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.debug;
29:
30: import org.antlr.runtime.IntStream;
31: import org.antlr.runtime.TokenStream;
32:
33: /** The default tracer mimics the traceParser behavior of ANTLR 2.x.
34: * This listens for debugging events from the parser and implies
35: * that you cannot debug and trace at the same time.
36: */
37: public class Tracer extends BlankDebugEventListener {
38: public IntStream input;
39: protected int level = 0;
40:
41: public Tracer(IntStream input) {
42: this .input = input;
43: }
44:
45: public void enterRule(String ruleName) {
46: for (int i = 1; i <= level; i++) {
47: System.out.print(" ");
48: }
49: System.out.println("> " + ruleName + " lookahead(1)="
50: + getInputSymbol(1));
51: level++;
52: }
53:
54: public void exitRule(String ruleName) {
55: level--;
56: for (int i = 1; i <= level; i++) {
57: System.out.print(" ");
58: }
59: System.out.println("< " + ruleName + " lookahead(1)="
60: + getInputSymbol(1));
61: }
62:
63: public Object getInputSymbol(int k) {
64: if (input instanceof TokenStream) {
65: return ((TokenStream) input).LT(k);
66: }
67: return new Character((char) input.LA(k));
68: }
69: }
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