/include/fpdi/filters/FilterLZW.php
PHP | 154 lines | 91 code | 32 blank | 31 comment | 25 complexity | a47ae27863ce33faf8f6ac004aa560bf MD5 | raw file
- <?php
- //
- // FPDI - Version 1.3.1
- //
- // Copyright 2004-2009 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 FilterLZW {
-
- var $sTable = array();
- var $data = null;
- var $dataLength = 0;
- var $tIdx;
- var $bitsToGet = 9;
- var $bytePointer;
- var $bitPointer;
- var $nextData = 0;
- var $nextBits = 0;
- var $andTable = array(511, 1023, 2047, 4095);
- function error($msg) {
- die($msg);
- }
-
- /**
- * Method to decode LZW compressed data.
- *
- * @param string data The compressed data.
- */
- function decode($data) {
- if($data[0] == 0x00 && $data[1] == 0x01) {
- $this->error('LZW flavour not supported.');
- }
- $this->initsTable();
- $this->data = $data;
- $this->dataLength = strlen($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 == $this->dataLength) {
- 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 $code;
- }
-
- function encode($in) {
- $this->error("LZW encoding not implemented.");
- }
- }