mirror of https://github.com/pret/pokecrystal.git
97 lines
1.4 KiB
NASM
97 lines
1.4 KiB
NASM
; Syntactic sugar macros
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MACRO lb ; r, hi, lo
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ld \1, ((\2) & $ff) << 8 | ((\3) & $ff)
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ENDM
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MACRO ln ; r, hi, lo
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ld \1, ((\2) & $f) << 4 | ((\3) & $f)
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ENDM
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; Design patterns
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MACRO jumptable
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ld a, [\2]
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ld e, a
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ld d, 0
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ld hl, \1
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add hl, de
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add hl, de
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ld a, [hli]
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ld h, [hl]
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ld l, a
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jp hl
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ENDM
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MACRO maskbits
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; masks just enough bits to cover values 0 to \1 - 1
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; \2 is an optional shift amount
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; e.g. "maskbits 26" becomes "and %00011111" (since 26 - 1 = %00011001)
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; and "maskbits 3, 2" becomes "and %00001100" (since "maskbits 3" becomes %00000011)
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; example usage in rejection sampling:
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; .loop
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; call Random
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; maskbits 26
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; cp 26
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; jr nc, .loop
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assert 0 < (\1) && (\1) <= $100, "bitmask must be 8-bit"
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DEF x = 1
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rept 8
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if x + 1 < (\1)
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DEF x = (x << 1) | 1
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endc
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endr
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if _NARG == 2
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and x << (\2)
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else
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and x
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endc
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ENDM
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MACRO calc_sine_wave
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; input: a = a signed 6-bit value
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; output: a = d * sin(a * pi/32)
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and %111111
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cp %100000
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jr nc, .negative\@
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call .apply\@
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ld a, h
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ret
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.negative\@
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and %011111
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call .apply\@
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ld a, h
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xor $ff
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inc a
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ret
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.apply\@
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ld e, a
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ld a, d
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ld d, 0
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if _NARG == 1
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ld hl, \1
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else
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ld hl, .sinetable\@
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endc
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add hl, de
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add hl, de
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ld e, [hl]
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inc hl
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ld d, [hl]
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ld hl, 0
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.multiply\@ ; factor amplitude
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srl a
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jr nc, .even\@
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add hl, de
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.even\@
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sla e
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rl d
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and a
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jr nz, .multiply\@
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ret
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if _NARG == 0
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.sinetable\@
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sine_table 32
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endc
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ENDM
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