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1 /*******************************************************************************
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2 * Copyright (c) 2000, 2006 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module org.eclipse.swt.internal.image.PngChunk;
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14
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15
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16 import org.eclipse.swt.SWT;
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17 import org.eclipse.swt.internal.image.LEDataInputStream;
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18 import org.eclipse.swt.internal.image.PngFileReadState;
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19 import org.eclipse.swt.internal.image.PngIhdrChunk;
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20 import org.eclipse.swt.internal.image.PngPlteChunk;
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21 import org.eclipse.swt.internal.image.PngIdatChunk;
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22 import org.eclipse.swt.internal.image.PngIendChunk;
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23 import org.eclipse.swt.internal.image.PngTrnsChunk;
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24 import java.lang.all;
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25
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26
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27 class PngChunk {
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28 byte[] reference;
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29
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30 static const int LENGTH_OFFSET = 0;
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31 static const int TYPE_OFFSET = 4;
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32 static const int DATA_OFFSET = 8;
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33
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34 static const int TYPE_FIELD_LENGTH = 4;
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35 static const int LENGTH_FIELD_LENGTH = 4;
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36 static const int MIN_LENGTH = 12;
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37
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38 static const int CHUNK_UNKNOWN = -1;
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39 // Critical chunks.
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40 static const int CHUNK_IHDR = 0;
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41 static const int CHUNK_PLTE = 1;
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42 static const int CHUNK_IDAT = 2;
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43 static const int CHUNK_IEND = 3;
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44 // Non-critical chunks.
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45 static const int CHUNK_tRNS = 5;
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46
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51
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47 static /+const+/ byte[] TYPE_IHDR = cast(byte[])"IHDR";//{(byte) 'I', (byte) 'H', (byte) 'D', (byte) 'R'};
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48 static /+const+/ byte[] TYPE_PLTE = cast(byte[])"PLTE";//{(byte) 'P', (byte) 'L', (byte) 'T', (byte) 'E'};
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49 static /+const+/ byte[] TYPE_IDAT = cast(byte[])"IDAT";//{(byte) 'I', (byte) 'D', (byte) 'A', (byte) 'T'};
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50 static /+const+/ byte[] TYPE_IEND = cast(byte[])"IEND";//{(byte) 'I', (byte) 'E', (byte) 'N', (byte) 'D'};
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51 static /+const+/ byte[] TYPE_tRNS = cast(byte[])"tRNS";//{(byte) 't', (byte) 'R', (byte) 'N', (byte) 'S'};
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25
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52
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113
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53 private static int[] _CRC_TABLE = null;
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54
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55 static int[] CRC_TABLE () {
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56 if (!_CRC_TABLE)
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57 static_this;
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58
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59 return _CRC_TABLE;
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60 }
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61
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62 private static void static_this () {
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63 _CRC_TABLE = new int[256];
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25
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64 for (int i = 0; i < 256; i++) {
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113
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65 _CRC_TABLE[i] = i;
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66 for (int j = 0; j < 8; j++) {
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113
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67 if ((_CRC_TABLE[i] & 0x1) is 0) {
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68 _CRC_TABLE[i] = (_CRC_TABLE[i] >> 1) & 0x7FFFFFFF;
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25
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69 } else {
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113
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70 _CRC_TABLE[i] = 0xEDB88320 ^ ((_CRC_TABLE[i] >> 1) & 0x7FFFFFFF);
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25
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71 }
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72 }
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73 }
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74 }
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75
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76 int length;
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77
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78 /**
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79 * Construct a PngChunk using the reference bytes
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80 * given.
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81 */
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82 this(byte[] reference) {
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83 setReference(reference);
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84 if (reference.length < LENGTH_OFFSET + LENGTH_FIELD_LENGTH) SWT.error(SWT.ERROR_INVALID_IMAGE);
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85 length = getInt32(LENGTH_OFFSET);
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86 }
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87
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88 /**
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89 * Construct a PngChunk with the specified number of
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90 * data bytes.
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91 */
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92 this(int dataLength) {
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93 this(new byte[MIN_LENGTH + dataLength]);
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94 setLength(dataLength);
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95 }
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96
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97 /**
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98 * Get the PngChunk's reference byteArray;
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99 */
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100 byte[] getReference() {
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101 return reference;
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102 }
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103
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104 /**
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105 * Set the PngChunk's reference byteArray;
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106 */
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107 void setReference(byte[] reference) {
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108 this.reference = reference;
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109 }
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110
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111 /**
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112 * Get the 16-bit integer from the reference byte
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113 * array at the given offset.
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114 */
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115 int getInt16(int offset) {
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116 int answer = 0;
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117 answer |= (reference[offset] & 0xFF) << 8;
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118 answer |= (reference[offset + 1] & 0xFF);
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119 return answer;
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120 }
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121
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122 /**
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123 * Set the 16-bit integer in the reference byte
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124 * array at the given offset.
