; -----------------------------------------------------------------------------------
;;
;;      Copyright 2008, 2009, 2012, 2013, 2021 Shane Tyler Yorks, Jure Sah
;;
;;      This stub is a part of LearnerKernel
;;
;;      LearnerKernel is free software: you can redistribute it and/or modify
;;      it under the terms of the GNU General Public License as published by
;;      the Free Software Foundation, either version 3 of the License, or
;;      (at your option) any later version.
;;
;;      Please refer to the README file for additional information.
;;
; -----------------------------------------------------------------------------------
flipISR:
        pushf   ;Preserve flags register
        cli ;Disable interrupts incase they were enabled
@@:     mov dx, 0x3DA   ;Move the hardware address of VGA Input Status Register #1 to dx register
        in al, dx   ;Read the value of the VGA Input Status Register #1 into the al register.
        and al, 1000b   ;Check if bit 3 (VRetrace/Vertical Retrace in progress)
        je @b       ;If happening, retry until it is not happening
@@:     in al, dx   ;Read again
        and al, 1000b   ;Check if is or isn't happening
        jne @b      ;If it's not happening, go back until it it is happening
        mov esi, dblBufLoc  ;Load the string source register with the back buffer
        mov edi, dword [VESAInfo+0x28]  ;Move the string destination register with the location of the front buffer the video card is sending to the screen
        mov ecx, scrsz/4    ;Load the size of the buffers (divided by 4, since we'll send 4 bytes at a time) into ECX
        rep movsd   ;Move 4 bytes from source to the data of destination until ECX is empty
        popf    ;restore the flags register (including interrupts if they were enabled)
        iret    ;Return to our regularly scheduled program