diff options
author | yenatch <yenatch@gmail.com> | 2018-04-04 21:04:14 -0400 |
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committer | GitHub <noreply@github.com> | 2018-04-04 21:04:14 -0400 |
commit | fe4377ce532d1fea1b28d2c52e4f62f0ca702a30 (patch) | |
tree | 6ce2635ce57ff2735839235e3061e7f3009cfe5d /engine/math/math.asm | |
parent | 0c446367ce79dfe2a26f4bd7668036477811a279 (diff) | |
parent | 38107209a6ad431b399cc36405c0af8b5babf5ef (diff) |
Merge pull request #501 from mid-kid/reorg
Organize the engine/ directory
Diffstat (limited to 'engine/math/math.asm')
-rw-r--r-- | engine/math/math.asm | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/engine/math/math.asm b/engine/math/math.asm new file mode 100644 index 000000000..0cd6b0b47 --- /dev/null +++ b/engine/math/math.asm @@ -0,0 +1,196 @@ +_Multiply:: ; 66de + +; hMultiplier is one byte. + ld a, 8 + ld b, a + + xor a + ld [hProduct], a + ld [hMathBuffer + 1], a + ld [hMathBuffer + 2], a + ld [hMathBuffer + 3], a + ld [hMathBuffer + 4], a + + +.loop + ld a, [hMultiplier] + srl a + ld [hMultiplier], a + jr nc, .next + + ld a, [hMathBuffer + 4] + ld c, a + ld a, [hMultiplicand + 2] + add c + ld [hMathBuffer + 4], a + + ld a, [hMathBuffer + 3] + ld c, a + ld a, [hMultiplicand + 1] + adc c + ld [hMathBuffer + 3], a + + ld a, [hMathBuffer + 2] + ld c, a + ld a, [hMultiplicand + 0] + adc c + ld [hMathBuffer + 2], a + + ld a, [hMathBuffer + 1] + ld c, a + ld a, [hProduct] + adc c + ld [hMathBuffer + 1], a + +.next + dec b + jr z, .done + + +; hMultiplicand <<= 1 + + ld a, [hMultiplicand + 2] + add a + ld [hMultiplicand + 2], a + + ld a, [hMultiplicand + 1] + rla + ld [hMultiplicand + 1], a + + ld a, [hMultiplicand + 0] + rla + ld [hMultiplicand + 0], a + + ld a, [hProduct] + rla + ld [hProduct], a + + jr .loop + + +.done + ld a, [hMathBuffer + 4] + ld [hProduct + 3], a + + ld a, [hMathBuffer + 3] + ld [hProduct + 2], a + + ld a, [hMathBuffer + 2] + ld [hProduct + 1], a + + ld a, [hMathBuffer + 1] + ld [hProduct + 0], a + + ret +; 673e + + +_Divide:: ; 673e + xor a + ld [hMathBuffer + 0], a + ld [hMathBuffer + 1], a + ld [hMathBuffer + 2], a + ld [hMathBuffer + 3], a + ld [hMathBuffer + 4], a + + ld a, 9 + ld e, a + +.loop + ld a, [hMathBuffer + 0] + ld c, a + ld a, [hDividend + 1] + sub c + ld d, a + + ld a, [hDivisor] + ld c, a + ld a, [hDividend + 0] + sbc c + jr c, .next + + ld [hDividend + 0], a + + ld a, d + ld [hDividend + 1], a + + ld a, [hMathBuffer + 4] + inc a + ld [hMathBuffer + 4], a + + jr .loop + +.next + ld a, b + cp 1 + jr z, .done + + ld a, [hMathBuffer + 4] + add a + ld [hMathBuffer + 4], a + + ld a, [hMathBuffer + 3] + rla + ld [hMathBuffer + 3], a + + ld a, [hMathBuffer + 2] + rla + ld [hMathBuffer + 2], a + + ld a, [hMathBuffer + 1] + rla + ld [hMathBuffer + 1], a + + dec e + jr nz, .next2 + + ld e, 8 + ld a, [hMathBuffer + 0] + ld [hDivisor], a + xor a + ld [hMathBuffer + 0], a + + ld a, [hDividend + 1] + ld [hDividend + 0], a + + ld a, [hDividend + 2] + ld [hDividend + 1], a + + ld a, [hDividend + 3] + ld [hDividend + 2], a + +.next2 + ld a, e + cp 1 + jr nz, .okay + dec b + +.okay + ld a, [hDivisor] + srl a + ld [hDivisor], a + + ld a, [hMathBuffer + 0] + rr a + ld [hMathBuffer + 0], a + + jr .loop + +.done + ld a, [hDividend + 1] + ld [hDivisor], a + + ld a, [hMathBuffer + 4] + ld [hDividend + 3], a + + ld a, [hMathBuffer + 3] + ld [hDividend + 2], a + + ld a, [hMathBuffer + 2] + ld [hDividend + 1], a + + ld a, [hMathBuffer + 1] + ld [hDividend + 0], a + + ret +; 67c1 |