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72 lines
834 B
NASM
72 lines
834 B
NASM
SmallFarFlagAction:
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; Perform action b on bit c in flag array hl.
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; If checking a flag, check flag array d:hl unless d is 0.
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; For longer flag arrays, see FlagAction.
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push hl
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push bc
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; Divide by 8 to get the byte we want.
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push bc
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srl c
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srl c
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srl c
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ld b, 0
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add hl, bc
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pop bc
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; Which bit we want from the byte
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ld a, c
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and 7
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ld c, a
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; Shift left until we can mask the bit
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ld a, 1
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jr z, .shifted
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.shift
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add a
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dec c
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jr nz, .shift
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.shifted
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ld c, a
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; What are we doing to this flag?
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dec b
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jr z, .set ; 1 = SET_FLAG
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dec b
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jr z, .check ; 2 = CHECK_FLAG
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; 0 = RESET_FLAG
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; reset
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ld a, c
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cpl
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and [hl]
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ld [hl], a
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jr .done
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.set
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ld a, [hl]
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or c
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ld [hl], a
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jr .done
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.check
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ld a, d
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cp 0
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jr nz, .farcheck
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ld a, [hl]
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and c
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jr .done
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.farcheck
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call GetFarByte
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and c
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.done
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pop bc
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pop hl
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ld c, a
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ret
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