Source for gnu.java.util.regex.REMatchEnumeration

   1: /* gnu/regexp/REMatchEnumeration.java
   2:    Copyright (C) 1998-2001, 2004 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package gnu.java.util.regex;
  39: import java.io.Serializable;
  40: import java.util.Enumeration;
  41: import java.util.NoSuchElementException;
  42: 
  43: /**
  44:  * An REMatchEnumeration enumerates regular expression matches over a
  45:  * given input text.  You obtain a reference to an enumeration using
  46:  * the <code>getMatchEnumeration()</code> methods on an instance of
  47:  * RE. 
  48:  *
  49:  * <P>
  50:  *
  51:  * REMatchEnumeration does lazy computation; that is, it will not
  52:  * search for a match until it needs to.  If you'd rather just get all
  53:  * the matches at once in a big array, use the
  54:  * <code>getAllMatches()</code> methods on RE.  However, using an
  55:  * enumeration can help speed performance when the entire text does
  56:  * not need to be searched immediately.
  57:  *
  58:  * <P>
  59:  * 
  60:  * The enumerated type is especially useful when searching on a Reader
  61:  * or InputStream, because the InputStream read position cannot be
  62:  * guaranteed after calling <code>getMatch()</code> (see the
  63:  * description of that method for an explanation of why).  Enumeration
  64:  * also saves a lot of overhead required when calling
  65:  * <code>getMatch()</code> multiple times.
  66:  * 
  67:  * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A> 
  68:  */
  69: public class REMatchEnumeration implements Enumeration, Serializable {
  70:   private static final int YES = 1;
  71:   private static final int MAYBE = 0;
  72:   private static final int NO = -1;
  73:   
  74:   private int more;
  75:   private REMatch match;
  76:   private RE expr;
  77:   private CharIndexed input;
  78:   private int eflags;
  79:     private int index;
  80: 
  81:   // Package scope constructor is used by RE.getMatchEnumeration()
  82:   REMatchEnumeration(RE expr, CharIndexed input, int index, int eflags) {
  83:     more = MAYBE;
  84:     this.expr = expr;
  85:     this.input = input;
  86:     this.index = index;
  87:     this.eflags = eflags;
  88:   }
  89: 
  90:   /** Returns true if there are more matches in the input text. */
  91:   public boolean hasMoreElements() {
  92:     return hasMoreMatches(null);
  93:   }
  94: 
  95:   /** Returns true if there are more matches in the input text. */
  96:   public boolean hasMoreMatches() {
  97:     return hasMoreMatches(null);
  98:   }
  99: 
 100:   /** Returns true if there are more matches in the input text.
 101:    * Saves the text leading up to the match (or to the end of the input)
 102:    * in the specified buffer.
 103:    */
 104:   public boolean hasMoreMatches(StringBuffer buffer) {
 105:     if (more == MAYBE) {
 106:     match = expr.getMatchImpl(input,index,eflags,buffer);
 107:     if (match != null) {
 108:         input.move((match.end[0] > 0) ? match.end[0] : 1);
 109:         
 110:         index = (match.end[0] > 0) ? match.end[0] + match.offset : index + 1;
 111:         more = YES;
 112:     } else more = NO;
 113:     }
 114:     return (more == YES);
 115:   }
 116: 
 117:   /** Returns the next match in the input text. */
 118:   public Object nextElement() throws NoSuchElementException {
 119:     return nextMatch();
 120:   }
 121: 
 122:   /** 
 123:    * Returns the next match in the input text. This method is provided
 124:    * for convenience to avoid having to explicitly cast the return value
 125:    * to class REMatch.
 126:    */
 127:   public REMatch nextMatch() throws NoSuchElementException {
 128:     if (hasMoreElements()) {
 129:     more = (input.isValid()) ? MAYBE : NO;
 130:     return match;
 131:     }
 132:     throw new NoSuchElementException();
 133:   }
 134: }