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Java > Open Source Codes > gnu > regexp > RETokenWordBoundary


1 /*
2  * gnu/regexp/RETokenWordBoundary.java
3  * Copyright (C) 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  */
19
20 package gnu.regexp;
21
22 /**
23  * Represents a combination lookahead/lookbehind for POSIX [:alnum:].
24  */
25 final class RETokenWordBoundary extends REToken {
26     private boolean negated;
27     private int where;
28     static final int BEGIN = 1;
29     static final int END = 2;
30
31     RETokenWordBoundary(int subIndex, int where, boolean negated) {
32     super(subIndex);
33     this.where = where;
34     this.negated = negated;
35     }
36     
37     boolean match(CharIndexed input, REMatch mymatch) {
38     // Word boundary means input[index-1] was a word character
39 // and input[index] is not, or input[index] is a word character
40 // and input[index-1] was not
41 // In the string "one two three", these positions match:
42 // |o|n|e| |t|w|o| |t|h|r|e|e|
43 // ^ ^ ^ ^ ^ ^
44 boolean after = false; // is current character a letter or digit?
45 boolean before = false; // is previous character a letter or digit?
46 char ch;
47
48     // TODO: Also check REG_ANCHORINDEX vs. anchor
49 if (((mymatch.eflags & RE.REG_ANCHORINDEX) != RE.REG_ANCHORINDEX)
50         || (mymatch.offset + mymatch.index > mymatch.anchor)) {
51         if ((ch = input.charAt(mymatch.index - 1)) != CharIndexed.OUT_OF_BOUNDS) {
52         before = Character.isLetterOrDigit(ch) || (ch == '_');
53         }
54     }
55
56     if ((ch = input.charAt(mymatch.index)) != CharIndexed.OUT_OF_BOUNDS) {
57         after = Character.isLetterOrDigit(ch) || (ch == '_');
58     }
59
60     // if (before) and (!after), we're at end (\>)
61 // if (after) and (!before), we're at beginning (\<)
62 boolean doNext = false;
63
64     if ((where & BEGIN) == BEGIN) {
65         doNext = after && !before;
66     }
67     if ((where & END) == END) {
68         doNext ^= before && !after;
69     }
70
71     if (negated) doNext = !doNext;
72
73     return (doNext ? next(input, mymatch) : false);
74     }
75     
76     void dump(StringBuffer JavaDoc os) {
77     if (where == (BEGIN | END)) {
78         os.append( negated ? "\\B" : "\\b" );
79     } else if (where == BEGIN) {
80         os.append("\\<");
81     } else {
82         os.append("\\>");
83     }
84     }
85 }
86
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