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Index > Windows > [Win32:VB6] Strings

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cod3b453



Joined: 25 Aug 2004
Posts: 619
cod3b453
I would like to convert my VB6 project to ASM to but I don't get how to declare, manipulate and use strings in ASM and their necessary functions like Left() Right() Len().

Many thanks,

cod3b453
Post 02 Dec 2004, 19:19
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Nikolay Petrov



Joined: 22 Apr 2004
Posts: 101
Location: Bulgaria
Nikolay Petrov
It's a easy
example:
VB:
Code:
....
Dim Name As String first As String
    Name = "Blah Bla" 
    first = Left(Name,4)
....
returned - Blah    


Assemler
Code:
....
mov esi,Name
mov edi,first
cld;-> read symbols left -> right. if you write std (not cld) - exchange the directon, and symbols read right -> left
 mov ecx,4
 repe movsb; -->returned in first - Blah
.....
in data section
Name db "Blah Bla",0
first rb 32    


but sometimes, you must "safe" registers like this Asm str proc examples

Code:
proc str_len,string ;it's proc - like WinAPI proc lstrlenA
    push edi esi;safe registers
    xor eax,eax
    mov edi [string]
    mov ecx,-1
@@: inc ecx
    scasb
    jne @r
    mov eax,ecx
    pop esi edi;restore registers
    return
endp ;returned lenght "string" in eax and ecx

proc copy_strn,dest,source,len ;copied "len" symbols from "source" in "dest"
    push esi edi    
    mov ecx,[len]
    mov esi,[source]
    mov edi [dest]
    rep movsb
    dec edi
    mov byte [edi],0
    pop edi esi
    return
endp    


In Windows you may use lstrcpy, lstrcat, lstrlen and other dll functions - look at SDK documentations; Or strcpy strlen... from msvcrt.dll
JohnFound is created a good str proc library - look at fasm IDE project

But i think that you must read more literature for basic assempler programe, if you wish.
Post 02 Dec 2004, 20:31
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cod3b453



Joined: 25 Aug 2004
Posts: 619
cod3b453
I forgot about lstrlen & lstrcat! Thanks for the quick reply and source code Nickolay - it was very helpful!
Post 02 Dec 2004, 21:35
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