Search moodle.org's
Developer Documentation

See Release Notes

  • Bug fixes for general core bugs in 4.2.x will end 22 April 2024 (12 months).
  • Bug fixes for security issues in 4.2.x will end 7 October 2024 (18 months).
  • PHP version: minimum PHP 8.0.0 Note: minimum PHP version has increased since Moodle 4.1. PHP 8.1.x is supported too.
<?php

/**
 * This file is part of FPDI
 *
 * @package   setasign\Fpdi
 * @copyright Copyright (c) 2020 Setasign GmbH & Co. KG (https://www.setasign.com)
 * @license   http://opensource.org/licenses/mit-license The MIT License
 */

namespace setasign\Fpdi\PdfParser\CrossReference;

use setasign\Fpdi\PdfParser\PdfParser;
use setasign\Fpdi\PdfParser\StreamReader;

/**
 * Class FixedReader
 *
 * This reader allows a very less overhead parsing of single entries of the cross-reference, because the main entries
 * are only read when needed and not in a single run.
 */
class FixedReader extends AbstractReader implements ReaderInterface
{
    /**
     * @var StreamReader
     */
    protected $reader;

    /**
     * Data of subsections.
     *
     * @var array
     */
    protected $subSections;

    /**
     * FixedReader constructor.
     *
     * @param PdfParser $parser
     * @throws CrossReferenceException
     */
    public function __construct(PdfParser $parser)
    {
        $this->reader = $parser->getStreamReader();
        $this->read();
        parent::__construct($parser);
    }

    /**
     * Get all subsection data.
     *
     * @return array
     */
    public function getSubSections()
    {
        return $this->subSections;
    }

    /**
     * @inheritdoc
> * @return int|false
*/ public function getOffsetFor($objectNumber) { foreach ($this->subSections as $offset => list($startObject, $objectCount)) { /** * @var int $startObject * @var int $objectCount */ if ($objectNumber >= $startObject && $objectNumber < ($startObject + $objectCount)) { $position = $offset + 20 * ($objectNumber - $startObject); $this->reader->ensure($position, 20); $line = $this->reader->readBytes(20); if ($line[17] === 'f') { return false; } return (int) \substr($line, 0, 10); } } return false; } /** * Read the cross-reference. * * This reader will only read the subsections in this method. The offsets were resolved individually by this * information. * * @throws CrossReferenceException */ protected function read() { $subSections = []; $startObject = $entryCount = $lastLineStart = null; $validityChecked = false; while (($line = $this->reader->readLine(20)) !== false) { if (\strpos($line, 'trailer') !== false) { $this->reader->reset($lastLineStart); break; } // jump over if line content doesn't match the expected string if (\sscanf($line, '%d %d', $startObject, $entryCount) !== 2) { continue; } $oldPosition = $this->reader->getPosition(); $position = $oldPosition + $this->reader->getOffset(); if (!$validityChecked && $entryCount > 0) { $nextLine = $this->reader->readBytes(21); /* Check the next line for maximum of 20 bytes and not longer * By catching 21 bytes and trimming the length should be still 21. */ if (\strlen(\trim($nextLine)) !== 21) { throw new CrossReferenceException( 'Cross-reference entries are larger than 20 bytes.', CrossReferenceException::ENTRIES_TOO_LARGE ); } /* Check for less than 20 bytes: cut the line to 20 bytes and trim; have to result in exactly 18 bytes. * If it would have less bytes the substring would get the first bytes of the next line which would * evaluate to a 20 bytes long string after trimming. */ if (\strlen(\trim(\substr($nextLine, 0, 20))) !== 18) { throw new CrossReferenceException( 'Cross-reference entries are less than 20 bytes.', CrossReferenceException::ENTRIES_TOO_SHORT ); } $validityChecked = true; } $subSections[$position] = [$startObject, $entryCount]; $lastLineStart = $position + $entryCount * 20; $this->reader->reset($lastLineStart); } // reset after the last correct parsed line $this->reader->reset($lastLineStart); if (\count($subSections) === 0) { throw new CrossReferenceException( 'No entries found in cross-reference.', CrossReferenceException::NO_ENTRIES ); } $this->subSections = $subSections; } /** * Fixes an invalid object number shift. * * This method can be used to repair documents with an invalid subsection header: * * <code> * xref * 1 7 * 0000000000 65535 f * 0000000009 00000 n * 0000412075 00000 n * 0000412172 00000 n * 0000412359 00000 n * 0000412417 00000 n * 0000412468 00000 n * </code> * * It shall only be called on the first table. * * @return bool */ public function fixFaultySubSectionShift() { $subSections = $this->getSubSections(); if (\count($subSections) > 1) { return false; } $subSection = \current($subSections); if ($subSection[0] != 1) { return false; } if ($this->getOffsetFor(1) === false) { foreach ($subSections as $offset => list($startObject, $objectCount)) { $this->subSections[$offset] = [$startObject - 1, $objectCount]; } return true; } return false; } }