Package org.antlr.runtime.debug

Class DebugEventHub

  • All Implemented Interfaces:
    DebugEventListener
    public class DebugEventHub
extends Object
implements DebugEventListener
    Broadcast debug events to multiple listeners. Lets you debug and still use the event mechanism to build parse trees etc... Not thread-safe. Don't add events in one thread while parser fires events in another.
    See Also:
    DebugEventRepeater

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void addChild​(Object root, Object child)
      Make childID a child of rootID.
      void addListener​(DebugEventListener listener)
      Add another listener to broadcast events too.
      void becomeRoot​(Object newRoot, Object oldRoot)
      Make a node the new root of an existing root.
      void beginBacktrack​(int level)  
      void beginResync()
      Indicates the recognizer is about to consume tokens to resynchronize the parser.
      void commence()
      Announce that parsing has begun.
      void consumeHiddenToken​(Token token)
      An off-channel input token was consumed.
      void consumeNode​(Object t)
      Input for a tree parser is an AST, but we know nothing for sure about a node except its type and text (obtained from the adaptor).
      void consumeToken​(Token token)
      An input token was consumed; matched by any kind of element.
      void createNode​(Object t)
      Announce a new node built from token elements such as type etc...
      void createNode​(Object node, Token token)
      Announce a new node built from an existing token.
      void endBacktrack​(int level, boolean successful)  
      void endResync()
      Indicates that the recognizer has finished consuming tokens in order to resychronize.
      void enterAlt​(int alt)
      Because rules can have lots of alternatives, it is very useful to know which alt you are entering.
      void enterDecision​(int decisionNumber, boolean couldBacktrack)
      Every decision, fixed k or arbitrary, has an enter/exit event so that a GUI can easily track what LT/consume events are associated with prediction.
      void enterRule​(String grammarFileName, String ruleName)
      The parser has just entered a rule.
      void enterSubRule​(int decisionNumber)
      Track entry into any (...) subrule other EBNF construct
      void errorNode​(Object t)
      Upon syntax error, recognizers bracket the error with an error node if they are building ASTs.
      void exitDecision​(int decisionNumber)  
      void exitRule​(String grammarFileName, String ruleName)
      This is the last thing executed before leaving a rule.
      void exitSubRule​(int decisionNumber)  
      void location​(int line, int pos)
      To watch a parser move through the grammar, the parser needs to inform the debugger what line/charPos it is passing in the grammar.
      void LT​(int index, Object t)
      The tree parser lookedahead.
      void LT​(int index, Token t)
      Somebody (anybody) looked ahead.
      void mark​(int index)
      The parser is going to look arbitrarily ahead; mark this location, the token stream's marker is sent in case you need it.
      void nilNode​(Object t)
      A nil was created (even nil nodes have a unique ID...
      void recognitionException​(RecognitionException e)
      A recognition exception occurred such as NoViableAltException.
      void rewind()
      Rewind to the input position of the last marker.
      void rewind​(int index)
      After an arbitrairly long lookahead as with a cyclic DFA (or with any backtrack), this informs the debugger that stream should be rewound to the position associated with marker.
      void semanticPredicate​(boolean result, String predicate)
      A semantic predicate was evaluate with this result and action text
      void setTokenBoundaries​(Object t, int tokenStartIndex, int tokenStopIndex)
      Set the token start/stop token index for a subtree root or node.
      void terminate()
      Parsing is over; successfully or not.

    • Method Detail

      • addListener

        public void addListener​(DebugEventListener listener)
        Add another listener to broadcast events too. Not thread-safe. Don't add events in one thread while parser fires events in another.

      • enterRule

        public void enterRule​(String grammarFileName,
                      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

      • exitRule

        public void exitRule​(String grammarFileName,
                     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

      • enterAlt

        public void enterAlt​(int alt)
        Description copied from interface: DebugEventListener
        Because rules can have lots of alternatives, it is very useful to know which alt you are entering. This is 1..n for n alts.
        Specified by:
        enterAlt in interface DebugEventListener

      • enterDecision

        public void enterDecision​(int decisionNumber,
                          boolean couldBacktrack)
        Description copied from interface: DebugEventListener
        Every decision, fixed k or arbitrary, has an enter/exit event so that a GUI can easily track what LT/consume events are associated with prediction. You will see a single enter/exit subrule but multiple enter/exit decision events, one for each loop iteration.
        Specified by:
        enterDecision in interface DebugEventListener

      • location

        public void location​(int line,
                     int pos)
        Description copied from interface: DebugEventListener
        To watch a parser move through the grammar, the parser needs to inform the debugger what line/charPos it is passing in the grammar. For now, this does not know how to switch from one grammar to the other and back for island grammars etc... This should also allow breakpoints because the debugger can stop the parser whenever it hits this line/pos.
        Specified by:
        location in interface DebugEventListener

      • consumeToken

        public void consumeToken​(Token token)
        Description copied from interface: DebugEventListener
        An input token was consumed; matched by any kind of element. Trigger after the token was matched by things like match(), matchAny().
        Specified by:
        consumeToken in interface DebugEventListener

      • consumeHiddenToken

        public void consumeHiddenToken​(Token token)
        Description copied from interface: DebugEventListener
        An off-channel input token was consumed. Trigger after the token was matched by things like match(), matchAny(). (unless of course the hidden token is first stuff in the input stream).
        Specified by:
        consumeHiddenToken in interface DebugEventListener

