shithub: pokered

ref: ce4c2d3d1247b7d90c7cf6d5b64ef486a88b70c7
dir: /home/count_set_bits.asm/

View raw version 
; function to count how many bits are set in a string of bytes
; INPUT:
; hl = address of string of bytes
; b = length of string of bytes
; OUTPUT:
; [wNumSetBits] = number of set bits
CountSetBits::
	ld c, 0
.loop
	ld a, [hli]
	ld e, a
	ld d, 8
.innerLoop ; count how many bits are set in the current byte
	srl e
	ld a, 0
	adc c
	ld c, a
	dec d
	jr nz, .innerLoop
	dec b
	jr nz, .loop
	ld a, c
	ld [wNumSetBits], a
	ret