Let's say I load a file into memory. Now I go to offset 4df2 in there. How would I check that it's dword aligned?

At the moment I did this:

;ebx has offset in mem
mov al bl
and al 00001111
cmp al 0
jz ok
cmp al 4
jz ok
cmp al 8
jz ok
cmp al 0C
jz ok
inc ebx
jmp start

Looks kindof silly to me though :rolleyes:

Anyone got a better idea?
Posted on 2004-06-22 22:13:04 by JimmyClif
To see if an address is DWORD aligned just AND it with 3 (ALIGNMENT - 1) and if the result is not zero it is not aligned...

mov eax, Address
and eax, 3
jnz NotAligned
Posted on 2004-06-22 22:16:43 by donkey
I'm a fool.

Thanks Donkey !

btw: I saw this before:

add offset, 4
and offset, -4

but I couldn't somehow figure out how the hell that was supposed to work :tongue:
Posted on 2004-06-22 22:22:11 by JimmyClif
It should be

add offset, 3
and offset, -4


The add makes sure that if the offset is not dword aligned, it will round up. The and just make it aligned to dword.
Posted on 2004-06-22 23:02:13 by roticv
Posted on 2004-06-22 23:19:16 by JimmyClif