Package org.antlr.v4.runtime.atn

Class ReachConfigSource

java.lang.Object

org.antlr.v4.runtime.atn.ReachConfigSource

final class ReachConfigSource
extends Object

Random-access view of ATN configurations for a single ParserATNSimulator.computeTargetState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState, org.antlr.v4.runtime.ParserRuleContext, int, boolean, org.antlr.v4.runtime.atn.PredictionContextCache) invocation.

Starts as a zero-allocation view over the source ATNConfigSet. When full-context prediction must rewrite every config with an appended return state, the view materializes a mutable list once and all subsequent reads go through that list. Callers iterate with size() / get(int) only — no dual-null checks in the reach loop.

PERF: A single instance is retained on ReachComputation (one per ParserATNSimulator) and rebound via reset(ATNConfigSet)/release() around each edge so the view object and the full-context rewrite ArrayList keep capacity across predictions. SLL paths never touch the list.

Package-private: owned by the ATN prediction hot path.

Field Summary

Fields

Modifier and Type	Field	Description
private ArrayList<ATNConfig>	list	Active read source after the first appendContext(int, org.antlr.v4.runtime.atn.PredictionContextCache); null while still viewing set directly.
private ArrayList<ATNConfig>	rewriteScratch	Capacity-preserving rewrite buffer.
private ATNConfigSet	set

Constructor Summary

Constructors

Constructor	Description
ReachConfigSource()

Method Summary

Modifier and Type	Method	Description
(package private) void	appendContext(int returnState, PredictionContextCache contextCache)	Appends returnState to every configuration's prediction context.
(package private) ATNConfig	get(int index)
(package private) boolean	isMaterialized()	Whether this source has materialized a mutable list (full-context rewrite path).
(package private) void	release()	Drop config-graph references held by the rewrite buffer; keep list capacity.
(package private) void	reset(ATNConfigSet set)	Bind this source to set for a new edge computation.
(package private) ArrayList<ATNConfig>	rewriteScratch()	Retained rewrite scratch after first materialization, else null.
(package private) int	size()

Methods inherited from class java.lang.Object

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

Field Details

set

@Nullable
private ATNConfigSet set

list

@Nullable
private ArrayList<ATNConfig> list

Active read source after the first appendContext(int, org.antlr.v4.runtime.atn.PredictionContextCache); null while still viewing set directly.

rewriteScratch

@Nullable
private ArrayList<ATNConfig> rewriteScratch

Capacity-preserving rewrite buffer. Assigned to list on first materialization; cleared by release().

Constructor Details

ReachConfigSource

ReachConfigSource()

Method Details

reset

void reset(@NotNull
 ATNConfigSet set)

Bind this source to set for a new edge computation. Always starts as a zero-copy view (no materialization).

release

void release()

Drop config-graph references held by the rewrite buffer; keep list capacity. Safe to call when reset(org.antlr.v4.runtime.atn.ATNConfigSet) was never invoked.

After release(), this view is invalid until the next reset(ATNConfigSet). size() / get(int) throw IllegalStateException if used while unbound.

size

int size()

get

@NotNull
ATNConfig get(int index)

appendContext

void appendContext(int returnState,
 @NotNull
 PredictionContextCache contextCache)

Appends returnState to every configuration's prediction context. Materializes a mutable copy of the source set on first call, reusing the retained rewrite scratch list when available.

isMaterialized

boolean isMaterialized()

Whether this source has materialized a mutable list (full-context rewrite path). Package-private for tests.

rewriteScratch

@Nullable
ArrayList<ATNConfig> rewriteScratch()

Retained rewrite scratch after first materialization, else null. Same-package tests may observe capacity-preserving reuse.