Zero-Copy Parsing of Binary Headers via Lifetime Reference Mapping

use std::convert::TryInto;
 
#[derive(Debug)]
pub struct BinaryPacket<'a> {
    pub magic: &'a [u8; 4],
    pub payload_len: u32,
    pub payload: &'a [u8],
}
 
impl<'a> BinaryPacket<'a> {
    pub fn parse(data: &'a [u8]) -> Result<Self, &'static str> {
        if data.len() < 8 {
            return Err("Data too short to contain header");
        }
        let magic: &'a [u8; 4] = data[0..4].try_into()
            .map_err(|_| "Failed to parse magic bytes")?;
        let len_bytes = data[4..8].try_into()
            .map_err(|_| "Failed to parse length bytes")?;
        let payload_len = u32::from_be_bytes(len_bytes);
        let end_idx = 8 + payload_len as usize;
        if data.len() < end_idx {
            return Err("Data length does not match payload header length");
        }
        let payload = &data[8..end_idx];
        Ok(Self { magic, payload_len, payload })
    }
}