ParserATNFactory.java 文件源码

/**
 * From {@code (blk)+} build
 *
 * <pre>
 *   |---------|
 *   v         |
 *  [o-blk-o]-&gt;o-&gt;o
 * </pre>
 *
 * We add a decision for loop back node to the existing one at {@code blk}
 * start.
 */

@Override
public Handle plus(GrammarAST plusAST, Handle blk) {
    PlusBlockStartState blkStart = (PlusBlockStartState)blk.left;
    BlockEndState blkEnd = (BlockEndState)blk.right;
    preventEpsilonClosureBlocks.add(new Triple<Rule, ATNState, ATNState>(currentRule, blkStart, blkEnd));

    PlusLoopbackState loop = newState(PlusLoopbackState.class, plusAST);
    loop.nonGreedy = !((QuantifierAST)plusAST).isGreedy();
    atn.defineDecisionState(loop);
    LoopEndState end = newState(LoopEndState.class, plusAST);
    blkStart.loopBackState = loop;
    end.loopBackState = loop;

    plusAST.atnState = loop;
    epsilon(blkEnd, loop);      // blk can see loop back

    BlockAST blkAST = (BlockAST)plusAST.getChild(0);
    if ( ((QuantifierAST)plusAST).isGreedy() ) {
        if (expectNonGreedy(blkAST)) {
            g.tool.errMgr.grammarError(ErrorType.EXPECTED_NON_GREEDY_WILDCARD_BLOCK, g.fileName, plusAST.getToken(), plusAST.getToken().getText());
        }

        epsilon(loop, blkStart);    // loop back to start
        epsilon(loop, end);         // or exit
    }
    else {
        // if not greedy, priority to exit branch; make it first
        epsilon(loop, end);         // exit
        epsilon(loop, blkStart);    // loop back to start
    }

    return new Handle(blkStart, end);
}