Function krb5_c_decrypt 

pub unsafe extern "C" fn krb5_c_decrypt(
    context: krb5_context,
    key: *const krb5_keyblock,
    usage: krb5_keyusage,
    cipher_state: *const krb5_data,
    input: *const krb5_enc_data,
    output: *mut krb5_data,
) -> krb5_error_code