/lib/lexer.php
PHP | 393 lines | 185 code | 24 blank | 184 comment | 33 complexity | c4e11fc35e8ea9f513abb871c336b892 MD5 | raw file
- <?php // $Id$
- /* PHP lexer code snarfed from the CVS tree for the lamplib project at
- * http://sourceforge.net/projects/lamplib
- * This project is administered by Markus Baker, Harry Fuecks and Matt
- * Mitchell, and the project code is in the public domain.
- *
- * Thanks, guys!
- */
- define("LEXER_ENTER", 1);
- define("LEXER_MATCHED", 2);
- define("LEXER_UNMATCHED", 3);
- define("LEXER_EXIT", 4);
- define("LEXER_SPECIAL", 5);
-
- /**
- * Compounded regular expression. Any of
- * the contained patterns could match and
- * when one does it's label is returned.
- */
- class ParallelRegex {
- var $_patterns;
- var $_labels;
- var $_regex;
- var $_case;
-
- /**
- * Constructor. Starts with no patterns.
- * @param $case True for case sensitive, false
- * for insensitive.
- * @public
- */
- function ParallelRegex($case) {
- $this->_case = $case;
- $this->_patterns = array();
- $this->_labels = array();
- $this->_regex = null;
- }
-
- /**
- * Adds a pattern with an optional label.
- * @param $pattern Perl style regex, but ( and )
- * lose the usual meaning.
- * @param $label Label of regex to be returned
- * on a match.
- * @public
- */
- function addPattern($pattern, $label = true) {
- $count = count($this->_patterns);
- $this->_patterns[$count] = $pattern;
- $this->_labels[$count] = $label;
- $this->_regex = null;
- }
-
- /**
- * Attempts to match all patterns at once against
- * a string.
- * @param $subject String to match against.
- * @param $match First matched portion of
- * subject.
- * @return True on success.
- * @public
- */
- function match($subject, &$match) {
- if (count($this->_patterns) == 0) {
- return false;
- }
- if (!preg_match($this->_getCompoundedRegex(), $subject, $matches)) {
- $match = "";
- return false;
- }
- $match = $matches[0];
- for ($i = 1; $i < count($matches); $i++) {
- if ($matches[$i]) {
- return $this->_labels[$i - 1];
- }
- }
- return true;
- }
-
- /**
- * Compounds the patterns into a single
- * regular expression separated with the
- * "or" operator. Caches the regex.
- * Will automatically escape (, ) and / tokens.
- * @param $patterns List of patterns in order.
- * @private
- */
- function _getCompoundedRegex() {
- if ($this->_regex == null) {
- for ($i = 0; $i < count($this->_patterns); $i++) {
- $this->_patterns[$i] = '(' . str_replace(
- array('/', '(', ')'),
- array('\/', '\(', '\)'),
- $this->_patterns[$i]) . ')';
- }
- $this->_regex = "/" . implode("|", $this->_patterns) . "/" . $this->_getPerlMatchingFlags();
- }
- return $this->_regex;
- }
-
- /**
- * Accessor for perl regex mode flags to use.
- * @return Flags as string.
- * @private
- */
- function _getPerlMatchingFlags() {
- return ($this->_case ? "msS" : "msSi");
- }
- }
-
- /**
- * States for a stack machine.
- */
- class StateStack {
- var $_stack;
-
- /**
- * Constructor. Starts in named state.
- * @param $start Starting state name.
- * @public
- */
- function StateStack($start) {
- $this->_stack = array($start);
- }
-
- /**
- * Accessor for current state.
- * @return State as string.
- * @public
- */
- function getCurrent() {
- return $this->_stack[count($this->_stack) - 1];
- }
-
- /**
- * Adds a state to the stack and sets it
- * to be the current state.
- * @param $state New state.
- * @public
- */
- function enter($state) {
- array_push($this->_stack, $state);
- }
-
- /**
- * Leaves the current state and reverts
- * to the previous one.
- * @return False if we drop off
- * the bottom of the list.
- * @public
- */
- function leave() {
- if (count($this->_stack) == 1) {
- return false;
- }
- array_pop($this->_stack);
- return true;
- }
- }
-
- /**
- * Accepts text and breaks it into tokens.
- * Some optimisation to make the sure the
- * content is only scanned by the PHP regex
- * parser once. Lexer modes must not start
- * with leading underscores.
- */
- class Lexer {
- var $_regexes;
- var $_parser;
- var $_mode;
- var $_mode_handlers;
- var $_case;
-
- /**
- * Sets up the lexer in case insensitive matching
- * by default.
- * @param $parser Handling strategy by
- * reference.
- * @param $start Starting handler.
- * @param $case True for case sensitive.
- * @public
- */
- function Lexer(&$parser, $start = "accept", $case = false) {
- $this->_case = $case;
- $this->_regexes = array();
- $this->_parser = &$parser;
- $this->_mode = new StateStack($start);
- $this->_mode_handlers = array();
- }
-
- /**
- * Adds a token search pattern for a particular
- * parsing mode. The pattern does not change the
- * current mode.
- * @param $pattern Perl style regex, but ( and )
- * lose the usual meaning.
- * @param $mode Should only apply this
- * pattern when dealing with
- * this type of input.
- * @public
- */
- function addPattern($pattern, $mode = "accept") {
- if (!isset($this->_regexes[$mode])) {
- $this->_regexes[$mode] = new ParallelRegex($this->_case);
- }
- $this->_regexes[$mode]->addPattern($pattern);
- }
-
- /**
- * Adds a pattern that will enter a new parsing
- * mode. Useful for entering parenthesis, strings,
- * tags, etc.
