diff options
Diffstat (limited to 'home/count_set_bits.asm')
| -rw-r--r-- | home/count_set_bits.asm | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/home/count_set_bits.asm b/home/count_set_bits.asm new file mode 100644 index 00000000..73f7fa9c --- /dev/null +++ b/home/count_set_bits.asm @@ -0,0 +1,24 @@ +; 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 |