Lexer.php

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<?php

class HTMLPurifier_Lexer
{

    public $tracksLineNumbers = false;

    // -- STATIC ----------------------------------------------------------

    public static function create($config) {

        if (!($config instanceof HTMLPurifier_Config)) {
            $lexer = $config;
            trigger_error("Passing a prototype to
              HTMLPurifier_Lexer::create() is deprecated, please instead
              use %Core.LexerImpl", E_USER_WARNING);
        } else {
            $lexer = $config->get('Core.LexerImpl');
        }

        $needs_tracking =
            $config->get('Core.MaintainLineNumbers') ||
            $config->get('Core.CollectErrors');

        $inst = null;
        if (is_object($lexer)) {
            $inst = $lexer;
        } else {

            if (is_null($lexer)) { do {
                // auto-detection algorithm

                if ($needs_tracking) {
                    $lexer = 'DirectLex';
                    break;
                }

                if (
                    class_exists('DOMDocument') &&
                    method_exists('DOMDocument', 'loadHTML') &&
                    !extension_loaded('domxml')
                ) {
                    // check for DOM support, because while it's part of the
                    // core, it can be disabled compile time. Also, the PECL
                    // domxml extension overrides the default DOM, and is evil
                    // and nasty and we shan't bother to support it
                    $lexer = 'DOMLex';
                } else {
                    $lexer = 'DirectLex';
                }

            } while(0); } // do..while so we can break

            // instantiate recognized string names
            switch ($lexer) {
                case 'DOMLex':
                    $inst = new HTMLPurifier_Lexer_DOMLex();
                    break;
                case 'DirectLex':
                    $inst = new HTMLPurifier_Lexer_DirectLex();
                    break;
                case 'PH5P':
                    $inst = new HTMLPurifier_Lexer_PH5P();
                    break;
                default:
                    throw new HTMLPurifier_Exception("Cannot instantiate unrecognized Lexer type " . htmlspecialchars($lexer));
            }
        }

        if (!$inst) throw new HTMLPurifier_Exception('No lexer was instantiated');

        // once PHP DOM implements native line numbers, or we
        // hack out something using XSLT, remove this stipulation
        if ($needs_tracking && !$inst->tracksLineNumbers) {
            throw new HTMLPurifier_Exception('Cannot use lexer that does not support line numbers with Core.MaintainLineNumbers or Core.CollectErrors (use DirectLex instead)');
        }

        return $inst;

    }

    // -- CONVENIENCE MEMBERS ---------------------------------------------

    public function __construct() {
        $this->_entity_parser = new HTMLPurifier_EntityParser();
    }

    protected $_special_entity2str =
            array(
                    '&quot;' => '"',
                    '&amp;'  => '&',
                    '&lt;'   => '<',
                    '&gt;'   => '>',
                    '&#39;'  => "'",
                    '&#039;' => "'",
                    '&#x27;' => "'"
            );

    public function parseData($string) {

        // following functions require at least one character
        if ($string === '') return '';

        // subtracts amps that cannot possibly be escaped
        $num_amp = substr_count($string, '&') - substr_count($string, '& ') -
            ($string[strlen($string)-1] === '&' ? 1 : 0);

        if (!$num_amp) return $string; // abort if no entities
        $num_esc_amp = substr_count($string, '&amp;');
        $string = strtr($string, $this->_special_entity2str);

        // code duplication for sake of optimization, see above
        $num_amp_2 = substr_count($string, '&') - substr_count($string, '& ') -
            ($string[strlen($string)-1] === '&' ? 1 : 0);

        if ($num_amp_2 <= $num_esc_amp) return $string;

        // hmm... now we have some uncommon entities. Use the callback.
        $string = $this->_entity_parser->substituteSpecialEntities($string);
        return $string;
    }

    public function tokenizeHTML($string, $config, $context) {
        trigger_error('Call to abstract class', E_USER_ERROR);
    }

    protected static function escapeCDATA($string) {
        return preg_replace_callback(
            '/<!\[CDATA\[(.+?)\]\]>/s',
            array('HTMLPurifier_Lexer', 'CDATACallback'),
            $string
        );
    }

    protected static function escapeCommentedCDATA($string) {
        return preg_replace_callback(
            '#<!--//--><!\[CDATA\[//><!--(.+?)//--><!\]\]>#s',
            array('HTMLPurifier_Lexer', 'CDATACallback'),
            $string
        );
    }

    protected static function removeIEConditional($string) {
        return preg_replace(
            '#<!--\[if [^>]+\]>.*?<!\[endif\]-->#si', // probably should generalize for all strings
            '',
            $string
        );
    }

    protected static function CDATACallback($matches) {
        // not exactly sure why the character set is needed, but whatever
        return htmlspecialchars($matches[1], ENT_COMPAT, 'UTF-8');
    }

    public function normalize($html, $config, $context) {

        // normalize newlines to \n
        if ($config->get('Core.NormalizeNewlines')) {
            $html = str_replace("\r\n", "\n", $html);
            $html = str_replace("\r", "\n", $html);
        }

        if ($config->get('HTML.Trusted')) {
            // escape convoluted CDATA
            $html = $this->escapeCommentedCDATA($html);
        }

        // escape CDATA
        $html = $this->escapeCDATA($html);

        $html = $this->removeIEConditional($html);

        // extract body from document if applicable
        if ($config->get('Core.ConvertDocumentToFragment')) {
            $e = false;
            if ($config->get('Core.CollectErrors')) {
                $e =& $context->get('ErrorCollector');
            }
            $new_html = $this->extractBody($html);
            if ($e && $new_html != $html) {
                $e->send(E_WARNING, 'Lexer: Extracted body');
            }
            $html = $new_html;
        }

        // expand entities that aren't the big five
        $html = $this->_entity_parser->substituteNonSpecialEntities($html);

        // clean into wellformed UTF-8 string for an SGML context: this has
        // to be done after entity expansion because the entities sometimes
        // represent non-SGML characters (horror, horror!)
        $html = HTMLPurifier_Encoder::cleanUTF8($html);

        // if processing instructions are to removed, remove them now
        if ($config->get('Core.RemoveProcessingInstructions')) {
            $html = preg_replace('#<\?.+?\?>#s', '', $html);
        }

        return $html;
    }

    public function extractBody($html) {
        $matches = array();
        $result = preg_match('!<body[^>]*>(.*)</body>!is', $html, $matches);
        if ($result) {
            return $matches[1];
        } else {
            return $html;
        }
    }

}

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