[antlr-interest] Binary support

[kleibi at gmx.net]

Hi,
I searched through the archives and through the ANTLR reference, but I got the feeling that building a parser for binary files is a bit hard.

Are there efforts to allow something like the following:


Interpretation of size

E.g. in binary formats you often have things like the following:

---------------------------------------------
| header | size of next block | block | ... |
---------------------------------------------

If I got everything correct I could handle this by reading the size in a size rule, storing it in a variable and pass/use it in a block rule. I think it's not very elegant, but should work.


Byte alignment

Often you have some sort of byte alignment in binary files. E.g. in a four byte alignment you end up with 0 to 3 empty bytes. I think it would also be possible to do this using a variable and then calling a rule from within an action -- but I find this also not very elegant.


Ranges for repetitive rule execution

ANTLR already supports executing a rule
 * exactly one time
 * zero or one time
 * zero or unlimited times
So I think it shouldn't be a problem to say "execute it at least 3 but not more than 89 times", e.g. This would also be nice, because binary formats often have especially upper limits in lists.


Specifying Hexadecimal values in rules

If I got everything correctly, in current ANTLR versions it's not possible to specify hexadecimal (or octal or ...) in rules. Because binary files most of the time do not use UTF or ASCII but hexadecimal values etc. for specifying magic numbers etc. this would be quite nice.


Bit handling

In binary files you often have to extract bits or bit ranges.


Perhaps I just didn't find or understand something correctly and some things mentioned above are already possible -- then just point me to the place where to look at.


Bye,
Andi
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