Decompile weapon 15 func_ptr_80170014 (#1121)

There are only a few weapons that make use of the func_ptr_80170014
function, and this is the first of them.

I don't really know how to pull in data for functions, so keeping these
as externs for now. Particularly, I can't find where in the assembly the
bytes of D_6D000_8017A2B0 exist. They don't appear to be in
asm/us/weapon/data.

We identify a couple members of the `ET_Weapon` struct, and since
they're a change to velocity, I named them acceleration. This breaks
weapon 29's code (it uses different datatypes at offset 0x9C), but since
there's already an ET_Weapon29 dedicated alternative entity, we can
continue to use that instead.

Been a while since I've done a PR, nice to pick it back up, hope this is
good :)

Co-authored-by: sozud <122322823+sozud@users.noreply.github.com>

include/entity.h

@@ -164,9 +164,8 @@ typedef struct {
     /* 0x90 */ s32 unk90;
     /* 0x94 */ s32 unk94;
     /* 0x98 */ s32 unk98;
-    /* 0x9C */ s16 unk9C;
-    /* 0x9E */ s16 unk9E;
-    /* 0xA0 */ s32 unkA0;
+    /* 0x9C */ s32 accelerationX;
+    /* 0xA0 */ s32 accelerationY;
     /* 0xA4 */ s32 unkA4;
     /* 0xA8 */ s32 unkA8;
     /* 0xAC */ u8 unkAC;
@@ -177,6 +176,17 @@ typedef struct {
 typedef struct {
     /* 0x7C */ u8 unk7C;
     /* 0x7D */ u8 unk7D;
+    /* 0x7E */ s16 unk7E;
+    /* 0x80 */ s16 unk80;
+    /* 0x82 */ s16 unk82;
+    /* 0x84 */ s32 unk84;
+    /* 0x88 */ s16 childPalette;
+    /* 0x8A */ s16 unk8A;
+    /* 0x8C */ struct Entity* parent;
+    /* 0x90 */ s32 unk90;
+    /* 0x94 */ s32 unk94;
+    /* 0x98 */ s32 unk98;
+    /* 0x9C */ s16 unk9C;
 } ET_Weapon29;
 
 typedef struct {

src/weapon/w_015.c

@@ -35,7 +35,53 @@ INCLUDE_ASM("weapon/nonmatchings/w_015", func_ptr_8017000C);
 
 INCLUDE_ASM("weapon/nonmatchings/w_015", func_ptr_80170010);
 
-INCLUDE_ASM("weapon/nonmatchings/w_015", func_ptr_80170014);
+extern SpriteParts D_6D000_8017A2B0[];
+extern AnimationFrame D_6D000_8017A770[];
+
+void func_ptr_80170014(Entity* self) {
+    s16 angle;
+
+    if (self->step == 0) {
+        if (self->ext.weapon.parent->entityId == 0) {
+            DestroyEntity(self);
+            return;
+        }
+        SetSpriteBank2(D_6D000_8017A2B0);
+        self->animSet = ANIMSET_OVL(17);
+        self->palette = 0x111;
+        self->unk5A = 101;
+        if (g_HandId != 0) {
+            self->animSet += 2;
+            self->palette += 24;
+            self->unk5A = 103;
+        }
+        self->unk4C = D_6D000_8017A770;
+        self->flags = FLAG_UNK_08000000 | FLAG_UNK_100000;
+        self->zPriority = PLAYER.zPriority - 2;
+        self->drawMode = DRAW_TPAGE | 0x20;
+        angle = ratan2(-self->ext.weapon.parent->velocityY,
+                       self->ext.weapon.parent->velocityX);
+        angle += (0x500 + (rand() % 0x600));
+        self->velocityX = rcos(angle) * 64;
+        self->velocityY = rsin(angle) * -64;
+        self->ext.weapon.accelerationX = -self->velocityX / 13;
+        self->ext.weapon.accelerationY = -self->velocityY / 13;
+        self->ext.weapon.equipId = self->ext.weapon.parent->ext.weapon.equipId;
+        SetWeaponProperties(self, 0);
+        self->enemyId = self->ext.weapon.parent->enemyId;
+        self->hitboxHeight = self->hitboxWidth = 12;
+        self->step++;
+        return;
+    }
+    if (self->animFrameDuration < 0) {
+        DestroyEntity(self);
+        return;
+    }
+    self->posY.val += self->velocityY;
+    self->posX.val += self->velocityX;
+    self->velocityX += self->ext.weapon.accelerationX;
+    self->velocityY += self->ext.weapon.accelerationY;
+}
 
 int GetWeaponId(void) { return 15; }
 

src/weapon/w_029.c

@@ -391,7 +391,7 @@ void func_ptr_80170024(Entity* self) {
             self->ext.weapon29.unk7D = 0;
         }
         self->flags |= 0x04800000;
-        self->ext.weapon.unk9C = 0x40;
+        self->ext.weapon29.unk9C = 0x40;
 
         for (i = 0, prim = &g_PrimBuf[self->primIndex]; prim != NULL; i++,
             prim = prim->next) {
@@ -504,9 +504,9 @@ void func_ptr_80170024(Entity* self) {
                 break;
             }
         }
-        self->ext.weapon.unk9C += 2;
-        if (self->ext.weapon.unk9C > 0x100) {
-            self->ext.weapon.unk9C = 0x100;
+        self->ext.weapon29.unk9C += 2;
+        if (self->ext.weapon29.unk9C > 0x100) {
+            self->ext.weapon29.unk9C = 0x100;
         }
     }
     firstPrim = prim = &g_PrimBuf[self->primIndex];
@@ -532,7 +532,7 @@ void func_ptr_80170024(Entity* self) {
     }
 
     var_s7 = &D_CF000_8017C9A0[dragonNumber][0];
-    size = ((self->ext.weapon.unk9C * 54 / 256) *
+    size = ((self->ext.weapon29.unk9C * 54 / 256) *
             (rsin(var_s7->unkE) * var_s7->unk14 / 256 + 4096)) /
            4096;
     nextX = (var_s7 + 1)->posX.i.hi;