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/jEdit/tags/jedit-4-0-pre5/gnu/regexp/CharIndexed.java

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Java | 65 lines | 7 code | 4 blank | 54 comment | 0 complexity | 5682dc9596eac9d979b8c7878e9d8806 MD5 | raw file
 1/*
 2 *  gnu/regexp/CharIndexed.java
 3 *  Copyright (C) 1998-2001 Wes Biggs
 4 *
 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.
 9 *
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.
14 *
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.
18 */
19package gnu.regexp;
20
21/**
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.
29 *
30 * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
31 */
32public interface CharIndexed {
33    /**
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.
37     */
38    char OUT_OF_BOUNDS = '\uFFFF';
39
40    /**
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).
47     *
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.
51     */
52    char charAt(int index);
53
54    /**
55     * Shifts the input buffer by a given number of positions.  Returns
56     * true if the new cursor position is valid.
57     */
58    boolean move(int index);
59
60    /**
61     * Returns true if the most recent move() operation placed the cursor
62     * position at a valid position in the input.
63     */
64    boolean isValid();
65}