The Hobbit (v1.0): Routine at 9AC7

9AC7: Call the routine at HL (if HL is not 0)

A general dispatcher used throughout the game for tables of routine addresses (the room-entry handlers, the timer table, the character table). All registers except AF are preserved, and a zero address means 'no routine', so tables can leave entries empty. The actual call is made by the JP (HL) at 9ADB.

Input
HL	Routine address, or 0

9AC7

PUSH IX

Save every register the routine we are about to call might disturb...

9AC9

PUSH IY

9ACB

PUSH DE

9ACC

PUSH BC

9ACD

PUSH HL

...including HL itself, which holds the address to call

9ACE

LD A,L

Is that address 0, meaning "there is nothing to call"?

9ACF

OR H

9AD0

CALL NZ,$9ADB

If it is not 0, make the call

9AD3

POP HL

Restore the registers, in the same order they were saved...

9AD4

POP BC

9AD5

POP DE

9AD6

POP IY

9AD8

POP IX

9ADA

RET