1/*
2 [The "BSD license"]
3 Copyright (c) 2005-2009 Terence Parr
4 All rights reserved.
5
6 Redistribution and use in source and binary forms, with or without
7 modification, are permitted provided that the following conditions
8 are met:
9 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 */
28package 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 */
43public 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
50	/** Where are you getting tokens from? normally the implication will simply
51	 *  ask lexers input stream.
52	 */
53	public String getSourceName();
54}
55