protected virtual void OptimizeExitBranches(DFAState d)
{
int sI = d.stateNumber;
if (_visited.Contains(sI))
{
return; // already visited
}
_visited.Add(sI);
int nAlts = d.dfa.NumberOfAlts;
for (int i = 0; i < d.NumberOfTransitions; i++)
{
Transition edge = (Transition)d.Transition(i);
DFAState edgeTarget = ((DFAState)edge.target);
/*
* [email protected](d.stateNumber+"-"+
* edge.label.toString(d.dfa.nfa.grammar)+"->"+
* edgeTarget.stateNumber);
*/
// if target is an accept state and that alt is the exit alt
if (edgeTarget.IsAcceptState &&
edgeTarget.GetUniquelyPredictedAlt() == nAlts)
{
/*
* [email protected]("ignoring transition "+i+" to max alt "+
* d.dfa.getNumberOfAlts());
*/
d.RemoveTransition(i);
i--; // back up one so that i++ of loop iteration stays within bounds
}
OptimizeExitBranches(edgeTarget);
}
}
// S U P P O R T
/** Given a start state and a target state, return true if start can reach
* target state. Also, compute the set of DFA states
* that are on a path from start to target; return in states parameter.
*/
protected virtual bool ReachesState(DFAState startState,
DFAState targetState,
HashSet <object> states)
{
if (startState == targetState)
{
states.Add(targetState);
//[email protected]("found target DFA state "+targetState.getStateNumber());
_stateReachable[startState.stateNumber] = REACHABLE_YES;
return(true);
}
DFAState s = startState;
// avoid infinite loops
_stateReachable[s.stateNumber] = REACHABLE_BUSY;
// look for a path to targetState among transitions for this state
// stop when you find the first one; I'm pretty sure there is
// at most one path to any DFA state with conflicting predictions
for (int i = 0; i < s.NumberOfTransitions; i++)
{
Transition t = s.Transition(i);
DFAState edgeTarget = (DFAState)t.target;
int targetStatus; //= stateReachable.get( edgeTarget.stateNumber );
if (_stateReachable.TryGetValue(edgeTarget.stateNumber, out targetStatus))
{
if (targetStatus == REACHABLE_BUSY)
{ // avoid cycles; they say nothing
continue;
}
if (targetStatus == REACHABLE_YES)
{ // return success!
_stateReachable[s.stateNumber] = REACHABLE_YES;
return(true);
}
if (targetStatus == REACHABLE_NO)
{ // try another transition
continue;
}
}
// if null, target must be REACHABLE_UNKNOWN (i.e., unvisited)
if (ReachesState(edgeTarget, targetState, states))
{
states.Add(s);
_stateReachable[s.stateNumber] = REACHABLE_YES;
return(true);
}
}
_stateReachable[s.stateNumber] = REACHABLE_NO;
return(false); // no path to targetState found.
}
protected virtual void OptimizeEOTBranches(DFAState d)
{
int sI = d.stateNumber;
if (_visited.Contains(sI))
{
return; // already visited
}
_visited.Add(sI);
for (int i = 0; i < d.NumberOfTransitions; i++)
{
Transition edge = (Transition)d.Transition(i);
DFAState edgeTarget = ((DFAState)edge.target);
/*
* [email protected](d.stateNumber+"-"+
* edge.label.toString(d.dfa.nfa.grammar)+"->"+
* edgeTarget.stateNumber);
*/
// if only one edge coming out, it is EOT, and target is accept prune
if (PRUNE_TOKENS_RULE_SUPERFLUOUS_EOT_EDGES &&
edgeTarget.IsAcceptState &&
d.NumberOfTransitions == 1 &&
edge.label.IsAtom &&
edge.label.Atom == Label.EOT)
{
//[email protected]("state "+d+" can be pruned");
// remove the superfluous EOT edge
d.RemoveTransition(i);
d.IsAcceptState = true; // make it an accept state
// force it to uniquely predict the originally predicted state
d.cachedUniquelyPredicatedAlt =
edgeTarget.GetUniquelyPredictedAlt();
i--; // back up one so that i++ of loop iteration stays within bounds
}
OptimizeEOTBranches(edgeTarget);
}
}
/** Do a depth-first walk of the state machine graph and
* fill a DOT description template. Keep filling the
* states and edges attributes.
*/
protected virtual void WalkCreatingDFADOT( StringTemplate dot,
DFAState s )
{
if ( markedStates.Contains( s.stateNumber ) )
{
return; // already visited this node
}
markedStates.Add( s.stateNumber ); // mark this node as completed.
