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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
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