151 lines
3.8 KiB
PHP
151 lines
3.8 KiB
PHP
<?php
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//
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// FPDI - Version 1.1
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//
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// Copyright 2004,2005 Setasign - Jan Slabon
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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class LZWDecode {
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var $sTable = array();
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var $data = null;
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var $tIdx;
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var $bitsToGet = 9;
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var $bytePointer;
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var $bitPointer;
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var $nextData = 0;
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var $nextBits = 0;
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var $andTable = array(511, 1023, 2047, 4095);
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function LZWDecode(&$fpdi) {
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$this->fpdi =& $fpdi;
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}
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/**
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* Method to decode LZW compressed data.
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*
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* @param string data The compressed data.
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*/
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function decode(&$data) {
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if($data[0] == 0x00 && $data[1] == 0x01) {
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$this->fpdi->error("LZW flavour not supported.");
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}
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$this->initsTable();
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$this->data =& $data;
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// Initialize pointers
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$this->bytePointer = 0;
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$this->bitPointer = 0;
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$this->nextData = 0;
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$this->nextBits = 0;
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$oldCode = 0;
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$string = "";
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$uncompData = "";
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while (($code = $this->getNextCode()) != 257) {
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if ($code == 256) {
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$this->initsTable();
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$code = $this->getNextCode();
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if ($code == 257) {
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break;
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}
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$uncompData .= $this->sTable[$code];
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$oldCode = $code;
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} else {
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if ($code < $this->tIdx) {
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$string = $this->sTable[$code];
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$uncompData .= $string;
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$this->addStringToTable($this->sTable[$oldCode], $string[0]);
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$oldCode = $code;
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} else {
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$string = $this->sTable[$oldCode];
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$string = $string.$string[0];
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$uncompData .= $string;
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$this->addStringToTable($string);
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$oldCode = $code;
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}
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}
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}
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return $uncompData;
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}
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/**
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* Initialize the string table.
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*/
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function initsTable() {
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$this->sTable = array();
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for ($i = 0; $i < 256; $i++)
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$this->sTable[$i] = chr($i);
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$this->tIdx = 258;
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$this->bitsToGet = 9;
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}
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/**
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* Add a new string to the string table.
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*/
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function addStringToTable ($oldString, $newString="") {
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$string = $oldString.$newString;
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// Add this new String to the table
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$this->sTable[$this->tIdx++] = $string;
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if ($this->tIdx == 511) {
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$this->bitsToGet = 10;
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} else if ($this->tIdx == 1023) {
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$this->bitsToGet = 11;
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} else if ($this->tIdx == 2047) {
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$this->bitsToGet = 12;
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}
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}
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// Returns the next 9, 10, 11 or 12 bits
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function getNextCode() {
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if ($this->bytePointer == strlen($this->data))
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return 257;
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$this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
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$this->nextBits += 8;
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if ($this->nextBits < $this->bitsToGet) {
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$this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
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$this->nextBits += 8;
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}
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$code = ($this->nextData >> ($this->nextBits - $this->bitsToGet)) & $this->andTable[$this->bitsToGet-9];
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$this->nextBits -= $this->bitsToGet;
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return $code;
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}
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}
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?>
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