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