Merge pull request 'reserved data variants for ECSS TM and TC' (#129) from ecss-tm-tc-reserved-data-variants into main

Reviewed-on: #129

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@1.81.0
+      - uses: dtolnay/rust-toolchain@1.70.0
       - run: cargo check --release
 
   cross-check:

CHANGELOG.md

@@ -8,10 +8,46 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+## Added
+
+- `PusTcCreatorWithReservedAppData` and `PusTmCreatorWithReservedSourceData` constructor variants
+  which allow writing source/app data into the serialization buffer directly without
+  requiring an extra buffer.
+
+# [v0.14.0] 2025-05-10
+
+## Changed
+
+- Moved CRC constants/implementations to dedicated `crc` module.
+- `crc::CRC_CCITT_FALSE_NO_TABLE` and `crc::CRC_CCITT_FALSE_BIG_TABLE` variants.
+- Renamed `PusPacket::crc16` to `PusPacket::opt_crc16`.
+
+## Added
+
+- `WritablePusPacket::write_to_bytes_crc_no_table` and `WritablePusPacket::write_to_bytes_no_crc`
+  variants.
+- `PusTmReader::new_crc_no_table` and `PusTcReader::new_crc_no_table` variants.
+- `crc16` methods for PUS TM and PUS TC reader.
+- PUS TM and PUS TC reader now return the reader instance directly instead of a tuple of the reader
+  and the read size. The instance `total_len` method can be used to retrieve the read lenght.
+
+# [v0.13.1] 2025-03-21
+
+- Bugfix due to operator precendence for `PusTcSecondaryHeader::pus_version`, 
+  `PusTcSecondaryHeaderWithoutTimestamp::pus_version`, `CdsTime::from_bytes_with_u16_days` and
+  `CdsTime::from_bytes_with_u24_days`
+
+# [v0.13.0] 2024-11-08
+
 - Bumped MSRV to 1.81.0
 - Bump `zerocopy` to v0.8.0
 - Bump `thiserror` to v2.0.0
 
+## Changed
+
+- Migrated all Error implementations to thiserror, improved some naming and error handling in
+  general
+
 # [v0.12.0] 2024-09-10
 
 - Bumped MSRV to 1.70.0
@@ -554,3 +590,9 @@ The timestamp of `PusTm` is now optional. See Added and Changed section for deta
 
 Initial release with CCSDS Space Packet Primary Header implementation and basic PUS TC and TM
 implementations.
+
+[unreleased]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.14.0...HEAD
+[v0.14.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.13.1...v0.14.0
+[v0.13.1]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.13.0...v0.13.1
+[v0.13.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.12.0...v0.13.0
+[v0.12.0]: https://egit.irs.uni-stuttgart.de/rust/spacepackets/compare/v0.11.2...v0.12.0

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "spacepackets"
-version = "0.12.0"
+version = "0.14.0"
 edition = "2021"
-rust-version = "1.81.0"
+rust-version = "1.70.0"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
 description = "Generic implementations for various CCSDS and ECSS packet standards"
 homepage = "https://egit.irs.uni-stuttgart.de/rust/spacepackets"
@@ -13,45 +13,18 @@ categories = ["aerospace", "aerospace::space-protocols", "no-std", "hardware-sup
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-crc = "3"
+crc = "3.3"
 delegate = ">=0.8, <=0.13"
 paste = "1"
+zerocopy = { version = "0.8", features = ["derive"] }
+thiserror = { version = "2", default-features = false }
+num_enum = { version = ">0.5, <=0.7", default-features = false }
+num-traits = { version = "0.2", default-features = false }
+serde = { version = "1", optional = true, default-features = false, features = ["derive"] }
 
-[dependencies.zerocopy]
-version = "0.8"
-features = ["derive"]
-
-[dependencies.thiserror]
-version = "2"
-default-features = false
-
-[dependencies.num_enum]
-version = ">0.5, <=0.7"
-default-features = false
-
-[dependencies.serde]
-version = "1"
-optional = true
-default-features = false
-features = ["derive"]
-
-[dependencies.time]
-version = "0.3"
-default-features = false
-optional = true
-
-[dependencies.chrono]
-version = "0.4"
-default-features = false
-optional = true
-
-[dependencies.num-traits]
-version = "0.2"
-default-features = false
-
-[dependencies.defmt]
-version = "0.3"
-optional = true
+time = { version = "0.3", default-features = false, optional = true }
+chrono = { version = "0.4", default-features = false, optional = true }
+defmt = { version = "1", default-features = false, optional = true }
 
 [features]
 default = ["std"]

FUNDING.yml

@@ -0,0 +1 @@
+github: robamu

README.md

@@ -1,7 +1,6 @@
 [![Crates.io](https://img.shields.io/crates/v/spacepackets)](https://crates.io/crates/spacepackets)
 [![docs.rs](https://img.shields.io/docsrs/spacepackets)](https://docs.rs/spacepackets)
 [![ci](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/us-irs/spacepackets-rs/actions/workflows/ci.yml)
-[![coverage](https://shields.io/endpoint?url=https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/coverage.json)](https://absatsw.irs.uni-stuttgart.de/projects/spacepackets/coverage-rs/latest/index.html)
 
 ECSS and CCSDS Spacepackets
 ======

src/cfdp/pdu/mod.rs

@@ -1,8 +1,8 @@
 //! CFDP Packet Data Unit (PDU) support.
 use crate::cfdp::*;
+use crate::crc::CRC_CCITT_FALSE;
 use crate::util::{UnsignedByteField, UnsignedByteFieldU8, UnsignedEnum};
 use crate::ByteConversionError;
-use crate::CRC_CCITT_FALSE;
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 
@@ -42,7 +42,9 @@ pub enum PduError {
     /// Invalid length for the entity ID detected. Only the values 1, 2, 4 and 8 are supported.
     #[error("invalid transaction ID length {0}")]
     InvalidTransactionSeqNumLen(u8),
-    #[error("missmatch of PDU source ID length {src_id_len} and destination ID length {dest_id_len}")]
+    #[error(
+        "missmatch of PDU source ID length {src_id_len} and destination ID length {dest_id_len}"
+    )]
     SourceDestIdLenMissmatch {
         src_id_len: usize,
         dest_id_len: usize,

