org.antlr.v4.runtime.dfa

Class DFA

java.lang.Object

org.antlr.v4.runtime.dfa.DFA

public class DFA
extends Object

Field Summary

Fields

Modifier and Type	Field and Description
ATNState	atnStartState From which ATN state did we create this DFA?
int	decision
AtomicReference<DFAState>	s0 This is the start state for SLL prediction.
AtomicReference<DFAState>	s0full This is the start state for full context prediction.
ConcurrentMap<DFAState,DFAState>	states A set of all DFA states.

Constructor Summary

Constructors

Constructor and Description
DFA(ATNState atnStartState) Constructs a DFA instance associated with a lexer mode.
DFA(ATNState atnStartState, int decision) Constructs a DFA instance associated with a decision.

Method Summary

Modifier and Type	Method and Description
DFAState	addState(DFAState state)
EmptyEdgeMap<DFAState>	getEmptyContextEdgeMap() Gets an empty edge map initialized with the minimum and maximum context values allowed to be stored in this DFA.
EmptyEdgeMap<DFAState>	getEmptyEdgeMap() Gets an empty edge map initialized with the minimum and maximum symbol values allowed to be stored in this DFA.
int	getMaxDfaEdge() Gets the maximum input symbol value which can be stored in this DFA.
int	getMinDfaEdge() Gets the minimum input symbol value which can be stored in this DFA.
DFAState	getPrecedenceStartState(int precedence, boolean fullContext) Get the start state for a specific precedence value.
boolean	isContextSensitive()
boolean	isEmpty()
boolean	isPrecedenceDfa() Gets whether this DFA is a precedence DFA.
void	setPrecedenceDfa(boolean precedenceDfa) Deprecated. This method no longer performs any action.
void	setPrecedenceStartState(int precedence, boolean fullContext, DFAState startState) Set the start state for a specific precedence value.
String	toLexerString()
String	toString()
String	toString(String[] tokenNames) Deprecated. Use toString(Vocabulary) instead.
String	toString(String[] tokenNames, String[] ruleNames) Deprecated. Use toString(Vocabulary, String[]) instead.
String	toString(Vocabulary vocabulary)
String	toString(Vocabulary vocabulary, String[] ruleNames)

Methods inherited from class java.lang.Object

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

Field Detail

states

@NotNull
public final ConcurrentMap<DFAState,DFAState> states

A set of all DFA states. Use Map so we can get old state back (Set only allows you to see if it's there).

Note that this collection of states holds the DFA states for both SLL and LL prediction. Only the start state needs to be differentiated for these cases, which is tracked by the s0 and s0full fields.

s0

@NotNull
public final AtomicReference<DFAState> s0

This is the start state for SLL prediction.

When isPrecedenceDfa() is true, this state is not used directly. Rather, getPrecedenceStartState(int, boolean) is used to obtain the true SLL start state by traversing an outgoing edge corresponding to the current precedence level in the parser.

s0full

@NotNull
public final AtomicReference<DFAState> s0full

This is the start state for full context prediction.

See Also:

s0

decision

public final int decision

atnStartState

@NotNull
public final ATNState atnStartState

From which ATN state did we create this DFA?

Constructor Detail

DFA

public DFA(@NotNull
           ATNState atnStartState)

Constructs a DFA instance associated with a lexer mode.

The start state for a DFA constructed with this method should be a TokensStartState, which is the start state for a lexer mode. The prediction made by this DFA determines the lexer rule which matches the current input.

Parameters:

atnStartState - The start state for the mode.

DFA

public DFA(@NotNull
           ATNState atnStartState,
           int decision)

Constructs a DFA instance associated with a decision.

Parameters:

atnStartState - The decision associated with this DFA.

decision - The decision number.

Method Detail

getMinDfaEdge

public final int getMinDfaEdge()

Gets the minimum input symbol value which can be stored in this DFA.

Returns:

The minimum input symbol which can be stored in this DFA.

See Also:

getEmptyEdgeMap()

getMaxDfaEdge

public final int getMaxDfaEdge()

Gets the maximum input symbol value which can be stored in this DFA.