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125 */
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126 void setInt16(int offset, int value) {
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127 reference[offset] = cast(byte) ((value >> 8) & 0xFF);
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128 reference[offset + 1] = cast(byte) (value & 0xFF);
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129 }
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130
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131 /**
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132 * Get the 32-bit integer from the reference byte
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133 * array at the given offset.
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134 */
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135 int getInt32(int offset) {
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136 int answer = 0;
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137 answer |= (reference[offset] & 0xFF) << 24;
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138 answer |= (reference[offset + 1] & 0xFF) << 16;
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139 answer |= (reference[offset + 2] & 0xFF) << 8;
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140 answer |= (reference[offset + 3] & 0xFF);
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141 return answer;
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142 }
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143
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144 /**
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145 * Set the 32-bit integer in the reference byte
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146 * array at the given offset.
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147 */
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148 void setInt32(int offset, int value) {
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149 reference[offset] = cast(byte) ((value >> 24) & 0xFF);
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150 reference[offset + 1] = cast(byte) ((value >> 16) & 0xFF);
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151 reference[offset + 2] = cast(byte) ((value >> 8) & 0xFF);
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152 reference[offset + 3] = cast(byte) (value & 0xFF);
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153 }
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154
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155 /**
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156 * Get the length of the data component of this chunk.
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157 * This is not the length of the entire chunk.
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158 */
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159 int getLength() {
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160 return length;
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161 }
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162
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163 /**
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164 * Set the length of the data component of this chunk.
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165 * This is not the length of the entire chunk.
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166 */
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167 void setLength(int value) {
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168 setInt32(LENGTH_OFFSET, value);
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169 length = value;
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170 }
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171
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172 /**
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173 * Get the chunk type. This is a four byte value.
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174 * Each byte should be an ASCII character.
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175 * The first byte is upper case if the chunk is critical.
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176 * The second byte is upper case if the chunk is publicly defined.
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177 * The third byte must be upper case.
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178 * The fourth byte is upper case if the chunk is unsafe to copy.
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179 * Public chunk types are defined by the PNG Development Group.
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180 */
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181 byte[] getTypeBytes() {
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182 byte[] type = new byte[4];
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183 System.arraycopy(reference, TYPE_OFFSET, type, 0, TYPE_FIELD_LENGTH);
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184 return type;
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185 }
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186
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187 /**
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188 * Set the chunk type. This is a four byte value.
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189 * Each byte should be an ASCII character.
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190 * The first byte is upper case if the chunk is critical.
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191 * The second byte is upper case if the chunk is publicly defined.
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192 * The third byte must be upper case.
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193 * The fourth byte is upper case if the chunk is unsafe to copy.
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194 * Public chunk types are defined by the PNG Development Group.
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195 */
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196 void setType(byte[] value) {
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197 if (value.length !is TYPE_FIELD_LENGTH) {
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198 SWT.error (SWT.ERROR_INVALID_ARGUMENT);
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199 }
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200 System.arraycopy(value, 0, reference, TYPE_OFFSET, TYPE_FIELD_LENGTH);
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201 }
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202
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203 /**
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204 * Get the chunk's data.
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205 */
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206 byte[] getData() {
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207 int dataLength = getLength();
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208 if (reference.length < MIN_LENGTH + dataLength) {
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209 SWT.error (SWT.ERROR_INVALID_RANGE);
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210 }
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211 byte[] data = new byte[dataLength];
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212 System.arraycopy(reference, DATA_OFFSET, data, 0, dataLength);
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213 return data;
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214 }
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215
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216 /**
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217 * Set the chunk's data.
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218 * This method has two side-effects.
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219 * 1. It will set the length field to be the length
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220 * of the data array given.
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221 * 2. It will set the CRC field to the computed CRC
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222 * value of the data array given.
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223 */
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224 void setData(byte[] data) {
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225 setLength(data.length);
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226 System.arraycopy(data, 0, reference, DATA_OFFSET, data.length);
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227 setCRC(computeCRC());
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228 }
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229
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230 /**
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231 * Get the CRC value for the chunk's data.
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232 * Ensure that the length field has a good
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233 * value before making this call.
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234 */
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235 int getCRC() {
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236 int crcOffset = DATA_OFFSET + getLength();
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237 return getInt32(crcOffset);
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238 }
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239
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240 /**
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241 * Set the CRC value for the chunk's data.
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242 * Ensure that the length field has a good
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243 * value before making this call.
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244 */
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245 void setCRC(int value) {
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246 int crcOffset = DATA_OFFSET + getLength();
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247 setInt32(crcOffset, value);
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248 }
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249
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250 /**
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251 * Get the chunk's total size including the length, type, and crc fields.
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252 */
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253 int getSize() {
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254 return MIN_LENGTH + getLength();
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255 }
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256
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257 /**
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258 * Compute the CRC value for the chunk's data. Answer
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259 * whether this value matches the value stored in the
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260 * chunk.
