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Lexer.php
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<?php /** * Forgivingly lexes HTML (SGML-style) markup into tokens. * * A lexer parses a string of SGML-style markup and converts them into * corresponding tokens. It doesn't check for well-formedness, although its * internal mechanism may make this automatic (such as the case of * HTMLPurifier_Lexer_DOMLex). There are several implementations to choose * from. * * A lexer is HTML-oriented: it might work with XML, but it's not * recommended, as we adhere to a subset of the specification for optimization * reasons. This might change in the future. Also, most tokenizers are not * expected to handle DTDs or PIs. * * This class should not be directly instantiated, but you may use create() to * retrieve a default copy of the lexer. Being a supertype, this class * does not actually define any implementation, but offers commonly used * convenience functions for subclasses. * * @note The unit tests will instantiate this class for testing purposes, as * many of the utility functions require a class to be instantiated. * This means that, even though this class is not runnable, it will * not be declared abstract. * * @par * * @note * We use tokens rather than create a DOM representation because DOM would: * * @par * -# Require more processing and memory to create, * -# Is not streamable, and * -# Has the entire document structure (html and body not needed). * * @par * However, DOM is helpful in that it makes it easy to move around nodes * without a lot of lookaheads to see when a tag is closed. This is a * limitation of the token system and some workarounds would be nice. */ class HTMLPurifier_Lexer { /** * Whether or not this lexer implements line-number/column-number tracking. * If it does, set to true. */ public $tracksLineNumbers = false; // -- STATIC ---------------------------------------------------------- /** * Retrieves or sets the default Lexer as a Prototype Factory. * * By default HTMLPurifier_Lexer_DOMLex will be returned. There are * a few exceptions involving special features that only DirectLex * implements. * * @note The behavior of this class has changed, rather than accepting * a prototype object, it now accepts a configuration object. * To specify your own prototype, set %Core.LexerImpl to it. * This change in behavior de-singletonizes the lexer object. * * @param HTMLPurifier_Config $config * @return HTMLPurifier_Lexer * @throws HTMLPurifier_Exception */ public static function create($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(); } /** * Most common entity to raw value conversion table for special entities. * @type array */ protected $_special_entity2str = array( '"' => '"', '&' => '&', '<' => '<', '>' => '>', ''' => "'", ''' => "'", ''' => "'" ); /** * Parses special entities into the proper characters. * * This string will translate escaped versions of the special characters * into the correct ones. * * @warning * You should be able to treat the output of this function as * completely parsed, but that's only because all other entities should * have been handled previously in substituteNonSpecialEntities() * * @param string $string String character data to be parsed. * @return string Parsed character data. */ public function parseData($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, '&'); $string = strtr($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; } /** * Lexes an HTML string into tokens. * @param $string String HTML. * @param HTMLPurifier_Config $config * @param HTMLPurifier_Context $context * @return HTMLPurifier_Token[] array representation of HTML. */ public function tokenizeHTML($string, $config, $context) { trigger_error('Call to abstract class', E_USER_ERROR); } /** * Translates CDATA sections into regular sections (through escaping). * @param string $string HTML string to process. * @return string HTML with CDATA sections escaped. */ protected static function escapeCDATA($string) { return preg_replace_callback( '/<!\[CDATA\[(.+?)\]\]>/s', array('HTMLPurifier_Lexer', 'CDATACallback'), $string ); } /** * Special CDATA case that is especially convoluted for <script> * @param string $string HTML string to process. * @return string HTML with CDATA sections escaped. */ protected static function escapeCommentedCDATA($string) { return preg_replace_callback( '#<!--//--><!\[CDATA\[//><!--(.+?)//--><!\]\]>#s', array('HTMLPurifier_Lexer', 'CDATACallback'), $string ); } /** * Special Internet Explorer conditional comments should be removed. * @param string $string HTML string to process. * @return string HTML with conditional comments removed. */ protected static function removeIEConditional($string) { return preg_replace( '#<!--\[if [^>]+\]>.*?<!\[endif\]-->#si', // probably should generalize for all strings '', $string ); } /** * Callback function for escapeCDATA() that does the work. * * @warning Though this is public in order to let the callback happen, * calling it directly is not recommended. * @param array $matches PCRE matches array, with index 0 the entire match * and 1 the inside of the CDATA section. * @return string Escaped internals of the CDATA section. */ protected static function CDATACallback($matches) { // not exactly sure why the character set is needed, but whatever return htmlspecialchars($matches[1], ENT_COMPAT, 'UTF-8'); } /** * Takes a piece of HTML and normalizes it by converting entities, fixing * encoding, extracting bits, and other good stuff. * @param string $html HTML. * @param HTMLPurifier_Config $config * @param HTMLPurifier_Context $context * @return string * @todo Consider making protected */ public function normalize($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 $html; } /** * Takes a string of HTML (fragment or document) and returns the content * @todo Consider making protected */ public function extractBody($html) { $matches = array(); $result = preg_match('!<body[^>]*>(.*)</body>!is', $html, $matches); if ($result) { return $matches[1]; } else { return $html; } } } // vim: et sw=4 sts=4
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