src/cfdp/pdu/nak.rs

@@ -61,7 +61,7 @@ impl<'seg_reqs> NakPduCreator<'seg_reqs> {
         start_of_scope: u32,
         end_of_scope: u32,
         segment_requests: &'seg_reqs [(u32, u32)],
-    ) -> Result<NakPduCreator, PduError> {
+    ) -> Result<NakPduCreator<'seg_reqs>, PduError> {
         let mut passed_segment_requests = None;
         if !segment_requests.is_empty() {
             passed_segment_requests = Some(SegmentRequests::U32Pairs(segment_requests));
@@ -79,7 +79,7 @@ impl<'seg_reqs> NakPduCreator<'seg_reqs> {
         start_of_scope: u64,
         end_of_scope: u64,
         segment_requests: &'seg_reqs [(u64, u64)],
-    ) -> Result<NakPduCreator, PduError> {
+    ) -> Result<NakPduCreator<'seg_reqs>, PduError> {
         let mut passed_segment_requests = None;
         if !segment_requests.is_empty() {
             passed_segment_requests = Some(SegmentRequests::U64Pairs(segment_requests));
@@ -97,7 +97,7 @@ impl<'seg_reqs> NakPduCreator<'seg_reqs> {
         start_of_scope: u64,
         end_of_scope: u64,
         segment_requests: Option<SegmentRequests<'seg_reqs>>,
-    ) -> Result<NakPduCreator, PduError> {
+    ) -> Result<NakPduCreator<'seg_reqs>, PduError> {
         // Force correct direction flag.
         pdu_header.pdu_conf.direction = Direction::TowardsSender;
         if let Some(ref segment_requests) = segment_requests {
@@ -269,7 +269,7 @@ impl SegReqFromBytes for u64 {
     }
 }
 
-impl<'a, T> Iterator for SegmentRequestIter<'a, T>
+impl<T> Iterator for SegmentRequestIter<'_, T>
 where
     T: SegReqFromBytes,
 {
@@ -282,8 +282,8 @@ where
     }
 }
 
-impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u32> {
-    fn eq(&self, other: &SegmentRequests) -> bool {
+impl<'a> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'_, u32> {
+    fn eq(&self, other: &SegmentRequests<'a>) -> bool {
         match other {
             SegmentRequests::U32Pairs(pairs) => self.compare_pairs(pairs),
             SegmentRequests::U64Pairs(pairs) => {
@@ -296,8 +296,8 @@ impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u32> {
     }
 }
 
-impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u64> {
-    fn eq(&self, other: &SegmentRequests) -> bool {
+impl<'a> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'_, u64> {
+    fn eq(&self, other: &SegmentRequests<'a>) -> bool {
         match other {
             SegmentRequests::U32Pairs(pairs) => {
                 if pairs.is_empty() && self.seq_req_raw.is_empty() {
@@ -310,7 +310,7 @@ impl<'a, 'b> PartialEq<SegmentRequests<'a>> for SegmentRequestIter<'b, u64> {
     }
 }
 
-impl<'a, T> SegmentRequestIter<'a, T>
+impl<T> SegmentRequestIter<'_, T>
 where
     T: SegReqFromBytes + PartialEq,
 {
@@ -374,11 +374,11 @@ impl CfdpPdu for NakPduReader<'_> {
 }
 
 impl<'seg_reqs> NakPduReader<'seg_reqs> {
-    pub fn new(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+    pub fn new(buf: &'seg_reqs [u8]) -> Result<NakPduReader<'seg_reqs>, PduError> {
         Self::from_bytes(buf)
     }
 
-    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
+    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPduReader<'seg_reqs>, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         // Minimum length of 9: 1 byte directive field and start and end of scope for normal file
@@ -474,7 +474,7 @@ impl<'seg_reqs> NakPduReader<'seg_reqs> {
     }
 }
 
-impl<'a, 'b> PartialEq<NakPduCreator<'a>> for NakPduReader<'b> {
+impl<'a> PartialEq<NakPduCreator<'a>> for NakPduReader<'_> {
     fn eq(&self, other: &NakPduCreator<'a>) -> bool {
         if self.pdu_header() != other.pdu_header()
             || self.end_of_scope() != other.end_of_scope()

src/cfdp/tlv/mod.rs

@@ -273,6 +273,15 @@ pub mod alloc_mod {
                 data: Vec::new(),
             }
         }
+
+        pub fn as_tlv(&self) -> Tlv<'_> {
+            Tlv {
+                tlv_type_field: self.tlv_type_field,
+                // The API should ensure that the data length is never to large, so the unwrap for the
+                // LV creation should never be an issue.
+                lv: Lv::new(&self.data).expect("lv creation failed unexpectedly"),
+            }
+        }
     }
 
     impl ReadableTlv for TlvOwned {
@@ -389,7 +398,7 @@ impl GenericTlv for EntityIdTlv {
     }
 }
 
-impl<'data> TryFrom<Tlv<'data>> for EntityIdTlv {
+impl TryFrom<Tlv<'_>> for EntityIdTlv {
     type Error = TlvLvError;
 
     fn try_from(value: Tlv) -> Result<Self, TlvLvError> {

src/cfdp/tlv/msg_to_user.rs

@@ -2,7 +2,10 @@
 #[cfg(feature = "alloc")]
 use super::TlvOwned;
 use super::{GenericTlv, ReadableTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
-use crate::{cfdp::{InvalidTlvTypeFieldError, TlvLvDataTooLargeError}, ByteConversionError};
+use crate::{
+    cfdp::{InvalidTlvTypeFieldError, TlvLvDataTooLargeError},
+    ByteConversionError,
+};
 use delegate::delegate;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -65,14 +68,16 @@ impl<'data> MsgToUserTlv<'data> {
                     return Err(InvalidTlvTypeFieldError {
                         found: tlv_type as u8,
                         expected: Some(TlvType::MsgToUser as u8),
-                    }.into());
+                    }
+                    .into());
                 }
             }
             TlvTypeField::Custom(raw) => {
                 return Err(InvalidTlvTypeFieldError {
                     found: raw,
                     expected: Some(TlvType::MsgToUser as u8),
-                }.into());
+                }
+                .into());
             }
         }
         Ok(msg_to_user)

src/crc.rs

@@ -0,0 +1,11 @@
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// a [crc::NoTable] as the CRC implementation.
+pub const CRC_CCITT_FALSE_NO_TABLE: crc::Crc<u16, crc::NoTable> =
+    crc::Crc::<u16, crc::NoTable>::new(&crc::CRC_16_IBM_3740);
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// [crc::Table<1>] as the CRC implementation.
+pub const CRC_CCITT_FALSE: crc::Crc<u16> = crc::Crc::<u16>::new(&crc::CRC_16_IBM_3740);
+/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard, using
+/// a [crc::Table<16>] large table as the CRC implementation.
+pub const CRC_CCITT_FALSE_BIG_TABLE: crc::Crc<u16, crc::Table<16>> =
+    crc::Crc::<u16, crc::Table<16>>::new(&crc::CRC_16_IBM_3740);

src/ecss/mod.rs

@@ -3,7 +3,10 @@
 //!
 //! You can find the PUS telecommand types in the [tc] module and the the PUS telemetry
 //! types inside the [tm] module.
-use crate::{ByteConversionError, CcsdsPacket, CRC_CCITT_FALSE};
+use crate::{
+    crc::{CRC_CCITT_FALSE, CRC_CCITT_FALSE_NO_TABLE},
+    ByteConversionError, CcsdsPacket,
+};
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 use core::fmt::Debug;
@@ -170,7 +173,7 @@ pub trait PusPacket: CcsdsPacket {
     fn service(&self) -> u8;
     fn subservice(&self) -> u8;
     fn user_data(&self) -> &[u8];
-    fn crc16(&self) -> Option<u16>;
+    fn opt_crc16(&self) -> Option<u16>;
 }
 
 pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, ByteConversionError> {
@@ -207,7 +210,7 @@ pub(crate) fn user_data_from_raw(
     }
 }
 