Returns:

The maximum input symbol which can be stored in this DFA.

See Also:

getEmptyEdgeMap()

getEmptyEdgeMap

@NotNull
public EmptyEdgeMap<DFAState> getEmptyEdgeMap()

Gets an empty edge map initialized with the minimum and maximum symbol values allowed to be stored in this DFA.

Setting a range of allowed symbol values for a DFA bounds the memory overhead for storing the map of outgoing edges. The various implementations of EdgeMap use this range to determine the best memory savings will be obtained from sparse storage (e.g. SingletonEdgeMap or SparseEdgeMap) or dense storage (ArrayEdgeMap). Symbols values outside the range are supported during prediction, but since DFA edges are never created for these symbols they will always recompute the target state through a match and closure operation.

Empty edge maps are immutable objects which track the allowed range of input symbols that can be stored as edges in the DFA. By storing an empty edge map instance in the DFA, new instances of DFAState created for the DFA can be initialized with a non-null outgoing edge map with the proper symbol range without incurring extra allocations.

Returns:

The empty edge map used for initializing DFAState instances associated with this DFA.

getEmptyContextEdgeMap

@NotNull
public EmptyEdgeMap<DFAState> getEmptyContextEdgeMap()

Gets an empty edge map initialized with the minimum and maximum context values allowed to be stored in this DFA.

The value assigned to a context edge within the DFA is an ATN state number, so the range of allowed values for the context edge map is ATNState.INVALID_STATE_NUMBER through the number of states stored in ATN.states for the ATN.

This empty edge map serves a purpose similar to getEmptyEdgeMap(). It is used for initializing DFAState instances without incurring memory overhead for the (especially) common case where no outgoing context edges are added to the DFA state.

Returns:

The empty context edge map used for initializing DFAState instances associated with this DFA.

isPrecedenceDfa

public final boolean isPrecedenceDfa()

Gets whether this DFA is a precedence DFA. Precedence DFAs use a special start state s0 which is not stored in states. The DFAState.edges array for this start state contains outgoing edges supplying individual start states corresponding to specific precedence values.

Returns:

true if this is a precedence DFA; otherwise, false.

See Also:

Parser.getPrecedence()

getPrecedenceStartState

public final DFAState getPrecedenceStartState(int precedence,
                                              boolean fullContext)

Get the start state for a specific precedence value.

Parameters:

precedence - The current precedence.

Returns:

The start state corresponding to the specified precedence, or null if no start state exists for the specified precedence.

Throws:

IllegalStateException - if this is not a precedence DFA.

See Also:

isPrecedenceDfa()

setPrecedenceStartState

public final void setPrecedenceStartState(int precedence,
                                          boolean fullContext,
                                          DFAState startState)

Set the start state for a specific precedence value.

Parameters:

precedence - The current precedence.

startState - The start state corresponding to the specified precedence.

Throws:

IllegalStateException - if this is not a precedence DFA.

See Also:

isPrecedenceDfa()

setPrecedenceDfa

@Deprecated
public final void setPrecedenceDfa(boolean precedenceDfa)

Deprecated. This method no longer performs any action.

Sets whether this is a precedence DFA.

Parameters:

precedenceDfa - true if this is a precedence DFA; otherwise, false

Throws:

UnsupportedOperationException - if precedenceDfa does not match the value of isPrecedenceDfa() for the current DFA.

isEmpty

public boolean isEmpty()

isContextSensitive

public boolean isContextSensitive()

addState

public DFAState addState(DFAState state)

toString

public String toString()

Overrides:

toString in class Object

toString

@Deprecated
public String toString(@Nullable
                                    String[] tokenNames)

Deprecated. Use toString(Vocabulary) instead.

toString

public String toString(@NotNull
                       Vocabulary vocabulary)

toString

@Deprecated
public String toString(@Nullable
                                    String[] tokenNames,
                                    @Nullable
                                    String[] ruleNames)

Deprecated. Use toString(Vocabulary, String[]) instead.

toString

public String toString(@NotNull
                       Vocabulary vocabulary,
                       @Nullable
                       String[] ruleNames)

toLexerString

public String toLexerString()