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/* 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

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

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 ();

  }

}