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<?php
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/**
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 * This file is part of FPDI
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 *
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 * @package   setasign\Fpdi
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 * @copyright Copyright (c) 2023 Setasign GmbH & Co. KG (https://www.setasign.com)
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 * @license   http://opensource.org/licenses/mit-license The MIT License
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 */
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namespace setasign\Fpdi\PdfParser\Filter;
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/**
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 * Class for handling LZW encoded data
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 */
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class Lzw implements FilterInterface
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{
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    /**
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     * @var null|string
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     */
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    protected $data;
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    /**
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     * @var array
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     */
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    protected $sTable = [];
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    /**
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     * @var int
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     */
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    protected $dataLength = 0;
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    /**
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     * @var int
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     */
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    protected $tIdx;
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    /**
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     * @var int
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     */
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    protected $bitsToGet = 9;
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    /**
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     * @var int
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     */
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    protected $bytePointer;
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    /**
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     * @var int
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     */
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    protected $nextData = 0;
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    /**
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     * @var int
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     */
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    protected $nextBits = 0;
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    /**
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     * @var array
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     */
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    protected $andTable = [511, 1023, 2047, 4095];
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    /**
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     * Method to decode LZW compressed data.
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     *
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     * @param string $data The compressed data
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     * @return string The uncompressed data
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     * @throws LzwException
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     */
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    public function decode($data)
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    {
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        if ($data[0] === "\x00" && $data[1] === "\x01") {
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            throw new LzwException(
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                'LZW flavour not supported.',
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                LzwException::LZW_FLAVOUR_NOT_SUPPORTED
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            );
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        }
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        $this->initsTable();
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        $this->data = $data;
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        $this->dataLength = \strlen($data);
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        // Initialize pointers
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        $this->bytePointer = 0;
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        $this->nextData = 0;
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        $this->nextBits = 0;
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        $prevCode = 0;
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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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                $this->initsTable();
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            } elseif ($prevCode === 256) {
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                $uncompData .= $this->sTable[$code];
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            } elseif ($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[$prevCode], $string[0]);
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            } else {
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                $string = $this->sTable[$prevCode];
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                $string .= $string[0];
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                $uncompData .= $string;
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                $this->addStringToTable($string);
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            }
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            $prevCode = $code;
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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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    protected function initsTable()
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    {
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        $this->sTable = [];
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        for ($i = 0; $i < 256; $i++) {
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            $this->sTable[$i] = \chr($i);
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        }
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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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     * @param string $oldString
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     * @param string $newString
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     */
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    protected function addStringToTable($oldString, $newString = '')
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    {
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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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            $this->bitsToGet = 10;
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        } elseif ($this->tIdx === 1023) {
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            $this->bitsToGet = 11;
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        } elseif ($this->tIdx === 2047) {
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            $this->bitsToGet = 12;
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        }
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    }
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    /**
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     * Returns the next 9, 10, 11 or 12 bits.
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     *
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     * @return int
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     */
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    protected function getNextCode()
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    {
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        if ($this->bytePointer === $this->dataLength) {
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            return 257;
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        }
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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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}