Proyectos de Subversion Moodle

<?php

/**

 * This file is part of FPDI

 *

 * @package   setasign\Fpdi

 * @copyright Copyright (c) 2023 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;

    }

}