fastCopy routine for tilemap

;##########################
;#UPDATEROTATION
;#After changing the x offset
;# of the map, we need to update
;# the rotation in the fastcopy
;# routine.
;#Explanation:
;#It's a bit confusing i admit,
;# if you have any questions about
;# this part it'd probably be better
;# for now just to ask me personally
;# about it.
;##########################
updateRotation:
    ld a,(xOff)         ;what is the xOffset?
    and 7               ;we're only interested in the lower three bits (essentially xOff % 8)
    ld hl,gbufMask
    ld e,a
    ld d,0
    add hl,de           ;pointer to the rotation mask
    ex af,af'           ;save a (swap with shadow register)
    ld a,(hl)
    ld hl,maskLeft
    ld (hl),a
    ld hl,maskRight
    cpl                 ;xor $FF
    ld (hl),a
    ex af,af'

    ld hl,rotateRight
    cp 4
    jr nc,rotarDer
    ld hl,rotateLeft
rotarDer:
    and %00000011
    ld e,a
    ld d,0
    add hl,de
    push hl
    ld de,rotLeft
    ldi
    ldi
    ldi
    ldi
    pop hl
    ld de,rotRight
    ldi
    ldi
    ldi
    ldi
    ret

rotateRight:       ;if offset greater than or equal to 4, rotate the gbuf right up to four times
    rrca
    rrca
    rrca
    rrca
rotateLeft:       ;the nops keep it smoother (same delay as rlca)
    nop          ; so whether we shift or not, it will take the same amount of cycles
    nop
    nop
    nop
    rlca
    rlca
    rlca
    rlca
gbufMask:
.db %11111111   ;0 display all of the first byte, none of the second
.db %11111110   ;1 after rotating left once, we only want the 7 leftern most bits of byte 1, and rightmost bit of byte 2
.db %11111100   ;2
.db %11111000   ;3
.db %11110000   ;4
.db %11100000   ;5
.db %11000000   ;6
.db %10000000   ;7

drawGbuf:
    ld a,$80
    out ($10),a     ;set row ($80: 0, to $BF:63)
    ld hl,saferam1-14+(14*64)-14    ;
                                    ;
xOff = $+1
    ld a,0          ;if xOff > 8, skip the first byte (it's offscreen)
    cp 8
    jr c,$+3
    inc hl
noSkip:
yOff = $+1
    ld b,0
    inc b
    ld de,14
    add hl,de
    djnz $-4
noSkip2:
    ld a,$20        ;$20: col 0, $2E: col 14
    ld c,a
    ld b,64         ;64 filas
fastCopyAgain:
    inc c           ;avanzar a proxima fila
    push bc
    ld de,-(14*64)
    out ($10),a     ;actualizar columna
    add hl,de
    ld de,13
    inc hl
fastCopyLoop:
    add hl,de
    ld a,(hl)       ;cargar valor en gbuf a a
rotLeft:
 .db 0,0,0,0            ;rotate the values we need
maskLeft = $+1
    and $FF         ;necesitamos los valores de la izquierda
    ld c,a
    inc hl
    ld a,(hl)       ;el proximo byte que llena el resto del primero
rotRight:
 .db 0,0,0,0
maskRight = $+1
    and 0
    or c
    out ($11),a
    djnz fastCopyLoop
    pop bc
    ld a,c
    cp $2B+1
    jr nz,fastCopyAgain
    ret