public int match(CharStream input, int mode) {
		this.mode = mode;
		int mark = input.mark();
		try {
			this.startIndex = input.index();
			this.prevAccept.reset();
			DFA dfa = decisionToDFA[mode];
			if ( dfa.s0==null ) {
				return matchATN(input);
			}
			else {
				return execATN(input, dfa.s0);
			}
		}
		finally {
			input.release(mark);
		}
	}
Used during DFA/ATN exec to record the most recent accept configuration info
runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java