Instantiate2 algorithm

With the instantiate2 algorithm you can create a contract address in a predictable and deterministic way. The underlying algorithm is rather simple.

We use SHA-256 as the underlying hashing algorithm.

You need to provide the following inputs:

• checksum: this is the checksum of the contract code (the Wasm module, for example); this has to be a SHA-256 hash,
• creator: this is the canonicalized address of the user instantiating the contract,
• salt: this is some byte string allowing you to distinguish multiple instantiations of the same contract by the same creator; this parameter has to be under 64 bytes in length,
• msg: the initialization message is usually unused; CosmWasm sets this to an empty byte string.

Assuming that the macro concat! joins two byte slices and the function hash_sha256 returns the SHA-256 hash of the provided input, the Instantiate2 algorithm would look like this:

let c_checksum = concat!((checksum.len() as u64).to_be_bytes(), checksum);
let c_creator = concat!((creator.len() as u64).to_be_bytes(), creator);
let c_salt = concat!((salt.len() as u64).to_be_bytes(), salt);
let c_msg = concat!((msg.len() as u64).to_be_bytes(), msg);
 
let canonical_address = hash_sha256(
    concat!(
        hash_sha256(b"module"),
        b"wasm\0",
        c_checksum,
        c_creator,
        c_salt,
        c_msg,
    ),
);