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flat assembler > Windows > Simple array

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Mino



Joined: 14 Jan 2018
Posts: 160
Hello, I would like to know how to make simple arrays in FASM, a bit like "C":
int MyArray[size];
I remember a tutorial that spoke in a way like that:
MyArray dw ?,?,?,?,?,?
But it's not working. Could you help me, please?
Tanks Smile

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Post 12 Feb 2018, 20:56
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1389
Location: Toronto, Canada
Code:
MyArray rw 16   ; 16 WORDs
    
Post 13 Feb 2018, 01:05
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Mino



Joined: 14 Jan 2018
Posts: 160
Thanks for the answer, that's great Smile
But how can you change this array now?
like that ? :
Code:
push MyArray
mov MyArray[0], 4
add MyArray[0], 6
    

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Post 13 Feb 2018, 08:23
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Mikl___



Joined: 30 Dec 2014
Posts: 93
Mino
Code:
;push MyArray <-- ?
mov [MyArray+0], 4 
add [MyArray+0], 6
mov bx,MyArray
mov [bx+10], word 4 
add word [bx+4], 6
xor di,di
lea si,[MyArray]
mov word [si+di], 4 
add [si+di], word 6
    


Last edited by Mikl___ on 13 Feb 2018, 09:13; edited 2 times in total
Post 13 Feb 2018, 08:58
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Mino



Joined: 14 Jan 2018
Posts: 160
EDIT:
It works! Thank you very much:)
Post 13 Feb 2018, 09:10
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Mikl___



Joined: 30 Dec 2014
Posts: 93
mino,
not at all!
An array of 13 words can be declared like this
Code:
MyArray   dw 13 dup(?)    
Post 13 Feb 2018, 09:15
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Mino



Joined: 14 Jan 2018
Posts: 160
If it is not too much to ask, could you give a concrete example? With for example an array of Hello World in different languages, then display them?
So I can understand better.
Thanks to you Smile
Post 13 Feb 2018, 09:28
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yeohhs



Joined: 19 Jan 2004
Posts: 171
Location: N 5.43564° E 100.3091°
I dug out something written about a decade ago.

Code:
;----------------------------------------------------------
; Program Name: arrayofintegers.asm
; Date        : August 2008
; Author      : Yeoh HS
; FASM        : Built using Flat Assembler version 1.67.27
;               edited and compiled with FASM's IDE.
;----------------------------------------------------------
format PE CONSOLE 4.0
entry start

include 'win32axp.inc'

macro showeax
{
   pushad
   cinvoke printf, '%d', eax
   cinvoke printf, CRLF
   popad
}

.data
    CRLF          db '',13,10,0

    intarray      dd 10 dup ?      ; An array of 10 dwords
    intarray.size dd 10            ;
    offsetfactor  dd 4
    recno         dd ?
    arrayoffset   dd ?
    arrayhead     dd ?
    arraypointer  dd ?

.code
start:
    ; Fills an array with values 1 to 10
    mov esi, intarray    ; esi = start of array
    mov ebx, 0           ; ebx = pointer to array item
    mov edx, 1           ; edx = value to put in array
    mov ecx, [intarray.size]  ; ecx = array item count

L0:
    mov [esi+ebx], edx  ;store a value in an array position
    add ebx, 4          ;move array pointer to next position, 4 bytes size
    add edx, 1          ;increment the data to be stored by 1
    loop L0             ;loop to store new data

    ; Loop through and print each integer
    mov esi, intarray   ; esi has start of array
    mov ebx, 0          ; pointer is a 0 location
    mov ecx, [intarray.size]  ; store array size in ecx
 L1:
    mov eax, [esi+ebx]     ;point to an array element
    showeax                ;show an array element
    add ebx, 4             ;move pointer to next dword value
    loop L1                ;point to the next array element

    ; Loop through backwards and print each integer
    mov esi, intarray         ; esi has start of array
    mov eax, [intarray.size]  ; mov 10 into eax
    mul [offsetfactor]        ; mul 10 by 4 so eax now is 40
    sub eax, 4                ; eax now is 36, the last position in the integer array
    mov ebx, eax              ; set pointer to last dword value
    mov ecx, [intarray.size]  ; store array size in ecx
L2:
    mov eax, [esi+ebx]        ; point to the last element
    showeax                   ; display it
    sub ebx, 4                ; move pointer backwords 1 dword
    loop L2                   ; display the previous element

    ; Loop through to find an integer, 6
    mov edx, 6                ; mov 6 into comparison variable
    mov esi, intarray         ; point to start of array
    mov ebx, 0                ; set point to first element
    mov ecx, [intarray.size]  ; store array size in ecx
L3:
    mov eax, [esi+ebx]        ; get an element
    cmp eax, edx              ; compare it with value in edx
    je L4                     ; if equal jump to L4 and show value
    add ebx, 4                ; move pointer to next element
    loop L3                   ; loop back to get another element
    jmp L5                    ; if not found jmp L5 and display message
L4:
    showeax
    jmp L6
L5: pushad
    cinvoke printf, '%s', 'Not found',0
    popad
L6:
    ; Get selected integer, the first record.
    mov [recno], 1         ;
    mov eax, [recno]       ;
    dec eax                ; array is zero-based
    mul [offsetfactor]     ; multiply by 4
    mov [arrayoffset], eax ; now offset computed
    ;mov [arrayoffset+4], edx

    mov esi, intarray       ; point to start of array
    mov eax, [arrayhead]    ;
    add eax, [arrayoffset]
    mov [arraypointer], eax
    mov ebx, [arraypointer]
    mov eax, [esi+ebx]
    showeax

