FPDI/pdf_context.php

<?php
/**
 * This file is part of FPDI
 *
 * @package   FPDI
 * @copyright Copyright (c) 2017 Setasign - Jan Slabon (https://www.setasign.com)
 * @license   http://opensource.org/licenses/mit-license The MIT License
 * @version   1.6.2
 */

/**
 * Class pdf_context
 */
class pdf_context
{
    /**
     * Mode
     *
     * @var integer 0 = file | 1 = string
     */
    protected $_mode = 0;

    /**
     * @var resource|string
     */
    public $file;

    /**
     * @var string
     */
    public $buffer;

    /**
     * @var integer
     */
    public $offset;

    /**
     * @var integer
     */
    public $length;

    /**
     * @var array
     */
    public $stack;

    /**
     * The constructor
     *
     * @param resource $f
     */
    public function __construct(&$f)
    {
        $this->file =& $f;
        if (is_string($this->file))
            $this->_mode = 1;

        $this->reset();
    }

    /**
     * Get the position in the file stream
     *
     * @return int
     */
    public function getPos()
    {
        if ($this->_mode == 0) {
            if (feof($this->file)) {
                $stat = fstat($this->file);
                fseek($this->file, $stat['size']);
            }

            $pos = ftell($this->file);

            return $pos;
        } else {
            return 0;
        }
    }

    /**
     * Reset the position in the file stream.
     *
     * Optionally move the file pointer to a new location and reset the buffered data.
     *
     * @param null $pos
     * @param int $l
     */
    public function reset($pos = null, $l = 100)
    {
        if ($this->_mode == 0) {
            if (!is_null($pos)) {
                fseek($this->file, $pos);
            }

            $this->buffer = $l > 0 ? fread($this->file, $l) : '';
            $this->length = strlen($this->buffer);
            if ($this->length < $l)
                $this->increaseLength($l - $this->length);
        } else {
            $this->buffer = $this->file;
            $this->length = strlen($this->buffer);
        }
        $this->offset = 0;
        $this->stack = array();
    }

    /**
     * Make sure that there is at least one character beyond the current offset in the buffer.
     *
     * To prevent the tokenizer from attempting to access data that does not exist.
     *
     * @return bool
     */
    public function ensureContent()
    {
        if ($this->offset >= $this->length - 1) {
            return $this->increaseLength();
        } else {
            return true;
        }
    }

    /**
     * Forcefully read more data into the buffer
     *
     * @param int $l
     * @return bool
     */
    public function increaseLength($l = 100)
    {
        if ($this->_mode == 0 && feof($this->file)) {
            return false;
        } else if ($this->_mode == 0) {
            $totalLength = $this->length + $l;
            do {
                $toRead = $totalLength - $this->length;
                if ($toRead < 1)
                    break;

                $this->buffer .= fread($this->file, $toRead);
            } while ((($this->length = strlen($this->buffer)) != $totalLength) && !feof($this->file));

            return true;
        } else {
            return false;
        }
    }
}