Use uncap decompressor

hUGEDriver.asm

@@ -255,9 +255,7 @@ ENDC
     pop de
     ld hl, order4
     ld bc, pattern4_buf
-    call .load_pattern
-
-    ret
+    ;; fallthrough
 
 .load_pattern:
     ld a, [hl+]
@@ -272,7 +270,12 @@ ENDC
     inc hl
     ld d, [hl]
 
-    call UNAPACK
+    ld h, d
+    ld l, e
+    ld d, b
+    ld e, c
+
+    call uncap
 
     ret
 

uncap.asm

@@ -0,0 +1,36 @@
+; resourced by tmk
+; visit Game Boy Compression Playground at https://github.com/gitendo/gbcp for more
+; Mega Man Xtreme 2 (USA, Europe).gbc uses exactly the same routine
+
+SECTION "Uncap Decompressor", ROM0
+
+uncap::
+	ld	a,[hl+]			; start with token
+	and	a			; 0 marks the end of packed data
+	ret	z
+	bit	7,a			; next byte is offset if 7th bit is set
+	jr	z,_literals             ; literals come next otherwise
+	and	$7F			; bits 0 - 6 define reference length
+	ld	c,a			; move length to c(ounter)
+	ld	a,[hl+]			; load offset
+	push	hl			; store packed data address
+	ld	l,a			; offset is negative because game boy cpu lacks
+	ld	h,$FF			; sub hl,de :)
+	add	hl,de			; locate reference
+_1:
+	ld	a,[hl+]			; and copy it
+	ld	[de],a
+	inc	de
+	dec	c
+	jr	nz,_1
+	pop	hl			; restore packed data address
+	jr	uncap			; continue
+_literals:
+	ld	c,a			; move length to c(ounter)
+_2:
+	ld	a,[hl+]			; and copy c literals
+	ld	[de],a
+	inc	de
+	dec	c
+	jr	nz,_2
+	jr	uncap			; continue