You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: xmac.rs
    path of file: ./repos/tock/capsules/extra/src/ieee802154
    
    the code of the file until where you have to start completion: // Licensed under the Apache License, Version 2.0 or the MIT License.
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Copyright Tock Contributors 2022.

//! X-MAC protocol layer for low power 802.15.4 reception, intended primarily
//! to manage an Atmel RF233 radio.
//!
//! Original X-MAC paper, on which this implementation is heavily based:
//!     <http://www.cs.cmu.edu/~andersoe/papers/xmac-sensys.pdf>
//!
//! Nodes using this layer place their radios to sleep for the vast majority of
//! the time, thereby reducing po
    
    pub fn new(radio: &'a R, alarm: &'a A, rng: &'a dyn Rng<'a>) -> XMac<'a, R, A> {
        XMac {
            radio: radio,
            alarm: alarm,
            rng: rng,
            tx_client: OptionalCell::empty(),
            rx_client: OptionalCell::empty(),
            state: Cell::new(XMacState::STARTUP),
            delay_sleep: Cell::new(false),
            tx_header: Cell::new(None),
            tx_payload: TakeCell::empty(),
            tx_len: Cell::new(0),
            tx_preamble_pending: Cell::new(false),
            tx_preamble_seq_num: Cell::new(0),
            tx_preamble_buf: TakeCell::empty(),
            rx_pending: Cell::new(false),
        }
    }