01: /*
02: [The "BSD licence"]
03: Copyright (c) 2005-2006 Terence Parr
04: All rights reserved.
05:
06: Redistribution and use in source and binary forms, with or without
07: modification, are permitted provided that the following conditions
08: are met:
09: 1. Redistributions of source code must retain the above copyright
10: notice, this list of conditions and the following disclaimer.
11: 2. Redistributions in binary form must reproduce the above copyright
12: notice, this list of conditions and the following disclaimer in the
13: documentation and/or other materials provided with the distribution.
14: 3. The name of the author may not be used to endorse or promote products
15: derived from this software without specific prior written permission.
16:
17: THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18: IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19: OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20: IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21: INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22: NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23: DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24: THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25: (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26: THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27: */
28: package org.antlr.runtime;
29:
30: /** A source of tokens must provide a sequence of tokens via nextToken()
31: * and also must reveal it's source of characters; CommonToken's text is
32: * computed from a CharStream; it only store indices into the char stream.
33: *
34: * Errors from the lexer are never passed to the parser. Either you want
35: * to keep going or you do not upon token recognition error. If you do not
36: * want to continue lexing then you do not want to continue parsing. Just
37: * throw an exception not under RecognitionException and Java will naturally
38: * toss you all the way out of the recognizers. If you want to continue
39: * lexing then you should not throw an exception to the parser--it has already
40: * requested a token. Keep lexing until you get a valid one. Just report
41: * errors and keep going, looking for a valid token.
42: */
43: public interface TokenSource {
44: /** Return a Token object from your input stream (usually a CharStream).
45: * Do not fail/return upon lexing error; keep chewing on the characters
46: * until you get a good one; errors are not passed through to the parser.
47: */
48: public Token nextToken();
49: }
|