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: handshake_random.rs
    path of file: ./repos/webrtc/dtls/src/handshake
    
    the code of the file until where you have to start completion: use std::io::{self, Read, Write};
use std::time::{Duration, SystemTime};

use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use rand::Rng;

pub const RANDOM_BYTES_LENGTH: usize = 28;
pub const HANDSHAKE_RANDOM_LENGTH: usize = RANDOM_BYTES_LENGTH + 4;

// https://tools.ietf.org/html/rfc4346#section-7.4.1.2
#[derive(Clone, Debug, PartialEq,
    
    pub fn unmarshal<R: Read>(reader: &mut R) -> io::Result<Self> {
        let secs = reader.read_u32::<BigEndian>()?;
        let gmt_unix_time = if let Some(unix_time) =
            SystemTime::UNIX_EPOCH.checked_add(Duration::new(secs as u64, 0))
        {
            unix_time
        } else {
            SystemTime::UNIX_EPOCH
        };

        let mut random_bytes = [0u8; RANDOM_BYTES_LENGTH];
        reader.read_exact(&mut random_bytes)?;

        Ok(HandshakeRandom {
            gmt_unix_time,
            random_bytes,
        })
    }