1 /* |
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2 * Copyright (c) 1995, 1997, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 package sun.misc; |
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26 |
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27 import java.io.OutputStream; |
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28 import java.io.InputStream; |
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29 import java.io.PrintStream; |
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30 import java.io.IOException; |
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31 |
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32 /** |
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33 * This class implements a robust character encoder. The encoder is designed |
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34 * to convert binary data into printable characters. The characters are |
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35 * assumed to exist but they are not assumed to be ASCII, the complete set |
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36 * is 0-9, A-Z, a-z, "(", and ")". |
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37 * |
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38 * The basic encoding unit is a 3 character atom. It encodes two bytes |
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39 * of data. Bytes are encoded into a 64 character set, the characters |
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40 * were chosen specifically because they appear in all codesets. |
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41 * We don't care what their numerical equivalent is because |
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42 * we use a character array to map them. This is like UUencoding |
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43 * with the dependency on ASCII removed. |
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44 * |
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45 * The three chars that make up an atom are encoded as follows: |
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46 * <pre> |
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47 * 00xxxyyy 00axxxxx 00byyyyy |
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48 * 00 = leading zeros, all values are 0 - 63 |
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49 * xxxyyy - Top 3 bits of X, Top 3 bits of Y |
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50 * axxxxx - a = X parity bit, xxxxx lower 5 bits of X |
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51 * byyyyy - b = Y parity bit, yyyyy lower 5 bits of Y |
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52 * </pre> |
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53 * |
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54 * The atoms are arranged into lines suitable for inclusion into an |
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55 * email message or text file. The number of bytes that are encoded |
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56 * per line is 48 which keeps the total line length under 80 chars) |
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57 * |
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58 * Each line has the form( |
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59 * <pre> |
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60 * *(LLSS)(DDDD)(DDDD)(DDDD)...(CRC) |
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61 * Where each (xxx) represents a three character atom. |
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62 * (LLSS) - 8 bit length (high byte), and sequence number |
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63 * modulo 256; |
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64 * (DDDD) - Data byte atoms, if length is odd, last data |
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65 * atom has (DD00) (high byte data, low byte 0) |
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66 * (CRC) - 16 bit CRC for the line, includes length, |
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67 * sequence, and all data bytes. If there is a |
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68 * zero pad byte (odd length) it is _NOT_ |
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69 * included in the CRC. |
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70 * </pre> |
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71 * |
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72 * @author Chuck McManis |
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73 * @see CharacterEncoder |
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74 * @see UCDecoder |
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75 */ |
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76 public class UCEncoder extends CharacterEncoder { |
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77 |
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78 /** this clase encodes two bytes per atom */ |
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79 protected int bytesPerAtom() { |
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80 return (2); |
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81 } |
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82 |
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83 /** this class encodes 48 bytes per line */ |
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84 protected int bytesPerLine() { |
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85 return (48); |
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86 } |
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87 |
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88 /* this is the UCE mapping of 0-63 to characters .. */ |
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89 private static final byte map_array[] = { |
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90 // 0 1 2 3 4 5 6 7 |
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91 (byte)'0',(byte)'1',(byte)'2',(byte)'3',(byte)'4',(byte)'5',(byte)'6',(byte)'7', // 0 |
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92 (byte)'8',(byte)'9',(byte)'A',(byte)'B',(byte)'C',(byte)'D',(byte)'E',(byte)'F', // 1 |
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93 (byte)'G',(byte)'H',(byte)'I',(byte)'J',(byte)'K',(byte)'L',(byte)'M',(byte)'N', // 2 |
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94 (byte)'O',(byte)'P',(byte)'Q',(byte)'R',(byte)'S',(byte)'T',(byte)'U',(byte)'V', // 3 |
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95 (byte)'W',(byte)'X',(byte)'Y',(byte)'Z',(byte)'a',(byte)'b',(byte)'c',(byte)'d', // 4 |
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96 (byte)'e',(byte)'f',(byte)'g',(byte)'h',(byte)'i',(byte)'j',(byte)'k',(byte)'l', // 5 |
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97 (byte)'m',(byte)'n',(byte)'o',(byte)'p',(byte)'q',(byte)'r',(byte)'s',(byte)'t', // 6 |
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98 (byte)'u',(byte)'v',(byte)'w',(byte)'x',(byte)'y',(byte)'z',(byte)'(',(byte)')' // 7 |
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99 }; |
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100 |
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101 private int sequence; |
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102 private byte tmp[] = new byte[2]; |
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103 private CRC16 crc = new CRC16(); |
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104 |
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105 /** |
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106 * encodeAtom - take two bytes and encode them into the correct |
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107 * three characters. If only one byte is to be encoded, the other |
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108 * must be zero. The padding byte is not included in the CRC computation. |
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109 */ |
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110 protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len) throws IOException |
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111 { |
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112 int i; |
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113 int p1, p2; // parity bits |
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114 byte a, b; |
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115 |
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116 a = data[offset]; |
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117 if (len == 2) { |
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118 b = data[offset+1]; |
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119 } else { |
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120 b = 0; |
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121 } |
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122 crc.update(a); |
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123 if (len == 2) { |
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124 crc.update(b); |
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125 } |
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126 outStream.write(map_array[((a >>> 2) & 0x38) + ((b >>> 5) & 0x7)]); |
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127 p1 = 0; p2 = 0; |
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128 for (i = 1; i < 256; i = i * 2) { |
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129 if ((a & i) != 0) { |
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130 p1++; |
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131 } |
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132 if ((b & i) != 0) { |
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133 p2++; |
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134 } |
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135 } |
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136 p1 = (p1 & 1) * 32; |
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137 p2 = (p2 & 1) * 32; |
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138 outStream.write(map_array[(a & 31) + p1]); |
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139 outStream.write(map_array[(b & 31) + p2]); |
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140 return; |
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141 } |
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142 |
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143 /** |
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144 * Each UCE encoded line starts with a prefix of '*[XXX]', where |
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145 * the sequence number and the length are encoded in the first |
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146 * atom. |
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147 */ |
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148 protected void encodeLinePrefix(OutputStream outStream, int length) throws IOException { |
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149 outStream.write('*'); |
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150 crc.value = 0; |
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151 tmp[0] = (byte) length; |
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152 tmp[1] = (byte) sequence; |
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153 sequence = (sequence + 1) & 0xff; |
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154 encodeAtom(outStream, tmp, 0, 2); |
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155 } |
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156 |
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157 |
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158 /** |
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159 * each UCE encoded line ends with YYY and encoded version of the |
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160 * 16 bit checksum. The most significant byte of the check sum |
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161 * is always encoded FIRST. |
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162 */ |
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163 protected void encodeLineSuffix(OutputStream outStream) throws IOException { |
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164 tmp[0] = (byte) ((crc.value >>> 8) & 0xff); |
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165 tmp[1] = (byte) (crc.value & 0xff); |
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166 encodeAtom(outStream, tmp, 0, 2); |
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167 super.pStream.println(); |
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168 } |
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169 |
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170 /** |
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171 * The buffer prefix code is used to initialize the sequence number |
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172 * to zero. |
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173 */ |
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174 protected void encodeBufferPrefix(OutputStream a) throws IOException { |
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175 sequence = 0; |
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176 super.encodeBufferPrefix(a); |
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177 } |
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178 } |
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