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EngineFlagAction::
; Do action b on engine flag de
;
; b = 0: reset flag
; = 1: set flag
; > 1: check flag, result in c
;
; Setting/resetting does not return a result.
; 16-bit flag ids are considered invalid, but it's nice
; to know that the infrastructure is there.
ld a, d
cp HIGH(NUM_ENGINE_FLAGS)
jr z, .ceiling
jr c, .read ; cp 0 can't set carry!
jr .invalid
; There are only NUM_ENGINE_FLAGS engine flags, so
; anything beyond that is invalid too.
.ceiling
ld a, e
cp LOW(NUM_ENGINE_FLAGS)
jr c, .read
; Invalid flags are treated as flag 00.
.invalid
xor a
ld e, a
ld d, a
; Get this flag's location.
.read
ld hl, EngineFlags
; location
add hl, de
add hl, de
; bit
add hl, de
; location
ld e, [hl]
inc hl
ld d, [hl]
inc hl
; bit
ld c, [hl]
; What are we doing with this flag?
ld a, b
cp 1
jr c, .reset ; b = 0
jr z, .set ; b = 1
; Return the given flag in c.
; check
ld a, [de]
and c
ld c, a
ret
; Set the given flag.
.set
ld a, [de]
or c
ld [de], a
ret
; Reset the given flag.
.reset
ld a, c
cpl ; AND all bits except the one in question
ld c, a
ld a, [de]
and c
ld [de], a
ret
INCLUDE "data/events/engine_flags.asm"
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