// first add this node
StringTemplate st;
if ( s.IsAcceptState )
{
st = stlib.GetInstanceOf( Path.Combine( dfaTemplateDirectoryName, "stopstate" ) );
}
else
{
st = stlib.GetInstanceOf( Path.Combine( dfaTemplateDirectoryName, "state" ) );
}
st.SetAttribute( "name", GetStateLabel( s ) );
dot.SetAttribute( "states", st );
// make a DOT edge for each transition
for ( int i = 0; i < s.NumberOfTransitions; i++ )
{
Transition edge = (Transition)s.Transition( i );
//Console.Out.WriteLine( "dfa " + s.dfa.decisionNumber + " edge from s"
// + s.stateNumber + " [" + i + "] of " + s.NumberOfTransitions );
if ( StripNonreducedStates )
{
if ( edge.target is DFAState &&
( (DFAState)edge.target ).AcceptStateReachable != DFA.REACHABLE_YES )
{
continue; // don't generate nodes for terminal states
}
}
st = stlib.GetInstanceOf( Path.Combine( dfaTemplateDirectoryName, "edge" ) );
st.SetAttribute( "label", GetEdgeLabel( edge ) );
st.SetAttribute( "src", GetStateLabel( s ) );
st.SetAttribute( "target", GetStateLabel( edge.target ) );
st.SetAttribute( "arrowhead", arrowhead );
dot.SetAttribute( "edges", st );
WalkCreatingDFADOT( dot, (DFAState)edge.target ); // keep walkin'
}
}
protected virtual void OptimizeExitBranches( DFAState d )
{
int sI = d.stateNumber;
if ( _visited.Contains( sI ) )
{
return; // already visited
}
_visited.Add( sI );
int nAlts = d.dfa.NumberOfAlts;
for ( int i = 0; i < d.NumberOfTransitions; i++ )
{
Transition edge = (Transition)d.Transition( i );
DFAState edgeTarget = ( (DFAState)edge.target );
/*
[email protected](d.stateNumber+"-"+
edge.label.toString(d.dfa.nfa.grammar)+"->"+
edgeTarget.stateNumber);
*/
// if target is an accept state and that alt is the exit alt
if ( edgeTarget.IsAcceptState &&
edgeTarget.GetUniquelyPredictedAlt() == nAlts )
{
/*
[email protected]("ignoring transition "+i+" to max alt "+
d.dfa.getNumberOfAlts());
*/
d.RemoveTransition( i );
i--; // back up one so that i++ of loop iteration stays within bounds
}
OptimizeExitBranches( edgeTarget );
}
}
protected virtual void OptimizeEOTBranches( DFAState d )
{
int sI = d.stateNumber;
if ( _visited.Contains( sI ) )
{
return; // already visited
}
_visited.Add( sI );
for ( int i = 0; i < d.NumberOfTransitions; i++ )
{
Transition edge = (Transition)d.Transition( i );
DFAState edgeTarget = ( (DFAState)edge.target );
/*
[email protected](d.stateNumber+"-"+
edge.label.toString(d.dfa.nfa.grammar)+"->"+
edgeTarget.stateNumber);
*/
// if only one edge coming out, it is EOT, and target is accept prune
if ( PRUNE_TOKENS_RULE_SUPERFLUOUS_EOT_EDGES &&
edgeTarget.IsAcceptState &&
d.NumberOfTransitions == 1 &&
edge.label.IsAtom &&
edge.label.Atom == Label.EOT )
{
//[email protected]("state "+d+" can be pruned");
// remove the superfluous EOT edge
d.RemoveTransition( i );
d.IsAcceptState = true; // make it an accept state
// force it to uniquely predict the originally predicted state
d.cachedUniquelyPredicatedAlt =
edgeTarget.GetUniquelyPredictedAlt();
i--; // back up one so that i++ of loop iteration stays within bounds
}
OptimizeEOTBranches( edgeTarget );
}
}
/** A special state is huge (too big for state tables) or has a predicated
* edge. Generate a simple if-then-else. Cannot be an accept state as
* they have no emanating edges. Don't worry about switch vs if-then-else
* because if you get here, the state is super complicated and needs an
* if-then-else. This is used by the new DFA scheme created June 2006.
