proc getPos, lParam, thisPos:RECT

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procyon

Joined: 07 Sep 2007
Posts: 12

procyon 14 Jun 2011, 10:09

Hi,

Code:

proc getPos, lParam, thisPos:RECT

isn't accepted by compliler, so I'm wondering how I can pass a RECT structure to a proc so that I can access

Code:

[thisPos.left]

etc in the proc.

btw, I know there are workarounds, I'm using

Code:

proc getPos, lParam, buff     ; buff is a RECT struct
                                         ; but I don't know how to pass it.
        pushad
        mov     eax, [lParam]
        mov     ebx, eax
        and     eax, 0xFFFF
        shr     ebx, 16
        mov     edi, [buff]
        mov     [edi], eax
        mov     [edi+04], ebx
        popad
        ret
endp

at the minute. Just want to know if there is something I'm missing about passing STRUCTS to a PROC so that I can access the 'proper' offsets (i.e. .left .top etc)

thx

pro

Last edited by procyon on 14 Jun 2011, 10:51; edited 2 times in total

14 Jun 2011, 10:09

ouadji

Joined: 24 Dec 2008
Posts: 1080
Location: Belgium

ouadji 14 Jun 2011, 10:46

Code:


mov eax,RECT
stdcall getPos,x,x,eax

proc getPos, lParam, thisPos:dword

mov ebx,[thisPos]
mov ecx,[ebx]

endp

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14 Jun 2011, 10:46

procyon

Joined: 07 Sep 2007
Posts: 12

procyon 14 Jun 2011, 10:49

Is that a typo ouadji?

You're passing 3 params to a 2 param proc

14 Jun 2011, 10:49

ouadji

Joined: 24 Dec 2008
Posts: 1080
Location: Belgium

ouadji 14 Jun 2011, 10:56

yes, typo, sorry !
BSOD for me ! Wink

Code:

stdcall getPos,x,eax

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I am not young enough to know everything (Oscar Wilde)-

14 Jun 2011, 10:56

bitshifter

Joined: 04 Dec 2007
Posts: 796
Location: Massachusetts, USA

bitshifter 14 Jun 2011, 18:50

Actually you dont need to put into eax first, just pass its offset.
In high level languages like C, there are internals to handle passing
structures to a procedure as opposed to passing a pointer to the structure.
With ASM we pass a pointer to the structure as ouadji has demonstrated.

14 Jun 2011, 18:50

r22

Joined: 27 Dec 2004
Posts: 805

r22 14 Jun 2011, 18:51

My fASM is a bit rusty but wouldn't this work...

------- text below may be completely untrue ------

Code:

proc getPos, lParam, thisPos
        pushad
        mov     eax, [lParam]
        mov     ebx, eax
        and     eax, 0xFFFF
        shr     ebx, 16
        mov     edi, [thisPos]
        mov     [edi + RECT.left], eax
        mov     [edi + RECT.top], ebx
        popad
        ret
endp

What would [thisPos.left] translate to?
thisPos is EQU to EBP+8
so you have to MOV edi, [EBP+8] ; MOV edi, [thisPos] to get the address to your RECT.
From there you can do a ? virtual at edi / RECT / end virtual ? may that would let you reference [edi .left]

14 Jun 2011, 18:51

ouadji

Joined: 24 Dec 2008
Posts: 1080
Location: Belgium

ouadji 14 Jun 2011, 19:04

.... as ouadji has demonstrated.

thank you bitshifter for the green color Razz

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I am not young enough to know everything (Oscar Wilde)-

14 Jun 2011, 19:04

procyon

Joined: 07 Sep 2007
Posts: 12

procyon 14 Jun 2011, 19:10

hi bitshifter, the RECT struct is being passed in [thisPos], not [lparam]. I move [lparam] into eax to manipulate it then move the results into [thisPos].

Hi r22, long time no speak Very Happy

It appears your fasm isn't as rusty as mine, lol. I knew there was a way to reference the RECT 'correctly', just couldn't get my head around it Embarassed

Many thanks

pro

14 Jun 2011, 19:10

bitshifter

Joined: 04 Dec 2007
Posts: 796
Location: Massachusetts, USA

bitshifter 14 Jun 2011, 21:53

I understand you, but what i meant was to pass thisPos -- not [thisPos]

thisPos == offset of structure
[thisPos] == first member of structure (RECT.left)

14 Jun 2011, 21:53

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