loadseg help

[BippyM]

Hey guys, im disassembling a prog and it loadseg's a file, with the base of the seglist is returned in d0.

How do I read the seglist and what is the structure of the seglist?

or is it irrelevent and the address of the loaded file is in d0?

[BippyM]

Okay i have figured out the following

Loadseg the file and it returns the address as a bcpl pointer

why do i need to multiply by 4 and then add 4 to get the real address?

lsl.l #2,d0
addq.l #4,d0
move.l d0,(_GameExeBase)

[Toni Wilen]

Pointer from LoadSeg is BCPL pointer -> need to multiply by 4. It points to BCPL pointer to next hunk (or zero if program has only one hunk).

Btw, pointer - 4 = points to size of hunk.

[Doc Mindie]

If I remember the 68k right.... from what I understand, your program here has an offset of 12, and it's faster to lsl twice+4 than to mul(tiply) it to twelve.

At least I think it's in those lines. Though, I've said it before, I'm nocoder and could be VERY wrong about this

[Asman]

Sorry, you're wrong. It's not offset 12 ( its BCPL*4+4 and gives address of start first hunk ), the fastest way is ( d0 = BCPL pointer to first hunk )

add.l d0,d0
add.l d0,d0
addq.l #4,d0 ; d0 = address of first hunk code or data

BCPL is address divided by 4, for example if you have adr = $10000 , then bcpl of adr = $10000 / 4.

So, dos function LoadSeg return a seglist ( read autodocs about dos.library or you can find more information in books ). It looks like

; hunk 00
label_0   dc.l label_1 / 4
 nop
 nop
 ... data or code
 ...

; hunk 01
label_1 dc.l label_2 /4
 rts 
 ...
 ...
 ...

; hunk 02
label_2 dc.l 0   ; thats mean end of seglist
 ...
 ...

Gretz