*/
public virtual StringTemplate GenerateSpecialState( DFAState s )
{
StringTemplate stateST;
stateST = templates.GetInstanceOf( "cyclicDFAState" );
stateST.SetAttribute( "needErrorClause", true );
stateST.SetAttribute( "semPredState", s.IsResolvedWithPredicates );
stateST.SetAttribute( "stateNumber", s.stateNumber );
stateST.SetAttribute( "decisionNumber", s.dfa.decisionNumber );
bool foundGatedPred = false;
StringTemplate eotST = null;
for ( int i = 0; i < s.NumberOfTransitions; i++ )
{
Transition edge = (Transition)s.Transition( i );
StringTemplate edgeST;
if ( edge.label.Atom == Label.EOT )
{
// this is the default clause; has to held until last
edgeST = templates.GetInstanceOf( "eotDFAEdge" );
stateST.RemoveAttribute( "needErrorClause" );
eotST = edgeST;
}
else
{
edgeST = templates.GetInstanceOf( "cyclicDFAEdge" );
StringTemplate exprST =
GenLabelExpr( templates, edge, 1 );
edgeST.SetAttribute( "labelExpr", exprST );
}
edgeST.SetAttribute( "edgeNumber", i + 1 );
edgeST.SetAttribute( "targetStateNumber",
edge.target.stateNumber );
// stick in any gated predicates for any edge if not already a pred
if ( !edge.label.IsSemanticPredicate )
{
DFAState t = (DFAState)edge.target;
SemanticContext preds = t.GetGatedPredicatesInNFAConfigurations();
if ( preds != null )
{
foundGatedPred = true;
StringTemplate predST = preds.GenExpr( this,
Templates,
t.dfa );
edgeST.SetAttribute( "predicates", predST.ToString() );
}
}
if ( edge.label.Atom != Label.EOT )
{
stateST.SetAttribute( "edges", edgeST );
}
}
if ( foundGatedPred )
{
// state has >= 1 edge with a gated pred (syn or sem)
// must rewind input first, set flag.
stateST.SetAttribute( "semPredState", foundGatedPred );
}
if ( eotST != null )
{
stateST.SetAttribute( "edges", eotST );
}
return stateST;
}
/** You can generate a switch rather than if-then-else for a DFA state
* if there are no semantic predicates and the number of edge label
* values is small enough; e.g., don't generate a switch for a state
* containing an edge label such as 20..52330 (the resulting byte codes
* would overflow the method 65k limit probably).
*/
protected internal virtual bool CanGenerateSwitch( DFAState s )
{
if ( !GenerateSwitchesWhenPossible )
{
return false;
}
int size = 0;
for ( int i = 0; i < s.NumberOfTransitions; i++ )
{
Transition edge = (Transition)s.Transition( i );
if ( edge.label.IsSemanticPredicate )
{
return false;
}
// can't do a switch if the edges are going to require predicates
if ( edge.label.Atom == Label.EOT )
{
int EOTPredicts = ( (DFAState)edge.target ).GetUniquelyPredictedAlt();
if ( EOTPredicts == NFA.INVALID_ALT_NUMBER )
{
// EOT target has to be a predicate then; no unique alt
return false;
}
}
// if target is a state with gated preds, we need to use preds on
// this edge then to reach it.
if ( ( (DFAState)edge.target ).GetGatedPredicatesInNFAConfigurations() != null )
{
return false;
}
size += edge.label.Set.Count;
}
if ( s.NumberOfTransitions < MinSwitchAlts ||
size > MaxSwitchCaseLabels )
{
return false;
}
return true;
}
protected virtual StringTemplate WalkFixedDFAGeneratingStateMachine(
StringTemplateGroup templates,
DFA dfa,
DFAState s,
int k )
{
//System.Console.Out.WriteLine( "walk " + s.stateNumber + " in dfa for decision " + dfa.decisionNumber );
if ( s.IsAcceptState )
{
StringTemplate dfaST2 = templates.GetInstanceOf( "dfaAcceptState" );
dfaST2.SetAttribute( "alt", s.GetUniquelyPredictedAlt() );
return dfaST2;
}
// the default templates for generating a state and its edges
// can be an if-then-else structure or a switch
string dfaStateName = "dfaState";
string dfaLoopbackStateName = "dfaLoopbackState";
string dfaOptionalBlockStateName = "dfaOptionalBlockState";
string dfaEdgeName = "dfaEdge";
if ( parentGenerator.CanGenerateSwitch( s ) )
{
dfaStateName = "dfaStateSwitch";
dfaLoopbackStateName = "dfaLoopbackStateSwitch";
dfaOptionalBlockStateName = "dfaOptionalBlockStateSwitch";
dfaEdgeName = "dfaEdgeSwitch";
}
StringTemplate dfaST = templates.GetInstanceOf( dfaStateName );
