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 Details

    • 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:

  • Constructor Details

    • DFA

      public DFA()

  • Method Details

    • 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 :(