[Decompilation] [th04] Bullets: Sprite selection by angle

Part of P0150, funded by Blue Bolt.

th04/main/bullet/add.cpp

@@ -419,3 +419,12 @@ void near bullet_template_speedtune_for_playperf(void)
 		bullet_template.speed.set(0.5f);
 	}
 }
+
+static const unsigned char ANGLE_PER_SPRITE = (0x80 / BULLET_D_CELS);
+
+unsigned char pascal near bullet_patnum_for_angle(unsigned char angle)
+{
+	return (
+		((angle + (ANGLE_PER_SPRITE / 2) - 1) & (0x80 - 1)) / ANGLE_PER_SPRITE
+	);
+}

th04/main/bullet/bullet.hpp

@@ -107,7 +107,7 @@ void pascal near bullet_update_patnum(bullet_t near *bullet);
 
 // Returns the offset for a directional bullet sprite that shows the given
 // [angle].
-int pascal near bullet_patnum_for_angle(unsigned char angle);
+unsigned char pascal near bullet_patnum_for_angle(unsigned char angle);
 
 // Turns every 4th bullet into a point item when zapping bullets.
 extern bool bullet_zap_drop_point_items;

th04/main/bullet/patnum_for_angle.asm

@@ -1,17 +0,0 @@
-public BULLET_PATNUM_FOR_ANGLE
-bullet_patnum_for_angle	proc near
-
-@@angle		= byte ptr  4
-
-	push	bp
-	mov	bp, sp
-	mov	al, [bp+@@angle]
-	mov	ah, 0
-	add	ax, 3
-	and	ax, 7Fh
-	mov	bx, 8
-	cwd
-	idiv	bx
-	pop	bp
-	retn	2
-bullet_patnum_for_angle	endp

th04_main.asm

@@ -28228,8 +28228,8 @@ main_033_TEXT	segment	byte public 'CODE' use16
 	BULLET_VELOCITY_AND_ANGLE_SET procdesc pascal near \
 		i:word
 	_bullet_template_speedtune_for_pl procdesc near
-
-include th04/main/bullet/patnum_for_angle.asm
+	BULLET_PATNUM_FOR_ANGLE procdesc pascal near \
+		angle:byte
 
 ; =============== S U B	R O U T	I N E =======================================