shithub: pokered

ref: 7b2eb6b2524db4c441e8c050e5dc703601575b23
dir: /home/count_set_bits.asm/

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; 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