struct question

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DenimJeans

Joined: 29 Dec 2023
Posts: 11

DenimJeans 04 Jan 2024, 14:39

Hi everyone, could you please help me understanding structs and arrays:

I have a struct like (hope the definition is correct):

Code:

struct TRIS
        pt1 POINT ?
        ...
ends

tp TRIS 1,2 ; <- error

how can I initialize the struct ?
also, how can I create an array of them?

like 10x
tp1 ... tp10

04 Jan 2024, 14:39

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 04 Jan 2024, 14:54

To supply multiple items to a single member use angle brackets.

Code:

tp TRIS <1,2>

04 Jan 2024, 14:54

DenimJeans

Joined: 29 Dec 2023
Posts: 11

DenimJeans 04 Jan 2024, 15:07

thanks revolution, indeed I tried all combinations of {[(, but not the angle brackets .. haha

perfect thanks!
and creating an array of the struct via macro to access them later via named label also possible?

so I access them later via
tp1 .. tp100 .....

Code:

mov eax,[tp1+TRIS.pt1.x]

04 Jan 2024, 15:07

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 04 Jan 2024, 15:25

Code:

tp1: rb sizeof.TRIS * 100

04 Jan 2024, 15:25

DenimJeans

Joined: 29 Dec 2023
Posts: 11

DenimJeans 04 Jan 2024, 15:45

ok, nice, thanks again.
just for completeness:

Code:

struct TRIS
        pt1 POINT 8,9       
ends

t1:
rept 100 {
    local pt
    pt TRIS
}

would also copy the initialized values (8,9) to the copies and your suggestion initialize with unknown (0) values.

Have a great day, thanks
DJ

04 Jan 2024, 15:45

AsmGuru62

Joined: 28 Jan 2004
Posts: 1738
Location: Toronto, Canada

AsmGuru62 04 Jan 2024, 19:10

Also, to use structures inside procedures as local variables:

Code:

proc foo uses ebx esi edi, param1:DWORD, param2:DWORD
    local   var1:TRIS
    local   arrayOfThose[16]:TRIS

    ;
    ; load a pointer to a single structure variable into EAX
    ;
    lea     eax, [var1]
    ;
    ; load a structure member of 'var1' into ECX
    ;
    mov     ecx, [eax + TRIS.xxxxxx]
    ;
    ; load pointer to array into ESI
    ;
    lea     esi, [arrayOfThose]
    add     esi, sizeof.TRIS        ; ESI --> next array element
    add     esi, sizeof.TRIS        ; ESI --> next array element
    add     esi, sizeof.TRIS        ; ESI --> next array element
    add     esi, sizeof.TRIS        ; ESI --> next array element

    ; ... you get it?..

    ret
endp

04 Jan 2024, 19:10

DenimJeans

Joined: 29 Dec 2023
Posts: 11

DenimJeans 05 Jan 2024, 07:28

that also nice, thanks AsmGuru62
how can I access for example the 10th element then? like so or is there a simpler way:

Code:

    local arrayOfThose[16]:TRIS 
    lea esi,[arrayOfThose]
    mov eax,10
    mov ecx,sizeof.TRIS
    mul ecx
    add esi ,eax
    mov [esi+TRIS.pt.x],0x11111111
    mov [esi+TRIS.pt.y],0x22222222

and 2nd question: assigning values to the 10th item would not be possible, right? I need to access them each single by using their members?:

Code:

arrayOfThose[10] <0x111111,0x222222>,0x555555,0x666666 ;wrong?
mov [esi+TRIS.pt.x],0x11111111 ;correct?

05 Jan 2024, 07:28

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 05 Jan 2024, 08:08

To access the 10th element.

Code:

mov [arrayOfThose + 9 * sizeof.TRIS + TRIS.pt.x],0x11111111 ; first element is index 0, second is 1, etc.

05 Jan 2024, 08:08

DenimJeans

Joined: 29 Dec 2023
Posts: 11

DenimJeans 05 Jan 2024, 09:06

thanks revolution. works now as expected.
and the ".data" section requires to be at the beginning and not end of the assembly, right? Otherwise it does not work for me.

05 Jan 2024, 09:06

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 05 Jan 2024, 09:27

There are no location requirements for any sections. Put them anywhere.

05 Jan 2024, 09:27

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