utils.asm

	PUBLIC	DIV_HL_C, MATH_ABS_HL, MATH_POS_HL, MATH_NEG_HL, MATH_CP_HL_DE

; THE FOLLOWING ROUTINE DIVIDES HL BY C AND PLACES THE QUOTIENT IN HL AND THE REMAINDER IN A
; https://wikiti.brandonw.net/index.php?title=Z80_Routines:Math:Division#16.2F16_division

DIV_HL_C:
	XOR	A
	LD	B, 16

LOOP:
	ADD	HL, HL
	RLA
	JR	C, DIV_HL_C1
	CP	C
	JR	C, DIV_HL_C2

DIV_HL_C1:
	SUB	C
	INC	L

DIV_HL_C2:
	DJNZ	LOOP
	RET

MATH_ABS_HL:
	BIT	7, H
	RET	Z
MATH_POS_HL:
	XOR	A
	SUB	L
	LD	L, A
	SBC	A, A
	SUB	H
	LD	H, A
	RET

MATH_NEG_HL:
	XOR	A
	SUB	L
	LD	L,A
	SBC	A,A
	SUB	H
	LD	H,A
	RET


; MATH_CP_HL_DE -> test if HL >= DE
; Input      HL=A, DE=B
; Output     C FLAG RESET IF TRUE
;            C FLAG SET IF FALSE
MATH_CP_HL_DE:
	LD	A, H
	XOR	D
	JP	M, MATH_CP_HL_DE2
	SBC	HL, DE
	RET	NC
MATH_CP_HL_DE1:
	SCF
	RET
MATH_CP_HL_DE2:
	BIT	7, D
	JR	Z, MATH_CP_HL_DE1
	RET