| Routines

7BB6: Control the hook while it's flying

The address of this uninterruptible subcommand routine is placed into bytes 0x12 and 0x13 of the hook's buffer by the routine at 7BE1. It controls the hook until the end of its flight, at which point it places a rope above the roof of no. 19 if necessary, or else restores the hook to its original location on the top floor of no. 74.
Input
H | 0xE5 (hook)
7BB6 | CALL $E9C8 | Update the SRB for the hook's current animatory state and location
7BB9 | LD L,$14 | Byte 0x14 of the hook's buffer holds the distance remaining in the hook's flight
7BBB | DEC (HL) | Decrease this by 1
7BBC | JR Z,$7BC8 | Jump if the hook's flight has ended
7BBE | RLCA | Set the carry flag if the hook is flying rightwards
7BBF | RRCA
7BC0 | DEC E | Decrement the hook's x-coordinate
7BC1 | JR NC,$7BC5 | Jump if the hook is flying leftwards
7BC3 | INC E | Otherwise increment the hook's x-coordinate
7BC4 | INC E
7BC5 | JP NZ,$E9D5 | Update the hook's animatory state and location and update the SRB (unless the hook has flown off the edge of the play area)
The hook's flight has ended (either naturally or by escaping the play area). Check whether it reached the roof of no. 17.
7BC8 | DEC L | L=0x13
7BC9 | XOR A | Remove the address of this routine from bytes 0x12 and 0x13 of the hook's buffer
7BCA | LD (HL),A
7BCB | LD L,$03 | Clear all flags in byte 0x03 of the hook's buffer
7BCD | LD (HL),A
7BCE | DEC L | Set the hook's y-coordinate to 50 (out of sight)
7BCF | LD (HL),$32
7BD1 | LD A,D | A=hook's y-coordinate while it was flying
7BD2 | CP $09 | Was it greater than 9?
7BD4 | JR NC,$7BDC | Jump if so
7BD6 | LD A,E | A=x-coordinate of the hook at the end of its flight
7BD7 | CP $DF | Did the hook reach the roof of no. 17?
7BD9 | JP NC,$FC25 | Jump if so
7BDC | LD HL,$7D1C | Reactivate the entry for the hook in the object table at 7D1C
7BDF | DEC (HL)
7BE0 | RET |