for i := l - 1; i >= 0; i-- {
		o := byte(n >> uint(i*7))
		o &= 0x7f
		if i != 0 {
			o |= 0x80
		}

		dst = append(dst, o)
	}

	return dst
}

func makeBigInt(n *big.Int) (encoder, error) {
	if n == nil {
		return nil, StructuralError{"empty integer"}
	}

	if n.Sign() < 0 {
		// A negative number has to be converted to two's-complement

		}
		if test.ok {
			if ret.String() != test.base10 {
				t.Errorf("#%d: bad result from %x, got %s want %s", i, test.in, ret.String(), test.base10)
			}
			e, err := makeBigInt(ret)
			if err != nil {
				t.Errorf("%d: err=%q", i, err)
				continue
			}
			result := make([]byte, e.Len())
			e.Encode(result)
			if !bytes.Equal(result, test.in) {