spacepackets/src/lib.rs

//! # CCSDS and ECSS packet standards implementations
//!
//! This crate contains generic implementations for various
//! CCSDS (Consultative Committee for Space Data Systems) and
//! ECSS (European Cooperation for Space Standardization) packet standards.
//! Currently, this includes the following components:
//!
//!  - Space Packet implementation according to
//!    [CCSDS Blue Book 133.0-B-2](https://public.ccsds.org/Pubs/133x0b2e1.pdf)
//!  - PUS Telecommand and PUS Telemetry implementation according to the
//!    [ECSS-E-ST-70-41C standard](https://ecss.nl/standard/ecss-e-st-70-41c-space-engineering-telemetry-and-telecommand-packet-utilization-15-april-2016/).
//!  - CDS Short Time Code implementation according to
//!    [CCSDS CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
//!
//! ## Features
//!
//! `spacepackets` supports various runtime environments and is also suitable
//! for suitable for `no_std` environments. It has several features which may be enabled
//! for disabled.
//!
//! It also offers support for [`serde`](https://serde.rs/). The Space Paccket, PUS TM and TC
//! implementations derive the `serde` `Serialize` and `Deserialize` trait. This allows serializing and
//! deserializing them with an appropriate `serde` provider like
//! [`postcard`](https://github.com/jamesmunns/postcard).
//!
//! Default features:
//!
//!  - [`std`](https://doc.rust-lang.org/std/): Enables functionality relying on the standard library.
//!  - [`alloc`](https://doc.rust-lang.org/alloc/): Enables features which operate on containers
//!     like [`alloc::vec::Vec`](https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html).
//!     Enabled by the `std` feature.
//!
//! ## Module
//!
//! This module contains helpers and data structures to generate Space Packets according to the
//! [CCSDS 133.0-B-2](https://public.ccsds.org/Pubs/133x0b2e1.pdf). This includes the
//! [SpHeader] class to generate the Space Packet Header component common to all space packets
//!
//! ## Example
//!
//! ```rust
//! use spacepackets::SpHeader;
//! let sp_header = SpHeader::tc(0x42, 12, 0).expect("Error creating SP header");
//! println!("{:?}", sp_header);
//! ```
#![no_std]
#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(feature = "std")]
extern crate std;

use crate::ecss::CCSDS_HEADER_LEN;
use delegate::delegate;

use serde::{Deserialize, Serialize};

pub mod ecss;
pub mod tc;
pub mod time;
pub mod tm;

#[derive(Debug, Copy, Clone, PartialEq)]
pub struct SizeMissmatch {
    pub found: usize,
    pub expected: usize,
}
#[derive(Debug, Copy, Clone, PartialEq)]
pub enum PacketError {
    /// The passed slice is too small. Returns the found and expected minimum size
    ToBytesSliceTooSmall(SizeMissmatch),
    /// The provider buffer it soo small. Returns the found and expected minimum size
    FromBytesSliceTooSmall(SizeMissmatch),
    /// The [zerocopy] library failed to write to bytes
    ToBytesZeroCopyError,
    FromBytesZeroCopyError,
}

#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
pub enum PacketType {
    Tm = 0,
    Tc = 1,
}

impl TryFrom<u8> for PacketType {
    type Error = ();

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            x if x == PacketType::Tm as u8 => Ok(PacketType::Tm),
            x if x == PacketType::Tc as u8 => Ok(PacketType::Tc),
            _ => Err(()),
        }
    }
}

pub fn packet_type_in_raw_packet_id(packet_id: u16) -> PacketType {
    PacketType::try_from((packet_id >> 12) as u8 & 0b1).unwrap()
}

#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
pub enum SequenceFlags {
    ContinuationSegment = 0b00,
    FirstSegment = 0b01,
    LastSegment = 0b10,
    Unsegmented = 0b11,
}

impl TryFrom<u8> for SequenceFlags {
    type Error = ();

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            x if x == SequenceFlags::ContinuationSegment as u8 => {
                Ok(SequenceFlags::ContinuationSegment)
            }
            x if x == SequenceFlags::FirstSegment as u8 => Ok(SequenceFlags::FirstSegment),
            x if x == SequenceFlags::LastSegment as u8 => Ok(SequenceFlags::LastSegment),
            x if x == SequenceFlags::Unsegmented as u8 => Ok(SequenceFlags::Unsegmented),
            _ => Err(()),
        }
    }
}

