Routines
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6A12: Get door
This is called by a few routines to turn a door index into a pointer to a door structure (a door_t). The doors[] array contains pairs of door structures. If the door_REVERSE flag is set in bit 7, the first of the pair is returned, otherwise the second is.
Used by the routines at door_handling_interior, get_nearest_door, get_target and target_reached.
Input
A Index of door + door_REVERSE flag in bit 7.
Output
HL Pointer to door_t.
get_door 6A12 LD C,A Save the original A so we can test its flag bit in a moment
6A13 ADD A,A First double A since doors[] contains pairs of doors. This also discards the door_REVERSE flag in bit 7
6A14 LD L,A Form the address of doors[A] in HL
6A15 LD H,$00
6A17 ADD HL,HL
6A18 ADD HL,HL
6A19 LD DE,$78D6
6A1C ADD HL,DE
6A1D BIT 7,C Was the door_REVERSE flag (bit 7) set on entry?
6A1F RET Z If not, return with HL pointing to the entry
6A20 LD A,L Otherwise, point to the next entry along
6A21 ADD A,$04
6A23 LD L,A
6A24 RET NC
6A25 INC H
6A26 RET Return
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