#[inline]
pub fn be_varint_u64<I, E: ParseError<I>>(mut i: I) -> IResult<I, u64, E>
where
    I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength,
{
    let mut result = 0;

    'end: {
        let mut byte;
        for _ in 0..(u64::BITS / 8) {
            (i, byte) = be_u8(i)?;
            result = (result << 7) + u64::from(byte & 0x7F);
            if byte < 0x80 {
                break 'end;
            }
        }
        (i, byte) = be_u8(i)?;
        result = (result << 8) + u64::from(byte);
    }

    Ok((i, result))
}