-pub(crate) fn verify_crc16_ccitt_false_from_raw_to_pus_error(
+pub fn verify_crc16_ccitt_false_from_raw_to_pus_error(
     raw_data: &[u8],
     crc16: u16,
 ) -> Result<(), PusError> {
@@ -216,6 +219,15 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw_to_pus_error(
         .ok_or(PusError::ChecksumFailure(crc16))
 }
 
+pub fn verify_crc16_ccitt_false_from_raw_to_pus_error_no_table(
+    raw_data: &[u8],
+    crc16: u16,
+) -> Result<(), PusError> {
+    verify_crc16_ccitt_false_from_raw_no_table(raw_data)
+        .then_some(())
+        .ok_or(PusError::ChecksumFailure(crc16))
+}
+
 pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
     let mut digest = CRC_CCITT_FALSE.digest();
     digest.update(raw_data);
@@ -225,6 +237,15 @@ pub(crate) fn verify_crc16_ccitt_false_from_raw(raw_data: &[u8]) -> bool {
     false
 }
 
+pub(crate) fn verify_crc16_ccitt_false_from_raw_no_table(raw_data: &[u8]) -> bool {
+    let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+    digest.update(raw_data);
+    if digest.finalize() == 0 {
+        return true;
+    }
+    false
+}
+
 macro_rules! ccsds_impl {
     () => {
         delegate!(to self.sp_header {
@@ -349,7 +370,34 @@ generic_ecss_enum_typedefs_and_from_impls! {
 /// on the serialization of those packets.
 pub trait WritablePusPacket {
     fn len_written(&self) -> usize;
-    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+
+    /// Writes the packet to the given slice without writing the CRC.
+    ///
+    /// The returned size is the written size WITHOUT the CRC.
+    fn write_to_bytes_no_crc(&self, slice: &mut [u8]) -> Result<usize, PusError>;
+
+    /// First uses [Self::write_to_bytes_no_crc] to write the packet to the given slice and then
+    /// uses the [CRC_CCITT_FALSE] to calculate the CRC and write it to the slice.
+    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        let mut curr_idx = self.write_to_bytes_no_crc(slice)?;
+        let mut digest = CRC_CCITT_FALSE.digest();
+        digest.update(&slice[0..curr_idx]);
+        slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
+        curr_idx += 2;
+        Ok(curr_idx)
+    }
+
+    /// First uses [Self::write_to_bytes_no_crc] to write the packet to the given slice and then
+    /// uses the [CRC_CCITT_FALSE_NO_TABLE] to calculate the CRC and write it to the slice.
+    fn write_to_bytes_crc_no_table(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        let mut curr_idx = self.write_to_bytes_no_crc(slice)?;
+        let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+        digest.update(&slice[0..curr_idx]);
+        slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
+        curr_idx += 2;
+        Ok(curr_idx)
+    }
+
     #[cfg(feature = "alloc")]
     fn to_vec(&self) -> Result<Vec<u8>, PusError> {
         // This is the correct way to do this. See

src/ecss/tc.rs

@@ -33,13 +33,14 @@
 //! assert_eq!(pus_tc.subservice(), 1);
 //! assert_eq!(pus_tc.apid(), 0x02);
 //! ```
+use crate::crc::{CRC_CCITT_FALSE, CRC_CCITT_FALSE_NO_TABLE};
 use crate::ecss::{
     ccsds_impl, crc_from_raw_data, sp_header_impls, user_data_from_raw,
     verify_crc16_ccitt_false_from_raw_to_pus_error, CrcType, PusError, PusPacket, PusVersion,
     WritablePusPacket,
 };
+use crate::SpHeader;
 use crate::{ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, CCSDS_HEADER_LEN};
-use crate::{SpHeader, CRC_CCITT_FALSE};
 use core::mem::size_of;
 use delegate::delegate;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
@@ -50,6 +51,8 @@ use zerocopy::{FromBytes, IntoBytes};
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 
+use super::verify_crc16_ccitt_false_from_raw_to_pus_error_no_table;
+
 /// PUS C secondary header length is fixed
 pub const PUC_TC_SECONDARY_HEADER_LEN: usize = size_of::<zc::PusTcSecondaryHeader>();
 pub const PUS_TC_MIN_LEN_WITHOUT_APP_DATA: usize =
@@ -115,7 +118,7 @@ pub mod zc {
     impl GenericPusTcSecondaryHeader for PusTcSecondaryHeader {
         #[inline]
         fn pus_version(&self) -> PusVersion {
-            PusVersion::try_from(self.version_ack >> 4 & 0b1111).unwrap_or(PusVersion::Invalid)
+            PusVersion::try_from((self.version_ack >> 4) & 0b1111).unwrap_or(PusVersion::Invalid)
         }
 
         #[inline]
@@ -239,13 +242,13 @@ impl<'app_data> PusTcCreator<'app_data> {
     /// # Arguments
     ///
     /// * `sp_header` - Space packet header information. The correct packet type and the secondary
-    ///     header flag are set correctly by the constructor.
+    ///   header flag are set correctly by the constructor.
     /// * `sec_header` - Information contained in the data field header, including the service
-    ///     and subservice type
+    ///   and subservice type
     /// * `app_data` - Custom application data
     /// * `set_ccsds_len` - Can be used to automatically update the CCSDS space packet data length
-    ///     field. If this is not set to true, [Self::update_ccsds_data_len] can be called to set
-    ///     the correct value to this field manually
+    ///   field. If this is not set to true, [Self::update_ccsds_data_len] can be called to set
+    ///   the correct value to this field manually
     #[inline]
     pub fn new(
         mut sp_header: SpHeader,
@@ -342,6 +345,17 @@ impl<'app_data> PusTcCreator<'app_data> {
         digest.finalize()
     }
 
