org.antlr.runtime

Class DFA

java.lang.Object

org.antlr.runtime.DFA

public class DFA
extends Object

A DFA implemented as a set of transition tables. Any state that has a semantic predicate edge is special; those states are generated with if-then-else structures in a specialStateTransition() which is generated by cyclicDFA template. There are at most 32767 states (16-bit signed short). Could get away with byte sometimes but would have to generate different types and the simulation code too. For a point of reference, the Java lexer's Tokens rule DFA has 326 states roughly.

Field Summary

Fields

Modifier and Type	Field and Description
protected short[]	accept
static boolean	debug
protected int	decisionNumber
protected short[]	eof
protected short[]	eot
protected char[]	max
protected char[]	min
protected BaseRecognizer	recognizer Which recognizer encloses this DFA? Needed to check backtracking
protected short[]	special
protected short[][]	transition

Constructor Summary

Constructors

Constructor and Description
DFA()

Method Summary

Methods

Modifier and Type	Method and Description
protected void	error(NoViableAltException nvae) A hook for debugging interface
String	getDescription()
protected void	noViableAlt(int s, IntStream input)
int	predict(IntStream input) From the input stream, predict what alternative will succeed using this DFA (representing the covering regular approximation to the underlying CFL).
int	specialStateTransition(int s, IntStream input)
static short[]	unpackEncodedString(String encodedString) Given a String that has a run-length-encoding of some unsigned shorts like "\1\2\3\9", convert to short[] {2,9,9,9}.
static char[]	unpackEncodedStringToUnsignedChars(String encodedString) Hideous duplication of code, but I need different typed arrays out :(

Methods inherited from class java.lang.Object

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

Field Detail

eot

protected short[] eot

eof

protected short[] eof

min

protected char[] min

max

protected char[] max

accept

protected short[] accept

special

protected short[] special

transition

protected short[][] transition

decisionNumber

protected int decisionNumber

recognizer

protected BaseRecognizer recognizer

Which recognizer encloses this DFA? Needed to check backtracking

debug

public static final boolean debug

See Also:

Constant Field Values

Constructor Detail

DFA

public DFA()

Method Detail

predict

public int predict(IntStream input)
            throws RecognitionException

From the input stream, predict what alternative will succeed using this DFA (representing the covering regular approximation to the underlying CFL). Return an alternative number 1..n. Throw an exception upon error.

Throws:

RecognitionException

noViableAlt

protected void noViableAlt(int s,
               IntStream input)
                    throws NoViableAltException

Throws:

NoViableAltException

error

protected void error(NoViableAltException nvae)

A hook for debugging interface

specialStateTransition

public int specialStateTransition(int s,
                         IntStream input)
                           throws NoViableAltException

Throws:

NoViableAltException

getDescription

public String getDescription()

unpackEncodedString

public static short[] unpackEncodedString(String encodedString)

Given a String that has a run-length-encoding of some unsigned shorts like "\1\2\3\9", convert to short[] {2,9,9,9}. We do this to avoid static short[] which generates so much init code that the class won't compile. :(

unpackEncodedStringToUnsignedChars

public static char[] unpackEncodedStringToUnsignedChars(String encodedString)

Hideous duplication of code, but I need different typed arrays out :(