1 files changed, 85 insertions, 0 deletions
diff --git a/src/home/objects.asm b/src/home/objects.asm
new file mode 100644
index 0000000..c9a9885
--- /dev/null
+++ b/src/home/objects.asm
@@ -0,0 +1,85 @@
+; set attributes for [hl] sprites starting from wOAM + [wOAMOffset] / 4
+; return carry if reached end of wOAM before finishing
+SetManyObjectsAttributes: ; 950 (0:950)
+	push hl
+	ld a, [wOAMOffset]
+	ld c, a
+	ld b, HIGH(wOAM)
+	cp 40 * 4
+	jr nc, .beyond_oam
+	pop hl
+	ld a, [hli] ; [hl] = how many obj?
+.copy_obj_loop
+	push af
+	ld a, [hli]
+	add e
+	ld [bc], a ; Y Position <- [hl + 1 + 4*i] + e
+	inc bc
+	ld a, [hli]
+	add d
+	ld [bc], a ; X Position <- [hl + 2 + 4*i] + d
+	inc bc
+	ld a, [hli]
+	ld [bc], a ; Tile/Pattern Number <- [hl + 3 + 4*i]
+	inc bc
+	ld a, [hli]
+	ld [bc], a ; Attributes/Flags <- [hl + 4 + 4*i]
+	inc bc
+	ld a, c
+	cp 40 * 4
+	jr nc, .beyond_oam
+	pop af
+	dec a
+	jr nz, .copy_obj_loop
+	or a
+.done
+	ld hl, wOAMOffset
+	ld [hl], c
+	ret
+.beyond_oam
+	pop hl
+	scf
+	jr .done
+
+; for the sprite at wOAM + [wOAMOffset] / 4, set its attributes from registers e, d, c, b
+; return carry if [wOAMOffset] > 40 * 4 (beyond the end of wOAM)
+SetOneObjectAttributes:
+	push hl
+	ld a, [wOAMOffset]
+	ld l, a
+	ld h, HIGH(wOAM)
+	cp 40 * 4
+	jr nc, .beyond_oam
+	ld [hl], e ; Y Position
+	inc hl
+	ld [hl], d ; X Position
+	inc hl
+	ld [hl], c ; Tile/Pattern Number
+	inc hl
+	ld [hl], b ; Attributes/Flags
+	inc hl
+	ld a, l
+	ld [wOAMOffset], a
+	pop hl
+	or a
+	ret
+.beyond_oam
+	pop hl
+	scf
+	ret
+
+; set the Y Position and X Position of all sprites in wOAM to $00
+ZeroObjectPositions:
+	xor a
+	ld [wOAMOffset], a
+	ld hl, wOAM
+	ld c, 40
+	xor a
+.loop
+	ld [hli], a
+	ld [hli], a
+	inc hl
+	inc hl
+	dec c
+	jr nz, .loop
+	ret