Implementing Input trait for bytes::Bytes

[StephanvanSchaik]

It would be useful to be able to use nom with the Bytes type from the bytes and the types from other similar crates such as arc-slice and byteview. While using these types does not speed up parsing with nom itself, they do help significantly in the post-processing stage in achieving zero-copy by avoiding unnecessary allocations as .clone() is much cheaper due to it incrementing an atomic reference counter and taking a subslice, rather than allocating more memory and copying over the subslice.

Unfortunately, it is not entirely clear to me how to implement the Input trait (and perhaps other traits) for such a type due to the lifetime used in type Iter = Copied<Iter<'a, u8>>; whereas Bytes lacks a lifetime (since it is akin to Arc<[u8]> rather than &'a u8). Implementation is rather trivial other than for the lifetime issue, but I am not sure how to proceed with fixing the lifetime issue itself:

impl Input for bytes::Bytes {
    type Item = u8;
    type Iter = Copied<Iter<'_, u8>>;
    type IterIndices = Enumerate<Self::Iter>;

    fn input_len(&self) -> usize {
        self.len()
    }

    #[inline]
    fn take(&self, index: usize) -> Self {
        self.slice(..index)
    }

    fn take_from(&self, index: usize) -> Self {
        self.slice(index..)
    }

    #[inline]
    fn take_split(&self, index: usize) -> (Self, Self) {
        let prefix = self.take(index);
        let suffix = self.take_from(index);

        (suffix, prefix)
    }

    #[inline]
    fn position<P>(&self, predicate: P) -> Option<usize>
    where
        P: Fn(Self::Item) -> bool,
    {
        self.iter().position(|b| predicate(*b))
    }

    #[inline]
    fn iter_elements(&self) -> Self::Iter {
        self.iter().copied()
    }

    // ...
}