ext	mpy16,sdelm
	public	rten1,radbin

; RTEN1 performs decimal conversion of the string at HL.

rten1:	ld	de,10		; Decimal radix base
				; Fall through to generalized
				; ..radix conversion routine

; This routine converts the string pointed to by HL using the radix
; passed in DE.  If the conversion is successful, the value is returned in BC.
; HL points to the character that terminated the number, and A contains that
; character.  If an invalid character is encountered, the routine returns with
; the carry flag set, and HL points to the offending character.

radbin:	ld	bc,0		; Initialize result
rdx1:	or	a		; Make sure carry is reset
	call	sdelm		; Test for delimiter (returns Z if delimiter)
	ret	z		; Return if delimiter encountered

	sub	'0'		; See if less than '0'
	ret	c		; Return with carry set if so
	cp	10		; See if in range '0'..'9'
	jr	c,rdx2		; Branch if it is valid
	cp	'A'-'0'		; Bad character if < 'A'
	ret	c		; ..so we return with carry set
	sub	7		; Convert to range 10..15
rdx2:
	cp	e		; Compare to radix in E
	ccf			; Carry should be set; this will clear it
	ret	c		; If carry now set, we have an error

	inc	hl		; Point to next character
	push	bc		; Push the result we are forming onto the stack
	ex	(sp),hl		; Now HL=result, (sp)=source pointer
	call	mpy16		; HLBC = previous$result * radix
	ld	h,0		; Discard high 16 bits and
	ld	l,a		; ..move current digit into HL
	add	hl,bc		; Form new result
	ld	c,l		; Move it into BC
	ld	b,h
	pop	hl		; Get string pointer back
	jr	rdx1		; Loop until delimiter

	end