tool/src/main/java/org/antlr/analysis/LL1DFA.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
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 *      derived from this software without specific prior written permission.
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package org.antlr.analysis;

import org.antlr.grammar.v3.ANTLRParser;
import org.antlr.misc.IntervalSet;
import org.antlr.misc.MultiMap;

import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/** 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;
	}
}