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annotate src/org/tmatesoft/hg/internal/ByteArrayDataAccess.java @ 599:55b7987c1796

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Do not instantiate intermediate arrays
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Fri, 03 May 2013 15:29:26 +0200
parents 6c22bdc0bdfd
children 46b56864b483
rev   line source
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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 *
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24 * @author Artem Tikhomirov
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25 * @author TMate Software Ltd.
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26 */
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27 public class ByteArrayDataAccess extends DataAccess {
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28
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29 private final byte[] data;
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30 private final int offset;
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31 private final int length;
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32 private int pos;
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33
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34 public ByteArrayDataAccess(byte[] data) {
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35 this(data, 0, data.length);
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36 }
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37
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38 public ByteArrayDataAccess(byte[] data, int offset, int length) {
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39 this.data = data;
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40 this.offset = offset;
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41 this.length = length;
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42 pos = 0;
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43 }
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44
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45 @Override
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46 public byte readByte() throws IOException {
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47 if (pos >= length) {
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48 throw new IOException();
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49 }
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50 return data[offset + pos++];
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51 }
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52 @Override
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53 public void readBytes(byte[] buf, int off, int len) throws IOException {
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54 if (len > (this.length - pos)) {
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55 throw new IOException();
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56 }
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57 System.arraycopy(data, offset+pos, buf, off, len);
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58 pos += len;
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59 }
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60 @Override
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61 public int readInt() throws IOException {
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62 // overridden not to create an intermediate array
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63 if (length - pos < 4) {
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64 throw new IOException();
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65 }
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66 int x = offset + pos;
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67 int rv = data[x++] << 24 | (data[x++] & 0xFF) << 16 | (data[x++] & 0xFF) << 8 | (data[x] & 0xFF);
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68 pos += 4;
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69 return rv;
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70 }
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71 @Override
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72 public long readLong() throws IOException {
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73 // overridden not to create an intermediate array
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74 if (length - pos < 8) {
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75 throw new IOException();
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76 }
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77 int x = offset + pos;
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78 int i1 = data[x++] << 24 | (data[x++] & 0xFF) << 16 | (data[x++] & 0xFF) << 8 | (data[x++] & 0xFF);
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79 int i2 = data[x++] << 24 | (data[x++] & 0xFF) << 16 | (data[x++] & 0xFF) << 8 | (data[x] & 0xFF);
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80 pos += 8;
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81 return ((long) i1) << 32 | ((long) i2 & 0x0FFFFFFFFl);
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82 }
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83
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84 @Override
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85 public ByteArrayDataAccess reset() {
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86 pos = 0;
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87 return this;
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88 }
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89 @Override
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90 public int length() {
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91 return length;
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92 }
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93 @Override
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94 public void seek(int offset) {
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95 pos = offset;
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96 }
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97 @Override
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98 public void skip(int bytes) throws IOException {
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99 seek(pos + bytes);
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100 }
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101 @Override
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102 public boolean isEmpty() {
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103 return pos >= length;
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104 }
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105
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106 //
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107
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108 // when byte[] needed from DA, we may save few cycles and some memory giving this (otherwise unsafe) access to underlying data
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109 @Override
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110 public byte[] byteArray() {
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111 return data;
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112 }
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113 }