Routines
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42358: Check Enemy Overlap
Used by the routines at MoveThief, MoveHunter, SpawnEnemies and MoveDome.
Checks whether the entity overlaps any of the ten entities that are enemies (entities 4 to 13), apart from itself.
Input
IX Entity
DE X position
HL Y position
Output
IY The entity that has been hit
F The carry flag is set if there is one
CheckEnemyOverlap 42358 PUSH BC Save the register.
42359 LD B,10 There are ten enemies to check.
42361 LD IY,38608 Point IY at EnemyEntities.
This entry point is used by the routine at CheckEntityOverlap.
CheckEnemyOverlap_Next 42365 PUSH BC Save the counter.
42366 LD A,(IY+0) Fetch the type of the entity.
42369 AND A Jump if the entity is not in use.
42370 JR Z,CheckEnemyOverlap_Skip
42372 PUSH HL Save the Y position.
42373 PUSH IX Copy the address of the entity being moved into HL...
42375 POP HL
42376 PUSH IY ...and the address of the entity that is being checked into BC.
42378 POP BC
42379 AND A Subtract one from the other...
42380 SBC HL,BC
42382 POP HL ...restoring the Y position...
42383 JR Z,CheckEnemyOverlap_Skip ...and jump if they are the same entity.
42385 LD BC,61680 Use 240 as the distance in both directions.
42388 CALL ComparePositions Compare the positions using ComparePositions.
42391 JR C,CheckEnemyOverlap_Hit Jump if they overlap.
CheckEnemyOverlap_Skip 42393 LD BC,16 Each entity is 16 bytes long.
42396 ADD IY,BC Move on to the next one.
42398 POP BC Restore the counter.
42399 DJNZ CheckEnemyOverlap_Next Loop back until every entity has been checked.
42401 AND A Clear the carry flag...
42402 POP BC ...restore the register...
42403 RET ...and return.
CheckEnemyOverlap_Hit 42404 POP BC Discard the counter...
42405 POP BC ...and restore the register.
42406 RET Return with the carry flag set.
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