Package org.antlr.v4.runtime.atn

Class PredictionContext

java.lang.Object

org.antlr.v4.runtime.atn.PredictionContext

Direct Known Subclasses:

ArrayPredictionContext, SingletonPredictionContext

public abstract class PredictionContext
extends Object

Field Summary

Fields

Modifier and Type	Field	Description
int	cachedHashCode	Stores the computed hash code of this PredictionContext.
static int	EMPTY_RETURN_STATE	Represents $ in an array in full context mode, when $ doesn't mean wildcard: $ + x = [$,x].
int	id

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	PredictionContext(int cachedHashCode)

Method Summary

Modifier and Type	Method	Description
protected static int	calculateEmptyHashCode()
protected static int	calculateHashCode(PredictionContext[] parents, int[] returnStates)
protected static int	calculateHashCode(PredictionContext parent, int returnState)
protected static void	combineCommonParents(PredictionContext[] parents)	Make pass over all M parents; merge any equals() ones.
abstract boolean	equals(Object obj)
static PredictionContext	fromRuleContext(ATN atn, RuleContext outerContext)	Convert a RuleContext tree to a PredictionContext graph.
static List<PredictionContext>	getAllContextNodes(PredictionContext context)
static void	getAllContextNodes_(PredictionContext context, List<PredictionContext> nodes, Map<PredictionContext,PredictionContext> visited)
static PredictionContext	getCachedContext(PredictionContext context, PredictionContextCache contextCache, IdentityHashMap<PredictionContext,PredictionContext> visited)
abstract PredictionContext	getParent(int index)
abstract int	getReturnState(int index)
boolean	hasEmptyPath()
int	hashCode()
boolean	isEmpty()	This means only the EmptyPredictionContext.Instance (wildcard? not sure) context is in set.
static PredictionContext	merge(PredictionContext a, PredictionContext b, boolean rootIsWildcard, DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)
static PredictionContext	mergeArrays(ArrayPredictionContext a, ArrayPredictionContext b, boolean rootIsWildcard, DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)	Merge two ArrayPredictionContext instances.
static PredictionContext	mergeRoot(SingletonPredictionContext a, SingletonPredictionContext b, boolean rootIsWildcard)	Handle case where at least one of a or b is EmptyPredictionContext.Instance.
static PredictionContext	mergeSingletons(SingletonPredictionContext a, SingletonPredictionContext b, boolean rootIsWildcard, DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)	Merge two SingletonPredictionContext instances.
abstract int	size()
static String	toDOTString(PredictionContext context)
String	toString(Recognizer<?,?> recog)
String[]	toStrings(Recognizer<?,?> recognizer, int currentState)
String[]	toStrings(Recognizer<?,?> recognizer, PredictionContext stop, int currentState)

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

EMPTY_RETURN_STATE

public static final int EMPTY_RETURN_STATE

Represents $ in an array in full context mode, when $ doesn't mean wildcard: $ + x = [$,x]. Here, $ = EMPTY_RETURN_STATE.

See Also:

Constant Field Values

id

public final int id

cachedHashCode

public final int cachedHashCode

Stores the computed hash code of this PredictionContext. The hash code is computed in parts to match the following reference algorithm.

  private int referenceHashCode() {
      int hash = MurmurHash.initialize(INITIAL_HASH);

      for (int i = 0; i < size(); i++) {
          hash = MurmurHash.update(hash, getParent(i));
      }

      for (int i = 0; i < size(); i++) {
          hash = MurmurHash.update(hash, getReturnState(i));
      }

      hash = MurmurHash.finish(hash, 2 * size());
      return hash;
  }
 

Constructor Detail

PredictionContext

protected PredictionContext(int cachedHashCode)

Method Detail

fromRuleContext

public static PredictionContext fromRuleContext(ATN atn,
                                                RuleContext outerContext)

Convert a RuleContext tree to a PredictionContext graph. Return EmptyPredictionContext.Instance if outerContext is empty or null.

