pub fn call(descriptor: *mut u8) {
    // This initializes safe wrapper for contract input and output
    let mut ctx = CallArgs::from_raw(descriptor);

    // Copies all contract input data to the separate buffer
    let data = ctx.context().to_vec();

    // Appends all input to the storage (as it is a logger contract)
    let _ = storage::append(&data);

    // Returns all that passed to this contract as an output
    *ctx.result_mut() = data;

    // Saves the wrapper state to commit return stream
    ctx.save(descriptor);
}
Full source with preamble