+    /// This function calculates and returns the CRC16 for the current packet.
+    pub fn calc_own_crc16_no_table(&self) -> u16 {
+        let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+        let sph_zc = crate::zc::SpHeader::from(self.sp_header);
+        digest.update(sph_zc.as_bytes());
+        let pus_tc_header = zc::PusTcSecondaryHeader::try_from(self.sec_header).unwrap();
+        digest.update(pus_tc_header.as_bytes());
+        digest.update(self.app_data);
+        digest.finalize()
+    }
+
     #[cfg(feature = "alloc")]
     pub fn append_to_vec(&self, vec: &mut Vec<u8>) -> usize {
         let sph_zc = crate::zc::SpHeader::from(self.sp_header);
@@ -358,6 +372,49 @@ impl<'app_data> PusTcCreator<'app_data> {
         vec.extend_from_slice(&digest.finalize().to_be_bytes());
         appended_len
     }
+
+    /// Write the raw PUS byte representation to a provided buffer.
+    pub fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, ByteConversionError> {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize())
+    }
+
+    /// Write the raw PUS byte representation to a provided buffer.
+    pub fn write_to_bytes_crc_no_table(
+        &self,
+        slice: &mut [u8],
+    ) -> Result<usize, ByteConversionError> {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize_crc_no_table())
+    }
+
+    /// Write the raw PUS byte representation to a provided buffer.
+    pub fn write_to_bytes_no_crc(&self, slice: &mut [u8]) -> Result<usize, ByteConversionError> {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize_no_crc())
+    }
+
+    fn common_write<'a>(
+        &self,
+        slice: &'a mut [u8],
+    ) -> Result<PusTcCreatorWithReservedAppData<'a>, ByteConversionError> {
+        if self.len_written() > slice.len() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: slice.len(),
+                expected: self.len_written(),
+            });
+        }
+        let mut writer_unfinalized = PusTcCreatorWithReservedAppData::write_to_bytes_partially(
+            slice,
+            self.sp_header,
+            self.sec_header,
+            self.app_data.len(),
+        )?;
+        writer_unfinalized
+            .app_data_mut()
+            .copy_from_slice(self.app_data);
+        Ok(writer_unfinalized)
+    }
 }
 
 impl WritablePusPacket for PusTcCreator<'_> {
@@ -367,32 +424,16 @@ impl WritablePusPacket for PusTcCreator<'_> {
     }
 
     /// Write the raw PUS byte representation to a provided buffer.
-    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
-        let mut curr_idx = 0;
-        let tc_header_len = size_of::<zc::PusTcSecondaryHeader>();
-        let total_size = self.len_written();
-        if total_size > slice.len() {
-            return Err(ByteConversionError::ToSliceTooSmall {
-                found: slice.len(),
-                expected: total_size,
-            }
-            .into());
-        }
-        self.sp_header.write_to_be_bytes(slice)?;
-        curr_idx += CCSDS_HEADER_LEN;
-        let sec_header = zc::PusTcSecondaryHeader::try_from(self.sec_header).unwrap();
-        sec_header
-            .write_to(&mut slice[curr_idx..curr_idx + tc_header_len])
-            .map_err(|_| ByteConversionError::ZeroCopyToError)?;
+    fn write_to_bytes_no_crc(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        Ok(Self::write_to_bytes_no_crc(self, slice)?)
+    }
 
-        curr_idx += tc_header_len;
-        slice[curr_idx..curr_idx + self.app_data.len()].copy_from_slice(self.app_data);
-        curr_idx += self.app_data.len();
-        let mut digest = CRC_CCITT_FALSE.digest();
-        digest.update(&slice[0..curr_idx]);
-        slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
-        curr_idx += 2;
-        Ok(curr_idx)
+    fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        Ok(Self::write_to_bytes(self, slice)?)
+    }
+
+    fn write_to_bytes_crc_no_table(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        Ok(Self::write_to_bytes_crc_no_table(self, slice)?)
     }
 }
 
@@ -416,7 +457,7 @@ impl PusPacket for PusTcCreator<'_> {
     }
 
     #[inline]
-    fn crc16(&self) -> Option<u16> {
+    fn opt_crc16(&self) -> Option<u16> {
         Some(self.calc_own_crc16())
     }
 }
@@ -438,6 +479,133 @@ impl GenericPusTcSecondaryHeader for PusTcCreator<'_> {
 