size

public abstract int size()

getParent

public abstract PredictionContext getParent(int index)

getReturnState

public abstract int getReturnState(int index)

isEmpty

public boolean isEmpty()

This means only the EmptyPredictionContext.Instance (wildcard? not sure) context is in set.

hasEmptyPath

public boolean hasEmptyPath()

hashCode

public final int hashCode()

Overrides:

hashCode in class Object

equals

public abstract boolean equals(Object obj)

Overrides:

equals in class Object

calculateEmptyHashCode

protected static int calculateEmptyHashCode()

calculateHashCode

protected static int calculateHashCode(PredictionContext parent,
                                       int returnState)

calculateHashCode

protected static int calculateHashCode(PredictionContext[] parents,
                                       int[] returnStates)

merge

public static PredictionContext merge(PredictionContext a,
                                      PredictionContext b,
                                      boolean rootIsWildcard,
                                      DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)

mergeSingletons

public static PredictionContext mergeSingletons(SingletonPredictionContext a,
                                                SingletonPredictionContext b,
                                                boolean rootIsWildcard,
                                                DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)

Merge two SingletonPredictionContext instances.

Stack tops equal, parents merge is same; return left graph.

Same stack top, parents differ; merge parents giving array node, then remainders of those graphs. A new root node is created to point to the merged parents.

Different stack tops pointing to same parent. Make array node for the root where both element in the root point to the same (original) parent.

Different stack tops pointing to different parents. Make array node for the root where each element points to the corresponding original parent.

Parameters:

a - the first SingletonPredictionContext

b - the second SingletonPredictionContext

rootIsWildcard - true if this is a local-context merge, otherwise false to indicate a full-context merge

mergeCache -

mergeRoot

public static PredictionContext mergeRoot(SingletonPredictionContext a,
                                          SingletonPredictionContext b,
                                          boolean rootIsWildcard)

Handle case where at least one of a or b is EmptyPredictionContext.Instance. In the following diagrams, the symbol $ is used to represent EmptyPredictionContext.Instance.

Local-Context Merges

These local-context merge operations are used when rootIsWildcard is true.

EmptyPredictionContext.Instance is superset of any graph; return EmptyPredictionContext.Instance.

EmptyPredictionContext.Instance and anything is #EMPTY, so merged parent is #EMPTY; return left graph.

Special case of last merge if local context.

Full-Context Merges

These full-context merge operations are used when rootIsWildcard is false.

Must keep all contexts; EmptyPredictionContext.Instance in array is a special value (and null parent).

Parameters:

a - the first SingletonPredictionContext

b - the second SingletonPredictionContext

rootIsWildcard - true if this is a local-context merge, otherwise false to indicate a full-context merge

mergeArrays

public static PredictionContext mergeArrays(ArrayPredictionContext a,
                                            ArrayPredictionContext b,
                                            boolean rootIsWildcard,
                                            DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache)

Merge two ArrayPredictionContext instances.

Different tops, different parents.

Shared top, same parents.

Shared top, different parents.

Shared top, all shared parents.

Equal tops, merge parents and reduce top to SingletonPredictionContext.

combineCommonParents

protected static void combineCommonParents(PredictionContext[] parents)

Make pass over all M parents; merge any equals() ones.

toDOTString

public static String toDOTString(PredictionContext context)

getCachedContext

public static PredictionContext getCachedContext(PredictionContext context,
                                                 PredictionContextCache contextCache,
                                                 IdentityHashMap<PredictionContext,PredictionContext> visited)

getAllContextNodes

public static List<PredictionContext> getAllContextNodes(PredictionContext context)

getAllContextNodes_

public static void getAllContextNodes_(PredictionContext context,
                                       List<PredictionContext> nodes,
                                       Map<PredictionContext,PredictionContext> visited)

toString

public String toString(Recognizer<?,?> recog)

toStrings

public String[] toStrings(Recognizer<?,?> recognizer,
                          int currentState)

toStrings

public String[] toStrings(Recognizer<?,?> recognizer,
                          PredictionContext stop,
                          int currentState)