start adding improved CCSDS packet support

src/lib.rs

@@ -71,6 +71,8 @@ use zerocopy::{FromBytes, IntoBytes};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use crate::crc::CRC_CCITT_FALSE;
+
 pub mod cfdp;
 pub mod crc;
 pub mod ecss;
@@ -83,14 +85,21 @@ mod private {
     pub trait Sealed {}
 }
 
+/// Length of the CCSDS header.
 pub const CCSDS_HEADER_LEN: usize = core::mem::size_of::<crate::zc::SpHeader>();
 
+/// Maximum allowed value for the 11-bit APID.
 pub const MAX_APID: u11 = u11::MAX;
+/// Maximum allowed value for the 14-bit APID.
 pub const MAX_SEQ_COUNT: u14 = u14::MAX;
 
-#[inline]
-pub fn packet_type_in_raw_packet_id(packet_id: u16) -> PacketType {
-    PacketType::try_from((packet_id >> 12) as u8 & 0b1).unwrap()
+/// Checksum types currently provided by the CCSDS packet support.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[non_exhaustive]
+pub enum ChecksumType {
+    Crc16CcittFalse,
 }
 
 /// Generic error type when converting to and from raw byte slices.
@@ -118,6 +127,22 @@ pub enum ZeroCopyError {
     ZeroCopyFromError,
 }
 
+#[derive(thiserror::Error, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[error("invalid payload length: {0}")]
+pub struct InvalidPayloadLengthError(usize);
+
+#[derive(thiserror::Error, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub enum CcsdsPacketCreationError {
+    #[error("byte conversion: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    #[error("invalid payload length: {0}")]
+    InvalidPayloadLength(#[from] InvalidPayloadLengthError),
+}
+
 /// CCSDS packet type enumeration.
 #[derive(Debug, PartialEq, Eq, num_enum::TryFromPrimitive)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -141,6 +166,29 @@ pub enum SequenceFlags {
     Unsegmented = 0b11,
 }
 
+#[inline]
+pub fn packet_type_in_raw_packet_id(packet_id: u16) -> PacketType {
+    PacketType::try_from((packet_id >> 12) as u8 & 0b1).unwrap()
+}
+
+#[inline]
+pub fn ccsds_packet_len_for_user_data_len(
+    data_len: usize,
+    checksum: Option<ChecksumType>,
+) -> usize {
+    data_len
+        + CCSDS_HEADER_LEN
+        + match checksum {
+            Some(ChecksumType::Crc16CcittFalse) => 2,
+            None => 0,
+        }
+}
+
+#[inline]
+pub fn packet_len_for_user_data_len_with_checksum(data_len: usize) -> usize {
+    ccsds_packet_len_for_user_data_len(data_len, Some(ChecksumType::Crc16CcittFalse))
+}
+
 /// Abstraction for the CCSDS Packet ID, which forms the last thirteen bits
 /// of the first two bytes in the CCSDS primary header.
 #[derive(Debug, Eq, Copy, Clone)]
@@ -372,6 +420,11 @@ pub trait CcsdsPacket {
     }
 }
 
+pub trait CcsdsTc: CcsdsPacket {
+    /// Shared access to the packet data field.
+    fn data(&self) -> &[u8];
+}
+
 pub trait CcsdsPrimaryHeader {
     fn from_composite_fields(
         packet_id: PacketId,
@@ -708,6 +761,376 @@ pub mod zc {
     sph_from_other!(SpHeader, crate::SpHeader);
 }
 
