Routines
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AA30: Swap an item when a character moves over it
Used by the routines at A92C and EB01.
Input
IY The base address of the character buffer (BC67 - BC6B)
AA30 PUSH HL Remember HL.
AA31 CALL $AA8C Get the static object buffer for this room.
AA34 INC HL Move to the flags and put them in A.
AA35 INC HL
AA36 INC HL
AA37 LD A,(HL)
AA38 AND (IY-$28) Is the current character allowed to pick it up?
AA3B JR Z,$AA74 Jump foward if they aren't.
The object the player is standing next to can be picked up, so do it.
AA3D LD A,(HL) Get the flag again.
AA3E AND $80 Is bit 7 set?
AA40 JR Z,$AA49 Jump if it isn't.
AA42 PUSH HL Is the buffer at iy pointing to the current character?
AA43 CALL $A921
AA46 POP HL
AA47 JR NZ,$AA74 Jump forward if it isn't.
The object can only be collected by this player, and can be done.
AA49 LD A,(HL) Put the flags in A.
AA4A RES 7,A Turn off bit 7.
AA4C LD D,A Store this in D.
AA4D LD A,(HL) Put the flags in A.
AA4E AND $80 Turn off bit 7.
AA50 OR (IY-$32) Merge it with the flags at BC35.
AA53 LD (HL),A Set this as the new value to use.
AA54 LD A,(IY-$37) Swap these flags with the values starting at BC3A.
AA57 LD (IY-$32),A
AA5A LD (IY-$37),D
AA5D LD A,(IY+$55) Set A to the second item held by this player.
AA60 DEC HL Move back to the start of the object buffer.
AA61 DEC HL
AA62 DEC HL
AA63 LD E,(HL) Put the old object ID in E.
AA64 LD (HL),A Replace it with this one.
AA65 LD A,(IY+$50) Set A to the first item held by this player.
AA68 LD (IY+$55),A Set it at the second item.
AA6B LD (IY+$50),E Set the item that was in the room as the second item.
AA6E CALL $A921 Is the buffer at IY pointing to the current character?
AA71 CALL Z,$E41D If so, need to update the inventory.
AA74 LD A,($B951) Is the player in the current room?
AA77 CP (IY+$0F)
AA7A CALL Z,$AA7F If so, play the "item swapped" sound.
AA7D POP HL Restore HL and return.
AA7E RET
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