#include "substdio.h"int substdio_copy(ssout,ssin)register substdio *ssout;register substdio *ssin;{  register int n;  register char *x;  for (;;) {    n = substdio_feed(ssin);    if (n < 0) return -2;    if (!n) return 0;    x = substdio_PEEK(ssin);    if (substdio_put(ssout,x,n) == -1) return -3;    substdio_SEEK(ssin,n);  }}