 impl IsPusTelecommand for PusTcCreator<'_> {}
 
+/// A specialized variant of [PusTcCreator] designed for efficiency when handling large source
+/// data.
+///
+/// Unlike [PusTcCreator], this type does not require the user to provide the application data
+/// as a separate slice. Instead, it allows writing the application data directly into the provided
+/// serialization buffer. This eliminates the need for an intermediate buffer and the associated
+/// memory copy, improving performance, particularly when working with large payloads.
+///
+/// **Important:** The total length of the source data must be known and specified in advance
+/// to ensure correct serialization behavior.
+///
+/// Note that this abstraction intentionally omits certain trait implementations that are available
+/// on [PusTcCreator], as they are not applicable in this optimized usage pattern.
+pub struct PusTcCreatorWithReservedAppData<'buf> {
+    buf: &'buf mut [u8],
+    app_data_offset: usize,
+    full_len: usize,
+}
+
+impl<'buf> PusTcCreatorWithReservedAppData<'buf> {
+    /// Generates a new instance with reserved space for the user application data.
+    ///
+    /// # Arguments
+    ///
+    /// * `sp_header` - Space packet header information. The correct packet type and the secondary
+    ///   header flag are set correctly by the constructor.
+    /// * `sec_header` - Information contained in the secondary header, including the service
+    ///   and subservice type
+    /// * `app_data_len` - Custom application data length
+    #[inline]
+    pub fn new(
+        buf: &'buf mut [u8],
+        mut sp_header: SpHeader,
+        sec_header: PusTcSecondaryHeader,
+        app_data_len: usize,
+    ) -> Result<Self, ByteConversionError> {
+        sp_header.set_packet_type(PacketType::Tc);
+        sp_header.set_sec_header_flag();
+        let len_written = PUS_TC_MIN_LEN_WITHOUT_APP_DATA + app_data_len;
+        if len_written > buf.len() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: len_written,
+            });
+        }
+        sp_header.data_len = len_written as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+        Self::write_to_bytes_partially(buf, sp_header, sec_header, app_data_len)
+    }
+
+    fn write_to_bytes_partially(
+        buf: &'buf mut [u8],
+        sp_header: SpHeader,
+        sec_header: PusTcSecondaryHeader,
+        app_data_len: usize,
+    ) -> Result<Self, ByteConversionError> {
+        let mut curr_idx = 0;
+        sp_header.write_to_be_bytes(&mut buf[0..CCSDS_HEADER_LEN])?;
+        curr_idx += CCSDS_HEADER_LEN;
+        let sec_header_len = size_of::<zc::PusTcSecondaryHeader>();
+        let sec_header_zc = zc::PusTcSecondaryHeader::try_from(sec_header).unwrap();
+        sec_header_zc
+            .write_to(&mut buf[curr_idx..curr_idx + sec_header_len])
+            .map_err(|_| ByteConversionError::ZeroCopyToError)?;
+        curr_idx += sec_header_len;
+        let app_data_offset = curr_idx;
+        curr_idx += app_data_len;
+        Ok(Self {
+            buf,
+            app_data_offset,
+            full_len: curr_idx + 2,
+        })
+    }
+
+    #[inline]
+    pub const fn len_written(&self) -> usize {
+        self.full_len
+    }
+
+    /// Mutable access to the application data buffer.
+    #[inline]
+    pub fn app_data_mut(&mut self) -> &mut [u8] {
+        &mut self.buf[self.app_data_offset..self.full_len - 2]
+    }
+
+    /// Access to the source data buffer.
+    #[inline]
+    pub fn app_data(&self) -> &[u8] {
+        &self.buf[self.app_data_offset..self.full_len - 2]
+    }
+
+    #[inline]
+    pub fn app_data_len(&self) -> usize {
+        self.full_len - 2 - self.app_data_offset
+    }
+
+    /// Finalize the TC packet by calculating and writing the CRC16.
+    ///
+    /// Returns the full packet length.
+    pub fn finalize(self) -> usize {
+        let mut digest = CRC_CCITT_FALSE.digest();
+        digest.update(&self.buf[0..self.full_len - 2]);
+        self.buf[self.full_len - 2..self.full_len]
+            .copy_from_slice(&digest.finalize().to_be_bytes());
+        self.full_len
+    }
+
+    /// Finalize the TC packet by calculating and writing the CRC16 using a table-less
+    /// implementation.
+    ///
+    /// Returns the full packet length.
+    pub fn finalize_crc_no_table(self) -> usize {
+        let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+        digest.update(&self.buf[0..self.full_len - 2]);
+        self.buf[self.full_len - 2..self.full_len]
+            .copy_from_slice(&digest.finalize().to_be_bytes());
+        self.full_len
+    }
+
+    /// Finalize the TC packet without writing the CRC16.
+    ///
+    /// Returns the length WITHOUT the CRC16.
+    #[inline]
+    pub fn finalize_no_crc(self) -> usize {
+        self.full_len - 2
+    }
+}
+
 /// This class can be used to read a PUS TC telecommand from raw memory.
 ///
 /// This class also derives the [serde::Serialize] and [serde::Deserialize] trait if the
@@ -465,7 +633,22 @@ impl<'raw_data> PusTcReader<'raw_data> {
     /// Create a [PusTcReader] instance from a raw slice. On success, it returns a tuple containing
     /// the instance and the found byte length of the packet. This function also performs a CRC
     /// check and will return an appropriate [PusError] if the check fails.
-    pub fn new(slice: &'raw_data [u8]) -> Result<(Self, usize), PusError> {
+    pub fn new(slice: &'raw_data [u8]) -> Result<Self, PusError> {
+        let pus_tc = Self::new_no_crc_check(slice)?;
+        verify_crc16_ccitt_false_from_raw_to_pus_error(pus_tc.raw_data(), pus_tc.crc16())?;
+        Ok(pus_tc)
+    }
+
+    /// Similar to [PusTcReader::new], but uses a table-less CRC16 algorithm which can reduce
+    /// binary size and memory usage.
+    pub fn new_crc_no_table(slice: &'raw_data [u8]) -> Result<Self, PusError> {
+        let pus_tc = Self::new_no_crc_check(slice)?;
+        verify_crc16_ccitt_false_from_raw_to_pus_error_no_table(pus_tc.raw_data(), pus_tc.crc16())?;
+        Ok(pus_tc)
+    }
+
+    /// Creates a new instance without performing a CRC check.
+    pub fn new_no_crc_check(slice: &'raw_data [u8]) -> Result<Self, PusError> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
             return Err(ByteConversionError::FromSliceTooSmall {
@@ -498,15 +681,13 @@ impl<'raw_data> PusTcReader<'raw_data> {
         .map_err(|_| ByteConversionError::ZeroCopyFromError)?;
         current_idx += PUC_TC_SECONDARY_HEADER_LEN;
         let raw_data = &slice[0..total_len];
-        let pus_tc = Self {
+        Ok(Self {
             sp_header,
             sec_header: PusTcSecondaryHeader::try_from(sec_header).unwrap(),
             raw_data,
             app_data: user_data_from_raw(current_idx, total_len, slice)?,
             crc16: crc_from_raw_data(raw_data)?,
-        };
-        verify_crc16_ccitt_false_from_raw_to_pus_error(raw_data, pus_tc.crc16)?;
-        Ok((pus_tc, total_len))
+        })
     }
 
     #[inline]
@@ -528,6 +709,11 @@ impl<'raw_data> PusTcReader<'raw_data> {
     pub fn sp_header(&self) -> &SpHeader {
         &self.sp_header
     }
+
+    #[inline]
+    pub fn crc16(&self) -> u16 {
+        self.crc16
+    }
 }
 
 impl PartialEq for PusTcReader<'_> {
@@ -557,7 +743,7 @@ impl PusPacket for PusTcReader<'_> {
     }
 
     #[inline]
-    fn crc16(&self) -> Option<u16> {
+    fn opt_crc16(&self) -> Option<u16> {
         Some(self.crc16)
     }
 }
@@ -597,8 +783,6 @@ impl PartialEq<PusTcReader<'_>> for PusTcCreator<'_> {
 
 #[cfg(all(test, feature = "std"))]
 mod tests {
-    use std::error::Error;
-
     use super::*;
     use crate::ecss::PusVersion::PusC;
     use crate::ecss::{PusError, PusPacket, WritablePusPacket};
@@ -640,11 +824,74 @@ mod tests {
             .expect("Error writing TC to buffer");
         assert_eq!(size, 13);
         assert_eq!(
-            pus_tc.crc16().unwrap(),
+            pus_tc.opt_crc16().unwrap(),
             u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
         );
     }
 