+/// CCSDS packet creator with optional support for a CRC16 CCITT checksum appended to the
+/// end of the packet and support for copying into the user buffer directly.
+///
+/// This packet creator variant reserves memory based on the required user data length specified
+/// by the user and then provides mutable or shared access to that memory. This is useful
+/// to avoid an additional slice for the user data and allow copying data directly
+/// into the packet.
+pub struct CcsdsPacketCreatorWithReservedData<'buf> {
+    sp_header: SpHeader,
+    buf: &'buf mut [u8],
+    checksum: Option<ChecksumType>,
+}
+
+impl<'buf> CcsdsPacketCreatorWithReservedData<'buf> {
+    #[inline]
+    pub fn packet_len_for_user_data_with_checksum(user_data_len: usize) -> usize {
+        ccsds_packet_len_for_user_data_len(user_data_len, Some(ChecksumType::Crc16CcittFalse))
+    }
+
+    pub fn new(
+        mut sp_header: SpHeader,
+        packet_type: PacketType,
+        payload_len: usize,
+        buf: &'buf mut [u8],
+        checksum: Option<ChecksumType>,
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        let full_packet_len = match checksum {
+            Some(crc_type) => match crc_type {
+                ChecksumType::Crc16CcittFalse => CCSDS_HEADER_LEN + payload_len + 2,
+            },
+            None => CCSDS_HEADER_LEN + payload_len,
+        };
+        if full_packet_len > buf.len() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: full_packet_len,
+            }
+            .into());
+        }
+        if full_packet_len - CCSDS_HEADER_LEN - 1 > u16::MAX as usize {
+            return Err(InvalidPayloadLengthError(payload_len).into());
+        }
+        sp_header.data_len = (full_packet_len - CCSDS_HEADER_LEN - 1) as u16;
+        sp_header.packet_id.packet_type = packet_type;
+
+        Ok(Self {
+            sp_header,
+            buf: buf[0..full_packet_len].as_mut(),
+            checksum,
+        })
+    }
+
+    pub fn new_with_checksum(
+        sp_header: SpHeader,
+        packet_type: PacketType,
+        payload_len: usize,
+        buf: &'buf mut [u8],
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        Self::new(
+            sp_header,
+            packet_type,
+            payload_len,
+            buf,
+            Some(ChecksumType::Crc16CcittFalse),
+        )
+    }
+
+    pub fn new_tm_with_checksum(
+        sp_header: SpHeader,
+        payload_len: usize,
+        buf: &'buf mut [u8],
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        Self::new(
+            sp_header,
+            PacketType::Tm,
+            payload_len,
+            buf,
+            Some(ChecksumType::Crc16CcittFalse),
+        )
+    }
+
+    pub fn new_tc_with_checksum(
+        sp_header: SpHeader,
+        payload_len: usize,
+        buf: &'buf mut [u8],
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        Self::new(
+            sp_header,
+            PacketType::Tc,
+            payload_len,
+            buf,
+            Some(ChecksumType::Crc16CcittFalse),
+        )
+    }
+}
+
+impl CcsdsPacketCreatorWithReservedData<'_> {
+    #[inline]
+    pub fn packet_len(&self) -> usize {
+        <Self as CcsdsPacket>::packet_len(self)
+    }
+
+    #[inline]
+    pub fn sp_header(&self) -> &SpHeader {
+        &self.sp_header
+    }
+
+    #[inline]
+    pub fn packet_data_mut(&mut self) -> &mut [u8] {
+        let len = self.buf.len();
+        &mut self.buf[CCSDS_HEADER_LEN..len - 2]
+    }
+
+    #[inline]
+    pub fn packet_data(&mut self) -> &[u8] {
+        let len = self.buf.len();
+        &self.buf[CCSDS_HEADER_LEN..len - 2]
+    }
+
