var dup (?) (Question 2/2) - Forums

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Okay... second question! i've seen code using NASM for shoving in a variable bunch of bytes into a program based on current position (e.g. for patching or use in a boot sector) like this:



  db SizeAtPosition - ($-$$) dup (?)





This doesn't work in MASM and i tried several work arounds.  no matter what i tried, i usually got some error about using a constant instead of a variable.



Thanks in advance :)


    Posted on 2002-07-24 20:49:40 by jademtech


   
    var dup (?) (Question 2/2)
    Desired_Size equ 512



Start_of_BootSector:

...

...

...

End_of_BootSector:

    db Desired_Size - ( $ - Start_of_BootSector) dup ("*")
MASM doesn't support $$.  IIRC, it is the start of the segment - should look in the MASM manual to find out how to reference the start of the segment. ;)
    Posted on 2002-07-24 21:10:16 by bitRAKE
   
   
    var dup (?) (Question 2/2)
    Possibly a label?



e.g.





Desired_Size equ 512



PositionStart  LABEL

Start_of_BootSector:

...

...

...

End_of_BootSector:

    db Desired_Size - ( $ - PositionStart) dup ("*")





anyway, i'll test this out (when i get a chance) and see what happens...  thanks :)
    Posted on 2002-07-25 08:47:44 by jademtech

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