libjava/gnu/regexp/RETokenLookAhead.java

   1 /*
   2  *  gnu/regexp/RETokenOneOf.java
   3  *  Copyright (C) 1998-2001 Wes Biggs
   4  *
   5  *  This library is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU Lesser General Public License as published
   7  *  by the Free Software Foundation; either version 2.1 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This library is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU Lesser General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU Lesser General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19 package gnu.regexp;
  20
  21 /**
  22  * @since gnu.regexp 1.1.3
  23  * @author Shashank Bapat
  24  */
  25 final class RETokenLookAhead extends REToken
  26 {
  27   REToken re;
  28   boolean negative;
  29
  30   RETokenLookAhead(REToken re, boolean negative) throws REException {
  31     super(0);
  32     this.re = re;
  33     this.negative = negative;
  34   }
  35
  36   boolean match(CharIndexed input, REMatch mymatch)
  37   {
  38     REMatch trymatch = (REMatch)mymatch.clone();
  39     REMatch trymatch1 = (REMatch)mymatch.clone();
  40     REMatch newMatch = null;
  41     if (re.match(input, trymatch)) {
  42       if (negative) return false;
  43       if (next(input, trymatch1))
  44         newMatch = trymatch1;
  45     }
  46
  47     if (newMatch != null) {
  48       if (negative) return false;
  49       //else
  50       mymatch.assignFrom(newMatch);
  51       return true;
  52     }
  53     else { // no match
  54       if (negative)
  55         return next(input, mymatch);
  56       //else
  57       return false;
  58     }
  59   }
  60
  61     void dump(StringBuffer os) {
  62         os.append("(?");
  63         os.append(negative ? '!' : '=');
  64         re.dumpAll(os);
  65         os.append(')');
  66     }
  67 }
  68