      • LT

        public void LT​(int index,
               Token t)
        Description copied from interface: DebugEventListener
        Somebody (anybody) looked ahead. Note that this actually gets triggered by both LA and LT calls. The debugger will want to know which Token object was examined. Like consumeToken, this indicates what token was seen at that depth. A remote debugger cannot look ahead into a file it doesn't have so LT events must pass the token even if the info is redundant.
        Specified by:
        LT in interface DebugEventListener

      • mark

        public void mark​(int index)
        Description copied from interface: DebugEventListener
        The parser is going to look arbitrarily ahead; mark this location, the token stream's marker is sent in case you need it.
        Specified by:
        mark in interface DebugEventListener

      • rewind

        public void rewind​(int index)
        Description copied from interface: DebugEventListener
        After an arbitrairly long lookahead as with a cyclic DFA (or with any backtrack), this informs the debugger that stream should be rewound to the position associated with marker.
        Specified by:
        rewind in interface DebugEventListener

      • rewind

        public void rewind()
        Description copied from interface: DebugEventListener
        Rewind to the input position of the last marker. Used currently only after a cyclic DFA and just before starting a sem/syn predicate to get the input position back to the start of the decision. Do not "pop" the marker off the state. mark(i) and rewind(i) should balance still.
        Specified by:
        rewind in interface DebugEventListener

      • 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

      • beginResync

        public void beginResync()
        Description copied from interface: DebugEventListener
        Indicates the recognizer is about to consume tokens to resynchronize the parser. Any consume events from here until the recovered event are not part of the parse--they are dead tokens.
        Specified by:
        beginResync in interface DebugEventListener

      • endResync

        public void endResync()
        Description copied from interface: DebugEventListener
        Indicates that the recognizer has finished consuming tokens in order to resychronize. There may be multiple beginResync/endResync pairs before the recognizer comes out of errorRecovery mode (in which multiple errors are suppressed). This will be useful in a gui where you want to probably grey out tokens that are consumed but not matched to anything in grammar. Anything between a beginResync/endResync pair was tossed out by the parser.
        Specified by:
        endResync in interface DebugEventListener

      • commence

        public void commence()
        Description copied from interface: DebugEventListener
        Announce that parsing has begun. Not technically useful except for sending events over a socket. A GUI for example will launch a thread to connect and communicate with a remote parser. The thread will want to notify the GUI when a connection is made. ANTLR parsers trigger this upon entry to the first rule (the ruleLevel is used to figure this out).
        Specified by:
        commence in interface DebugEventListener

      • terminate

        public void terminate()
        Description copied from interface: DebugEventListener
        Parsing is over; successfully or not. Mostly useful for telling remote debugging listeners that it's time to quit. When the rule invocation level goes to zero at the end of a rule, we are done parsing.
        Specified by:
        terminate in interface DebugEventListener

      • consumeNode

        public void consumeNode​(Object t)
        Description copied from interface: DebugEventListener
        Input for a tree parser is an AST, but we know nothing for sure about a node except its type and text (obtained from the adaptor). This is the analog of the consumeToken method. Again, the ID is the hashCode usually of the node so it only works if hashCode is not implemented. If the type is UP or DOWN, then the ID is not really meaningful as it's fixed--there is just one UP node and one DOWN navigation node.
        Specified by:
        consumeNode in interface DebugEventListener

      • LT

        public void LT​(int index,
               Object t)
        Description copied from interface: DebugEventListener
        The tree parser lookedahead. If the type is UP or DOWN, then the ID is not really meaningful as it's fixed--there is just one UP node and one DOWN navigation node.
        Specified by:
        LT in interface DebugEventListener

      • nilNode

        public void nilNode​(Object t)
        Description copied from interface: DebugEventListener
        A nil was created (even nil nodes have a unique ID... they are not "null" per se). As of 4/28/2006, this seems to be uniquely triggered when starting a new subtree such as when entering a subrule in automatic mode and when building a tree in rewrite mode. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only t.ID is set.
        Specified by:
        nilNode in interface DebugEventListener

      • errorNode

        public void errorNode​(Object t)
        Description copied from interface: DebugEventListener
        Upon syntax error, recognizers bracket the error with an error node if they are building ASTs.
        Specified by:
        errorNode in interface DebugEventListener

      • createNode

        public void createNode​(Object t)
        Description copied from interface: DebugEventListener
        Announce a new node built from token elements such as type etc... If you are receiving this event over a socket via RemoteDebugEventSocketListener then only t.ID, type, text are set.
        Specified by:
        createNode in interface DebugEventListener

      • createNode

        public void createNode​(Object node,
                       Token token)
        Description copied from interface: DebugEventListener
        Announce a new node built from an existing token. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only node.ID and token.tokenIndex are set.
        Specified by:
        createNode in interface DebugEventListener

      • becomeRoot

        public void becomeRoot​(Object newRoot,
                       Object oldRoot)
        Description copied from interface: DebugEventListener
        Make a node the new root of an existing root. See Note: the newRootID parameter is possibly different than the TreeAdaptor.becomeRoot() newRoot parameter. In our case, it will always be the result of calling TreeAdaptor.becomeRoot() and not root_n or whatever. The listener should assume that this event occurs only when the current subrule (or rule) subtree is being reset to newRootID. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only IDs are set.
        Specified by:
        becomeRoot in interface DebugEventListener
        See Also:
        TreeAdaptor.becomeRoot(java.lang.Object, java.lang.Object)

      • setTokenBoundaries

        public void setTokenBoundaries​(Object t,
                               int tokenStartIndex,
                               int tokenStopIndex)
        Description copied from interface: DebugEventListener
        Set the token start/stop token index for a subtree root or node. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only t.ID is set.
        Specified by:
        setTokenBoundaries in interface DebugEventListener