/** identify the ATN states where we need to set the outer alt number.
* For regular rules, that's the block at the target to rule start state.
* For left-recursive rules, we track the primary block, which looks just
* like a regular rule's outer block, and the star loop block (always
* there even if 1 alt).
*/
public virtual BitSet FindOuterMostDecisionStates()
{
BitSet track = new BitSet(atn.states.Count);
int numberOfDecisions = atn.NumberOfDecisions;
for (int i = 0; i < numberOfDecisions; i++)
{
DecisionState decisionState = atn.GetDecisionState(i);
RuleStartState startState = atn.ruleToStartState[decisionState.ruleIndex];
// Look for StarLoopEntryState that is in any left recursive rule
if (decisionState is StarLoopEntryState)
{
StarLoopEntryState loopEntry = (StarLoopEntryState)decisionState;
if (loopEntry.precedenceRuleDecision)
{
// Recursive alts always result in a (...)* in the transformed
// left recursive rule and that always has a BasicBlockStartState
// even if just 1 recursive alt exists.
ATNState blockStart = loopEntry.Transition(0).target;
// track the StarBlockStartState associated with the recursive alternatives
track.Set(blockStart.stateNumber);
}
}
else if (startState.Transition(0).target == decisionState)
{
// always track outermost block for any rule if it exists
track.Set(decisionState.stateNumber);
}
}
return(track);
}
/** identify the ATN states where we need to set the outer alt number.
* For regular rules, that's the block at the target to rule start state.
* For left-recursive rules, we track the primary block, which looks just
* like a regular rule's outer block, and the star loop block (always
* there even if 1 alt).
*/
public virtual BitSet FindOuterMostDecisionStates()
{
BitSet track = new BitSet(atn.states.Count);
int numberOfDecisions = atn.NumberOfDecisions;
for (int i = 0; i < numberOfDecisions; i++)
{
DecisionState decisionState = atn.GetDecisionState(i);
RuleStartState startState = atn.ruleToStartState[decisionState.ruleIndex];
// Look for StarLoopEntryState that is in any left recursive rule
if (decisionState is StarLoopEntryState)
{
StarLoopEntryState loopEntry = (StarLoopEntryState)decisionState;
if (loopEntry.precedenceRuleDecision)
{
// Recursive alts always result in a (...)* in the transformed
// left recursive rule and that always has a BasicBlockStartState
// even if just 1 recursive alt exists.
ATNState blockStart = loopEntry.Transition(0).target;
// track the StarBlockStartState associated with the recursive alternatives
track.Set(blockStart.stateNumber);
}
}
else if (startState.Transition(0).target == decisionState)
{
// always track outermost block for any rule if it exists
track.Set(decisionState.stateNumber);
}
}
return track;
}
