; Return in register RAX a MAC-address obtained from an ASCIIZ string starting
; at an address in register RDI. The string is in hexadecimal format with a
; punctuation mark as a delimiter between the bytes, e.g. 00-0C-76-1F-C5-EB.

option prologue:none, epilogue:none
.code
getmacst proc
_getmacst proc
	MOV	RSI,RDI		; LODSB works with RSI
	XOR	RDX,RDX		; Start from zeros
	.repeat
		.for (AH = 0 : : ) ; New byte - start accumulating from 0
			LODSB			; Load the next character
			.break .if (AL < '0')	; Punctuation mark
			.if (AL > '9')		; Not a digit
				AND	AL,NOT ('a'-'A'); Convert to uppercase
				.break .if (AL < 'A' || AL > 'F') ; Delimiter
				SUB	AL,'A'-10-'0';Convert from ASCII/step1
			.endif
			SUB	AL,'0'	; Convert from ASCII
			SHL	AH,4	; Make room for the new hex digit
			OR	AH,AL	; and add it to the current value
		.endfor			; Continue with the next character
		SHL	RDX,8	; Make room for a new byte in the MAC-address
		MOV	DL,AH	; Write there the current byte from the right
	.until (AL == 0)	; Continue with the next byte till string ends
	XCHG	RAX,RDX		; Return the MAC-address in RAX
	RET
_getmacst endp
getmacst endp
end