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/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.runtime.atn;

import org.antlr.v4.runtime.Recognizer;
import org.antlr.v4.runtime.misc.MurmurHash;

/** A tuple: (ATN state, predicted alt, syntactic, semantic context).
 *  The syntactic context is a graph-structured stack node whose
 *  path(s) to the root is the rule invocation(s)
 *  chain used to arrive at the state.  The semantic context is
 *  the tree of semantic predicates encountered before reaching
 *  an ATN state.
 */
public class ATNConfig {
	/**
	 * This field stores the bit mask for implementing the
	 * {@link #isPrecedenceFilterSuppressed} property as a bit within the
	 * existing {@link #reachesIntoOuterContext} field.
	 */
	private static final int SUPPRESS_PRECEDENCE_FILTER = 0x40000000;

	/** The ATN state associated with this configuration */
	public final ATNState state;

	/** What alt (or lexer rule) is predicted by this configuration */
	public final int alt;

	/** The stack of invoking states leading to the rule/states associated
	 *  with this config.  We track only those contexts pushed during
	 *  execution of the ATN simulator.
	 */
	public PredictionContext context;

	/**
	 * We cannot execute predicates dependent upon local context unless
	 * we know for sure we are in the correct context. Because there is
	 * no way to do this efficiently, we simply cannot evaluate
	 * dependent predicates unless we are in the rule that initially
	 * invokes the ATN simulator.
	 *
	 * 

* closure() tracks the depth of how far we dip into the outer context: * depth > 0. Note that it may not be totally accurate depth since I * don't ever decrement. TODO: make it a boolean then

* *

* For memory efficiency, the {@link #isPrecedenceFilterSuppressed} method * is also backed by this field. Since the field is publicly accessible, the * highest bit which would not cause the value to become negative is used to * store this field. This choice minimizes the risk that code which only * compares this value to 0 would be affected by the new purpose of the * flag. It also ensures the performance of the existing {@link ATNConfig} * constructors as well as certain operations like * {@link ATNConfigSet#add(ATNConfig, DoubleKeyMap)} method are * completely unaffected by the change.

*/ public int reachesIntoOuterContext; public final SemanticContext semanticContext; public ATNConfig(ATNConfig old) { // dup this.state = old.state; this.alt = old.alt; this.context = old.context; this.semanticContext = old.semanticContext; this.reachesIntoOuterContext = old.reachesIntoOuterContext; } public ATNConfig(ATNState state, int alt, PredictionContext context) { this(state, alt, context, SemanticContext.NONE); } public ATNConfig(ATNState state, int alt, PredictionContext context, SemanticContext semanticContext) { this.state = state; this.alt = alt; this.context = context; this.semanticContext = semanticContext; } public ATNConfig(ATNConfig c, ATNState state) { this(c, state, c.context, c.semanticContext); } public ATNConfig(ATNConfig c, ATNState state, SemanticContext semanticContext) { this(c, state, c.context, semanticContext); } public ATNConfig(ATNConfig c, SemanticContext semanticContext) { this(c, c.state, c.context, semanticContext); } public ATNConfig(ATNConfig c, ATNState state, PredictionContext context) { this(c, state, context, c.semanticContext); } public ATNConfig(ATNConfig c, ATNState state, PredictionContext context, SemanticContext semanticContext) { this.state = state; this.alt = c.alt; this.context = context; this.semanticContext = semanticContext; this.reachesIntoOuterContext = c.reachesIntoOuterContext; } /** * This method gets the value of the {@link #reachesIntoOuterContext} field * as it existed prior to the introduction of the * {@link #isPrecedenceFilterSuppressed} method. */ public final int getOuterContextDepth() { return reachesIntoOuterContext & ~SUPPRESS_PRECEDENCE_FILTER; } public final boolean isPrecedenceFilterSuppressed() { return (reachesIntoOuterContext & SUPPRESS_PRECEDENCE_FILTER) != 0; } public final void setPrecedenceFilterSuppressed(boolean value) { if (value) { this.reachesIntoOuterContext |= 0x40000000; } else { this.reachesIntoOuterContext &= ~SUPPRESS_PRECEDENCE_FILTER; } } /** An ATN configuration is equal to another if both have * the same state, they predict the same alternative, and * syntactic/semantic contexts are the same. */ @Override public boolean equals(Object o) { if (!(o instanceof ATNConfig)) { return false; } return this.equals((ATNConfig)o); } public boolean equals(ATNConfig other) { if (this == other) { return true; } else if (other == null) { return false; } return this.state.stateNumber==other.state.stateNumber && this.alt==other.alt && (this.context==other.context || (this.context != null && this.context.equals(other.context))) && this.semanticContext.equals(other.semanticContext) && this.isPrecedenceFilterSuppressed() == other.isPrecedenceFilterSuppressed(); } @Override public int hashCode() { int hashCode = MurmurHash.initialize(7); hashCode = MurmurHash.update(hashCode, state.stateNumber); hashCode = MurmurHash.update(hashCode, alt); hashCode = MurmurHash.update(hashCode, context); hashCode = MurmurHash.update(hashCode, semanticContext); hashCode = MurmurHash.finish(hashCode, 4); return hashCode; } @Override public String toString() { return toString(null, true); } public String toString(Recognizer recog, boolean showAlt) { StringBuilder buf = new StringBuilder(); // if ( state.ruleIndex>=0 ) { // if ( recog!=null ) buf.append(recog.getRuleNames()[state.ruleIndex]+":"); // else buf.append(state.ruleIndex+":"); // } buf.append('('); buf.append(state); if ( showAlt ) { buf.append(","); buf.append(alt); } if ( context!=null ) { buf.append(",["); buf.append(context.toString()); buf.append("]"); } if ( semanticContext!=null && semanticContext != SemanticContext.NONE ) { buf.append(","); buf.append(semanticContext); } if ( getOuterContextDepth()>0 ) { buf.append(",up=").append(getOuterContextDepth()); } buf.append(')'); return buf.toString(); } }




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