The Hobbit: Routine at 9B93

9B93: Step to the next three-byte entry

Used by the routines at NEXT_OBJECT_KEEP_A, ROOM_LEFT, FIND_NAMED_OBJECT, ROOM_BY_NAME, FIND_EXIT and EXIT_TO. Adds 3 to IX and returns Z at the $FF that ends a list. Shared with other lists of three-byte entries, which is why it also loads IY from bytes 1 and 2 -- for an exit those are the object it goes through and the destination, not an address.
NEXT_EXIT	9B93	EXX	Keep the caller's BC, DE and HL
	9B94	LD DE,$0003	On three bytes to the next entry
	9B97	ADD IX,DE	On three bytes to the next entry
	9B99	LD D,(IX+$02)	IY = bytes 1 and 2 of it, which for an object index entry is the record's address
	9B9C	LD E,(IX+$01)
	9B9F	PUSH DE
	9BA0	POP IY
	9BA2	LD A,(IX+$00)	Z if this is the $FF that ends the list
	9BA5	CP $FF	Z if this is the $FF that ends the list
	9BA7	EXX
	9BA8	RET