Function scrypt_c 

#[unsafe(export_name = "scrypt_kdf")]
pub unsafe extern "C" fn scrypt_c(
    password: *const u8,
    password_len: usize,
    salt: *const u8,
    salt_len: usize,
    n: u64,
    r: u32,
    p: u32,
    output: *mut u8,
    output_len: usize,
) -> c_int

C export for scrypt_kdf using a libscrypt-kdf compatible API.