Merge branch 'yenatch/split-predefs-specials-stds' into fix-split-predefs-specials-stds

https://github.com/kanzure/pokecrystal/pull/198

1 files changed, 76 insertions, 0 deletions

diff --git a/common/math.asm b/common/math.asm
new file mode 100644
index 000000000..87a00c412
--- /dev/null
+++ b/common/math.asm
@@ -0,0 +1,76 @@
+SimpleMultiply: ; 3105
+; Return a * c.
+	and a
+	ret z
+
+	push bc
+	ld b, a
+	xor a
+.loop
+	add c
+	dec b
+	jr nz, .loop
+	pop bc
+	ret
+; 3110
+
+
+SimpleDivide: ; 3110
+; Divide a by c. Return quotient b and remainder a.
+	ld b, 0
+.loop
+	inc b
+	sub c
+	jr nc, .loop
+	dec b
+	add c
+	ret
+; 3119
+
+
+Multiply: ; 3119
+; Multiply hMultiplicand (3 bytes) by hMultiplier. Result in hProduct.
+; All values are big endian.
+	push hl
+	push bc
+
+	callab _Multiply
+
+	pop bc
+	pop hl
+	ret
+; 3124
+
+
+Divide: ; 3124
+; Divide hDividend length b (max 4 bytes) by hDivisor. Result in hQuotient.
+; All values are big endian.
+	push hl
+	push de
+	push bc
+	ld a, [hROMBank]
+	push af
+	ld a, BANK(_Divide)
+	rst Bankswitch
+
+	call _Divide
+
+	pop af
+	rst Bankswitch
+	pop bc
+	pop de
+	pop hl
+	ret
+; 3136
+
+
+SubtractSigned: ; 3136
+; Return a - b, sign in carry.
+	sub b
+	ret nc
+	cpl
+	add 1
+	scf
+	ret
+; 313d
+