/**
* From (blk)* build ( blk+ )? with *two* decisions, one for entry and one for choosing alts of
* blk.
*
* <p>|-------------| v | o--[o-blk-o]->o o | ^ -----------------|
*
* <p>Note that the optional bypass must jump outside the loop as (A|B)* is not the same thing as
* (A|B|)+.
*/
@NotNull
public Handle star(@NotNull GrammarAST starAST, @NotNull Handle elem) {
StarBlockStartState blkStart = (StarBlockStartState) elem.left;
BlockEndState blkEnd = (BlockEndState) elem.right;
StarLoopEntryState entry = newState(StarLoopEntryState.class, starAST);
atn.defineDecisionState(entry);
LoopEndState end = newState(LoopEndState.class, starAST);
StarLoopbackState loop = newState(StarLoopbackState.class, starAST);
entry.loopBackState = loop;
end.loopBackStateNumber = loop.stateNumber;
BlockAST blkAST = (BlockAST) starAST.getChild(0);
entry.isGreedy = isGreedy(blkAST);
if (!g.isLexer() || entry.isGreedy) {
epsilon(entry, blkStart); // loop enter edge (alt 1)
epsilon(entry, end); // bypass loop edge (alt 2)
} else { // only lexers flip entry/exit branches for nongreedy
// if not greedy, priority to exit branch; make it first
epsilon(entry, end); // bypass loop edge (alt 1)
epsilon(entry, blkStart); // loop enter edge (alt 2)
}
epsilon(blkEnd, loop); // block end hits loop back
epsilon(loop, entry); // loop back to entry/exit decision
starAST.atnState = entry; // decision is to enter/exit; blk is its own decision
return new Handle(entry, end);
}
/**
* From {@code (blk)*} build {@code ( blk+ )?} with *two* decisions, one for entry and one for
* choosing alts of {@code blk}.
*
* <pre>
* |-------------|
* v |
* o--[o-blk-o]->o o
* | ^
* -----------------|
* </pre>
*
* Note that the optional bypass must jump outside the loop as {@code (A|B)*} is not the same
* thing as {@code (A|B|)+}.
*/
@NotNull
@Override
public Handle star(@NotNull GrammarAST starAST, @NotNull Handle elem) {
StarBlockStartState blkStart = (StarBlockStartState) elem.left;
BlockEndState blkEnd = (BlockEndState) elem.right;
preventEpsilonClosureBlocks.add(
new Triple<Rule, ATNState, ATNState>(currentRule, blkStart, blkEnd));
StarLoopEntryState entry = newState(StarLoopEntryState.class, starAST);
entry.nonGreedy = !((QuantifierAST) starAST).isGreedy();
atn.defineDecisionState(entry);
LoopEndState end = newState(LoopEndState.class, starAST);
StarLoopbackState loop = newState(StarLoopbackState.class, starAST);
entry.loopBackState = loop;
end.loopBackState = loop;
BlockAST blkAST = (BlockAST) starAST.getChild(0);
if (((QuantifierAST) starAST).isGreedy()) {
if (expectNonGreedy(blkAST)) {
g.tool.errMgr.grammarError(
ErrorType.EXPECTED_NON_GREEDY_WILDCARD_BLOCK,
g.fileName,
starAST.getToken(),
starAST.getToken().getText());
}
epsilon(entry, blkStart); // loop enter edge (alt 1)
epsilon(entry, end); // bypass loop edge (alt 2)
} else {
// if not greedy, priority to exit branch; make it first
epsilon(entry, end); // bypass loop edge (alt 1)
epsilon(entry, blkStart); // loop enter edge (alt 2)
}
epsilon(blkEnd, loop); // block end hits loop back
epsilon(loop, entry); // loop back to entry/exit decision
starAST.atnState = entry; // decision is to enter/exit; blk is its own decision
return new Handle(entry, end);
}
