/* * CombineElement.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. */ using System.IO; namespace PerCederberg.Grammatica.Parser.RE { /** * A regular expression combination element. This element matches * two consecutive elements. * * @author Per Cederberg, <per at percederberg dot net> * @version 1.0 */ internal class CombineElement : Element { /** * The first element. */ private Element elem1; /** * The second element. */ private Element elem2; /** * Creates a new combine element. * * @param first the first element * @param second the second element */ public CombineElement(Element first, Element second) { elem1 = first; elem2 = second; } /** * Creates a copy of this element. The copy will be an * instance of the same class matching the same strings. * Copies of elements are necessary to allow elements to cache * intermediate results while matching strings without * interfering with other threads. * * @return a copy of this element */ public override object Clone() { return new CombineElement(elem1, elem2); } /** * Returns the length of a matching string starting at the * specified position. The number of matches to skip can also be * specified, but numbers higher than zero (0) cause a failed * match for any element that doesn't attempt to combine other * elements. * * @param m the matcher being used * @param str the string to match * @param start the starting position * @param skip the number of matches to skip * * @return the length of the longest matching string, or * -1 if no match was found */ public override int Match(Matcher m, string str, int start, int skip) { int length1 = -1; int length2 = 0; int skip1 = 0; int skip2 = 0; while (skip >= 0) { length1 = elem1.Match(m, str, start, skip1); if (length1 < 0) { return -1; } length2 = elem2.Match(m, str, start + length1, skip2); if (length2 < 0) { skip1++; skip2 = 0; } else { skip2++; skip--; } } return length1 + length2; } /** * Prints this element to the specified output stream. * * @param output the output stream to use * @param indent the current indentation */ public override void PrintTo(TextWriter output, string indent) { elem1.PrintTo(output, indent); elem2.PrintTo(output, indent); } } }