BytesN in a Rust Smart Contract

Example code demo using BytesN

If you’re used to using symbol_short! macro, note how for more than 9 characters we need to use Symbol::new

We’ll use a fixed length 32 bytes array here so we need BytesN in Stellar :

#![no_std]
use soroban_sdk::{contract, contractimpl, Env, Symbol,BytesN};

#[contract]
pub struct MyContract;

#[contractimpl]
impl MyContract {
    // Store a fixed-length byte array (BytesN) in contract storage
    pub fn set_data(env: Env, data: BytesN<32>) {
        let key = Symbol::new(&env,"stored__data");
        env.storage().instance().set(&key, &data);
    }

    // Retrieve the stored fixed-length byte array (BytesN)
    pub fn get_data(env: Env) -> Option<BytesN<32>> {
        let key = Symbol::new(&env,"stored__data");
        env.storage().instance().get(&key)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_set_and_get_data() {
        let env = Env::default(); // Create an environment instance for testing

        // Define a 32-byte array to use as test data
        let bytes: [u8; 32] = [
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
            17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32
        ];

        let data = BytesN::<32>::from(bytes); // Convert the array into a BytesN

        // Set the data in the contract storage
        MyContract::set_data(env.clone(), data.clone());

        // Retrieve the data from the contract storage
        let retrieved_data = MyContract::get_data(env);

        // Check if the retrieved data is equal to the original data
        assert_eq!(retrieved_data, Some(data));
    }
}

You could also use base64 encoded :

use base64::{encode};

fn main() {
    // 32-byte array (can represent any data you want)
    let bytes: [u8; 32] = [
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32
    ];

    // Encode to Base64
    let encoded = encode(&bytes);

    // Print the Base64 encoded string
    println!("Base64 Encoded: {}", encoded);
}