#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
pub struct PacketId {
    pub ptype: PacketType,
    pub sec_header_flag: bool,
    apid: u16,
}

impl PacketId {
    pub fn new(ptype: PacketType, sec_header_flag: bool, apid: u16) -> Option<PacketId> {
        let mut pid = PacketId {
            ptype,
            sec_header_flag,
            apid: 0,
        };
        pid.set_apid(apid).then(|| pid)
    }

    /// Set a new Application Process ID (APID). If the passed number is invalid, the APID will
    /// not be set and false will be returned. The maximum allowed value for the 11-bit field is
    /// 2047
    pub fn set_apid(&mut self, apid: u16) -> bool {
        if apid > 2u16.pow(11) - 1 {
            return false;
        }
        self.apid = apid;
        true
    }

    pub fn apid(&self) -> u16 {
        self.apid
    }

    pub fn raw(&self) -> u16 {
        ((self.ptype as u16) << 12) | ((self.sec_header_flag as u16) << 11) | self.apid
    }
}

impl From<u16> for PacketId {
    fn from(raw_id: u16) -> Self {
        PacketId {
            ptype: PacketType::try_from(((raw_id >> 12) & 0b1) as u8).unwrap(),
            sec_header_flag: ((raw_id >> 11) & 0b1) != 0,
            apid: raw_id & 0x7FF,
        }
    }
}

#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
pub struct PacketSequenceCtrl {
    pub seq_flags: SequenceFlags,
    seq_count: u16,
}

impl PacketSequenceCtrl {
    pub fn new(seq_flags: SequenceFlags, ssc: u16) -> Option<PacketSequenceCtrl> {
        let mut psc = PacketSequenceCtrl {
            seq_flags,
            seq_count: 0,
        };
        psc.set_seq_count(ssc).then(|| psc)
    }
    pub fn raw(&self) -> u16 {
        ((self.seq_flags as u16) << 14) | self.seq_count
    }

    /// Set a new sequence count. If the passed number is invalid, the sequence count will not be
    /// set and false will be returned. The maximum allowed value for the 14-bit field is 16383
    pub fn set_seq_count(&mut self, ssc: u16) -> bool {
        if ssc > 2u16.pow(14) - 1 {
            return false;
        }
        self.seq_count = ssc;
        true
    }

    pub fn ssc(&self) -> u16 {
        self.seq_count
    }
}

impl From<u16> for PacketSequenceCtrl {
    fn from(raw_id: u16) -> Self {
        PacketSequenceCtrl {
            seq_flags: SequenceFlags::try_from(((raw_id >> 14) & 0b11) as u8).unwrap(),
            seq_count: raw_id & SSC_MASK,
        }
    }
}

macro_rules! sph_from_other {
    ($Self: path, $other: path) => {
        impl From<$other> for $Self {
            fn from(other: $other) -> Self {
                Self::from_composite_fields(
                    other.packet_id(),
                    other.psc(),
                    other.data_len(),
                    Some(other.ccsds_version()),
                )
            }
        }
    };
}

const SSC_MASK: u16 = 0x3FFF;
const VERSION_MASK: u16 = 0xE000;

/// Generic trait to access fields of a CCSDS space packet header according to CCSDS 133.0-B-2
pub trait CcsdsPacket {
    fn ccsds_version(&self) -> u8;
    fn packet_id(&self) -> PacketId;
    fn psc(&self) -> PacketSequenceCtrl;

    /// Retrieve data length field
    fn data_len(&self) -> u16;
    /// Retrieve the total packet size based on the data length field
    fn total_len(&self) -> usize {
        usize::from(self.data_len()) + CCSDS_HEADER_LEN + 1
    }

    /// Retrieve 13 bit Packet Identification field. Can usually be retrieved with a bitwise AND
    /// of the first 2 bytes with 0x1FFF
    #[inline]
    fn packet_id_raw(&self) -> u16 {
        self.packet_id().raw()
    }
    /// Retrieve Packet Sequence Count
    #[inline]
    fn psc_raw(&self) -> u16 {
        self.psc().raw()
    }

    #[inline]
    /// Retrieve Packet Type (TM: 0, TC: 1)
    fn ptype(&self) -> PacketType {
        // This call should never fail because only 0 and 1 can be passed to the try_from call
        self.packet_id().ptype
    }

    #[inline]
    fn is_tm(&self) -> bool {
        self.ptype() == PacketType::Tm
    }

    #[inline]
    fn is_tc(&self) -> bool {
        self.ptype() == PacketType::Tc
    }

