From 53b7926f5e2c06384f228dccd03c70c960ae16b0 Mon Sep 17 00:00:00 2001
From: yenatch <yenatch@gmail.com>
Date: Mon, 9 Sep 2013 01:21:36 -0400
Subject: move multiplication/division functions into common/math.asm

---
 common/math.asm | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 common/math.asm

(limited to 'common/math.asm')

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
+
-- 
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