Update.

[mediawiki.git] / includes / StringUtils.php

<?php

class StringUtils {
        /**
         * Perform an operation equivalent to 
         *
         *     preg_replace( "!$startDelim(.*?)$endDelim!", $replace, $subject );
         *
         * except that it's worst-case O(N) instead of O(N^2)
         *
         * Compared to delimiterReplace(), this implementation is fast but memory-
         * hungry and inflexible. The memory requirements are such that I don't 
         * recommend using it on anything but guaranteed small chunks of text.
         */
        static function hungryDelimiterReplace( $startDelim, $endDelim, $replace, $subject ) {
                $segments = explode( $startDelim, $subject );
                $output = array_shift( $segments );
                foreach ( $segments as $s ) {
                        $endDelimPos = strpos( $s, $endDelim );
                        if ( $endDelimPos === false ) {
                                $output .= $startDelim . $s;
                        } else {
                                $output .= $replace . substr( $s, $endDelimPos + strlen( $endDelim ) );
                        }
                }
                return $output;
        }
        
        /**
         * Perform an operation equivalent to 
         *
         *   preg_replace_callback( "!$startDelim(.*)$endDelim!s$flags", $callback, $subject )
         *
         * This implementation is slower than hungryDelimiterReplace but uses far less
         * memory. The delimiters are literal strings, not regular expressions.
         *
         * @param string $flags Regular expression flags
         */
        # If the start delimiter ends with an initial substring of the end delimiter,
        # e.g. in the case of C-style comments, the behaviour differs from the model
        # regex. In this implementation, the end must share no characters with the 
        # start, so e.g. /*/ is not considered to be both the start and end of a 
        # comment. /*/xy/*/ is considered to be a single comment with contents /xy/. 
        static function delimiterReplaceCallback( $startDelim, $endDelim, $callback, $subject, $flags = '' ) {
                $inputPos = 0;
                $outputPos = 0;
                $output = '';
                $foundStart = false;
                $encStart = preg_quote( $startDelim, '!' );
                $encEnd = preg_quote( $endDelim, '!' );
                $strcmp = strpos( $flags, 'i' ) === false ? 'strcmp' : 'strcasecmp';
                $endLength = strlen( $endDelim );
                $m = array();
                
                while ( $inputPos < strlen( $subject ) && 
                  preg_match( "!($encStart)|($encEnd)!S$flags", $subject, $m, PREG_OFFSET_CAPTURE, $inputPos ) ) 
                {
                        $tokenOffset = $m[0][1];
                        if ( $m[1][0] != '' ) {
                                if ( $foundStart && 
                                  $strcmp( $endDelim, substr( $subject, $tokenOffset, $endLength ) ) == 0 )
                                {
                                        # An end match is present at the same location
                                        $tokenType = 'end';
                                        $tokenLength = $endLength;
                                } else {
                                        $tokenType = 'start';
                                        $tokenLength = strlen( $m[0][0] );
                                }
                        } elseif ( $m[2][0] != '' ) {
                                $tokenType = 'end';
                                $tokenLength = strlen( $m[0][0] );
                        } else {
                                throw new MWException( 'Invalid delimiter given to ' . __METHOD__ );
                        }

                        if ( $tokenType == 'start' ) {
                                $inputPos = $tokenOffset + $tokenLength;
                                # Only move the start position if we haven't already found a start
                                # This means that START START END matches outer pair
                                if ( !$foundStart ) {
                                        # Found start
                                        # Write out the non-matching section
                                        $output .= substr( $subject, $outputPos, $tokenOffset - $outputPos );
                                        $outputPos = $tokenOffset;
                                        $contentPos = $inputPos;
                                        $foundStart = true;
                                }
                        } elseif ( $tokenType == 'end' ) {
                                if ( $foundStart ) {
                                        # Found match
                                        $output .= call_user_func( $callback, array(
                                                substr( $subject, $outputPos, $tokenOffset + $tokenLength - $outputPos ),
                                                substr( $subject, $contentPos, $tokenOffset - $contentPos )
                                        ));
                                        $foundStart = false;
                                } else {
                                        # Non-matching end, write it out
                                        $output .= substr( $subject, $inputPos, $tokenOffset + $tokenLength - $outputPos );
                                }
                                $inputPos = $outputPos = $tokenOffset + $tokenLength;
                        } else {
                                throw new MWException( 'Invalid delimiter given to ' . __METHOD__ );
                        }
                }
                if ( $outputPos < strlen( $subject ) ) {
                        $output .= substr( $subject, $outputPos );
                }
                return $output;
        }

