Function passwords::hasher::bcrypt

pub fn bcrypt<T: ?Sized + AsRef<[u8]>, K: ?Sized + AsRef<[u8]>>(
    cost: u8, 
    salt: &K, 
    password: &T
) -> Result<[u8; 24], &'static str>

Use bcrypt to hash a password whose length is not bigger than 72 bytes to 24 bytes data. If the salt is not 16 bytes, it will be MD5 hashed first.