01: /*
02: * Element.java
03: *
04: * This work is free software; you can redistribute it and/or modify
05: * it under the terms of the GNU General Public License as published
06: * by the Free Software Foundation; either version 2 of the License,
07: * or (at your option) any later version.
08: *
09: * This work is distributed in the hope that it will be useful, but
10: * WITHOUT ANY WARRANTY; without even the implied warranty of
11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12: * General Public License for more details.
13: *
14: * You should have received a copy of the GNU General Public License
15: * along with this program; if not, write to the Free Software
16: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
17: * USA
18: *
19: * As a special exception, the copyright holders of this library give
20: * you permission to link this library with independent modules to
21: * produce an executable, regardless of the license terms of these
22: * independent modules, and to copy and distribute the resulting
23: * executable under terms of your choice, provided that you also meet,
24: * for each linked independent module, the terms and conditions of the
25: * license of that module. An independent module is a module which is
26: * not derived from or based on this library. If you modify this
27: * library, you may extend this exception to your version of the
28: * library, but you are not obligated to do so. If you do not wish to
29: * do so, delete this exception statement from your version.
30: *
31: * Copyright (c) 2003 Per Cederberg. All rights reserved.
32: */
33:
34: package net.percederberg.grammatica.parser.re;
35:
36: import java.io.PrintStream;
37: import java.io.PrintWriter;
38:
39: /**
40: * A regular expression element. This is the common base class for all
41: * regular expression elements, i.e. the parts of the regular
42: * expression.
43: *
44: * @author Per Cederberg, <per at percederberg dot net>
45: * @version 1.0
46: */
47: abstract class Element implements Cloneable {
48:
49: /**
50: * Creates a copy of this element. The copy will be an instance
51: * of the same class matching the same strings. Copies of elements
52: * are necessary to allow elements to cache intermediate results
53: * while matching strings without interfering with other threads.
54: *
55: * @return a copy of this element
56: */
57: public abstract Object clone();
58:
59: /**
60: * Returns the length of a matching string starting at the
61: * specified position. The number of matches to skip can also be
62: * specified, but numbers higher than zero (0) cause a failed
63: * match for any element that doesn't attempt to combine other
64: * elements.
65: *
66: * @param m the matcher being used
67: * @param str the string to match
68: * @param start the starting position
69: * @param skip the number of matches to skip
70: *
71: * @return the length of the longest matching string, or
72: * -1 if no match was found
73: */
74: public abstract int match(Matcher m, CharBuffer str, int start,
75: int skip);
76:
77: /**
78: * Prints this element to the specified output stream.
79: *
80: * @param output the output stream to use
81: * @param indent the current indentation
82: */
83: public final void printTo(PrintStream output, String indent) {
84: PrintWriter writer = new PrintWriter(output);
85:
86: printTo(writer, indent);
87: writer.flush();
88: }
89:
90: /**
91: * Prints this element to the specified output stream.
92: *
93: * @param output the output stream to use
94: * @param indent the current indentation
95: */
96: public abstract void printTo(PrintWriter output, String indent);
97:
98: }
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