vasm - Use defined object code in macros/expressions?

[dansalvato]

I'm currently working on simplifying my workflow and was wondering if something like this is possible.

SomeLabel:
  dc.b   $3f                     ;Can this value be used in expressions?
  INCBIN "data.bin"              ;Same as above, but externally sourced, so no constants

SomeValue = INCBIN "data.bin"    ;Obviously doesn't work, but it's basically what I'm trying to do

I'm interested in doing this because I have some pre-generated binary files that need permuted versions of them to also be included in memory. I was thinking I could cut down on the amount of external file generation if I could use assembler expressions to do the permutation instead, during assembly.

I know that macros can retrieve the decimal/hex value of SomeLabel, but I don't know if they can retrieve the data present *at* SomeLabel. I know it would be easy if the data is always a constant that's directly present in code, but if I'm loading data via INCBIN then I'm not sure if it's possible.

Thanks for any insight!

[phx]

Originally Posted by Haxxy

wondering if something like this is possible.

No. A symbol, like

SomeLabel

, is either an absolute number (equate) or a label (memory address). You can make your macro generate code, which reads and permutates data at

SomeLabel

, but that would execute only at run-time.

I was thinking I could cut down on the amount of external file generation

What is the contents of these external files? A single byte?

would be easy if the data is always a constant that's directly present in code, but if I'm loading data via INCBIN then I'm not sure if it's possible.

I don't understand what you want to do, but does it have to be a binary file? Instead of

data.bin

you could generate a source file

data.inc

like this:

SomeValue = $3f

Then include it with

include "data.inc"

and use

SomeValue

in your macros?

But maybe you can give some more details? There may be other ways to help you, if we knew what you are trying to achieve.

[dansalvato]

Originally Posted by phx

But maybe you can give some more details? There may be other ways to help you, if we knew what you are trying to achieve.

Thank you for your help. It was more of a curiosity rather than something I'm stuck on. The use case that first came to mind was to generate mirrored versions of sprites. Right now, I run my sprites through a script to generate mirrored versions, but I thought if I could do it in vasm using an expression (a very long one), I could eliminate that step. I know it sounds silly! It might make more sense to mirror the sprites at runtime anyway, and save myself the disk space.