    /// Retrieve the secondary header flag. Returns true if a secondary header is present
    /// and false if it is not
    #[inline]
    fn sec_header_flag(&self) -> bool {
        self.packet_id().sec_header_flag
    }

    /// Retrieve Application Process ID
    #[inline]
    fn apid(&self) -> u16 {
        self.packet_id().apid
    }

    #[inline]
    fn seq_count(&self) -> u16 {
        self.psc().seq_count
    }

    #[inline]
    fn sequence_flags(&self) -> SequenceFlags {
        // This call should never fail because the mask ensures that only valid values are passed
        // into the try_from function
        self.psc().seq_flags
    }
}

pub trait CcsdsPrimaryHeader {
    fn from_composite_fields(
        packet_id: PacketId,
        psc: PacketSequenceCtrl,
        data_len: u16,
        version: Option<u8>,
    ) -> Self;
}

/// Space Packet Primary Header according to CCSDS 133.0-B-2
///
/// # Arguments
///
/// * `version` - CCSDS version field, occupies the first 3 bits of the raw header
/// * `packet_id` - Packet Identifier, which can also be used as a start marker. Occupies the last
///    13 bits of the first two bytes of the raw header
/// * `psc` - Packet Sequence Control, occupies the third and fourth byte of the raw header
/// * `data_len` - Data length field occupies the fifth and the sixth byte of the raw header
#[derive(serde::Serialize, serde::Deserialize, Debug, PartialEq, Copy, Clone)]
pub struct SpHeader {
    pub version: u8,
    pub packet_id: PacketId,
    pub psc: PacketSequenceCtrl,
    pub data_len: u16,
}
impl Default for SpHeader {
    fn default() -> Self {
        SpHeader {
            version: 0,
            packet_id: PacketId {
                ptype: PacketType::Tm,
                apid: 0,
                sec_header_flag: false,
            },
            psc: PacketSequenceCtrl {
                seq_flags: SequenceFlags::Unsegmented,
                seq_count: 0,
            },
            data_len: 0,
        }
    }
}
impl SpHeader {
    pub fn new(
        ptype: PacketType,
        sec_header: bool,
        apid: u16,
        ssc: u16,
        data_len: u16,
    ) -> Option<Self> {
        if ssc > 2u16.pow(14) - 1 || apid > 2u16.pow(11) - 1 {
            return None;
        }
        let mut header = SpHeader::default();
        header.packet_id.sec_header_flag = sec_header;
        header.packet_id.apid = apid;
        header.packet_id.ptype = ptype;
        header.psc.seq_count = ssc;
        header.data_len = data_len;
        Some(header)
    }

    pub fn tm(apid: u16, seq_count: u16, data_len: u16) -> Option<Self> {
        Self::new(PacketType::Tm, false, apid, seq_count, data_len)
    }

    pub fn tc(apid: u16, seq_count: u16, data_len: u16) -> Option<Self> {
        Self::new(PacketType::Tc, false, apid, seq_count, data_len)
    }

    //noinspection RsTraitImplementation
    delegate!(to self.packet_id {
        pub fn set_apid(&mut self, apid: u16) -> bool;
    });

    delegate!(to self.psc {
        pub fn set_seq_count(&mut self, seq_count: u16) -> bool;
    });

    pub fn set_seq_flags(&mut self, seq_flags: SequenceFlags) {
        self.psc.seq_flags = seq_flags;
    }

    pub fn set_sec_header_flag(&mut self) {
        self.packet_id.sec_header_flag = true;
    }

    pub fn clear_sec_header_flag(&mut self) {
        self.packet_id.sec_header_flag = false;
    }

    pub fn set_packet_type(&mut self, packet_type: PacketType) {
        self.packet_id.ptype = packet_type;
    }

    pub fn from_raw_slice(buf: &[u8]) -> Result<Self, PacketError> {
        if buf.len() < CCSDS_HEADER_LEN + 1 {
            return Err(PacketError::FromBytesSliceTooSmall(SizeMissmatch {
                found: buf.len(),
                expected: CCSDS_HEADER_LEN + 1,
            }));
        }
        let zc_header = zc::SpHeader::from_bytes(&buf[0..CCSDS_HEADER_LEN])
            .ok_or(PacketError::FromBytesZeroCopyError)?;
        Ok(Self::from(zc_header))
    }
}

impl CcsdsPacket for SpHeader {
    #[inline]
    fn ccsds_version(&self) -> u8 {
        self.version
    }

