libjava/classpath/gnu/regexp/REMatchEnumeration.java

   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.regexp;
  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 }
 135