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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(
- '&quot;' => '"',
- '&amp;' => '&',
- '&lt;' => '<',
- '&gt;' => '>',
- '&#39;' => "'",
- '&#039;' => "'",
- '&#x27;' => "'"
- );
-
- /**
- * 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, '&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;
- }
-
- /**
- * 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