SYSMOUSE_MAXFRAMES
sysmouse_start = (sysmouse_start + 1) % SYSMOUSE_MAXFRAMES;
if (sysmouse_buffer == NULL || sysmouse_length == SYSMOUSE_MAXFRAMES)
idx = (sysmouse_start + sysmouse_length) % SYSMOUSE_MAXFRAMES;
buf = malloc(MOUSE_SYS_PACKETSIZE * SYSMOUSE_MAXFRAMES,