tokenstreambasicfilter.java

SRI international 发布的OAA框架软件

package antlr_oaa;

/* ANTLR Translator Generator
 * Project led by Terence Parr at http://www.jGuru.com
 * Software rights: http://www.antlr.org/RIGHTS.html
 *
 * $Id: TokenStreamBasicFilter.java,v 1.1 2002/11/08 17:37:37 agno Exp $
 */

import antlr_oaa.collections.impl.BitSet;

/** This object is a TokenStream that passes through all
 *  tokens except for those that you tell it to discard.
 *  There is no buffering of the tokens.
 */
public class TokenStreamBasicFilter implements TokenStream {
    /** The set of token types to discard */
    protected BitSet discardMask;

    /** The input stream */
    protected TokenStream input;

    public TokenStreamBasicFilter(TokenStream input) {
	this.input = input;
	discardMask = new BitSet();
    }
    public void discard(int ttype) {
	discardMask.add(ttype);
    }
    public void discard(BitSet mask) {
	discardMask = mask;
    }
    public Token nextToken() throws TokenStreamException {
	Token tok = input.nextToken();
	while ( tok!=null && discardMask.member(tok.getType()) ) {
	    tok = input.nextToken();
	}
	return tok;
    }
}