UpdateScreen.C

extern void UpdateScreen(void);
#pragma aux UpdateScreen =      \
    "mov si, ScreenBuff"        \
    "mov di, 00h"               \
    "mov ax, [ScreenSeg]"       \
    "mov es, ax"                \
    "mov cx, SCREEN_SIZE"       \
    "mov dx, 03DAh"  /* Port to read vblank status */ \
                                \
    /* Check for reduced snow flag */ \
    "cmp [ReduceCGASnow], 1"    \
    "je _LessSnow"              \
                                \
    /* Check for VSYNC flag */  \
    "cmp [UseVSYNC], 1"         \
    "jne _SkipSync"             \
                                \
    "_blk:"                     \
    "in al, dx"                 \
    "test al, 8"                \
    "jz _blk"                   \
    "_SkipSync:"                \
    "rep movsw"                 \
    "jmp End"                   \
                                \
    /* Reduced CGA snow routine */ \
    "_LessSnow:"                \
    "in al, dx"                 \
    "test al, 9"                \
    "jz _LessSnow"              \
    "movsw"                     \
    "movsw"                     \
    "movsw"                     \
    "movsw"                     \
    "sub cx, 4"                 \
    "jnz _LessSnow"             \
    "End:"                      \
    modify [ax cx dx si di es];