Class ParseTreeBuilder

  • All Implemented Interfaces:
    DebugEventListener

    public class ParseTreeBuilder
    extends BlankDebugEventListener
    This parser listener tracks rule entry/exit and token matches to build a simple parse tree using ParseTree nodes.
    • Constructor Detail

      • ParseTreeBuilder

        public ParseTreeBuilder​(String grammarName)
    • Method Detail

      • create

        public ParseTree create​(Object payload)
        What kind of node to create. You might want to override so I factored out creation here.
      • epsilonNode

        public ParseTree epsilonNode()
      • enterRule

        public void enterRule​(String filename,
                              String ruleName)
        Description copied from interface: DebugEventListener
        The parser has just entered a rule. No decision has been made about which alt is predicted. This is fired AFTER init actions have been executed. Attributes are defined and available etc... The grammarFileName allows composite grammars to jump around among multiple grammar files.
        Specified by:
        enterRule in interface DebugEventListener
        Overrides:
        enterRule in class BlankDebugEventListener
      • exitRule

        public void exitRule​(String filename,
                             String ruleName)
        Description copied from interface: DebugEventListener
        This is the last thing executed before leaving a rule. It is executed even if an exception is thrown. This is triggered after error reporting and recovery have occurred (unless the exception is not caught in this rule). This implies an "exitAlt" event. The grammarFileName allows composite grammars to jump around among multiple grammar files.
        Specified by:
        exitRule in interface DebugEventListener
        Overrides:
        exitRule in class BlankDebugEventListener
      • recognitionException

        public void recognitionException​(RecognitionException e)
        Description copied from interface: DebugEventListener
        A recognition exception occurred such as NoViableAltException. I made this a generic event so that I can alter the exception hierachy later without having to alter all the debug objects. Upon error, the stack of enter rule/subrule must be properly unwound. If no viable alt occurs it is within an enter/exit decision, which also must be rewound. Even the rewind for each mark must be unwount. In the Java target this is pretty easy using try/finally, if a bit ugly in the generated code. The rewind is generated in DFA.predict() actually so no code needs to be generated for that. For languages w/o this "finally" feature (C++?), the target implementor will have to build an event stack or something. Across a socket for remote debugging, only the RecognitionException data fields are transmitted. The token object or whatever that caused the problem was the last object referenced by LT. The immediately preceding LT event should hold the unexpected Token or char. Here is a sample event trace for grammar: b : C ({;}A|B) // {;} is there to prevent A|B becoming a set | D ; The sequence for this rule (with no viable alt in the subrule) for input 'c c' (there are 3 tokens) is: commence LT(1) enterRule b location 7 1 enter decision 3 LT(1) exit decision 3 enterAlt1 location 7 5 LT(1) consumeToken [c/<4>,1:0] location 7 7 enterSubRule 2 enter decision 2 LT(1) LT(1) recognitionException NoViableAltException 2 1 2 exit decision 2 exitSubRule 2 beginResync LT(1) consumeToken [c/<4>,1:1] LT(1) endResync LT(-1) exitRule b terminate
        Specified by:
        recognitionException in interface DebugEventListener
        Overrides:
        recognitionException in class BlankDebugEventListener