2 * gnu/regexp/CharIndexed.java
3 * Copyright (C) 1998-2001 Wes Biggs
5 * This library is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU Lesser General Public License as published
7 * by the Free Software Foundation; either version 2.1 of the License, or
8 * (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 * Defines the interface used internally so that different types of source
23 * text can be accessed in the same way. Built-in concrete classes provide
24 * support for String, StringBuffer, InputStream and char[] types.
25 * A class that is CharIndexed supports the notion of a cursor within a
26 * block of text. The cursor must be able to be advanced via the move()
27 * method. The charAt() method returns the character at the cursor position
28 * plus a given offset.
30 * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
32 public interface CharIndexed {
34 * Defines a constant (0xFFFF was somewhat arbitrarily chosen)
35 * that can be returned by the charAt() function indicating that
36 * the specified index is out of range.
38 char OUT_OF_BOUNDS = '\uFFFF';
41 * Returns the character at the given offset past the current cursor
42 * position in the input. The index of the current position is zero.
43 * It is possible for this method to be called with a negative index.
44 * This happens when using the '^' operator in multiline matching mode
45 * or the '\b' or '\<' word boundary operators. In any case, the lower
46 * bound is currently fixed at -2 (for '^' with a two-character newline).
48 * @param index the offset position in the character field to examine
49 * @return the character at the specified index, or the OUT_OF_BOUNDS
50 * character defined by this interface.
52 char charAt(int index);
55 * Shifts the input buffer by a given number of positions. Returns
56 * true if the new cursor position is valid.
58 boolean move(int index);
61 * Returns true if the most recent move() operation placed the cursor
62 * position at a valid position in the input.