+    pub fn finish(self) -> usize {
+        self.sp_header
+            .write_to_be_bytes(&mut self.buf[0..CCSDS_HEADER_LEN])
+            .unwrap();
+        let len = self.buf.len();
+        match self.checksum {
+            Some(ChecksumType::Crc16CcittFalse) => {
+                let crc16 = CRC_CCITT_FALSE.checksum(&self.buf[0..len - 2]);
+                self.buf[len - 2..len].copy_from_slice(&crc16.to_be_bytes());
+            }
+            None => (),
+        };
+        len
+    }
+}
+
+impl CcsdsPacket for CcsdsPacketCreatorWithReservedData<'_> {
+    #[inline]
+    fn ccsds_version(&self) -> arbitrary_int::u3 {
+        self.sp_header.ccsds_version()
+    }
+
+    #[inline]
+    fn packet_id(&self) -> PacketId {
+        self.sp_header.packet_id()
+    }
+
+    #[inline]
+    fn psc(&self) -> PacketSequenceControl {
+        self.sp_header.psc()
+    }
+
+    #[inline]
+    fn data_len(&self) -> u16 {
+        self.sp_header.data_len()
+    }
+}
+
+/// CCSDS packet creator with optional support for a CRC16 CCITT checksum appended to the
+/// end of the packet.
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct CcsdsPacketCreator<'app_data> {
+    sp_header: SpHeader,
+    packet_data: &'app_data [u8],
+    checksum: Option<ChecksumType>,
+}
+
+impl<'app_data> CcsdsPacketCreator<'app_data> {
+    #[inline]
+    pub fn packet_len_for_user_data_with_checksum(user_data_len: usize) -> usize {
+        ccsds_packet_len_for_user_data_len(user_data_len, Some(ChecksumType::Crc16CcittFalse))
+    }
+
+    pub fn new(
+        mut sp_header: SpHeader,
+        packet_type: PacketType,
+        packet_data: &'app_data [u8],
+        checksum: Option<ChecksumType>,
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        sp_header.data_len = (packet_data.len()
+            + match checksum {
+                Some(ChecksumType::Crc16CcittFalse) => 2,
+                None => 0,
+            }
+            - 1) as u16;
+
+        let full_packet_len = match checksum {
+            Some(crc_type) => match crc_type {
+                ChecksumType::Crc16CcittFalse => CCSDS_HEADER_LEN + packet_data.len() + 2,
+            },
+            None => CCSDS_HEADER_LEN + packet_data.len(),
+        };
+        if full_packet_len - CCSDS_HEADER_LEN - 1 > u16::MAX as usize {
+            return Err(InvalidPayloadLengthError(packet_data.len()).into());
+        }
+        sp_header.data_len = (full_packet_len - CCSDS_HEADER_LEN - 1) as u16;
+        sp_header.packet_id.packet_type = packet_type;
+        Ok(Self {
+            sp_header,
+            packet_data,
+            checksum,
+        })
+    }
+
+    pub fn new_with_checksum(
+        sp_header: SpHeader,
+        packet_type: PacketType,
+        app_data: &'app_data [u8],
+    ) -> Result<Self, CcsdsPacketCreationError> {
+        Self::new(
+            sp_header,
+            packet_type,
+            app_data,
+            Some(ChecksumType::Crc16CcittFalse),
+        )
+    }
+}
+
+impl CcsdsPacketCreator<'_> {
+    pub fn len_written(&self) -> usize {
+        ccsds_packet_len_for_user_data_len(self.packet_data.len(), self.checksum)
+    }
+
+    pub fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        let len_written = self.len_written();
+        if len_written > buf.len() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: len_written,
+            });
+        }
+        self.sp_header
+            .write_to_be_bytes(&mut buf[0..CCSDS_HEADER_LEN])?;
+        buf[CCSDS_HEADER_LEN..CCSDS_HEADER_LEN + self.packet_data.len()]
+            .copy_from_slice(self.packet_data);
+        match self.checksum {
+            Some(ChecksumType::Crc16CcittFalse) => {
