The Hobbit (v1.0): Routine at 91B9

The handler for putting the target into (or on) a container, the instrument. The target must be something that can be picked up (8CBA), and not already in the container ('I cannot do that'). Except for PUT ON, the container must be open ('the chest is closed'). There must be room: the container's size (byte 2), minus the target's size, minus the size of what is already inside (9C3D), must be positive ('the chest is too full'). Then the target takes the container's location and the container becomes its holder.

The handler for putting the target into (or on) a container, the instrument. The target must be something that can be picked up (8CBA), and not already in the container ('I cannot do that'). Except for PUT ON, the container must be open ('the chest is closed'). There must be room: the container's size (byte 2), minus the target's size, minus the size of what is already inside (9C3D), must be positive ('the chest is too full'). Then the target takes the container's location and the container becomes its holder.
91B9	CALL $8CBA	Is the target something that can even be picked up at all?
91BC	LD A,($B5DA)	Is the instrument (the container) actually the same object as the target's own holder already?
91BF	CP (IX+$01)
91C2	JP Z,$72C5	Yes: "I cannot do that." (it's already there)
91C5	LD IY,($B5FA)	IY = the instrument's (the container's) own record
91C9	LD A,($B5D8)	Is this actually PUT ON (action 18), rather than PUT IN or DROP IN?
91CC	CP $12
91CE	JR Z,$91D6	PUT ON: no need for the container to be open
91D0	BIT 5,(IY+$07)	PUT IN or DROP IN: is the container open?
91D4	JR Z,$9201	No: say so and stop, below
91D6	LD A,(IY+$02)	A = the container's own capacity (its size)
91D9	SUB (IX+$02)	Subtract the target's own size
91DC	JR C,$91E8	Already too big even on its own: fail, below
91DE	PUSH AF	Save what is left
91DF	LD A,($B5DA)	A = how much the container already holds
91E2	CALL $9C3D
91E5	LD B,A
91E6	POP AF	Subtract that too
91E7	SUB B	Subtract that too
91E8	LD HL,$AD0D	"the X is too full."
91EB	JP C,$72D4	Not enough room at all: say so and stop
91EE	JP Z,$72D4	Exactly full, with no room to spare: likewise
91F1	CALL $9C99	Dry run? Then stop here: it would work
91F4	LD A,(IY+$10)	The target moves to the container's own room...
91F7	LD (IX+$10),A	The target moves to the container's own room...
91FA	LD A,($B5DA)	...and the container becomes its new holder
91FD	LD (IX+$01),A
9200	RET
9201	LD A,$05	A = the state code for OPEN/CLOSED
9203	JP $A094	"the X is closed."