1 | <?php
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2 | //
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3 | // FPDI - Version 1.2
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4 | //
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5 | // Copyright 2004-2007 Setasign - Jan Slabon
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6 | //
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7 | // Licensed under the Apache License, Version 2.0 (the "License");
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8 | // you may not use this file except in compliance with the License.
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9 | // You may obtain a copy of the License at
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10 | //
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11 | // http://www.apache.org/licenses/LICENSE-2.0
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12 | //
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13 | // Unless required by applicable law or agreed to in writing, software
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14 | // distributed under the License is distributed on an "AS IS" BASIS,
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15 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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16 | // See the License for the specific language governing permissions and
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17 | // limitations under the License.
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18 | //
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19 |
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20 | class LZWDecode {
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21 |
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22 | var $sTable = array();
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23 | var $data = null;
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24 | var $tIdx;
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25 | var $bitsToGet = 9;
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26 | var $bytePointer;
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27 | var $bitPointer;
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28 | var $nextData = 0;
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29 | var $nextBits = 0;
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30 | var $andTable = array(511, 1023, 2047, 4095);
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31 |
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32 | function LZWDecode(&$fpdi) {
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33 | $this->fpdi =& $fpdi;
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34 | }
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35 |
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36 | /**
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37 | * Method to decode LZW compressed data.
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38 | *
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39 | * @param string data The compressed data.
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40 | */
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41 | function decode(&$data) {
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42 |
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43 | if($data[0] == 0x00 && $data[1] == 0x01) {
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44 | $this->fpdi->error("LZW flavour not supported.");
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45 | }
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46 |
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47 | $this->initsTable();
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48 |
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49 | $this->data =& $data;
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50 |
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51 | // Initialize pointers
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52 | $this->bytePointer = 0;
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53 | $this->bitPointer = 0;
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54 |
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55 | $this->nextData = 0;
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56 | $this->nextBits = 0;
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57 |
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58 | $oldCode = 0;
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59 |
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60 | $string = "";
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61 | $uncompData = "";
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62 |
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63 | while (($code = $this->getNextCode()) != 257) {
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64 | if ($code == 256) {
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65 | $this->initsTable();
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66 | $code = $this->getNextCode();
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67 |
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68 | if ($code == 257) {
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69 | break;
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70 | }
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71 |
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72 | $uncompData .= $this->sTable[$code];
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73 | $oldCode = $code;
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74 |
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75 | } else {
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76 |
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77 | if ($code < $this->tIdx) {
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78 | $string = $this->sTable[$code];
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79 | $uncompData .= $string;
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80 |
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81 | $this->addStringToTable($this->sTable[$oldCode], $string[0]);
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82 | $oldCode = $code;
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83 | } else {
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84 | $string = $this->sTable[$oldCode];
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85 | $string = $string.$string[0];
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86 | $uncompData .= $string;
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87 |
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88 | $this->addStringToTable($string);
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89 | $oldCode = $code;
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90 | }
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91 | }
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92 | }
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93 |
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94 | return $uncompData;
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95 | }
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96 |
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97 |
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98 | /**
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99 | * Initialize the string table.
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100 | */
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101 | function initsTable() {
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102 | $this->sTable = array();
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103 |
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104 | for ($i = 0; $i < 256; $i++)
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105 | $this->sTable[$i] = chr($i);
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106 |
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107 | $this->tIdx = 258;
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108 | $this->bitsToGet = 9;
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109 | }
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110 |
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111 | /**
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112 | * Add a new string to the string table.
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113 | */
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114 | function addStringToTable ($oldString, $newString="") {
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115 | $string = $oldString.$newString;
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116 |
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117 | // Add this new String to the table
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118 | $this->sTable[$this->tIdx++] = $string;
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119 |
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120 | if ($this->tIdx == 511) {
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121 | $this->bitsToGet = 10;
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122 | } else if ($this->tIdx == 1023) {
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123 | $this->bitsToGet = 11;
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124 | } else if ($this->tIdx == 2047) {
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125 | $this->bitsToGet = 12;
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126 | }
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127 | }
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128 |
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129 | // Returns the next 9, 10, 11 or 12 bits
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130 | function getNextCode() {
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131 | if ($this->bytePointer == strlen($this->data))
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132 | return 257;
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133 |
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134 | $this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
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135 | $this->nextBits += 8;
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136 |
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137 | if ($this->nextBits < $this->bitsToGet) {
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138 | $this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
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139 | $this->nextBits += 8;
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140 | }
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141 |
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142 | $code = ($this->nextData >> ($this->nextBits - $this->bitsToGet)) & $this->andTable[$this->bitsToGet-9];
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143 | $this->nextBits -= $this->bitsToGet;
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144 |
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145 | return $code;
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146 | }
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147 | }
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148 |
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149 |
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150 |
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151 | ?> |
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