCount < 0 || newCount > length) {
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75 throw new IllegalArgumentException();
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76 }
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77 seek(length - newCount);
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78 /*
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79 can't use next code because don't want to rewind backing DataAccess on reset()
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80 i.e. this.reset() modifies state of this instance only, while filtered DA may go further.
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81 Only actual this.skip/seek/read would rewind it to desired position
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82 dataAccess.skip(bytes);
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83 count = newCount;
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84 */
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85
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86 }
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87
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88 @Override
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89 public byte readByte() throws IOException {
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90 if (count <= 0) {
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91 throw new IllegalArgumentException("Underflow"); // XXX be descriptive
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92 }
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93 if (count == length) {
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94 dataAccess.seek(offset);
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95 }
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96 count--;
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97 return dataAccess.readByte();
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98 }
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99
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100 @Override
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101 public void readBytes(byte[] b, int off, int len) throws IOException {
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102 if (len == 0) {
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103 return;
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104 }
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105 if (count <= 0 || len > count) {
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106 throw new IllegalArgumentException(String.format("Underflow. Bytes left: %d, asked to read %d", count, len));
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107 }
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108 if (count == length) {
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109 dataAccess.seek(offset);
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110 }
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111 dataAccess.readBytes(b, off, len);
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112 count -= len;
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113 }
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114
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115 // done shall be no-op, as we have no idea what's going on with DataAccess we filter
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116 }