+                let crc16 = CRC_CCITT_FALSE.checksum(&buf[0..len_written - 2]);
+                buf[len_written - 2..len_written].copy_from_slice(&crc16.to_be_bytes());
+            }
+            None => (),
+        };
+        Ok(len_written)
+    }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_vec(&self) -> alloc::vec::Vec<u8> {
+        let mut vec = alloc::vec![0u8; self.len_written()];
+        // Can not fail, unless we messed up the len_written method..
+        self.write_to_bytes(&mut vec).unwrap();
+        vec
+    }
+}
+
+#[derive(thiserror::Error, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub enum CcsdsPacketReadError {
+    #[error("byte conversion: {0}")]
+    ByteConversion(#[from] ByteConversionError),
+    #[error("CRC error")]
+    CrcError,
+}
+
+/// CCSDS packet reader structure.
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct CcsdsPacketReader<'buf> {
+    sp_header: SpHeader,
+    packet_data: &'buf [u8],
+}
+
+impl<'buf> CcsdsPacketReader<'buf> {
+    pub fn new_with_checksum(
+        buf: &'buf [u8],
+    ) -> Result<CcsdsPacketReader<'buf>, CcsdsPacketReadError> {
+        Self::new(buf, Some(ChecksumType::Crc16CcittFalse))
+    }
+
+    pub fn new(
+        buf: &'buf [u8],
+        checksum: Option<ChecksumType>,
+    ) -> Result<Self, CcsdsPacketReadError> {
+        let sp_header = SpHeader::from_be_bytes(&buf[0..CCSDS_HEADER_LEN])
+            .unwrap()
+            .0;
+        if sp_header.packet_len() > buf.len() {
+            return Err(ByteConversionError::FromSliceTooSmall {
+                found: sp_header.packet_len(),
+                expected: buf.len(),
+            }
+            .into());
+        }
+        let user_data = match checksum {
+            Some(ChecksumType::Crc16CcittFalse) => {
+                if CRC_CCITT_FALSE.checksum(&buf[0..sp_header.packet_len()]) != 0 {
+                    return Err(CcsdsPacketReadError::CrcError);
+                }
+                &buf[CCSDS_HEADER_LEN..sp_header.packet_len() - 2]
+            }
+            None => &buf[CCSDS_HEADER_LEN..sp_header.packet_len()],
+        };
+        Ok(Self {
+            sp_header,
+            packet_data: user_data,
+        })
+    }
+}
+
+impl CcsdsPacketReader<'_> {
+    #[inline]
+    pub fn sp_header(&self) -> &SpHeader {
+        &self.sp_header
+    }
+
+    #[inline]
+    pub fn packet_data(&self) -> &[u8] {
+        self.packet_data
+    }
+
+    #[inline]
+    pub fn apid(&self) -> u11 {
+        self.sp_header.apid()
+    }
+
+    #[inline]
+    pub fn packet_id(&self) -> PacketId {
+        self.sp_header.packet_id()
+    }
+
+    #[inline]
+    pub fn psc(&self) -> PacketSequenceControl {
+        self.sp_header.psc()
+    }
+
+    #[inline]
+    pub fn packet_len(&self) -> usize {
+        <Self as CcsdsPacket>::packet_len(self)
+    }
+
+    #[inline]
+    pub fn data_len(&self) -> u16 {
+        self.sp_header.data_len()
+    }
+}
+
+impl CcsdsPacket for CcsdsPacketReader<'_> {
+    #[inline]
+    fn ccsds_version(&self) -> arbitrary_int::u3 {
+        self.sp_header.ccsds_version()
+    }
+
+    #[inline]
+    fn packet_id(&self) -> PacketId {
+        self.packet_id()
+    }
+
+    #[inline]
+    fn psc(&self) -> PacketSequenceControl {
+        self.psc()
+    }
+
+    #[inline]
+    fn data_len(&self) -> u16 {
+        self.data_len()
+    }
+}
+
 #[cfg(all(test, feature = "std"))]
 pub(crate) mod tests {
     use std::collections::HashSet;
@@ -1058,4 +1481,7 @@ pub(crate) mod tests {
             .0;
         assert_eq!(sp_header, sp_header_read_back);
     }
+
+    #[test]
+    fn test_ccsds_size_function() {}
 }