static int r_forward(RSFD rfd, void *buf, const void *untilbuf);
static void r_pos (RSFD rfd, double *current, double *total);
static int r_read (RSFD rfd, void *buf);
static int r_forward(RSFD rfd, void *buf, const void *untilbuf);
static void r_pos (RSFD rfd, double *current, double *total);
static int r_read (RSFD rfd, void *buf);