    #[inline]
    fn packet_id(&self) -> PacketId {
        self.packet_id
    }

    #[inline]
    fn psc(&self) -> PacketSequenceCtrl {
        self.psc
    }

    #[inline]
    fn data_len(&self) -> u16 {
        self.data_len
    }
}

impl CcsdsPrimaryHeader for SpHeader {
    fn from_composite_fields(
        packet_id: PacketId,
        psc: PacketSequenceCtrl,
        data_len: u16,
        version: Option<u8>,
    ) -> Self {
        let mut version_to_set = 0b000;
        if let Some(version) = version {
            version_to_set = version;
        }
        SpHeader {
            version: version_to_set,
            packet_id,
            psc,
            data_len,
        }
    }
}

sph_from_other!(SpHeader, crate::zc::SpHeader);

pub mod zc {
    use crate::{CcsdsPacket, CcsdsPrimaryHeader, PacketId, PacketSequenceCtrl, VERSION_MASK};
    use zerocopy::byteorder::NetworkEndian;
    use zerocopy::{AsBytes, FromBytes, Unaligned, U16};

    #[derive(FromBytes, AsBytes, Unaligned, Debug)]
    #[repr(C)]
    pub struct SpHeader {
        version_packet_id: U16<NetworkEndian>,
        psc: U16<NetworkEndian>,
        data_len: U16<NetworkEndian>,
    }

    impl SpHeader {
        pub fn new(
            packet_id: PacketId,
            psc: PacketSequenceCtrl,
            data_len: u16,
            version: Option<u8>,
        ) -> Self {
            let mut version_packet_id = packet_id.raw();
            if let Some(version) = version {
                version_packet_id = ((version as u16) << 13) | packet_id.raw()
            }
            SpHeader {
                version_packet_id: U16::from(version_packet_id),
                psc: U16::from(psc.raw()),
                data_len: U16::from(data_len),
            }
        }

        pub fn from_bytes(slice: &[u8]) -> Option<Self> {
            SpHeader::read_from(slice)
        }

        pub fn to_bytes(&self, slice: &mut [u8]) -> Option<()> {
            self.write_to(slice)
        }
    }

    impl CcsdsPacket for SpHeader {
        #[inline]
        fn ccsds_version(&self) -> u8 {
            ((self.version_packet_id.get() >> 13) as u8) & 0b111
        }

        fn packet_id(&self) -> PacketId {
            PacketId::from(self.packet_id_raw())
        }
        fn psc(&self) -> PacketSequenceCtrl {
            PacketSequenceCtrl::from(self.psc_raw())
        }

        #[inline]
        fn data_len(&self) -> u16 {
            self.data_len.get()
        }

        fn packet_id_raw(&self) -> u16 {
            self.version_packet_id.get() & (!VERSION_MASK)
        }

        fn psc_raw(&self) -> u16 {
            self.psc.get()
        }
    }

    impl CcsdsPrimaryHeader for SpHeader {
        fn from_composite_fields(
            packet_id: PacketId,
            psc: PacketSequenceCtrl,
            data_len: u16,
            version: Option<u8>,
        ) -> Self {
            SpHeader::new(packet_id, psc, data_len, version)
        }
    }

    sph_from_other!(SpHeader, crate::SpHeader);
}

#[cfg(test)]
mod tests {
    #[cfg(feature = "std")]
    use crate::CcsdsPrimaryHeader;
    use crate::SpHeader;
    use crate::{
        packet_type_in_raw_packet_id, zc, CcsdsPacket, PacketId, PacketSequenceCtrl, PacketType,
        SequenceFlags,
    };
    use alloc::vec;
    #[cfg(not(feature = "std"))]
    use num::pow;
    #[cfg(feature = "std")]
    use num_traits::pow;
    use postcard::from_bytes;
    #[cfg(feature = "alloc")]
    use postcard::to_allocvec;

    #[test]
    fn test_seq_flag_helpers() {
        assert_eq!(
            SequenceFlags::try_from(0b00).expect("SEQ flag creation failed"),
            SequenceFlags::ContinuationSegment
        );
        assert_eq!(
            SequenceFlags::try_from(0b01).expect("SEQ flag creation failed"),
            SequenceFlags::FirstSegment
        );
        assert_eq!(
            SequenceFlags::try_from(0b10).expect("SEQ flag creation failed"),
            SequenceFlags::LastSegment
        );
        assert_eq!(
            SequenceFlags::try_from(0b11).expect("SEQ flag creation failed"),
            SequenceFlags::Unsegmented
        );
        assert!(SequenceFlags::try_from(0b100).is_err());
    }

