x86 Assembly Code on String to Integer Help!

[blakMole]

Help! How do I convert a string input (numbers) to its equivalent integer value. similar to function atoi in c#.

thankx is advance

[Matt Taylor]

"blakMole" <obliv...@yahoo.com> wrote in message
news:3ff7532be9e80aaa...@localhost.talkaboutprogramming.com...

> Help! How do I convert a string input (numbers) to its equivalent integer
value. similar to function atoi in c#.
>
> thankx is advance

What do you have so far? Have you looked at the implementation of atoi() in
the C runtime library? The idea is really simple:

"1234" = 1*10^3 + 2*10^2 + 3*10^1 + 4*10^0

Here's a hint. The equation can be rearranged like so:

(((1*10+2)*10)+3*10)+4

You should be able to use that to construct a loop that reads a digit and
accumulates it.

-Matt

[John H. Guillory]

This may not be the best, but this is working code for A386 real
mode....

jmp start

str1: db '1024',0
mult1: dw 10

eostr1 equ $

start: mov si, str1
CALL AtoI
RET

atoi: sub edx, edx ; Value = 0
sub eax, eax ; eax = 0
cld ; increment
lop: lodsb
OR AL, AL ; AL = 0?
JZ End1 ; If So, Exit Loop
PUSH AX ; Save AX
XCHG DX, AX ; Swap DX and AX
SUB DX, DX ; Clear DX
MUL WORD [mult1] ; Multiply by 10
XCHG DX, AX ; Move back to DX
POP AX
sub al, 30h ; Convert to dec.
SUB AH, AH
ADD DX, AX ; Add the next digit in...
JMP Lop ; Keep going till we hit the null....
End1: RET

[Randall Hyde]

Check out tons of library code on Webster at
http://webster.cs.ucr.edu.
Both the UCR stdlib, HLA stdlib, and the MASM32 lib have
routines that do several different types of string<->numeric
translations.
cheers,
Randy Hyde

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