z80.asm

; z80asm z80.asm && docker run -v `pwd | sed "s /mnt  "`:/golf esolang/z80 sh -c "z80 /golf/a.bin < /golf/in" | xxd | head
    ld ix, $1000
    call read_int
    ld ix, $1001
    call read_int
    ld ix, $1002
    call read_int
    ld ix, $1003
    call read_int
    ld ix, $1004
    call read_int
    ld ix, $1005
    call read_int
    ld ix, $1006
    call read_int
    ld ix, $1007
    call read_int
    ld ix, $1008
    call read_int
    ld ix, $1009
    call read_int
    ld ix, $100A
    call read_int
    ld ix, $100B
    call read_int

    ld ix, $1000
    ld a, ($1003)
    sub (ix+$0)
    ld ($1003), a
    ld a, ($1006)
    sub (ix+$0)
    ld ($1006), a
    ld a, ($1009)
    sub (ix+$0)
    ld ($1009), a

    ld ix, $1001
    ld a, ($1004)
    sub (ix+$0)
    ld ($1004), a
    ld a, ($1007)
    sub (ix+$0)
    ld ($1007), a
    ld a, ($100A)
    sub (ix+$0)
    ld ($100A), a

    ld ix, $1002
    ld a, ($1005)
    sub (ix+$0)
    ld ($1005), a
    ld a, ($1008)
    sub (ix+$0)
    ld ($1008), a
    ld a, ($100B)
    sub (ix+$0)
    ld ($100B), a

    ld ix, $2000
    ld (ix+0), 3
    ld (ix+1), 7
    ld (ix+2), 11
    call calc_mul3
    call nz, negate
    ld a, (ix+3)
    ld (ix+6), a
    ld a, (ix+4)
    ld (ix+7), a
    ld a, (ix+5)
    ld (ix+8), a

    ld (ix+0), 4
    ld (ix+1), 8
    ld (ix+2), 9
    call calc_mul3
    call nz, negate
    call add3

    ld (ix+0), 5
    ld (ix+1), 6
    ld (ix+2), 10
    call calc_mul3
    call nz, negate
    call add3

    ld (ix+0), 3
    ld (ix+1), 8
    ld (ix+2), 10
    call calc_mul3
    call z, negate
    call add3

    ld (ix+0), 4
    ld (ix+1), 6
    ld (ix+2), 11
    call calc_mul3
    call z, negate
    call add3

    ld (ix+0), 5
    ld (ix+1), 7
    ld (ix+2), 9
    call calc_mul3
    call z, negate
    call add3

    ld h, (ix+6)
    ld l, (ix+7)
    ld c, 6
    call div

    ld h, a
    ld d, l
    ld l, (ix+8)
    ld c, 6
    call div

    ; now answer is dl

    ld h, d
    ld c, 10
    ld ix, $2000
    ld b, 6
modloop:
    call div
    ld (ix+0), a
    inc ix
    djnz modloop

    ld ix, $2005
    ld b, 6
printloop:
    ld c, b
    call div
    ld a, (ix+0)
    add a, '0'
    call $8000
    ld b, c
    dec ix
    djnz printloop

    halt

read_int: ; read int into (ix)
    call $8003 ; getchar
    sub '0'
    ld b, a
    sla b
    sla b
    sla b ; b = a * 8
    sla a ; a = a * 2
    add a, b
    ld b, a
    call $8003 ; getchar
    sub '0'
    add a, b
    ld (ix+$0), a
    call $8003 ; getchar
    ret

mul: ; store result of de*c into ahl
    ld hl, 0
    ld a, c
    or a
    ret z ; return zero if c is 0
    ld b, c
    xor a ; a = 0
mul_loop:
    add hl, de
    jp nc, non_carry
    inc a
non_carry:
    djnz mul_loop
    ret

abs: ; a = abs(a)
    bit 7, a
    ret z
    neg
    ret

calc_mul3:
    ld hl, $1000
    ld b, 0
    ld c, (ix+0)
    add hl, bc
    ld a, (hl)
    call abs
    ld d, $0
    ld e, a

    ld hl, $1000
    ld b, 0
    ld c, (ix+1)
    add hl, bc
    ld a, (hl)
    call abs
    ld c, a

    call mul

    ld d, h
    ld e, l

    ld hl, $1000
    ld b, 0
    ld c, (ix+2)
    add hl, bc
    ld a, (hl)
    call abs
    ld c, a

    call mul

    ld (ix+3), a
    ld (ix+4), h
    ld (ix+5), l

    ; calculate sign of multiplication
    ld b, 0
    ld hl, $1000
    ld d, 0
    ld e, (ix+0)
    add hl, de
    ld a, (hl)
    bit 7, a
    jp z, skip0
    ld a, b
    xor $1
    ld b, a
skip0:
    ld hl, $1000
    ld d, 0
    ld e, (ix+1)
    add hl, de
    ld a, (hl)
    bit 7, a
    jp z, skip1
    ld a, b
    xor $1
    ld b, a
skip1:
    ld hl, $1000
    ld d, 0
    ld e, (ix+2)
    add hl, de
    ld a, (hl)
    bit 7, a
    jp z, skip2
    ld a, b
    xor $1
    ld b, a
skip2:
    bit 0, b
    ret

negate: ; negate (ix+3) - (ix+5)
    ld a, (ix+3)
    cpl
    ld d, a
    ld a, (ix+4)
    cpl
    ld b, a
    ld a, (ix+5)
    cpl
    ld c, a
    inc bc ; FIXME
    ld (ix+3), d
    ld (ix+4), b
    ld (ix+5), c
    ret

add3: ; add (ix+6) - (ix+8) by (ix+3) - (ix+5)
    ld a, (ix+3)
    ld b, (ix+4)
    ld c, (ix+5)
    ld d, (ix+6)
    ld h, (ix+7)
    ld l, (ix+8)
    add hl, bc
    adc a, d
    ld (ix+6), a
    ld (ix+7), h
    ld (ix+8), l
    ret

; divide hl by c
; http://wikiti.brandonw.net/index.php?title=Z80_Routines:Math:Division#16.2F8_division
div:
    xor a
    ld b, 16 ; loop counter
divloop:
    add hl, hl
    rla
    jr c, $+5
    cp c
    jr c, $+4
    sub c
    inc l
    djnz divloop
    ret