Pentagram: Routine at C6CC

C6CC: Mark Room Visited

Used by the routine at BuildRoom.

Sets the bit for a room in the table of the rooms that the player has visited, RoomsVisitedBitmap. The room number is in eight bits: the upper five choose the byte, and the lower three choose the bit, starting from the top of the byte.

Input
IX	Record of the legs, which holds the number of the room

Find the byte for this room.

MarkRoomVisited

C6CC

LD A,(IX+$08)

Fetch the room.

C6CF

RRA

Move the upper five bits of the room to the lower five.

C6D0

RRA

C6D1

RRA

C6D2

AND %00011111

Keep only those bits.

C6D4

LD E,A

Set the offset of the byte in E.

C6D5

LD A,(IX+$08)

Fetch the room again.

Make the bit for this room.

C6D8

AND %00000111

Keep only the lower three bits.

C6DA

LD B,A

Keep the bit number.

C6DB

INC B

Add one to it, to be the number of times to rotate.

C6DC

XOR A

Start with all of the bits clear.

C6DD

SCF

Set the carry flag.

MarkRoomVisited_Rotate

C6DE

RRA

Rotate the carry flag in from the left.

C6DF

DJNZ MarkRoomVisited_Rotate

Decrease the counter and loop until the bit is in place.

Set the bit in the table of rooms visited.

C6E1

LD D,$00

Set D to zero, to make the offset of the byte a whole number.

C6E3

LD HL,$A74F

Start at the table of rooms visited.

C6E6

ADD HL,DE

Add the offset to get the address of the byte.

C6E7

OR (HL)

Add the bit for this room to those that are set.

C6E8

LD (HL),A

Set the byte.

C6E9

RET

Return.