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<?php
//
// FPDI - Version 1.2
//
// Copyright 2004-2007 Setasign - Jan Slabon
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
class LZWDecode {
var $sTable = array();
var $data = null;
var $tIdx;
var $bitsToGet = 9;
var $bytePointer;
var $bitPointer;
var $nextData = 0;
var $nextBits = 0;
var $andTable = array(511, 1023, 2047, 4095);
function LZWDecode(&$fpdi) {
$this->fpdi =& $fpdi;
}
/**
* Method to decode LZW compressed data.
*
* @param string data The compressed data.
*/
function decode(&$data) {
if($data[0] == 0x00 && $data[1] == 0x01) {
$this->fpdi->error("LZW flavour not supported.");
}
$this->initsTable();
$this->data =& $data;
// Initialize pointers
$this->bytePointer = 0;
$this->bitPointer = 0;
$this->nextData = 0;
$this->nextBits = 0;
$oldCode = 0;
$string = "";
$uncompData = "";
while (($code = $this->getNextCode()) != 257) {
if ($code == 256) {
$this->initsTable();
$code = $this->getNextCode();
if ($code == 257) {
break;
}
$uncompData .= $this->sTable[$code];
$oldCode = $code;
} else {
if ($code < $this->tIdx) {
$string = $this->sTable[$code];
$uncompData .= $string;
$this->addStringToTable($this->sTable[$oldCode], $string[0]);
$oldCode = $code;
} else {
$string = $this->sTable[$oldCode];
$string = $string.$string[0];
$uncompData .= $string;
$this->addStringToTable($string);
$oldCode = $code;
}
}
}
return $uncompData;
}
/**
* Initialize the string table.
*/
function initsTable() {
$this->sTable = array();
for ($i = 0; $i < 256; $i++)
$this->sTable[$i] = chr($i);
$this->tIdx = 258;
$this->bitsToGet = 9;
}
/**
* Add a new string to the string table.
*/
function addStringToTable ($oldString, $newString="") {
$string = $oldString.$newString;
// Add this new String to the table
$this->sTable[$this->tIdx++] = $string;
if ($this->tIdx == 511) {
$this->bitsToGet = 10;
} else if ($this->tIdx == 1023) {
$this->bitsToGet = 11;
} else if ($this->tIdx == 2047) {
$this->bitsToGet = 12;
}
}
// Returns the next 9, 10, 11 or 12 bits
function getNextCode() {
if ($this->bytePointer == strlen($this->data))
return 257;
$this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
$this->nextBits += 8;
if ($this->nextBits < $this->bitsToGet) {
$this->nextData = ($this->nextData << 8) | (ord($this->data[$this->bytePointer++]) & 0xff);
$this->nextBits += 8;
}
$code = ($this->nextData >> ($this->nextBits - $this->bitsToGet)) & $this->andTable[$this->bitsToGet-9];
$this->nextBits -= $this->bitsToGet;
return $code;
}
}
?>
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