/interpreter/tags/at2-build060407/src/edu/vub/util/regexp/CharIndexed.java

 1/* gnu/regexp/CharIndexed.java
 2   Copyright (C) 1998-2001, 2004, 2006 Free Software Foundation, Inc.
 3
 4This file is part of GNU Classpath.
 5
 6GNU Classpath is free software; you can redistribute it and/or modify
 7it under the terms of the GNU General Public License as published by
 8the Free Software Foundation; either version 2, or (at your option)
 9any later version.
10
11GNU Classpath is distributed in the hope that it will be useful, but
12WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14General Public License for more details.
15
16You should have received a copy of the GNU General Public License
17along with GNU Classpath; see the file COPYING.  If not, write to the
18Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
1902110-1301 USA.
20
21Linking this library statically or dynamically with other modules is
22making a combined work based on this library.  Thus, the terms and
23conditions of the GNU General Public License cover the whole
24combination.
25
26As a special exception, the copyright holders of this library give you
27permission to link this library with independent modules to produce an
28executable, regardless of the license terms of these independent
29modules, and to copy and distribute the resulting executable under
30terms of your choice, provided that you also meet, for each linked
31independent module, the terms and conditions of the license of that
32module.  An independent module is a module which is not derived from
33or based on this library.  If you modify this library, you may extend
34this exception to your version of the library, but you are not
35obligated to do so.  If you do not wish to do so, delete this
36exception statement from your version. */
37
38package edu.vub.util.regexp;
39
40/**
41 * Defines the interface used internally so that different types of source
42 * text can be accessed in the same way.  Built-in concrete classes provide
43 * support for String, StringBuffer, InputStream and char[] types.
44 * A class that is CharIndexed supports the notion of a cursor within a
45 * block of text.  The cursor must be able to be advanced via the move()
46 * method.  The charAt() method returns the character at the cursor position
47 * plus a given offset.
48 *
49 * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
50 */
51public interface CharIndexed {
52    /**
53     * Defines a constant (0xFFFF was somewhat arbitrarily chosen)
54     * that can be returned by the charAt() function indicating that
55     * the specified index is out of range.
56     */
57    char OUT_OF_BOUNDS = '\uFFFF';
58
59    /**
60     * Returns the character at the given offset past the current cursor
61     * position in the input.  The index of the current position is zero.
62     * It is possible for this method to be called with a negative index.
63     * This happens when using the '^' operator in multiline matching mode
64     * or the '\b' or '\<' word boundary operators.  In any case, the lower
65     * bound is currently fixed at -2 (for '^' with a two-character newline).
66     *
67     * @param index the offset position in the character field to examine
68     * @return the character at the specified index, or the OUT_OF_BOUNDS
69     *   character defined by this interface.
70     */
71    char charAt(int index);
72
73    /**
74     * Shifts the input buffer by a given number of positions.  Returns
75     * true if the new cursor position is valid.
76     */
77    boolean move(int index);
78
79    /**
80     * Returns true if the most recent move() operation placed the cursor
81     * position at a valid position in the input.
82     */
83    boolean isValid();
84
85    /**
86     * Returns another CharIndexed containing length characters to the left
87     * of the given index. The given length is an expected maximum and
88     * the returned CharIndexed may not necessarily contain so many characters.
89     */
90    CharIndexed lookBehind(int index, int length);
91
92    /**
93     * Returns the effective length of this CharIndexed
94     */
95    int length();
96}