public static Create ( |
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state | ||
alt | int | |
context | PredictionContext | |
return | Antlr4.Runtime.Atn.ATNConfig |
/// <summary> /// Since the alternatives within any lexer decision are ordered by /// preference, this method stops pursuing the closure as soon as an accept /// state is reached. /// </summary> /// <remarks> /// Since the alternatives within any lexer decision are ordered by /// preference, this method stops pursuing the closure as soon as an accept /// state is reached. After the first accept state is reached by depth-first /// search from /// <code>config</code> /// , all other (potentially reachable) states for /// this rule would have a lower priority. /// </remarks> /// <returns> /// /// <code>true</code> /// if an accept state is reached, otherwise /// <code>false</code> /// . /// </returns> protected internal virtual bool Closure(ICharStream input, ATNConfig config, ATNConfigSet configs, bool speculative) { if (config.State is RuleStopState) { PredictionContext context = config.Context; if (context.IsEmpty) { configs.AddItem(config); return(true); } else { if (context.HasEmpty) { configs.AddItem(config.Transform(config.State, PredictionContext.EmptyFull)); return(true); } } for (int i = 0; i < context.Size; i++) { int returnStateNumber = context.GetReturnState(i); if (returnStateNumber == PredictionContext.EmptyFullStateKey) { continue; } PredictionContext newContext = context.GetParent(i); // "pop" return state ATNState returnState = atn.states[returnStateNumber]; ATNConfig c = ATNConfig.Create(returnState, config.Alt, newContext); if (Closure(input, c, configs, speculative)) { return(true); } } return(false); } // optimization if (!config.State.OnlyHasEpsilonTransitions) { configs.AddItem(config); } ATNState p = config.State; for (int i_1 = 0; i_1 < p.NumberOfOptimizedTransitions; i_1++) { Transition t = p.GetOptimizedTransition(i_1); ATNConfig c = GetEpsilonTarget(input, config, t, configs, speculative); if (c != null) { if (Closure(input, c, configs, speculative)) { return(true); } } } return(false); }
protected internal virtual ATNConfigSet ComputeStartState(ICharStream input, ATNState p) { PredictionContext initialContext = PredictionContext.EmptyFull; ATNConfigSet configs = new OrderedATNConfigSet(); for (int i = 0; i < p.NumberOfTransitions; i++) { ATNState target = p.Transition(i).target; ATNConfig c = ATNConfig.Create(target, i + 1, initialContext); Closure(input, c, configs, false, false, false); } return(configs); }
/// <summary> /// Compute set of tokens that can follow /// <code>s</code> /// in the ATN in the /// specified /// <code>ctx</code> /// . /// <p/> /// If /// <code>ctx</code> /// is /// <see cref="PredictionContext.EmptyLocal">PredictionContext.EmptyLocal</see> /// and /// <code>stopState</code> /// or the end of the rule containing /// <code>s</code> /// is reached, /// <see cref="TokenConstants.Epsilon"/> /// is added to the result set. If /// <code>ctx</code> /// is not /// <see cref="PredictionContext.EmptyLocal">PredictionContext.EmptyLocal</see> /// and /// <code>addEOF</code> /// is /// <code>true</code> /// and /// <code>stopState</code> /// or the end of the outermost rule is reached, /// <see cref="TokenConstants.Eof"/> /// is added to the result set. /// </summary> /// <param name="s">the ATN state.</param> /// <param name="stopState"> /// the ATN state to stop at. This can be a /// <see cref="BlockEndState">BlockEndState</see> /// to detect epsilon paths through a closure. /// </param> /// <param name="ctx"> /// The outer context, or /// <see cref="PredictionContext.EmptyLocal">PredictionContext.EmptyLocal</see> /// if /// the outer context should not be used. /// </param> /// <param name="look">The result lookahead set.</param> /// <param name="lookBusy"> /// A set used for preventing epsilon closures in the ATN /// from causing a stack overflow. Outside code should pass /// <code>new HashSet<ATNConfig></code> /// for this argument. /// </param> /// <param name="calledRuleStack"> /// A set used for preventing left recursion in the /// ATN from causing a stack overflow. Outside code should pass /// <code>new BitSet()</code> /// for this argument. /// </param> /// <param name="seeThruPreds"> /// /// <code>true</code> /// to true semantic predicates as /// implicitly /// <code>true</code> /// and "see through them", otherwise /// <code>false</code> /// to treat semantic predicates as opaque and add /// <see cref="HitPred">HitPred</see> /// to the /// result if one is encountered. /// </param> /// <param name="addEOF"> /// Add /// <see cref="TokenConstants.Eof"/> /// to the result if the end of the /// outermost context is reached. This parameter has no effect if /// <code>ctx</code> /// is /// <see cref="PredictionContext.EmptyLocal">PredictionContext.EmptyLocal</see> /// . /// </param> protected internal virtual void Look(ATNState s, ATNState stopState, PredictionContext ctx, IntervalSet look, HashSet <ATNConfig> lookBusy, BitSet calledRuleStack, bool seeThruPreds, bool addEOF) { // System.out.println("_LOOK("+s.stateNumber+", ctx="+ctx); ATNConfig c = ATNConfig.Create(s, 0, ctx); if (!lookBusy.Add(c)) { return; } if (s == stopState) { if (PredictionContext.IsEmptyLocal(ctx)) { look.Add(TokenConstants.Epsilon); return; } else { if (ctx.IsEmpty && addEOF) { look.Add(TokenConstants.Eof); return; } } } if (s is RuleStopState) { if (PredictionContext.IsEmptyLocal(ctx)) { look.Add(TokenConstants.Epsilon); return; } else { if (ctx.IsEmpty && addEOF) { look.Add(TokenConstants.Eof); return; } } for (int i = 0; i < ctx.Size; i++) { if (ctx.GetReturnState(i) != PredictionContext.EmptyFullStateKey) { ATNState returnState = atn.states[ctx.GetReturnState(i)]; // System.out.println("popping back to "+retState); for (int j = 0; j < ctx.Size; j++) { bool removed = calledRuleStack.Get(returnState.ruleIndex); try { calledRuleStack.Clear(returnState.ruleIndex); Look(returnState, stopState, ctx.GetParent(j), look, lookBusy, calledRuleStack, seeThruPreds , addEOF); } finally { if (removed) { calledRuleStack.Set(returnState.ruleIndex); } } } return; } } } int n = s.NumberOfTransitions; for (int i_1 = 0; i_1 < n; i_1++) { Transition t = s.Transition(i_1); if (t.GetType() == typeof(RuleTransition)) { if (calledRuleStack.Get(((RuleTransition)t).target.ruleIndex)) { continue; } PredictionContext newContext = ctx.GetChild(((RuleTransition)t).followState.stateNumber ); try { calledRuleStack.Set(((RuleTransition)t).target.ruleIndex); Look(t.target, stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds , addEOF); } finally { calledRuleStack.Clear(((RuleTransition)t).target.ruleIndex); } } else { if (t is AbstractPredicateTransition) { if (seeThruPreds) { Look(t.target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF ); } else { look.Add(HitPred); } } else { if (t.IsEpsilon) { Look(t.target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF ); } else { if (t.GetType() == typeof(WildcardTransition)) { look.AddAll(IntervalSet.Of(TokenConstants.MinUserTokenType, atn.maxTokenType)); } else { // System.out.println("adding "+ t); IntervalSet set = t.Label; if (set != null) { if (t is NotSetTransition) { set = set.Complement(IntervalSet.Of(TokenConstants.MinUserTokenType, atn.maxTokenType )); } look.AddAll(set); } } } } } } }