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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\CrossReference;
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use setasign\Fpdi\PdfParser\PdfParser;
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use setasign\Fpdi\PdfParser\StreamReader;
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/**
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 * Class LineReader
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 *
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 * This reader class read all cross-reference entries in a single run.
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 * It supports reading cross-references with e.g. invalid data (e.g. entries with a length < or > 20 bytes).
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 */
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class LineReader extends AbstractReader implements ReaderInterface
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{
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    /**
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     * The object offsets.
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     *
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     * @var array
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     */
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    protected $offsets;
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    /**
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     * LineReader constructor.
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     *
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     * @param PdfParser $parser
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     * @throws CrossReferenceException
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     */
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    public function __construct(PdfParser $parser)
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    {
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        $this->read($this->extract($parser->getStreamReader()));
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        parent::__construct($parser);
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    }
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    /**
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     * @inheritdoc
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     * @return int|false
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     */
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    public function getOffsetFor($objectNumber)
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    {
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        if (isset($this->offsets[$objectNumber])) {
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            return $this->offsets[$objectNumber][0];
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        }
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        return false;
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    }
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    /**
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     * Get all found offsets.
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     *
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     * @return array
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     */
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    public function getOffsets()
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    {
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        return $this->offsets;
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    }
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    /**
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     * Extracts the cross reference data from the stream reader.
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     *
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     * @param StreamReader $reader
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     * @return string
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     * @throws CrossReferenceException
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     */
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    protected function extract(StreamReader $reader)
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    {
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        $bytesPerCycle = 100;
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        $reader->reset(null, $bytesPerCycle);
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        $cycles = 0;
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        do {
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            // 6 = length of "trailer" - 1
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            $pos = \max(($bytesPerCycle * $cycles) - 6, 0);
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            $trailerPos = \strpos($reader->getBuffer(false), 'trailer', $pos);
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            $cycles++;
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        } while ($trailerPos === false && $reader->increaseLength($bytesPerCycle) !== false);
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        if ($trailerPos === false) {
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            throw new CrossReferenceException(
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                'Unexpected end of cross reference. "trailer"-keyword not found.',
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                CrossReferenceException::NO_TRAILER_FOUND
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            );
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        }
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        $xrefContent = \substr($reader->getBuffer(false), 0, $trailerPos);
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        $reader->reset($reader->getPosition() + $trailerPos);
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        return $xrefContent;
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    }
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    /**
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     * Read the cross-reference entries.
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     *
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     * @param string $xrefContent
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     * @throws CrossReferenceException
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     */
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    protected function read($xrefContent)
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    {
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        // get eol markers in the first 100 bytes
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        \preg_match_all("/(\r\n|\n|\r)/", \substr($xrefContent, 0, 100), $m);
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        if (\count($m[0]) === 0) {
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            throw new CrossReferenceException(
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                'No data found in cross-reference.',
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                CrossReferenceException::INVALID_DATA
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            );
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        }
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        // count(array_count_values()) is faster then count(array_unique())
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        // @see https://github.com/symfony/symfony/pull/23731
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        // can be reverted for php7.2
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        $differentLineEndings = \count(\array_count_values($m[0]));
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        if ($differentLineEndings > 1) {
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            $lines = \preg_split("/(\r\n|\n|\r)/", $xrefContent, -1, PREG_SPLIT_NO_EMPTY);
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        } else {
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            $lines = \explode($m[0][0], $xrefContent);
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        }
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        unset($differentLineEndings, $m);
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        if (!\is_array($lines)) {
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            $this->offsets = [];
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            return;
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        }
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        $start = 0;
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        $offsets = [];
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        // trim all lines and remove empty lines
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        $lines = \array_filter(\array_map('\trim', $lines));
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        foreach ($lines as $line) {
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            $pieces = \explode(' ', $line);
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            switch (\count($pieces)) {
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                case 2:
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                    $start = (int) $pieces[0];
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                    break;
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                case 3:
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                    switch ($pieces[2]) {
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                        case 'n':
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                            $offsets[$start] = [(int) $pieces[0], (int) $pieces[1]];
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                            $start++;
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                            break 2;
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                        case 'f':
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                            $start++;
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                            break 2;
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                    }
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                    // fall through if pieces doesn't match
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                default:
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                    throw new CrossReferenceException(
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                        \sprintf('Unexpected data in xref table (%s)', \implode(' ', $pieces)),
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                        CrossReferenceException::INVALID_DATA
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                    );
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            }
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        }
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        $this->offsets = $offsets;
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    }
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}