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menambahkan program simple atoi #13

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menambahkan program simple atoi #13

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5916caf
menbahkan program print angka multigit
Rino-Saputra Jun 8, 2022
a0cf87c
menambhkan program atoi
Rino-Saputra Jun 19, 2022
c26534c
menambhkan program atoi
Rino-Saputra Jun 19, 2022
13fce27
Merge https://github.com/bellshade/Assembly
Rino-Saputra Jun 20, 2022
5e872a6
Merge https://github.com/Rino-Saputra/Assembly
Rino-Saputra Jun 23, 2022
2d62ed6
add: menambahkan program atoi(versi sendiri)
Rino-Saputra Jun 23, 2022
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50 changes: 50 additions & 0 deletions simple_asm/simple_atoi.asm
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Original file line number Diff line number Diff line change
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;program untuk menconvert input dari user menjadi angka karena input yang di dapat
;berupa karakter ascii bukan angka
;atau program ini atoi pada bahasa c dengan versi saya sendiri
;algoritmanya adalah kali sepuluh hasil yang ditampung terus ditambah dengan digit baru


section .data
num db 0

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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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num db 0 cuma allocate 1 byte saja, tapi di syscall readnya specify buffer
length 3 bytes. Overflow write to memory!!!

Kenapa tidak pakai uninitialized storage saja di .bss?

Misal:

section .bss
	num resb 32

dan juga kenapa cuma 3 karakter doang readnya?

section .text
global _start

_start:
;code here
mov eax,3 ;sys_read
mov ebx,0 ;file desceiptor stdin
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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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xor ebx, ebx?

mov ecx,num
mov edx,3
int 0x80
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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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Read 3 bytes, kamu masukin angka 2 karakter, lalu enter itu sudah 3 bytes.
Gimana kalau inputnya lebih dari 2 karakter? Hmmm?


mov edi,num

mov al, byte 0 ;hasil perkalian

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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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xor eax, eax?

get_char:

movzx edx, byte[edi] ;mov one byte edi to edx / dl

cmp dl,48 ;jika kurang dari 0 end program
jl end

cmp dl,57 ;jika lebih dari 9 end program
jg end

mov bl,byte [edi]
sub bl, byte '0'
mov dl, byte 10
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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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Inconsistent spaces.


mul dl ;kali angka
add al,bl ;tambahkan hasil perkalian dengan digit input

inc edi ;char selanjutnya
jmp get_char
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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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This is very wrong atoi().

Simple test cases that prove this wrong:

+-------+-------+
| Input | Hasil |
+-------+-------+
| 3333  | 773   |
| 4444  | 1884  |
| 5555  | 435   |
+-------+-------+



;hasil nya berada pada register eax tepatnya di al berukuran 1 byte
end:
mov eax,1
mov ebx,0
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@ammarfaizi2 ammarfaizi2 Jul 28, 2022

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xor ebx, ebx?

int 0x80