[antlr-interest] Bit Mask Field Indicator – newbie question

[Ashley Neal Hornbeck]

I need to parse network messages from a legacy system.  The messages use a hex
encoded bit mask that indicates which optional fields are present.  For example:

01T105FOO::BAR

01 -> Message Version number
T1 -> Message Type 1
05 -> Hex encoded bit mask - 0000 0101
FOO -> Optional field position 3 (indicated by 0x04)
:: -> Header terminator
BAR -> Optional payload (indicated by 0x01)

There are a number of message types with similar but different structure for this
system.  I am considering ANTLR as a potential solution so I don't have to hand code
a lexer/parser for each of the variants.  So far the only thing I can figure out is
to define 2^8 tokens with a rather large look ahead – not practical.  Being new to
ANTLR I am either missing something or trying to use the wrong tool.

Guidance please.  Am I missing something or using the wrong tool.  If the wrong
tool, any thoughts on another Java solution? 

Thanks in advance,

-Ash