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use fuels_types::ByteArray;
use sha2::{Digest, Sha256};

/// Hashes an encoded function selector using SHA256 and returns the first 4 bytes.
/// The function selector has to have been already encoded following the ABI specs defined
/// [here](https://github.com/FuelLabs/fuel-specs/blob/1be31f70c757d8390f74b9e1b3beb096620553eb/specs/protocol/abi.md)
pub fn first_four_bytes_of_sha256_hash(string: &str) -> ByteArray {
    let string_as_bytes = string.as_bytes();
    let mut hasher = Sha256::new();
    hasher.update(string_as_bytes);
    let result = hasher.finalize();
    let mut output = ByteArray::default();
    output[4..].copy_from_slice(&result[..4]);
    output
}