How to create XOR Hashes in Substrate

Question

Say you have two account ids Aid(A) and Aid(B) and you want to combine them.e.g. XOR( Aid(A), Aid(B) ).

Basically, I want to achieve this;

T::Hashing::hash_of(&(idA, idB)) == T::Hashing::hash_of(&(idB, idA))

Answer 1

We can always represent types inside of the runtime as their encoded blobs (Vec<u8>), so this question breaks down to "How do you XOR two Vec<u8>"?

For that, I see this thread:

https://users.rust-lang.org/t/how-to-xor-two-vec-u8/31071

So a full solution would look like:

let idA: T::AccountId = account_a;
let idB: T::AccountId = account_b;

let mut bytesA: Vec<u8> = idA.encode();
let bytesB: Vec<u8> = idB.encode();

// `bytesA` is being modified in place.
// You could also allocate a new vector if you want.
bytesA.iter_mut()
    .zip(bytesB.iter())
    .for_each(|(x1, x2)| *x1 ^= *x2);

let new_account = T::AccountId::decode(bytesA)
    .expect(
        "all bytes are valid accounts, and the source of
        these bytes is the xor of two other accounts, thus
        this must also be a valid account. qed"
    );