        /*
         * Perform an operation equivalent to 
         *
         *   preg_replace( "!$startDelim(.*)$endDelim!$flags", $replace, $subject )
         *
         * @param string $startDelim Start delimiter regular expression
         * @param string $endDelim End delimiter regular expression
         * @param string $replace Replacement string. May contain $1, which will be 
         *               replaced by the text between the delimiters
         * @param string $subject String to search
         * @return string The string with the matches replaced
         */
        static function delimiterReplace( $startDelim, $endDelim, $replace, $subject, $flags = '' ) {
                $replacer = new RegexlikeReplacer( $replace );
                return self::delimiterReplaceCallback( $startDelim, $endDelim,
                        $replacer->cb(), $subject, $flags );
        }

        /**
         * More or less "markup-safe" explode()
         * Ignores any instances of the separator inside <...>
         * @param string $separator
         * @param string $text
         * @return array
         */
        static function explodeMarkup( $separator, $text ) {
                $placeholder = "\x00";
                
                // Remove placeholder instances
                $text = str_replace( $placeholder, '', $text );
                
                // Replace instances of the separator inside HTML-like tags with the placeholder
                $replacer = new DoubleReplacer( $separator, $placeholder );
                $cleaned = StringUtils::delimiterReplaceCallback( '<', '>', $replacer->cb(), $text );

                // Explode, then put the replaced separators back in
                $items = explode( $separator, $cleaned );
                foreach( $items as $i => $str ) {
                        $items[$i] = str_replace( $placeholder, $separator, $str );
                }
                
                return $items;
        }

        /**
         * Escape a string to make it suitable for inclusion in a preg_replace()
         * replacement parameter.
         *
         * @param string $string
         * @return string
         */
        static function escapeRegexReplacement( $string ) {
                $string = str_replace( '\\', '\\\\', $string );
                $string = str_replace( '$', '\\$', $string );
                return $string;
        }
}

/**
 * Base class for "replacers", objects used in preg_replace_callback() and 
 * StringUtils::delimiterReplaceCallback()
 */
class Replacer {
        function cb() {
                return array( &$this, 'replace' );
        }
}

/**
 * Class to replace regex matches with a string similar to that used in preg_replace()
 */
class RegexlikeReplacer extends Replacer {
        var $r;
        function __construct( $r ) {
                $this->r = $r;
        }

        function replace( $matches ) {
                $pairs = array();
                foreach ( $matches as $i => $match ) {
                        $pairs["\$$i"] = $match;
                }
                return strtr( $this->r, $pairs );
        }

}

/**
 * Class to perform secondary replacement within each replacement string
 */
class DoubleReplacer extends Replacer {
        function __construct( $from, $to, $index = 0 ) {
                $this->from = $from;
                $this->to = $to;
                $this->index = $index;
        }
        
        function replace( $matches ) {
                return str_replace( $this->from, $this->to, $matches[$this->index] );
        }
}

/**
 * Class to perform replacement based on a simple hashtable lookup
 */
class HashtableReplacer extends Replacer {
        var $table, $index;

        function __construct( $table, $index = 0 ) {
                $this->table = $table;
                $this->index = $index;
        }

        function replace( $matches ) {
                return $this->table[$matches[$this->index]];
        }
}

/**
 * Replacement array for FSS with fallback to strtr()
 * Supports lazy initialisation of FSS resource
 */
class ReplacementArray {
        /*mostly private*/ var $data = false;
        /*mostly private*/ var $fss = false;

        /**
         * Create an object with the specified replacement array
         * The array should have the same form as the replacement array for strtr()
         */
        function __construct( $data = array() ) {
                $this->data = $data;
        }

        function __sleep() {
                return array( 'data' );
        }

        function __wakeup() {
                $this->fss = false;
        }

        /**
         * Set the whole replacement array at once
         */
        function setArray( $data ) {
                $this->data = $data;
                $this->fss = false;
        }

        function getArray() {
                return $this->data;
        }

        /**
         * Set an element of the replacement array
         */
        function setPair( $from, $to ) {
                $this->data[$from] = $to;
                $this->fss = false;
        }

        function mergeArray( $data ) {
                $this->data = array_merge( $this->data, $data );
                $this->fss = false;
        }

        function merge( $other ) {
                $this->data = array_merge( $this->data, $other->data );
                $this->fss = false;
        }

        function replace( $subject ) {
                if ( function_exists( 'fss_prep_replace' ) ) {
                        wfProfileIn( __METHOD__.'-fss' );
                        if ( $this->fss === false ) {
                                $this->fss = fss_prep_replace( $this->data );
                        }
                        $result = fss_exec_replace( $this->fss, $subject );
                        wfProfileOut( __METHOD__.'-fss' );
                } else {
                        wfProfileIn( __METHOD__.'-strtr' );
                        $result = strtr( $subject, $this->data );
                        wfProfileOut( __METHOD__.'-strtr' );
                }
                return $result;
        }
}

?>