; Compile and execute with:
; $ cat > main.c << EOF
; int asm_main();
; int main() { return asm_main(); }
; EOF
; $ nasm -f elf fizzbuzz.asm && gcc -m32 -Wall -o fizzbuzz main.c fizzbuzz.o && ./fizzbuzz
;

%define MAX_ITER 100
        
segment .data
        Fizz db "Fizz", 0
        Buzz db "Buzz", 0

segment .text
global asm_main
        
asm_main:
        enter 0,0
        push ebx

        mov ecx, MAX_ITER       ; initialize loop counter
        dec ecx                 ; skip zero iteration

Fizz_Loop:
        mov eax, MAX_ITER
        sub eax, ecx        ; current iteration: MAX_ITER - loop count
        
        xor ebx, ebx            ; clear ebx
        xor edx, edx            ; clear edx

        push ebx
        mov ebx, 3
        div ebx                 ; edx = edx:eax % 3
        pop ebx

        cmp edx, 0
        jne No_Fizz
        inc ebx                 ; indicate Fizz usage
        mov eax, Fizz
        call print_string

No_Fizz:        
        mov eax, MAX_ITER
        sub eax, ecx            ; current iteration: MAX_ITER - loop count

        xor edx, edx            ; clear edx

        push ebx
        mov ebx, 5
        div ebx                 ; edx = edx:eax % 5
        pop ebx

        cmp edx, 0
        jne No_Buzz
        inc ebx                 ; indicate Buzz usage
        mov eax, Buzz
        call print_string

No_Buzz:        
        cmp ebx, 0
        jne Got_Fizzed_or_Buzzed
        mov eax, MAX_ITER
        sub eax, ecx        ; current iteration: MAX_ITER - loop count
        call print_int

Got_Fizzed_or_Buzzed:
        call print_nl 
        loop Fizz_Loop

        mov eax, 0

        pop ebx
        leave
        ret

;
; Various output helpers using C library printf, putchar functions
;

%define NL 10                   ; 10 == ASCII code for \n

segment .data
        int_format    db "%i", 0
        string_format db "%s", 0

segment .text
extern printf, putchar

print_int:
	enter	0,0
	pusha
	pushf

	push	eax
	push	dword int_format
	call	printf
	pop	ecx
	pop	ecx

	popf
	popa
	leave
	ret

print_nl:
	enter	0,0
	pusha
	pushf

	push	NL
	call	putchar
	pop	ecx

	popf
	popa
	leave
	ret

print_string:
	enter	0,0
	pusha
	pushf

	push	eax
	push    dword string_format
	call	printf
	pop	ecx
	pop	ecx

	popf
	popa
	leave
	ret