Routines
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37510: Get Other Door Half
Used by the routines at EnterDoor, OpenDoorway and CloseDoorway.
A door is held as two 8-byte entities, one for each of the two rooms that it joins, and these are 8 bytes apart with one of them on an address that has bit 3 reset. This flips bit 3 of IX to get the other.
Input
IX One half of the door
Output
IX The other half of the door
GetOtherDoorHalf 37510 PUSH IX Copy IX into HL.
37512 POP HL
37513 LD A,L Fetch the low byte of the address of this half.
37514 XOR %00001000 Flip bit 3.
37516 LD L,A Keep the address of the other half of the door in L.
37517 PUSH HL Copy HL into IX, as the other half of the door.
37518 POP IX
37520 RET Return.
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