global	hextostr 
extern	printf

section .data
	f	db	'Digit: %x',10,0

section .text
hextostr:
	push	rbp
	mov	rbp, rsp

	push	rbx
	push	rcx
	push	rdx
	push	rsi
	push	rdi

	mov	rax,[rbp+24] ; source
	mov	rcx,[rbp+16] ; buffer 
	xor	rbx, rbx
	mov	bx,16
	xor	rsi,rsi ; for counter
	xor	rdx,rdx ; for div

lstart:	div	bx
	cmp	dx, 0xA	
	jl	digit
	jmp	letter	
digit	add	dx, '0'
	jmp	putc
letter:	add	dx, 'A'-10
putc:	
	mov	[rcx+rsi], dx 
	xor	dx,dx
	inc	rsi
	cmp	rsi,4
	jl	lstart	
	mov	rdx,rcx
	mov	rcx,2
revert:	
	mov	rdi,4
	sub	rdi,rcx
	mov	al,[rdx+rdi]
	mov	bl,[rdx+rcx-1]
	mov	[rdx+rdi],bl
	mov	[rdx+rcx-1],al
	loop	revert
	mov	rax,0
	jmp	lend
error:	
	mov	rax,1	
lend:	
	pop	rdi
	pop	rsi
	pop	rdx
	pop	rcx
	pop	rbx
	pop	rbp
	ret	16