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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 zlib/deflate encoded data
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 */
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class Flate implements FilterInterface
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{
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    /**
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     * Checks whether the zlib extension is loaded.
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     *
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     * Used for testing purpose.
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     *
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     * @return boolean
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     * @internal
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     */
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    protected function extensionLoaded()
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    {
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        return \extension_loaded('zlib');
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    }
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    /**
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     * Decodes a flate compressed string.
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     *
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     * @param string|false $data The input string
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     * @return string
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     * @throws FlateException
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     */
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    public function decode($data)
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    {
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        if ($this->extensionLoaded()) {
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            $oData = $data;
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            $data = (($data !== '') ? @\gzuncompress($data) : '');
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            if ($data === false) {
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                // let's try if the checksum is CRC32
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                $fh = fopen('php://temp', 'w+b');
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                fwrite($fh, "\x1f\x8b\x08\x00\x00\x00\x00\x00" . $oData);
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                // "window" == 31 -> 16 + (8 to 15): Uses the low 4 bits of the value as the window size logarithm.
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                //                   The input must include a gzip header and trailer (via 16).
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                stream_filter_append($fh, 'zlib.inflate', STREAM_FILTER_READ, ['window' => 31]);
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                fseek($fh, 0);
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                $data = @stream_get_contents($fh);
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                fclose($fh);
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                if ($data) {
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                    return $data;
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                }
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                // Try this fallback (remove the zlib stream header)
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                $data = @(gzinflate(substr($oData, 2)));
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                if ($data === false) {
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                    throw new FlateException(
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                        'Error while decompressing stream.',
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                        FlateException::DECOMPRESS_ERROR
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                    );
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                }
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            }
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        } else {
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            throw new FlateException(
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                'To handle FlateDecode filter, enable zlib support in PHP.',
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                FlateException::NO_ZLIB
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            );
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        }
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        return $data;
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    }
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}