charindexedstringbuffer.java

java写的多功能文件编辑器

/*
 *  gnu/regexp/CharIndexedStringBuffer.java
 *  Copyright (C) 1998-2001 Wes Biggs
 *
 *  This library is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published
 *  by the Free Software Foundation; either version 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  This library 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package gnu.regexp;
import java.io.Serializable;

class CharIndexedStringBuffer implements CharIndexed, Serializable {
    private StringBuffer s;
    private int anchor;

    CharIndexedStringBuffer(StringBuffer str, int index) {
	s = str;
	anchor = index;
    }

  public char charAt(int index) {
      int pos = anchor + index;
    return ((pos < s.length()) && (pos >= 0)) ? s.charAt(pos) : OUT_OF_BOUNDS;
  }

  public boolean isValid() {
    return (anchor < s.length());
  }

  public boolean move(int index) {
    return ((anchor += index) < s.length());
  }
}