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| author | dannye <33dannye@gmail.com> | 2020-11-04 00:06:44 -0600 |
|---|---|---|
| committer | dannye <33dannye@gmail.com> | 2020-11-04 00:06:44 -0600 |
| commit | 5647ca687b92954dcf37a6ea6bfbc9a341c32de4 (patch) | |
| tree | dde1937a1bfdb3a835f4155e1c2eb8f1aaf86f63 /home/count_set_bits.asm | |
| parent | 53fcd05aa24693093d8af1dc8ec4fedd3957decc (diff) | |
Sync with pokered
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 |