org.antlr.runtime.debug
Class ParseTreeBuilder

java.lang.Object
  org.antlr.runtime.debug.BlankDebugEventListener
      org.antlr.runtime.debug.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.

Field Summary

static String

EPSILON_PAYLOAD

Fields inherited from interface org.antlr.runtime.debug.DebugEventListener

FALSE, PROTOCOL_VERSION, TRUE

Constructor Summary

ParseTreeBuilder(String grammarName)

Method Summary

void	consumeHiddenToken(Token token) An off-channel input token was consumed.
void	consumeToken(Token token) An input token was consumed; matched by any kind of element.
ParseTree	create(Object payload) What kind of node to create.
void	enterDecision(int d, boolean couldBacktrack) Backtracking or cyclic DFA, don't want to add nodes to tree
void	enterRule(String filename, String ruleName) The parser has just entered a rule.
ParseTree	epsilonNode()
void	exitDecision(int i)
void	exitRule(String filename, String ruleName) This is the last thing executed before leaving a rule.
ParseTree	getTree()
void	recognitionException(RecognitionException e) A recognition exception occurred such as NoViableAltException.

Methods inherited from class org.antlr.runtime.debug.BlankDebugEventListener

addChild, becomeRoot, beginBacktrack, beginResync, commence, consumeNode, createNode, createNode, endBacktrack, endResync, enterAlt, enterSubRule, errorNode, exitSubRule, location, LT, LT, mark, nilNode, rewind, rewind, semanticPredicate, setTokenBoundaries, terminate

Methods inherited from class java.lang.Object

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

Field Detail

EPSILON_PAYLOAD

public static final String EPSILON_PAYLOAD

See Also:

Constant Field Values

Constructor Detail

ParseTreeBuilder

public ParseTreeBuilder(String grammarName)

Method Detail

getTree

public ParseTree getTree()

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()

enterDecision

public void enterDecision(int d,
                          boolean couldBacktrack)

Backtracking or cyclic DFA, don't want to add nodes to tree

Specified by:

enterDecision in interface DebugEventListener

Overrides:

enterDecision in class BlankDebugEventListener

exitDecision

public void exitDecision(int i)

Specified by:

exitDecision in interface DebugEventListener

Overrides:

exitDecision in class BlankDebugEventListener

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

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

Overrides:

consumeToken in class BlankDebugEventListener

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

Overrides:

consumeHiddenToken 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