Routines
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40381: Index ID Table
Used by the routines at Start, Drawing, DisplayLocateHelpMessage, Action_Direction, Turn_RunTheActionHandler, Turn_RunTheHandlerIfPresent, Turn_UseASpecialObject, TableFindAnActionRecord, LocateObject and Event_DayDawnsOnTheTrolls.
Looks an id up in a table of id-and-address pairs.
Input
A Key ID
IX Address of table data
Output
IX The address in the table which matches the key ID
Searches through what is essentially key value data to find a key match.
IndexIdTable 40381 EXX Exchange registers.
40382 PUSH IX Point HL at the table in IX and keep the sought id in B.
40384 POP HL
40385 LD B,A
40386 LD E,3 Each index entry is 3 bytes.
40388 LD D,0 The index stride's high byte is zero.
Begin searching the table.
IndexIdTable_Loop 40390 LD A,(HL) Grab the next ID.
40391 CP B Jump to IndexIdTable_Found if this entry's id is the one sought.
40392 JR Z,IndexIdTable_Found
40394 CP 255 Jump to IndexIdTable_Found at the end of the index.
40396 JR Z,IndexIdTable_Found
40398 ADD HL,DE Step 3 bytes to the next id.
40399 JP IndexIdTable_Loop Jump back to IndexIdTable_Loop to begin searching the table.
Handle the output.
IndexIdTable_Found 40402 PUSH HL Set flags (checking if the key ID was not found).
40403 POP IX
40405 CP 255
40407 EXX Exchange registers.
40408 RET Return.
View the equivalent code in;
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