Function hashing_copy::copy_and_hash

pub fn copy_and_hash<R: ?Sized, W: ?Sized, H>(
    reader: &mut R, 
    writer: &mut W
) -> Result<(u64, GenericArray<u8, H::OutputSize>)> where
    R: Read,
    W: Write,
    H: Digest, 

Copy data from reader to writer, along the way hashing using H which must implement Digest. Return value is the same as for std::io::copy except that it returns a 2 tuple of the bytes copied, and the hash value, or an io::Error.

use std::io;
use sha2::Sha256;

let mut reader: &[u8] = b"hello world";
let mut writer: Vec<u8> = vec![];

let (bytes_copied, hash) = copy_and_hash::<_, _, Sha256>(&mut reader, &mut writer)
                                .expect("Couldn't copy data");

assert_eq!(11, bytes_copied);
assert_eq!(&b"hello world"[..], &writer[..]);
assert_eq!(hash[..=8], [0xb9, 0x4d, 0x27, 0xb9, 0x93, 0x4d, 0x3e, 0x08, 0xa5]);