Function bao::decode::hash_from_encoded_nostd

pub fn hash_from_encoded_nostd<F, E>(read_exact_fn: F) -> Result<Hash, E> where
    F: FnMut(&mut [u8]) -> Result<(), E>, 

Given a combined encoding, quickly determine the root hash by reading just the root node.

The read_exact_fn callback will be called exactly twice.

Example

let (hash1, encoded) = bao::encode::encode_to_vec(b"foobar");
let mut reader = &*encoded;
let hash2 = bao::decode::hash_from_encoded_nostd(|buf| {
    let take = buf.len();
    buf.copy_from_slice(&reader[..take]);
    reader = &reader[take..];
    Ok::<(), ()>(())
}).unwrap();
assert_eq!(hash1, hash2);