Warning

This post was published 55 days ago. The information described in this article may have changed.

Info

This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: Newbie :: explain different behavior

I am using smoltcp-rs smoltcp · GitHub

I have created 4 functions doing similar stuff, however parse_udp enforced me to use the lifetime while previous calls didn't.
But finally parse_dhcp isn't working because "returns a value referencing data owned by the current function"

Please explain me the differences...

fn parse_ethernet(payload: &[u8])
            -> Result<(&[u8], EthernetRepr), PacketParseError> {
    let eth_frame = 
        EthernetFrame::new_checked(payload)
            .map_err(PacketParseError::EthernetError)?;
    let eth_repr = 
        EthernetRepr::parse(&eth_frame)
            .map_err(PacketParseError::EthernetError)?;
    Ok((eth_frame.payload(), eth_repr))
}

fn parse_ipv4(payload: &[u8])
              -> Result<(&[u8], Ipv4Repr), PacketParseError> {
    let ipv4_packet =
        Ipv4Packet::new_checked(payload)
            .map_err(|e| PacketParseError::Ipv4PacketError(e))?;

    let ipv4_repr =
        Ipv4Repr::parse(&ipv4_packet, &ChecksumCapabilities::ignored())
            .map_err(PacketParseError::Ipv4ReprParseError)?; // shorthand for |e| PacketParseError::Ipv4ReprParseError(e)
    Ok((ipv4_packet.payload(), ipv4_repr))
}

fn parse_udp<'a>(payload: &'a [u8], ipv4_repr: &Ipv4Repr)
                 -> Result<(&'a [u8], UdpRepr), PacketParseError> {
    let udp_packet =
        UdpPacket::new_checked(payload)
            .map_err(PacketParseError::UdpPacketError)?;
    let udp_repr =
        UdpRepr::parse(
            &udp_packet,
            &IpAddress::from(ipv4_repr.src_addr), // Convert Ipv4Address to IpAddress
            &IpAddress::from(ipv4_repr.dst_addr), // Convert Ipv4Address to IpAddress
            &ChecksumCapabilities::ignored())
        .map_err(PacketParseError::UdpReprParseError)?;
    Ok((udp_packet.payload(), udp_repr))
}

fn parse_dhcp(payload: &[u8])
              -> Result<DhcpRepr, PacketParseError> {
    let dhcp_packet =
        DhcpPacket::new_checked(payload)
            .map_err(PacketParseError::DhcpPacketError)?;
    let dhcp_repr =
        DhcpRepr::parse(&dhcp_packet)
            .map_err(PacketParseError::DhcpReprParseError)?;
    Ok(dhcp_repr) // this gives an error :: returns a value referencing data owned by the current function
}

Thanx.

9 posts - 3 participants

Read full topic

🏷️ rust_feed