sf_write
sf_write(b, digits + 1, copy);
sf_write(b, digits, copy);
sf_write(b, digits, copy);
sf_write(b, digits + decpt, copy);
sf_write(b, digits, ndig);
sf_write(b, digits, copy);
sf_write(b, digits + decpt, frac);
sf_write(b, digits + 1, ndig - 1);
sf_write(b, digits + 1, after);
sf_write(b, digits + 1, copy);