    ;Insert value 7 in position no. 2
    mov [recno], 2
    mov eax, [recno]
    dec eax
    mul [offsetfactor]
    mov [arrayoffset], eax
    ;mov [arrayoffset+4], edx

    mov esi, intarray
    mov eax, [arrayhead]
    add eax, [arrayoffset]
    mov [arraypointer], eax
    mov ebx, [arraypointer]
    mov eax, 7
    mov [esi+ebx], eax

    ;Display value in position no. 2
    mov [recno], 2
    mov eax, [recno]
    dec eax
    mul [offsetfactor]
    mov [arrayoffset], eax
    ;mov [arrayoffset+4], edx

    mov esi, intarray
    mov eax, [arrayhead]
    add eax, [arrayoffset]
    mov [arraypointer], eax
    mov ebx, [arraypointer]
    mov eax, [esi+ebx]
    showeax


    cinvoke printf, '  Press the Enter key...'
    cinvoke getchar
    invoke  ExitProcess,0


section '.idata' import data readable writeable

library kernel32,'kernel32.dll',\
        user32,  'user32.dll',\
        msvcrt,  'msvcrt.dll'

include 'api\kernel32.inc'
include 'api\user32.inc'

import msvcrt,\
       printf, 'printf',\
       getchar,'getchar'

;==========================================================
; end of file

    

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Post 13 Feb 2018, 12:21
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Mikl___



Joined: 30 Dec 2014
Posts: 93
Mino
Quote:
an array of Hello World in different languages, then display them?
So I can understand better
Code:
format PE GUI
include 'win32ax.inc'
; import data in the same section

   invoke MessageBox,NULL,wText1,wTitle,MB_OK
   retn
wTitle db   'Iczelion Tutorial #2:MessageBox',0
wText1 db 87,105,110,51,50,32,65,115,115,101,109,98,108,121,32,119, 105,116,104,32,70,65,83,77,32,105,115,32,71,114,101,97,116,33,10
wText2 dw 26967, 13166, 8242, 29505, 25971, 25197, 31084, 30496, 29801, 8296, 16710, 19795, 26912, 8307, 29255, 24933, 8564, 3338
wText3 dd 5.55095E-8,1.5300999E31,1.0947971E21,3.2548056E33, 1.9689681E-19,2.21516896E8,2.0617684E-19,2.6453368E20,4.25648E-31
wText4 dq 8304954587831232855, 8583994396182930803, 5571868933434668137,7018141244139464992,8564
data import

 library user32,'USER32.DLL'
 import user32,\
        MessageBox,'MessageBoxA'

end data    
Let's try to compile and run Image


Last edited by Mikl___ on 16 Feb 2018, 00:35; edited 7 times in total
Post 13 Feb 2018, 15:16
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fasmnewbie



Joined: 01 Mar 2011
Posts: 547
Mino wrote:
If it is not too much to ask, could you give a concrete example? Thanks to you Smile
Now that you ask...
Code:
format ELF64 
public main

section '.data' writeable
  MyArray:
        .content db 'H','e','l','l','o',20h,'W','o','r','l','d',0ah,0
        .size = ($ - .content) - 1

section '.text' executable
  main:
        sub     rsp,8
                
        ;Addressing individual byte (try byte 'W')
        
        mov     al,byte[MyArray.content+6] ;copy 'W' to AL register
        
        ;do anything you want with the value in AL        
        
        ;Display the entire string
        
        mov     rdx,MyArray.size        ;size
        mov     rsi,MyArray.content     ;address
        mov     rdi,1                   ;stdout
        mov     rax,1                   ;write
        syscall
        add     rsp,8
        ret    


That's one way how array is actually implemented in ASM. It's in Linux ofc but just ignore it and focus on the constructions, structure, addressing and anything related to 'array'.

Is this enough for you?
Post 14 Feb 2018, 00:18
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Mino



Joined: 14 Jan 2018
Posts: 160
Thank you very much for your explanations Smile
Post 14 Feb 2018, 16:20
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Mikl___



Joined: 30 Dec 2014
Posts: 93
Mino,
did you try to compile and run my sample?
Post 15 Feb 2018, 00:55
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Mino



Joined: 14 Jan 2018
Posts: 160
I haven't had the time yet, and I'm unable to do it for now, or even before. I'll release the results soon, if it doesn't bother you of course Smile

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The best way to predict the future is to invent it.
Post 15 Feb 2018, 09:25
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Mino



Joined: 14 Jan 2018
Posts: 160
Win32 Assembly with FASM is Gread, indeed ^^'!
Post 15 Feb 2018, 13:23
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Mikl___



Joined: 30 Dec 2014
Posts: 93
Mino,
Win32 Assembly with FASM is Great! Image
Post 15 Feb 2018, 15:29
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Mino



Joined: 14 Jan 2018
Posts: 160
Must be the French accent Laughing

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The best way to predict the future is to invent it.
Post 15 Feb 2018, 15:53
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Mikl___



Joined: 30 Dec 2014
Posts: 93
Mino,
peut-être...
Post 15 Feb 2018, 22:48
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