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Upload literally everything from the pokecrystal16 expand-move-ID branch

engine/events/engine_flags.asm

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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"