    #[test]
    fn test_packet_type_helper() {
        assert_eq!(PacketType::try_from(0b00).unwrap(), PacketType::Tm);
        assert_eq!(PacketType::try_from(0b01).unwrap(), PacketType::Tc);
        assert!(PacketType::try_from(0b10).is_err());
    }

    #[test]
    fn test_packet_id() {
        let packet_id =
            PacketId::new(PacketType::Tm, false, 0x42).expect("Packet ID creation failed");
        assert_eq!(packet_id.raw(), 0x0042);
        let packet_id_from_raw = PacketId::from(packet_id.raw());
        assert_eq!(
            packet_type_in_raw_packet_id(packet_id.raw()),
            PacketType::Tm
        );
        assert_eq!(packet_id_from_raw, packet_id);
        let packet_id_from_new = PacketId::new(PacketType::Tm, false, 0x42).unwrap();
        assert_eq!(packet_id_from_new, packet_id);
    }

    #[test]
    fn test_invalid_packet_id() {
        let packet_id_invalid = PacketId::new(PacketType::Tc, true, 0xFFFF);
        assert!(packet_id_invalid.is_none());
    }

    #[test]
    fn test_invalid_apid_setter() {
        let mut packet_id =
            PacketId::new(PacketType::Tm, false, 0x42).expect("Packet ID creation failed");
        assert!(!packet_id.set_apid(0xffff));
    }

    #[test]
    fn test_invalid_seq_count() {
        let mut psc = PacketSequenceCtrl::new(SequenceFlags::ContinuationSegment, 77)
            .expect("PSC creation failed");
        assert!(!psc.set_seq_count(0xffff));
    }

    #[test]
    fn test_packet_seq_ctrl() {
        let mut psc = PacketSequenceCtrl::new(SequenceFlags::ContinuationSegment, 77)
            .expect("PSC creation failed");
        assert_eq!(psc.raw(), 77);
        let psc_from_raw = PacketSequenceCtrl::from(psc.raw());
        assert_eq!(psc_from_raw, psc);
        // Fails because SSC is limited to 14 bits
        assert!(!psc.set_seq_count(2u16.pow(15)));
        assert_eq!(psc.raw(), 77);

        let psc_invalid = PacketSequenceCtrl::new(SequenceFlags::FirstSegment, 0xFFFF);
        assert!(psc_invalid.is_none());
        let psc_from_new = PacketSequenceCtrl::new(SequenceFlags::ContinuationSegment, 77).unwrap();
        assert_eq!(psc_from_new, psc);
    }

    #[test]
    #[cfg(feature = "std")]
    fn test_serde_sph() {
        let sp_header = SpHeader::tc(0x42, 12, 0).expect("Error creating SP header");
        assert_eq!(sp_header.ccsds_version(), 0b000);
        assert!(sp_header.is_tc());
        assert!(!sp_header.sec_header_flag());
        assert_eq!(sp_header.ptype(), PacketType::Tc);
        assert_eq!(sp_header.seq_count(), 12);
        assert_eq!(sp_header.apid(), 0x42);
        assert_eq!(sp_header.sequence_flags(), SequenceFlags::Unsegmented);
        assert_eq!(sp_header.data_len(), 0);
        let output = to_allocvec(&sp_header).unwrap();
        let sp_header: SpHeader = from_bytes(&output).unwrap();
        assert_eq!(sp_header.version, 0b000);
        assert!(!sp_header.packet_id.sec_header_flag);
        assert_eq!(sp_header.ptype(), PacketType::Tc);
        assert_eq!(sp_header.seq_count(), 12);
        assert_eq!(sp_header.apid(), 0x42);
        assert_eq!(sp_header.sequence_flags(), SequenceFlags::Unsegmented);
        assert_eq!(sp_header.packet_id_raw(), 0x1042);
        assert_eq!(sp_header.psc_raw(), 0xC00C);
        assert_eq!(sp_header.ccsds_version(), 0b000);
        assert_eq!(sp_header.data_len, 0);