+    #[test]
+    fn test_serialization_with_trait_1() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = WritablePusPacket::write_to_bytes(&pus_tc, test_buf.as_mut_slice())
+            .expect("Error writing TC to buffer");
+        assert_eq!(size, 13);
+        assert_eq!(
+            pus_tc.opt_crc16().unwrap(),
+            u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
+        );
+    }
+
+    #[test]
+    fn test_serialization_with_trait_2() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = WritablePusPacket::write_to_bytes_crc_no_table(&pus_tc, test_buf.as_mut_slice())
+            .expect("Error writing TC to buffer");
+        assert_eq!(size, 13);
+        assert_eq!(
+            pus_tc.opt_crc16().unwrap(),
+            u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
+        );
+    }
+
+    #[test]
+    fn test_serialization_crc_no_table() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = pus_tc
+            .write_to_bytes_crc_no_table(test_buf.as_mut_slice())
+            .expect("error writing tc to buffer");
+        assert_eq!(size, 13);
+        assert_eq!(
+            pus_tc.opt_crc16().unwrap(),
+            u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
+        );
+    }
+
+    #[test]
+    fn test_serialization_no_crc() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = pus_tc
+            .write_to_bytes_no_crc(test_buf.as_mut_slice())
+            .expect("error writing tc to buffer");
+        assert_eq!(size, 11);
+        assert_eq!(test_buf[11], 0);
+        assert_eq!(test_buf[12], 0);
+    }
+
+    #[test]
+    fn test_serialization_no_crc_with_trait() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = WritablePusPacket::write_to_bytes_no_crc(&pus_tc, test_buf.as_mut_slice())
+            .expect("error writing tc to buffer");
+        assert_eq!(size, 11);
+        assert_eq!(test_buf[11], 0);
+        assert_eq!(test_buf[12], 0);
+    }
+
     #[test]
     fn test_deserialization() {
         let pus_tc = base_ping_tc_simple_ctor();
@@ -653,9 +900,48 @@ mod tests {
             .write_to_bytes(test_buf.as_mut_slice())
             .expect("Error writing TC to buffer");
         assert_eq!(size, 13);
-        let (tc_from_raw, size) =
+        let tc_from_raw =
             PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
+        assert_eq!(tc_from_raw.total_len(), 13);
+        verify_test_tc_with_reader(&tc_from_raw, false, 13);
+        assert!(tc_from_raw.user_data().is_empty());
+        verify_test_tc_raw(&test_buf);
+        verify_crc_no_app_data(&test_buf);
+    }
+
+    #[test]
+    fn test_deserialization_alt_ctor() {
+        let sph = SpHeader::new_for_unseg_tc_checked(0x02, 0x34, 0).unwrap();
+        let tc_header = PusTcSecondaryHeader::new_simple(17, 1);
+        let mut test_buf: [u8; 32] = [0; 32];
+        let mut pus_tc =
+            PusTcCreatorWithReservedAppData::new(&mut test_buf, sph, tc_header, 0).unwrap();
+        assert_eq!(pus_tc.len_written(), 13);
+        assert_eq!(pus_tc.app_data_len(), 0);
+        assert_eq!(pus_tc.app_data(), &[]);
+        assert_eq!(pus_tc.app_data_mut(), &[]);
+        let size = pus_tc.finalize();
         assert_eq!(size, 13);
+        let tc_from_raw =
+            PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
+        assert_eq!(tc_from_raw.total_len(), 13);
+        verify_test_tc_with_reader(&tc_from_raw, false, 13);
+        assert!(tc_from_raw.user_data().is_empty());
+        verify_test_tc_raw(&test_buf);
+        verify_crc_no_app_data(&test_buf);
+    }
+
+    #[test]
+    fn test_deserialization_no_table() {
+        let pus_tc = base_ping_tc_simple_ctor();
+        let mut test_buf: [u8; 32] = [0; 32];
+        let size = pus_tc
+            .write_to_bytes(test_buf.as_mut_slice())
+            .expect("Error writing TC to buffer");
+        assert_eq!(size, 13);
+        let tc_from_raw = PusTcReader::new_crc_no_table(&test_buf)
+            .expect("Creating PUS TC struct from raw buffer failed");
+        assert_eq!(tc_from_raw.total_len(), 13);
         verify_test_tc_with_reader(&tc_from_raw, false, 13);
         assert!(tc_from_raw.user_data().is_empty());
         verify_test_tc_raw(&test_buf);
@@ -667,9 +953,9 @@ mod tests {
         let pus_tc = base_ping_tc_simple_ctor();
         let tc_vec = pus_tc.to_vec().expect("Error writing TC to buffer");
         assert_eq!(tc_vec.len(), 13);
-        let (tc_from_raw, size) = PusTcReader::new(tc_vec.as_slice())
+        let tc_from_raw = PusTcReader::new(tc_vec.as_slice())
             .expect("Creating PUS TC struct from raw buffer failed");
-        assert_eq!(size, 13);
+        assert_eq!(tc_from_raw.total_len(), 13);
         verify_test_tc_with_reader(&tc_from_raw, false, 13);
         assert!(tc_from_raw.user_data().is_empty());
         verify_test_tc_raw(&tc_vec);
@@ -684,6 +970,7 @@ mod tests {
         tc.update_ccsds_data_len();
         assert_eq!(tc.data_len(), 6);
     }
+
     #[test]
     fn test_deserialization_with_app_data() {
         let pus_tc = base_ping_tc_simple_ctor_with_app_data(&[1, 2, 3]);
@@ -692,15 +979,15 @@ mod tests {
             .write_to_bytes(test_buf.as_mut_slice())
             .expect("Error writing TC to buffer");
         assert_eq!(size, 16);
-        let (tc_from_raw, size) =
+        let tc_from_raw =
             PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
-        assert_eq!(size, 16);
+        assert_eq!(tc_from_raw.total_len(), 16);
         verify_test_tc_with_reader(&tc_from_raw, true, 16);
         let user_data = tc_from_raw.user_data();
         assert_eq!(tc_from_raw.user_data(), tc_from_raw.app_data());
         assert_eq!(tc_from_raw.raw_data(), &test_buf[..size]);
         assert_eq!(
-            tc_from_raw.crc16().unwrap(),
+            tc_from_raw.opt_crc16().unwrap(),
             u16::from_be_bytes(test_buf[size - 2..size].try_into().unwrap())
         );
         assert_eq!(user_data[0], 1);
@@ -715,9 +1002,9 @@ mod tests {
         pus_tc
             .write_to_bytes(test_buf.as_mut_slice())
             .expect("Error writing TC to buffer");
-        let (tc_from_raw_0, _) =
+        let tc_from_raw_0 =
             PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
-        let (tc_from_raw_1, _) =
+        let tc_from_raw_1 =
             PusTcReader::new(&test_buf).expect("Creating PUS TC struct from raw buffer failed");
         assert_eq!(tc_from_raw_0, tc_from_raw_1);
     }
@@ -786,22 +1073,17 @@ mod tests {
         let res = pus_tc.write_to_bytes(test_buf.as_mut_slice());
         assert!(res.is_err());
         let err = res.unwrap_err();
-        if let PusError::ByteConversion(e) = err {
-            assert_eq!(
-                e,
-                ByteConversionError::ToSliceTooSmall {
-                    found: 12,
-                    expected: 13
-                }
-            );
-            assert_eq!(
-                err.to_string(),
-                "pus error: target slice with size 12 is too small, expected size of at least 13"
-            );
-            assert_eq!(err.source().unwrap().to_string(), e.to_string());
-        } else {
-            panic!("unexpected error {err}");
-        }
+        assert_eq!(
+            err,
+            ByteConversionError::ToSliceTooSmall {
+                found: 12,
+                expected: 13
+            }
+        );
+        assert_eq!(
+            err.to_string(),
+            "target slice with size 12 is too small, expected size of at least 13"
+        );
     }
 
     #[test]
@@ -869,7 +1151,7 @@ mod tests {
         assert_eq!(*tc.sp_header(), comp_header);
     }
 