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261 */
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262 bool checkCRC() {
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263 int crc = computeCRC();
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264 int storedCRC = getCRC();
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265 return crc is storedCRC;
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266 }
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267
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268 /**
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269 * Answer the CRC value of chunk's data.
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270 */
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271 int computeCRC() {
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272 int crc = 0xFFFFFFFF;
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273 int start = TYPE_OFFSET;
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274 int stop = DATA_OFFSET + getLength();
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275 for (int i = start; i < stop; i++) {
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276 int index = (crc ^ reference[i]) & 0xFF;
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277 crc = CRC_TABLE[index] ^ ((crc >> 8) & 0x00FFFFFF);
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278 }
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279 return ~crc;
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280 }
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281
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282 bool typeMatchesArray(byte[] array) {
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283 for (int i = 0; i < TYPE_FIELD_LENGTH; i++) {
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284 if (reference[TYPE_OFFSET + i] !is array[i]){
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285 return false;
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286 }
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287 }
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288 return true;
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289 }
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290
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291 bool isCritical() {
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292 char c = cast(char) getTypeBytes()[0];
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293 return 'A' <= c && c <= 'Z';
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294 }
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295
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296 int getChunkType() {
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297 if (typeMatchesArray(TYPE_IHDR)) return CHUNK_IHDR;
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298 if (typeMatchesArray(TYPE_PLTE)) return CHUNK_PLTE;
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299 if (typeMatchesArray(TYPE_IDAT)) return CHUNK_IDAT;
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300 if (typeMatchesArray(TYPE_IEND)) return CHUNK_IEND;
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301 if (typeMatchesArray(TYPE_tRNS)) return CHUNK_tRNS;
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302 return CHUNK_UNKNOWN;
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303 }
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304
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305 /**
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306 * Read the next PNG chunk from the input stream given.
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307 * If unable to read a chunk, return null.
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308 */
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309 static PngChunk readNextFromStream(LEDataInputStream stream) {
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310 try {
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311 int headerLength = LENGTH_FIELD_LENGTH + TYPE_FIELD_LENGTH;
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312 byte[] headerBytes = new byte[headerLength];
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313 int result = stream.read(headerBytes, 0, headerLength);
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314 stream.unread(headerBytes);
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315 if (result !is headerLength) return null;
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316
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317 PngChunk tempChunk = new PngChunk(headerBytes);
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318
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319 int chunkLength = tempChunk.getSize();
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320 byte[] chunk = new byte[chunkLength];
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321
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322 result = stream.read(chunk, 0, chunkLength);
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323 if (result !is chunkLength) return null;
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324
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325 switch (tempChunk.getChunkType()) {
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326 case CHUNK_IHDR:
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327 return new PngIhdrChunk(chunk);
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328 case CHUNK_PLTE:
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329 return new PngPlteChunk(chunk);
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330 case CHUNK_IDAT:
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331 return new PngIdatChunk(chunk);
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332 case CHUNK_IEND:
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333 return new PngIendChunk(chunk);
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334 case CHUNK_tRNS:
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335 return new PngTrnsChunk(chunk);
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336 default:
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337 return new PngChunk(chunk);
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338 }
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339 } catch (IOException e) {
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340 return null;
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341 }
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342 }
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343
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344 /**
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345 * Answer whether the chunk is a valid PNG chunk.
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346 */
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347 void validate(PngFileReadState readState, PngIhdrChunk headerChunk) {
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348 if (reference.length < MIN_LENGTH) SWT.error(SWT.ERROR_INVALID_IMAGE);
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349
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350 byte[] type = getTypeBytes();
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351
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352 // The third character MUST be upper case.
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353 char c = cast(char) type[2];
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354 if (!('A' <= c && c <= 'Z')) SWT.error(SWT.ERROR_INVALID_IMAGE);
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355
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356 // All characters must be letters.
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357 for (int i = 0; i < TYPE_FIELD_LENGTH; i++) {
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358 c = cast(char) type[i];
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359 if (!(('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'))) {
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360 SWT.error(SWT.ERROR_INVALID_IMAGE);
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361 }
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362 }
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363
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364 // The stored CRC must match the data's computed CRC.
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365 if (!checkCRC()) SWT.error(SWT.ERROR_INVALID_IMAGE);
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366 }
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367
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368 /**
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369 * Provided so that subclasses can override and add
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370 * data to the toString() call.
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371 */
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372 String contributeToString() {
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373 return "";
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374 }
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375
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376 /**
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377 * Returns a string containing a concise, human-readable
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378 * description of the receiver.
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379 *
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380 * @return a string representation of the event
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381 */
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382 public override String toString() {
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383 String buffer = Format( "{\n\tLength: {}\n\tType: {}{}\n\tCRC: {:X}\n}",
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384 getLength(),
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385 cast(String) getTypeBytes(),
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386 contributeToString(),
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387 getCRC());
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388 return buffer;
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389 }
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390
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391 }
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