/interpreter/tags/at2dist170907/src/edu/vub/util/regexp/REMatchEnumeration.java

  1/* gnu/regexp/REMatchEnumeration.java
  2   Copyright (C) 1998-2001, 2004 Free Software Foundation, Inc.
  3
  4This file is part of GNU Classpath.
  5
  6GNU Classpath is free software; you can redistribute it and/or modify
  7it under the terms of the GNU General Public License as published by
  8the Free Software Foundation; either version 2, or (at your option)
  9any later version.
 10
 11GNU Classpath is distributed in the hope that it will be useful, but
 12WITHOUT ANY WARRANTY; without even the implied warranty of
 13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 14General Public License for more details.
 15
 16You should have received a copy of the GNU General Public License
 17along with GNU Classpath; see the file COPYING.  If not, write to the
 18Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 1902110-1301 USA.
 20
 21Linking this library statically or dynamically with other modules is
 22making a combined work based on this library.  Thus, the terms and
 23conditions of the GNU General Public License cover the whole
 24combination.
 25
 26As a special exception, the copyright holders of this library give you
 27permission to link this library with independent modules to produce an
 28executable, regardless of the license terms of these independent
 29modules, and to copy and distribute the resulting executable under
 30terms of your choice, provided that you also meet, for each linked
 31independent module, the terms and conditions of the license of that
 32module.  An independent module is a module which is not derived from
 33or based on this library.  If you modify this library, you may extend
 34this exception to your version of the library, but you are not
 35obligated to do so.  If you do not wish to do so, delete this
 36exception statement from your version. */
 37
 38package edu.vub.util.regexp;
 39import java.io.Serializable;
 40import java.util.Enumeration;
 41import 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 */
 69public 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