-    fn verify_test_tc_generic(tc: &(impl CcsdsPacket + PusPacket + GenericPusTcSecondaryHeader)) {
+    fn verify_test_tc_generic(tc: &(impl PusPacket + GenericPusTcSecondaryHeader)) {
         assert_eq!(PusPacket::service(tc), 17);
         assert_eq!(GenericPusTcSecondaryHeader::service(tc), 17);
         assert_eq!(PusPacket::subservice(tc), 1);
@@ -933,8 +1215,8 @@ mod tests {
         let pus_tc = base_ping_tc_simple_ctor();
         let mut buf = [0; 32];
         pus_tc.write_to_bytes(&mut buf).unwrap();
-        assert_eq!(pus_tc, PusTcReader::new(&buf).unwrap().0);
-        assert_eq!(PusTcReader::new(&buf).unwrap().0, pus_tc);
+        assert_eq!(pus_tc, PusTcReader::new(&buf).unwrap());
+        assert_eq!(PusTcReader::new(&buf).unwrap(), pus_tc);
     }
 
     #[test]

src/ecss/tm.rs

@@ -35,13 +35,14 @@
 //! println!("{:?}", &test_buf[0..written_size]);
 //!
 //! // Deserialize from the raw byte representation
-//! let (ping_tm_reader, read_size) = PusTmReader::new(&test_buf, 7).expect("Deserialization failed");
-//! assert_eq!(written_size, read_size);
+//! let ping_tm_reader = PusTmReader::new(&test_buf, 7).expect("Deserialization failed");
+//! assert_eq!(written_size, ping_tm_reader.total_len());
 //! assert_eq!(ping_tm_reader.service(), 17);
 //! assert_eq!(ping_tm_reader.subservice(), 2);
 //! assert_eq!(ping_tm_reader.apid(), 0x02);
 //! assert_eq!(ping_tm_reader.timestamp(), &time_buf);
 //! ```
+use crate::crc::{CRC_CCITT_FALSE, CRC_CCITT_FALSE_NO_TABLE};
 use crate::ecss::{
     calc_pus_crc16, ccsds_impl, crc_from_raw_data, sp_header_impls, user_data_from_raw,
     verify_crc16_ccitt_false_from_raw_to_pus_error, CrcType, PusError, PusPacket, PusVersion,
@@ -49,7 +50,7 @@ use crate::ecss::{
 };
 use crate::{
     ByteConversionError, CcsdsPacket, PacketType, SequenceFlags, SpHeader, CCSDS_HEADER_LEN,
-    CRC_CCITT_FALSE, MAX_APID, MAX_SEQ_COUNT,
+    MAX_APID, MAX_SEQ_COUNT,
 };
 use core::mem::size_of;
 #[cfg(feature = "serde")]
@@ -64,6 +65,8 @@ use crate::time::{TimeWriter, TimestampError};
 
 use self::zc::PusTmSecHeaderWithoutTimestamp;
 
+use super::verify_crc16_ccitt_false_from_raw_to_pus_error_no_table;
+
 pub trait IsPusTelemetry {}
 
 /// Length without timestamp
@@ -120,7 +123,7 @@ pub mod zc {
     impl GenericPusTmSecondaryHeader for PusTmSecHeaderWithoutTimestamp {
         #[inline]
         fn pus_version(&self) -> PusVersion {
-            PusVersion::try_from(self.pus_version_and_sc_time_ref_status >> 4 & 0b1111)
+            PusVersion::try_from((self.pus_version_and_sc_time_ref_status >> 4) & 0b1111)
                 .unwrap_or(PusVersion::Invalid)
         }
 
@@ -277,13 +280,13 @@ impl<'time, 'src_data> PusTmCreator<'time, 'src_data> {
     /// # Arguments
     ///
     /// * `sp_header` - Space packet header information. The correct packet type and the secondary
-    ///     header flag are set correctly by the constructor.
+    ///   header flag are set correctly by the constructor.
     /// * `sec_header` - Information contained in the secondary header, including the service
-    ///     and subservice type
+    ///   and subservice type
     /// * `source_data` - Custom application data
     /// * `set_ccsds_len` - Can be used to automatically update the CCSDS space packet data length
-    ///     field. If this is not set to true, [Self::update_ccsds_data_len] can be called to set
-    ///     the correct value to this field manually
+    ///   field. If this is not set to true, [Self::update_ccsds_data_len] can be called to set
+    ///   the correct value to this field manually
     #[inline]
     pub fn new(
         mut sp_header: SpHeader,
@@ -389,33 +392,45 @@ impl<'time, 'src_data> PusTmCreator<'time, 'src_data> {
 
     /// Write the raw PUS byte representation to a provided buffer.
     pub fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, ByteConversionError> {
-        let mut curr_idx = 0;
-        let total_size = self.len_written();
-        if total_size > slice.len() {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize())
+    }
+
+    /// Write the raw PUS byte representation to a provided buffer.
+    pub fn write_to_bytes_crc_no_table(
+        &self,
+        slice: &mut [u8],
+    ) -> Result<usize, ByteConversionError> {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize_crc_no_table())
+    }
+
+    /// Write the raw PUS byte representation to a provided buffer.
+    pub fn write_to_bytes_no_crc(&self, slice: &mut [u8]) -> Result<usize, ByteConversionError> {
+        let writer_unfinalized = self.common_write(slice)?;
+        Ok(writer_unfinalized.finalize_no_crc())
+    }
+
+    fn common_write<'a>(
+        &self,
+        slice: &'a mut [u8],
+    ) -> Result<PusTmCreatorWithReservedSourceData<'a>, ByteConversionError> {
+        if self.len_written() > slice.len() {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: slice.len(),
-                expected: total_size,
+                expected: self.len_written(),
             });
         }
-        self.sp_header
-            .write_to_be_bytes(&mut slice[0..CCSDS_HEADER_LEN])?;
-        curr_idx += CCSDS_HEADER_LEN;
-        let sec_header_len = size_of::<zc::PusTmSecHeaderWithoutTimestamp>();
-        let sec_header = zc::PusTmSecHeaderWithoutTimestamp::try_from(self.sec_header).unwrap();
-        sec_header
-            .write_to(&mut slice[curr_idx..curr_idx + sec_header_len])
-            .map_err(|_| ByteConversionError::ZeroCopyToError)?;
-        curr_idx += sec_header_len;
-        slice[curr_idx..curr_idx + self.sec_header.timestamp.len()]
-            .copy_from_slice(self.sec_header.timestamp);
-        curr_idx += self.sec_header.timestamp.len();
-        slice[curr_idx..curr_idx + self.source_data.len()].copy_from_slice(self.source_data);
-        curr_idx += self.source_data.len();
-        let mut digest = CRC_CCITT_FALSE.digest();
-        digest.update(&slice[0..curr_idx]);
-        slice[curr_idx..curr_idx + 2].copy_from_slice(&digest.finalize().to_be_bytes());
-        curr_idx += 2;
-        Ok(curr_idx)
+        let mut writer_unfinalized = PusTmCreatorWithReservedSourceData::write_to_bytes_partially(
+            slice,
+            self.sp_header,
+            self.sec_header,
+            self.source_data.len(),
+        )?;
+        writer_unfinalized
+            .source_data_mut()
+            .copy_from_slice(self.source_data);
+        Ok(writer_unfinalized)
     }
 
