/* *  gnu/regexp/CharIndexed.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;/** * Defines the interface used internally so that different types of source * text can be accessed in the same way.  Built-in concrete classes provide * support for String, StringBuffer, InputStream and char[] types. * A class that is CharIndexed supports the notion of a cursor within a * block of text.  The cursor must be able to be advanced via the move() * method.  The charAt() method returns the character at the cursor position * plus a given offset. * * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A> */public interface CharIndexed {    /**     * Defines a constant (0xFFFF was somewhat arbitrarily chosen)     * that can be returned by the charAt() function indicating that     * the specified index is out of range.     */    char OUT_OF_BOUNDS = '\uFFFF';    /**     * Returns the character at the given offset past the current cursor     * position in the input.  The index of the current position is zero.     * It is possible for this method to be called with a negative index.     * This happens when using the '^' operator in multiline matching mode     * or the '\b' or '\<' word boundary operators.  In any case, the lower     * bound is currently fixed at -2 (for '^' with a two-character newline).     *     * @param index the offset position in the character field to examine     * @return the character at the specified index, or the OUT_OF_BOUNDS     *   character defined by this interface.     */    char charAt(int index);    /**     * Shifts the input buffer by a given number of positions.  Returns     * true if the new cursor position is valid.     */    boolean move(int index);    /**     * Returns true if the most recent move() operation placed the cursor     * position at a valid position in the input.     */    boolean isValid();}