- * @param $pattern Perl style regex, but ( and )
- * lose the usual meaning.
- * @param $mode Should only apply this
- * pattern when dealing with
- * this type of input.
- * @param $new_mode Change parsing to this new
- * nested mode.
- * @public
- */
- function addEntryPattern($pattern, $mode, $new_mode) {
- if (!isset($this->_regexes[$mode])) {
- $this->_regexes[$mode] = new ParallelRegex($this->_case);
- }
- $this->_regexes[$mode]->addPattern($pattern, $new_mode);
- }
-
- /**
- * Adds a pattern that will exit the current mode
- * and re-enter the previous one.
- * @param $pattern Perl style regex, but ( and )
- * lose the usual meaning.
- * @param $mode Mode to leave.
- * @public
- */
- function addExitPattern($pattern, $mode) {
- if (!isset($this->_regexes[$mode])) {
- $this->_regexes[$mode] = new ParallelRegex($this->_case);
- }
- $this->_regexes[$mode]->addPattern($pattern, "__exit");
- }
-
- /**
- * Adds a pattern that has a special mode.
- * Acts as an entry and exit pattern in one go.
- * @param $pattern Perl style regex, but ( and )
- * lose the usual meaning.
- * @param $mode Should only apply this
- * pattern when dealing with
- * this type of input.
- * @param $special Use this mode for this one token.
- * @public
- */
- function addSpecialPattern($pattern, $mode, $special) {
- if (!isset($this->_regexes[$mode])) {
- $this->_regexes[$mode] = new ParallelRegex($this->_case);
- }
- $this->_regexes[$mode]->addPattern($pattern, "_$special");
- }
-
- /**
- * Adds a mapping from a mode to another handler.
- * @param $mode Mode to be remapped.
- * @param $handler New target handler.
- * @public
- */
- function mapHandler($mode, $handler) {
- $this->_mode_handlers[$mode] = $handler;
- }
-
- /**
- * Splits the page text into tokens. Will fail
- * if the handlers report an error or if no
- * content is consumed. If successful then each
- * unparsed and parsed token invokes a call to the
- * held listener.
- * @param $raw Raw HTML text.
- * @return True on success, else false.
- * @public
- */
- function parse($raw) {
- if (!isset($this->_parser)) {
- return false;
- }
- $length = strlen($raw);
- while (is_array($parsed = $this->_reduce($raw))) {
- list($unmatched, $matched, $mode) = $parsed;
- if (!$this->_dispatchTokens($unmatched, $matched, $mode)) {
- return false;
- }
- if (strlen($raw) == $length) {
- return false;
- }
- $length = strlen($raw);
- }
- if (!$parsed) {
- return false;
- }
- return $this->_invokeParser($raw, LEXER_UNMATCHED);
- }
-
- /**
- * Sends the matched token and any leading unmatched
- * text to the parser changing the lexer to a new
- * mode if one is listed.
- * @param $unmatched Unmatched leading portion.
- * @param $matched Actual token match.
- * @param $mode Mode after match. The "_exit"
- * mode causes a stack pop. An
- * false mode causes no change.
- * @return False if there was any error
- * from the parser.
- * @private
- */
- function _dispatchTokens($unmatched, $matched, $mode = false) {
- if (!$this->_invokeParser($unmatched, LEXER_UNMATCHED)) {
- return false;
- }
- if ($mode === "__exit") {
- if (!$this->_invokeParser($matched, LEXER_EXIT)) {
- return false;
- }
- return $this->_mode->leave();
- }
- if (strncmp($mode, "_", 1) == 0) {
- $mode = substr($mode, 1);
- $this->_mode->enter($mode);
- if (!$this->_invokeParser($matched, LEXER_SPECIAL)) {
- return false;
- }
- return $this->_mode->leave();
- }
- if (is_string($mode)) {
- $this->_mode->enter($mode);
- return $this->_invokeParser($matched, LEXER_ENTER);
- }
- return $this->_invokeParser($matched, LEXER_MATCHED);
- }
-
- /**
- * Calls the parser method named after the current
- * mode. Empty content will be ignored.
- * @param $content Text parsed.
- * @param $is_match Token is recognised rather
- * than unparsed data.
- * @private
- */
- function _invokeParser($content, $is_match) {
- if (($content === "") || ($content === false)) {
- return true;
- }
- $handler = $this->_mode->getCurrent();
- if (isset($this->_mode_handlers[$handler])) {
- $handler = $this->_mode_handlers[$handler];
- }
- return $this->_parser->$handler($content, $is_match);
- }
-
- /**
- * Tries to match a chunk of text and if successful
- * removes the recognised chunk and any leading
- * unparsed data. Empty strings will not be matched.
- * @param $raw The subject to parse. This is the
- * content that will be eaten.
- * @return Three item list of unparsed
- * content followed by the
- * recognised token and finally the
- * action the parser is to take.
- * True if no match, false if there
- * is a parsing error.
- * @private
- */
- function _reduce(&$raw) {
- if (!isset($this->_regexes[$this->_mode->getCurrent()])) {
- return false;
- }
- if ($raw === "") {
- return true;
- }
- if ($action = $this->_regexes[$this->_mode->getCurrent()]->match($raw, $match)) {
- $count = strpos($raw, $match);
- $unparsed = substr($raw, 0, $count);
- $raw = substr($raw, $count + strlen($match));
- return array($unparsed, $match, $action);
- }
- return true;
- }
- }
- ?>