if ( dfa.NFADecisionStartState.decisionStateType == NFAState.LOOPBACK )
{
dfaST = templates.GetInstanceOf( dfaLoopbackStateName );
}
else if ( dfa.NFADecisionStartState.decisionStateType == NFAState.OPTIONAL_BLOCK_START )
{
dfaST = templates.GetInstanceOf( dfaOptionalBlockStateName );
}
dfaST.SetAttribute( "k", k );
dfaST.SetAttribute( "stateNumber", s.stateNumber );
dfaST.SetAttribute( "semPredState",
s.IsResolvedWithPredicates );
/*
string description = dfa.getNFADecisionStartState().Description;
description = parentGenerator.target.getTargetStringLiteralFromString( description );
//System.Console.Out.WriteLine( "DFA: " + description + " associated with AST " + dfa.getNFADecisionStartState() );
if ( description != null )
{
dfaST.SetAttribute( "description", description );
}
*/
int EOTPredicts = NFA.INVALID_ALT_NUMBER;
DFAState EOTTarget = null;
//System.Console.Out.WriteLine( "DFA state " + s.stateNumber );
for ( int i = 0; i < s.NumberOfTransitions; i++ )
{
Transition edge = (Transition)s.Transition( i );
//System.Console.Out.WriteLine( "edge " + s.stateNumber + "-" + edge.label.ToString() + "->" + edge.target.stateNumber );
if ( edge.label.Atom == Label.EOT )
{
// don't generate a real edge for EOT; track alt EOT predicts
// generate that prediction in the else clause as default case
EOTTarget = (DFAState)edge.target;
EOTPredicts = EOTTarget.GetUniquelyPredictedAlt();
/*
System.Console.Out.WriteLine("DFA s"+s.stateNumber+" EOT goes to s"+
edge.target.stateNumber+" predicates alt "+
EOTPredicts);
*/
continue;
}
StringTemplate edgeST = templates.GetInstanceOf( dfaEdgeName );
// If the template wants all the label values delineated, do that
if ( edgeST.GetFormalArgument( "labels" ) != null )
{
List<string> labels = edge.Label.Set.Select( value => parentGenerator.GetTokenTypeAsTargetLabel( value ) ).ToList();
edgeST.SetAttribute( "labels", labels );
}
else
{ // else create an expression to evaluate (the general case)
edgeST.SetAttribute( "labelExpr",
parentGenerator.GenLabelExpr( templates, edge, k ) );
}
// stick in any gated predicates for any edge if not already a pred
if ( !edge.label.IsSemanticPredicate )
{
DFAState target = (DFAState)edge.target;
SemanticContext preds =
target.GetGatedPredicatesInNFAConfigurations();
if ( preds != null )
{
//System.Console.Out.WriteLine( "preds=" + target.getGatedPredicatesInNFAConfigurations() );
StringTemplate predST = preds.GenExpr( parentGenerator,
parentGenerator.Templates,
dfa );
edgeST.SetAttribute( "predicates", predST );
}
}
StringTemplate targetST =
WalkFixedDFAGeneratingStateMachine( templates,
dfa,
(DFAState)edge.target,
k + 1 );
edgeST.SetAttribute( "targetState", targetST );
dfaST.SetAttribute( "edges", edgeST );
//System.Console.Out.WriteLine( "back to DFA " + dfa.decisionNumber + "." + s.stateNumber );
}
// HANDLE EOT EDGE
if ( EOTPredicts != NFA.INVALID_ALT_NUMBER )
{
// EOT unique predicts an alt
dfaST.SetAttribute( "eotPredictsAlt", EOTPredicts );
}
else if ( EOTTarget != null && EOTTarget.NumberOfTransitions > 0 )
{
// EOT state has transitions so must split on predicates.
// Generate predicate else-if clauses and then generate
// NoViableAlt exception as else clause.
// Note: these predicates emanate from the EOT target state
// rather than the current DFAState s so the error message
// might be slightly misleading if you are looking at the
// state number. Predicates emanating from EOT targets are
// hoisted up to the state that has the EOT edge.
for ( int i = 0; i < EOTTarget.NumberOfTransitions; i++ )
{
Transition predEdge = (Transition)EOTTarget.Transition( i );
StringTemplate edgeST = templates.GetInstanceOf( dfaEdgeName );
edgeST.SetAttribute( "labelExpr",
parentGenerator.GenSemanticPredicateExpr( templates, predEdge ) );
// the target must be an accept state
//System.Console.Out.WriteLine( "EOT edge" );
StringTemplate targetST =
WalkFixedDFAGeneratingStateMachine( templates,
dfa,
(DFAState)predEdge.target,
k + 1 );
edgeST.SetAttribute( "targetState", targetST );
dfaST.SetAttribute( "edges", edgeST );
}
}
return dfaST;
}
