_get_degree:
; input: hl = ptr to binary polynomial (little endian-encoded)
; degree in a
; destroys: bc, flags
	ld bc, 29
	add hl, bc
	ld b, 30
	ld d, 240
.byte_loop:
	ld a, (hl)
	or a			; if byte is 0
	jr nz, .found_byte
	ld a, d
	sub a, 8
	ld d, a
	djnz .byte_loop

.found_byte:
; process bits
	ld b, 8
.bit_loop:
	rla
	jr c, .found_bit
	dec d
	djnz .bit_loop

.found_bit:
	dec d
	ld a, d
	ret