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Java > Open Source Codes > gnu > regexp > REMatchEnumeration


1 /*
2  * gnu/regexp/REMatchEnumeration.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 import java.io.Serializable JavaDoc;
21 import java.util.Enumeration JavaDoc;
22 import java.util.NoSuchElementException JavaDoc;
23
24 /**
25  * An REMatchEnumeration enumerates regular expression matches over a
26  * given input text. You obtain a reference to an enumeration using
27  * the <code>getMatchEnumeration()</code> methods on an instance of
28  * RE.
29  *
30  * <P>
31  *
32  * REMatchEnumeration does lazy computation; that is, it will not
33  * search for a match until it needs to. If you'd rather just get all
34  * the matches at once in a big array, use the
35  * <code>getAllMatches()</code> methods on RE. However, using an
36  * enumeration can help speed performance when the entire text does
37  * not need to be searched immediately.
38  *
39  * <P>
40  *
41  * The enumerated type is especially useful when searching on a Reader
42  * or InputStream, because the InputStream read position cannot be
43  * guaranteed after calling <code>getMatch()</code> (see the
44  * description of that method for an explanation of why). Enumeration
45  * also saves a lot of overhead required when calling
46  * <code>getMatch()</code> multiple times.
47  *
48  * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
49  */
50 public class REMatchEnumeration implements Enumeration JavaDoc, Serializable JavaDoc {
51   private static final int YES = 1;
52   private static final int MAYBE = 0;
53   private static final int NO = -1;
54   
55   private int more;
56   private REMatch match;
57   private RE expr;
58   private CharIndexed input;
59   private int eflags;
60     private int index;
61
62   // Package scope constructor is used by RE.getMatchEnumeration()
63 REMatchEnumeration(RE expr, CharIndexed input, int index, int eflags) {
64     more = MAYBE;
65     this.expr = expr;
66     this.input = input;
67     this.index = index;
68     this.eflags = eflags;
69   }
70
71   /** Returns true if there are more matches in the input text. */
72   public boolean hasMoreElements() {
73     return hasMoreMatches(null);
74   }
75
76   /** Returns true if there are more matches in the input text. */
77   public boolean hasMoreMatches() {
78     return hasMoreMatches(null);
79   }
80
81   /** Returns true if there are more matches in the input text.
82    * Saves the text leading up to the match (or to the end of the input)
83    * in the specified buffer.
84    */
85   public boolean hasMoreMatches(StringBuffer JavaDoc buffer) {
86     if (more == MAYBE) {
87     match = expr.getMatchImpl(input,index,eflags,buffer);
88     if (match != null) {
89         input.move((match.end[0] > 0) ? match.end[0] : 1);
90         
91         index = (match.end[0] > 0) ? match.end[0] + match.offset : index + 1;
92         more = YES;
93     } else more = NO;
94     }
95     return (more == YES);
96   }
97
98   /** Returns the next match in the input text. */
99   public Object JavaDoc nextElement() throws NoSuchElementException JavaDoc {
100     return nextMatch();
101   }
102
103   /**
104    * Returns the next match in the input text. This method is provided
105    * for convenience to avoid having to explicitly cast the return value
106    * to class REMatch.
107    */
108   public REMatch nextMatch() throws NoSuchElementException JavaDoc {
109     if (hasMoreElements()) {
110     more = (input.isValid()) ? MAYBE : NO;
111     return match;
112     }
113     throw new NoSuchElementException JavaDoc();
114   }
115 }
116
117
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