/* * Matcher.cs * * This work is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published * by the Free Software Foundation; either version 2 of the License, * or (at your option) any later version. * * This work is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 * USA * * As a special exception, the copyright holders of this library give * you permission to link this library with independent modules to * produce an executable, regardless of the license terms of these * independent modules, and to copy and distribute the resulting * executable under terms of your choice, provided that you also meet, * for each linked independent module, the terms and conditions of the * license of that module. An independent module is a module which is * not derived from or based on this library. If you modify this * library, you may extend this exception to your version of the * library, but you are not obligated to do so. If you do not wish to * do so, delete this exception statement from your version. * * Copyright (c) 2003 Per Cederberg. All rights reserved. */ namespace PerCederberg.Grammatica.Parser.RE { /** * A regular expression string matcher. This class handles the * matching of a specific string with a specific regular * expression. It contains state information about the matching * process, as for example the position of the latest match, and a * number of flags that were set. This class is not thread-safe. * * @author Per Cederberg, <per at percederberg dot net> * @version 1.0 */ public class Matcher { /** * The base regular expression element. */ private Element element; /** * The string to work with */ private string str; /** * The start of the latest match found. */ private int start; /** * The length of the latest match found. */ private int length; /** * The end of string reached flag. This flag is set if the end * of the string was encountered during the latest match. */ private bool endOfString; /** * Creates a new matcher with the specified element. * * @param e the base regular expression element * @param str the string to work with */ internal Matcher(Element e, string str) { this.element = e; this.str = str; this.start = 0; Reset(); } /** * Resets the information about the last match. This will * clear all flags and set the match length to a negative * value. This method is automatically called by all matching * methods. */ public void Reset() { length = -1; endOfString = false; } /** * Returns the start position of the latest match. If no match * has been encountered, this method returns zero (0). * * @return the start position of the latest match */ public int Start() { return start; } /** * Returns the end position of the latest match. This is one * character after the match end, i.e. the first character * after the match. If no match has been encountered, this * method returns the same value as start(). * * @return the end position of the latest match */ public int End() { if (length > 0) { return start + length; } else { return start; } } /** * Returns the length of the latest match. * * @return the length of the latest match, or * -1 if no match was found */ public int Length() { return length; } /** * Checks if the end of the string was encountered during the * last match attempt. This flag signals that more input may * be needed in order to get a match (or a longer match). * * @return true if the end of string was encountered, or * false otherwise */ public bool HasReadEndOfString() { return endOfString; } /** * Attempts to find a match starting at the beginning of the * string. * * @return true if a match was found, or * false otherwise */ public bool MatchFromBeginning() { return MatchFrom(0); } /** * Attempts to find a match starting at the specified position * in the string. * * @param pos the starting position of the match * * @return true if a match was found, or * false otherwise */ public bool MatchFrom(int pos) { Reset(); start = pos; length = element.Match(this, str, start, 0); return length >= 0; } /** * Returns the latest matched string. If no string has been * matched, an empty string will be returned. * * @return the latest matched string */ public override string ToString() { if (length <= 0) { return ""; } else { return str.Substring(start, length); } } /** * Sets the end of string encountered flag. This method is * called by the various elements analyzing the string. */ internal void SetReadEndOfString() { endOfString = true; } } }