Function copy_buf_hashed 

pub async fn copy_buf_hashed<'a, R, W>(
    reader: &'a mut R,
    writer: &'a mut W,
    algo: HashAlgo,
) -> Result<(u64, NixHash)>
where
    R: AsyncBufRead + Unpin + ?Sized,
    W: AsyncWrite + Unpin + ?Sized,

Available on crate feature async only.

Asynchronously copies the entire contents of a reader into a writer while hashing.