/* gnu/regexp/REMatchEnumeration.java
   Copyright (C) 1998-2001, 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02110-1301 USA.

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permission to link this library with independent modules to produce an
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package gnu.java.util.regex;

import gnu.java.lang.CPStringBuilder;

import java.io.Serializable;
import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * An REMatchEnumeration enumerates regular expression matches over a
 * given input text.  You obtain a reference to an enumeration using
 * the <code>getMatchEnumeration()</code> methods on an instance of
 * RE. 
 *
 * <P>
 *
 * REMatchEnumeration does lazy computation; that is, it will not
 * search for a match until it needs to.  If you'd rather just get all
 * the matches at once in a big array, use the
 * <code>getAllMatches()</code> methods on RE.  However, using an
 * enumeration can help speed performance when the entire text does
 * not need to be searched immediately.
 *
 * <P>
 * 
 * The enumerated type is especially useful when searching on a Reader
 * or InputStream, because the InputStream read position cannot be
 * guaranteed after calling <code>getMatch()</code> (see the
 * description of that method for an explanation of why).  Enumeration
 * also saves a lot of overhead required when calling
 * <code>getMatch()</code> multiple times.
 * 
 * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A> 
 */
public class REMatchEnumeration
  implements Enumeration < REMatch >, Serializable
{
  private static final int YES = 1;
  private static final int MAYBE = 0;
  private static final int NO = -1;

  private int more;
  private REMatch match;
  private final RE expr;
  private final CharIndexed input;
  private final int eflags;
  private int index;

  // Package scope constructor is used by RE.getMatchEnumeration()
    REMatchEnumeration (RE expr, CharIndexed input, int index, int eflags)
  {
    more = MAYBE;
    this.expr = expr;
    this.input = input;
    this.index = index;
    this.eflags = eflags;
  }

  /** Returns true if there are more matches in the input text. */
  public boolean hasMoreElements ()
  {
    return hasMoreMatches (null);
  }

  /** Returns true if there are more matches in the input text. */
  public boolean hasMoreMatches ()
  {
    return hasMoreMatches (null);
  }

  /** Returns true if there are more matches in the input text.
   * Saves the text leading up to the match (or to the end of the input)
   * in the specified buffer.
   */
  public boolean hasMoreMatches (CPStringBuilder buffer)
  {
    if (more == MAYBE)
      {
	match = expr.getMatchImpl (input, index, eflags, buffer);
	if (match != null)
	  {
	    input.move ((match.end[0] > 0) ? match.end[0] : 1);

	    index =
	      (match.end[0] > 0) ? match.end[0] + match.offset : index + 1;
	    more = YES;
	  }
	else
	  more = NO;
      }
    return (more == YES);
  }

  /** Returns the next match in the input text. */
  public REMatch nextElement () throws NoSuchElementException
  {
    if (hasMoreElements ())
      {
	more = (input.isValid ())? MAYBE : NO;
	return match;
      }
    throw new NoSuchElementException ();
  }
}