/*
[The "BSD licence"]
Copyright (c) 2005-2008 Terence Parr
All rights reserved.
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derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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*/
package org.antlr.analysis;
import org.antlr.misc.IntervalSet;
import org.antlr.misc.MultiMap;
import org.antlr.tool.ANTLRParser;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
/** A special DFA that is exactly LL(1) or LL(1) with backtracking mode
* predicates to resolve edge set collisions.
*/
public class LL1DFA extends DFA {
/** From list of lookahead sets (one per alt in decision), create
* an LL(1) DFA. One edge per set.
*
* s0-{alt1}->:o=>1
* | \
* | -{alt2}->:o=>2
* |
* ...
*/
public LL1DFA(int decisionNumber, NFAState decisionStartState, LookaheadSet[] altLook) {
DFAState s0 = newState();
startState = s0;
nfa = decisionStartState.nfa;
nAlts = nfa.grammar.getNumberOfAltsForDecisionNFA(decisionStartState);
this.decisionNumber = decisionNumber;
this.decisionNFAStartState = decisionStartState;
initAltRelatedInfo();
unreachableAlts = null;
for (int alt=1; alt<altLook.length; alt++) {
DFAState acceptAltState = newState();
acceptAltState.acceptState = true;
setAcceptState(alt, acceptAltState);
acceptAltState.k = 1;
acceptAltState.cachedUniquelyPredicatedAlt = alt;
Label e = getLabelForSet(altLook[alt].tokenTypeSet);
s0.addTransition(acceptAltState, e);
}
}
/** From a set of edgeset->list-of-alts mappings, create a DFA
* that uses syn preds for all |list-of-alts|>1.
*/
public LL1DFA(int decisionNumber,
NFAState decisionStartState,
MultiMap<IntervalSet, Integer> edgeMap)
{
DFAState s0 = newState();
startState = s0;
nfa = decisionStartState.nfa;
nAlts = nfa.grammar.getNumberOfAltsForDecisionNFA(decisionStartState);
this.decisionNumber = decisionNumber;
this.decisionNFAStartState = decisionStartState;
initAltRelatedInfo();
unreachableAlts = null;
for (Iterator it = edgeMap.keySet().iterator(); it.hasNext();) {
IntervalSet edge = (IntervalSet)it.next();
List<Integer> alts = edgeMap.get(edge);
Collections.sort(alts); // make sure alts are attempted in order
//System.out.println(edge+" -> "+alts);
DFAState s = newState();
s.k = 1;
Label e = getLabelForSet(edge);
s0.addTransition(s, e);
if ( alts.size()==1 ) {
s.acceptState = true;
int alt = alts.get(0);
setAcceptState(alt, s);
s.cachedUniquelyPredicatedAlt = alt;
}
else {
// resolve with syntactic predicates. Add edges from
// state s that test predicates.
s.resolvedWithPredicates = true;
for (int i = 0; i < alts.size(); i++) {
int alt = (int)alts.get(i);
s.cachedUniquelyPredicatedAlt = NFA.INVALID_ALT_NUMBER;
DFAState predDFATarget = getAcceptState(alt);
if ( predDFATarget==null ) {
predDFATarget = newState(); // create if not there.
predDFATarget.acceptState = true;
predDFATarget.cachedUniquelyPredicatedAlt = alt;
setAcceptState(alt, predDFATarget);
}
// add a transition to pred target from d
/*
int walkAlt =
decisionStartState.translateDisplayAltToWalkAlt(alt);
NFAState altLeftEdge = nfa.grammar.getNFAStateForAltOfDecision(decisionStartState, walkAlt);
NFAState altStartState = (NFAState)altLeftEdge.transition[0].target;
SemanticContext ctx = nfa.grammar.ll1Analyzer.getPredicates(altStartState);
System.out.println("sem ctx = "+ctx);
if ( ctx == null ) {
ctx = new SemanticContext.TruePredicate();
}
s.addTransition(predDFATarget, new Label(ctx));
*/
SemanticContext.Predicate synpred =
getSynPredForAlt(decisionStartState, alt);
if ( synpred == null ) {
synpred = new SemanticContext.TruePredicate();
}
s.addTransition(predDFATarget, new PredicateLabel(synpred));
}
}
}
//System.out.println("dfa for preds=\n"+this);
}
protected Label getLabelForSet(IntervalSet edgeSet) {
Label e = null;
int atom = edgeSet.getSingleElement();
if ( atom != Label.INVALID ) {
e = new Label(atom);
}
else {
e = new Label(edgeSet);
}
return e;
}
protected SemanticContext.Predicate getSynPredForAlt(NFAState decisionStartState,
int alt)
{
int walkAlt =
decisionStartState.translateDisplayAltToWalkAlt(alt);
NFAState altLeftEdge =
nfa.grammar.getNFAStateForAltOfDecision(decisionStartState, walkAlt);
NFAState altStartState = (NFAState)altLeftEdge.transition[0].target;
//System.out.println("alt "+alt+" start state = "+altStartState.stateNumber);
if ( altStartState.transition[0].isSemanticPredicate() ) {
SemanticContext ctx = altStartState.transition[0].label.getSemanticContext();
if ( ctx.isSyntacticPredicate() ) {
SemanticContext.Predicate p = (SemanticContext.Predicate)ctx;
if ( p.predicateAST.getType() == ANTLRParser.BACKTRACK_SEMPRED ) {
/*
System.out.println("syn pred for alt "+walkAlt+" "+
((SemanticContext.Predicate)altStartState.transition[0].label.getSemanticContext()).predicateAST);
*/
if ( ctx.isSyntacticPredicate() ) {
nfa.grammar.synPredUsedInDFA(this, ctx);
}
return (SemanticContext.Predicate)altStartState.transition[0].label.getSemanticContext();
}
}
}
return null;
}
}