Handle covert channel in antlr 3

Question

I am writing ANTRL grammar to translate one language into another, but the documentation for using the HIDDEN channel is very scarce. I cannot find an example anywhere. The only thing I found is the FAQ at www.antlr.org, which tells you how to access the hidden channel, but not how best to use this feature. The target language is Java.

In my grammar file, I pass spaces and comments like this:

// Send runs of space and tab characters to the hidden channel.        
WHITESPACE 
    :   (SPACE | TAB)+ { $channel = HIDDEN; }
    ;

// Single-line comments begin with --
SINGLE_COMMENT 
    :    ('--' COMMENT_CHARS NEWLINE) {
            $channel=HIDDEN;
        }
    ;

fragment COMMENT_CHARS 
    :   ~('\r' | '\n')*
    ;

// Treat runs of newline characters as a single NEWLINE token.
NEWLINE 
    :   ('\r'? '\n')+ { $channel = HIDDEN; }
    ;

In the "My Members" section, I defined a method for writing hidden channel tokens to my StringStream output ...

@members {

private int savedIndex = 0;

void ProcessHiddenChannel(TokenStream input) {      
    List<Token> tokens = ((CommonTokenStream)input).getTokens(savedIndex, input.index());
    for(Token token: tokens) {
        if(token.getChannel() == token.HIDDEN_CHANNEL) {
            output.append(token.getText());

        }
    }
    savedIndex = input.index();
}
}

Now, to use this, I have to call the method after every single token in my grammar.

myParserRule
        :       MYTOKEN1 { ProcessHiddenChannel(input); }
                MYTOKEN2 { ProcessHiddenChannel(input); }
        ;

Is there really a better way?

EDIT: This is an example of an input language:

-- -----------------------------------------------------------------
--
--
--  Name                Description
--  ==================================
--  IFM1/183         Freq Spectrum Inversion
--                     
-- -----------------------------------------------------------------

PROCEDURE IFM1/183

TITLE "Freq Spectrum Inversion";

HELP
      Freq Spectrum Inversion

ENDHELP;

PRIVILEGE CTRL;

WINDOW MANDATORY;

INPUT

   $Input : @NO_YES
   DEFAULT select %YES when /IFMS1/183.VALUE = %NO;
                  %NO otherwise
           endselect
   PROMPT "Spec Inv";

   $Forced_Cmd : BOOLEAN
   Default FALSE
   Prompt  "Forced Commanding";

DEFINE
   &RetCode   : @PSTATUS := %OK;
   &msg       : STRING;
   &Input     : BOOLEAN;

REQUIRE AVAILABLE(/IFMS1)
        MSG "IFMS1 not available";

REQUIRE /IFMS1/001.VALUE = %MON_AND_CTRL
        MSG "IFMS1 not in control mode";

BEGIN  -- Procedure Body --

    &msg := "IFMS1/183 -> " + toString($Input) + " : "; 

-- pre-check

   IF /IFMS1/183.VALUE = $Input
      AND $Forced_Cmd = FALSE THEN
      EXIT (%OK, MSG &msg + "already set");
   ENDIF;

-- command

   IF $Input =  %YES THEN &Input:= TRUE;
    ELSE  &Input:= FALSE;
   ENDIF;

   SET &RetCode := SEND IFMS1.FREQPLAN
        ( $FreqSpecInv := &Input);
   IF &RetCode <> %OK THEN
      EXIT (&RetCode, MSG &msg + "command failed");
   ENDIF;

-- verify

   SET &RetCode := VERIFY /IFMS1/183.VALUE = $Input TIMEOUT '10';
   IF &RetCode <> %OK THEN
      EXIT (&RetCode, MSG &msg + "verification failed");
   ELSE
      EXIT (&RetCode, MSG &msg + "verified");
   ENDIF;

END

Answer 1

CommonTokenStream ANTLR. , , , , 3.

.

Answer 2

, , . , - StringTemplate. . ANTLR , "cminus", , .