check how many functions failed

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randomdude

Joined: 01 Jun 2012
Posts: 83

randomdude 26 Mar 2014, 11:33

so i have been using this to know the number of functions that have failed

Code:

        xor     ebx,ebx
        xor     edi,edi ;fuck, i need addzx instruction :S
        invoke  RegisterHotKey,0,VK_F5,0,VK_F1
        test    eax,eax
        setz    bl
        add     edi,ebx
        invoke  RegisterHotKey,0,VK_F6,0,VK_F2
        test    eax,eax
        setz    bl
        add     edi,ebx
        ...

edi = number of functions that returned 0

but im feeling that this is not the best way. does anyone know how can i optimize it?

26 Mar 2014, 11:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20340
Location: In your JS exploiting you and your system

revolution 26 Mar 2014, 16:14

Use a table maybe:

Code:

hot_key_table:
dd VK_F5,VK_F1
dd VK_F6,VK_F2
dd 0
;...
xor edi,edi
mov esi,hot_key_table
.loop:
invoke  RegisterHotKey,0,dword[esi+0],0,dword[esi+4]
test eax,eax
setz al
movzx eax,al
add edi,eax
add esi,8
cmp dword[esi],0
jnz .loop

26 Mar 2014, 16:14

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 26 Mar 2014, 17:13

Given that RegisterHotKey return type is BOOL, it might be as simple as invoke/add edi,eax with a cmp at the end.

26 Mar 2014, 17:13

tthsqe

Joined: 20 May 2009
Posts: 767

tthsqe 26 Mar 2014, 18:33

I don't think we can assume MS bool is 0 or 1, right?
I just had an idea for edi += BoolToInt(eax), I think it should work because adding eax to 0xFFFFFFFF only doesn't produce a carry when eax is zero.

Code:

; increment edi if eax != 0
neg  eax    ; or add  eax,-1   ; carry flag is now the bool represented by eax
adc  edi,0                     ; increment edi by carry flag

I don't think you can do do this with fewer than 2 instructions.

Also,

Code:

; increment edi if eax = 0
cmp  eax,1  ; or sub  eax,1    ; carry flag is now the bool represented by !eax
adc  edi,0                     ; increment edi by carry flag

Last edited by tthsqe on 27 Mar 2014, 03:31; edited 2 times in total

26 Mar 2014, 18:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20340
Location: In your JS exploiting you and your system

revolution 26 Mar 2014, 23:37

I think it is not safe to assume bool returns -1 for true. It might return +1, or 482. Glad to see tthsqe saw that. Anyhow, it hardly seems worth the effort to save a single instruction for an API call that executes an unknown number of instructions and in a place that is called only once upon program startup.

26 Mar 2014, 23:37

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 27 Mar 2014, 01:50

tthsqe,

neg instruction does exactly that (sets CF if operand is non-zero, clears otherwise), though its primary function may render it unusable in this case.

cmp eax, 1 could be better than sub eax, 1.

27 Mar 2014, 01:50

tthsqe

Joined: 20 May 2009
Posts: 767

tthsqe 27 Mar 2014, 03:27

baldr, I though 'neg' doesn't affect carry flags, or is that 'not'? I don't know because I never use those...
Anyways I read the docs and changed my post.

27 Mar 2014, 03:27

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