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With inspiration from other libraries
/*
* 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();
}
}