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Java > Open Source Codes > persistence > antlr > TokenStreamBasicFilter


1 package persistence.antlr;
2
3 /* ANTLR Translator Generator
4  * Project led by Terence Parr at http://www.jGuru.com
5  * Software rights: http://www.antlr.org/license.html
6  *
7  */
8
9 import persistence.antlr.collections.impl.BitSet;
10
11 /** This object is a TokenStream that passes through all
12  * tokens except for those that you tell it to discard.
13  * There is no buffering of the tokens.
14  */
15 public class TokenStreamBasicFilter implements TokenStream {
16     /** The set of token types to discard */
17     protected BitSet discardMask;
18
19     /** The input stream */
20     protected TokenStream input;
21
22     public TokenStreamBasicFilter(TokenStream input) {
23         this.input = input;
24         discardMask = new BitSet();
25     }
26
27     public void discard(int ttype) {
28         discardMask.add(ttype);
29     }
30
31     public void discard(BitSet mask) {
32         discardMask = mask;
33     }
34
35     public Token nextToken() throws TokenStreamException {
36         Token tok = input.nextToken();
37         while (tok != null && discardMask.member(tok.getType())) {
38             tok = input.nextToken();
39         }
40         return tok;
41     }
42 }
43
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