use byteorder::BigEndian;
use zerocopy::byteorder::U16;
use zerocopy::{AsBytes, ByteSlice, FromBytes, LayoutVerified};

pub const SIZE_IP4_HEADER: usize = 16;
pub const SIZE_IP6_HEADER: usize = 36;

pub const VERSION_IP4: u8 = 4;
pub const VERSION_IP6: u8 = 6;

pub const OFFSET_IP4_SRC: usize = 12;
pub const OFFSET_IP6_SRC: usize = 8;

pub const OFFSET_IP4_DST: usize = 16;
pub const OFFSET_IP6_DST: usize = 24;

pub const TYPE_TRANSPORT: u8 = 4;

#[repr(packed)]
#[derive(Copy, Clone, FromBytes, AsBytes)]
pub struct IPv4Header {
    _f_space1: [u8; 2],
    pub f_total_len: U16<BigEndian>,
    _f_space2: [u8; 8],
    pub f_source: [u8; 4],
    pub f_destination: [u8; 4],
}

#[repr(packed)]
#[derive(Copy, Clone, FromBytes, AsBytes)]
pub struct IPv6Header {
    _f_pre: [u8; 4],
    pub f_len: U16<BigEndian>,
    _f_space2: [u8; 2],
    pub f_source: [u8; 16],
    pub f_destination: [u8; 16],
}