        let sp_header = SpHeader::tm(0x7, 22, 36).expect("Error creating SP header");
        assert_eq!(sp_header.ccsds_version(), 0b000);
        assert!(sp_header.is_tm());
        assert!(!sp_header.sec_header_flag());
        assert_eq!(sp_header.ptype(), PacketType::Tm);
        assert_eq!(sp_header.seq_count(), 22);
        assert_eq!(sp_header.apid(), 0x07);
        assert_eq!(sp_header.sequence_flags(), SequenceFlags::Unsegmented);
        assert_eq!(sp_header.packet_id_raw(), 0x0007);
        assert_eq!(sp_header.psc_raw(), 0xC016);
        assert_eq!(sp_header.data_len(), 36);
        assert_eq!(sp_header.ccsds_version(), 0b000);

        let from_comp_fields = SpHeader::from_composite_fields(
            PacketId::new(PacketType::Tc, true, 0x42).unwrap(),
            PacketSequenceCtrl::new(SequenceFlags::Unsegmented, 0x7).unwrap(),
            0,
            None,
        );
        assert_eq!(from_comp_fields.ptype(), PacketType::Tc);
        assert_eq!(from_comp_fields.apid(), 0x42);
        assert!(from_comp_fields.sec_header_flag());
        assert_eq!(
            from_comp_fields.sequence_flags(),
            SequenceFlags::Unsegmented
        );
        assert_eq!(from_comp_fields.seq_count(), 0x7);
        assert_eq!(from_comp_fields.data_len(), 0);
    }

    #[test]
    fn test_sp_header_setters() {
        let mut sp_header = SpHeader::tc(0x42, 12, 0).expect("Error creating SP header");
        assert_eq!(sp_header.apid(), 0x42);
        sp_header.set_apid(0x12);
        assert_eq!(sp_header.apid(), 0x12);

        sp_header.set_sec_header_flag();
        assert!(sp_header.sec_header_flag());
        sp_header.clear_sec_header_flag();
        assert!(!sp_header.sec_header_flag());
        sp_header.set_seq_count(0x45);
        assert_eq!(sp_header.seq_count(), 0x45);
        assert_eq!(sp_header.ptype(), PacketType::Tc);
        sp_header.set_packet_type(PacketType::Tm);
        assert_eq!(sp_header.ptype(), PacketType::Tm);
    }

    #[test]
    fn test_zc_sph() {
        use zerocopy::AsBytes;

        let sp_header = SpHeader::tc(0x7FF, pow(2, 14) - 1, 0).expect("Error creating SP header");
        assert_eq!(sp_header.ptype(), PacketType::Tc);
        assert_eq!(sp_header.apid(), 0x7FF);
        assert_eq!(sp_header.data_len(), 0);
        assert_eq!(sp_header.ccsds_version(), 0b000);
        assert!(sp_header.is_tc());
        let sp_header_zc = zc::SpHeader::from(sp_header);
        let slice = sp_header_zc.as_bytes();
        assert_eq!(slice.len(), 6);
        assert_eq!(slice[0], 0x17);
        assert_eq!(slice[1], 0xFF);
        assert_eq!(slice[2], 0xFF);
        assert_eq!(slice[3], 0xFF);
        assert_eq!(slice[4], 0x00);
        assert_eq!(slice[5], 0x00);

        let mut slice = [0; 6];
        sp_header_zc.write_to(slice.as_mut_slice());
        assert_eq!(slice.len(), 6);
        assert_eq!(slice[0], 0x17);
        assert_eq!(slice[1], 0xFF);
        assert_eq!(slice[2], 0xFF);
        assert_eq!(slice[3], 0xFF);
        assert_eq!(slice[4], 0x00);
        assert_eq!(slice[5], 0x00);

        let mut test_vec = vec![0_u8; 6];
        let slice = test_vec.as_mut_slice();
        sp_header_zc.write_to(slice);
        let slice = test_vec.as_slice();
        assert_eq!(slice.len(), 6);
        assert_eq!(slice[0], 0x17);
        assert_eq!(slice[1], 0xFF);
        assert_eq!(slice[2], 0xFF);
        assert_eq!(slice[3], 0xFF);
        assert_eq!(slice[4], 0x00);
        assert_eq!(slice[5], 0x00);

        let sp_header = zc::SpHeader::from_bytes(slice);
        assert!(sp_header.is_some());
        let sp_header = sp_header.unwrap();
        assert_eq!(sp_header.ccsds_version(), 0b000);
        assert_eq!(sp_header.packet_id_raw(), 0x17FF);
        assert_eq!(sp_header.apid(), 0x7FF);
        assert_eq!(sp_header.ptype(), PacketType::Tc);
        assert_eq!(sp_header.data_len(), 0);
    }
}