;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-

;;############ HANDLES BIG MEMORY MANAGMENTS ############
;;Move memory from B_start B_end to A_start , (implied address)
;; B_start and B_end gets modified under execution.
.proc memcpy
        A_start = $FAFB
        B_start = $FCFD
        B_end = $FEFF

        ;; Let Y + A_start lower nibble represent A_start
        ;; therefor: A_start = Y - A_start
        ;; With Y we mean what Y will represent later aka >B_start
        Sub_16 >A_start, <A_start, >B_start, #$00

        ;;Lets move B_start lover-nibble to Y
        LDY >B_start
        LDA #$00
        STA >B_start
loop:
        ;Lag_16 >B_end, <B_end, >B_start, <B_start, end_loop
        Lag_16y >B_end, <B_end, <B_start, end_loop
        ;Lag_16y <B_start, >B_end, <B_end, end_loop ; IF B_end >B_start stop the loop
        LDA (>B_start), Y
        STA (>A_start), Y
        ;Tip save time by counting downward, fast to check if Y ==0 // hugo
        INY
        TYA
        CMP #$ff
        BNE loop
        ;BPL loop; Branch if Y dont overflow
        ;; Fix overflow
        LDY #$00
        INC <A_start
        INC <B_start
        JMP loop
end_loop:
RTS
.endproc