     /// Append the raw PUS byte representation to a provided [alloc::vec::Vec]
@@ -446,12 +461,21 @@ impl WritablePusPacket for PusTmCreator<'_, '_> {
             + self.source_data.len()
     }
     /// Write the raw PUS byte representation to a provided buffer.
+    fn write_to_bytes_no_crc(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        Ok(Self::write_to_bytes_no_crc(self, slice)?)
+    }
+
     fn write_to_bytes(&self, slice: &mut [u8]) -> Result<usize, PusError> {
         Ok(Self::write_to_bytes(self, slice)?)
     }
+
+    fn write_to_bytes_crc_no_table(&self, slice: &mut [u8]) -> Result<usize, PusError> {
+        Ok(Self::write_to_bytes_crc_no_table(self, slice)?)
+    }
 }
 
 impl PartialEq for PusTmCreator<'_, '_> {
+    #[inline]
     fn eq(&self, other: &Self) -> bool {
         self.sp_header == other.sp_header
             && self.sec_header == other.sec_header
@@ -479,7 +503,7 @@ impl PusPacket for PusTmCreator<'_, '_> {
     }
 
     #[inline]
-    fn crc16(&self) -> Option<u16> {
+    fn opt_crc16(&self) -> Option<u16> {
         Some(self.calc_own_crc16())
     }
 }
@@ -503,6 +527,136 @@ impl GenericPusTmSecondaryHeader for PusTmCreator<'_, '_> {
 
 impl IsPusTelemetry for PusTmCreator<'_, '_> {}
 
+/// A specialized variant of [PusTmCreator] designed for efficiency when handling large source
+/// data.
+///
+/// Unlike [PusTmCreator], this type does not require the user to provide the source data
+/// as a separate slice. Instead, it allows writing the source data directly into the provided
+/// serialization buffer. This eliminates the need for an intermediate buffer and the associated
+/// memory copy, improving performance, particularly when working with large payloads.
+///
+/// **Important:** The total length of the source data must be known and specified in advance
+/// to ensure correct serialization behavior.
+///
+/// Note that this abstraction intentionally omits certain trait implementations that are available
+/// on [PusTmCreator], as they are not applicable in this optimized usage pattern.
+pub struct PusTmCreatorWithReservedSourceData<'buf> {
+    buf: &'buf mut [u8],
+    source_data_offset: usize,
+    full_len: usize,
+}
+
+impl<'buf> PusTmCreatorWithReservedSourceData<'buf> {
+    /// Generates a new instance with reserved space for the user source data.
+    ///
+    /// # Arguments
+    ///
+    /// * `sp_header` - Space packet header information. The correct packet type and the secondary
+    ///   header flag are set correctly by the constructor.
+    /// * `sec_header` - Information contained in the secondary header, including the service
+    ///   and subservice type
+    /// * `src_data_len` - Custom source data length
+    #[inline]
+    pub fn new(
+        buf: &'buf mut [u8],
+        mut sp_header: SpHeader,
+        sec_header: PusTmSecondaryHeader,
+        src_data_len: usize,
+    ) -> Result<Self, ByteConversionError> {
+        sp_header.set_packet_type(PacketType::Tm);
+        sp_header.set_sec_header_flag();
+        let len_written =
+            PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA + sec_header.timestamp.len() + src_data_len;
+        if len_written > buf.len() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: len_written,
+            });
+        }
+        sp_header.data_len = len_written as u16 - size_of::<crate::zc::SpHeader>() as u16 - 1;
+        Self::write_to_bytes_partially(buf, sp_header, sec_header, src_data_len)
+    }
+
+    fn write_to_bytes_partially(
+        buf: &'buf mut [u8],
+        sp_header: SpHeader,
+        sec_header: PusTmSecondaryHeader,
+        src_data_len: usize,
+    ) -> Result<Self, ByteConversionError> {
+        let mut curr_idx = 0;
+        sp_header.write_to_be_bytes(&mut buf[0..CCSDS_HEADER_LEN])?;
+        curr_idx += CCSDS_HEADER_LEN;
+        let sec_header_len = size_of::<zc::PusTmSecHeaderWithoutTimestamp>();
+        let sec_header_zc = zc::PusTmSecHeaderWithoutTimestamp::try_from(sec_header).unwrap();
+        sec_header_zc
+            .write_to(&mut buf[curr_idx..curr_idx + sec_header_len])
+            .map_err(|_| ByteConversionError::ZeroCopyToError)?;
+        curr_idx += sec_header_len;
+        buf[curr_idx..curr_idx + sec_header.timestamp.len()].copy_from_slice(sec_header.timestamp);
+        curr_idx += sec_header.timestamp.len();
+        let source_data_offset = curr_idx;
+        curr_idx += src_data_len;
+        Ok(Self {
+            buf,
+            source_data_offset,
+            full_len: curr_idx + 2,
+        })
+    }
+
+    #[inline]
+    pub const fn len_written(&self) -> usize {
+        self.full_len
+    }
+
+    /// Mutable access to the source data buffer.
+    #[inline]
+    pub fn source_data_mut(&mut self) -> &mut [u8] {
+        &mut self.buf[self.source_data_offset..self.full_len - 2]
+    }
+
+    /// Access to the source data buffer.
+    #[inline]
+    pub fn source_data(&self) -> &[u8] {
+        &self.buf[self.source_data_offset..self.full_len - 2]
+    }
+
+    #[inline]
+    pub fn source_data_len(&self) -> usize {
+        self.full_len - 2 - self.source_data_offset
+    }
+
+    /// Finalize the TM packet by calculating and writing the CRC16.
+    ///
+    /// Returns the full packet length.
+    pub fn finalize(self) -> usize {
+        let mut digest = CRC_CCITT_FALSE.digest();
+        digest.update(&self.buf[0..self.full_len - 2]);
+        self.buf[self.full_len - 2..self.full_len]
+            .copy_from_slice(&digest.finalize().to_be_bytes());
+        self.full_len
+    }
+
+    /// Finalize the TM packet by calculating and writing the CRC16 using a table-less
+    /// implementation.
+    ///
+    /// Returns the full packet length.
+    pub fn finalize_crc_no_table(self) -> usize {
+        let mut digest = CRC_CCITT_FALSE_NO_TABLE.digest();
+        digest.update(&self.buf[0..self.full_len - 2]);
+        self.buf[self.full_len - 2..self.full_len]
+            .copy_from_slice(&digest.finalize().to_be_bytes());
+        self.full_len
+    }
+
+    /// Finalize the TM packet without writing the CRC16.
+    ///
+    /// Returns the length WITHOUT the CRC16.
+    #[inline]
+    pub fn finalize_no_crc(self) -> usize {
+        self.full_len - 2
+    }
+}
+
 /// This class models the PUS C telemetry packet. It is the primary data structure to read
 /// a telemetry packet from raw bytes.
 ///
@@ -534,7 +688,26 @@ impl<'raw_data> PusTmReader<'raw_data> {
     ///
     /// This function will check the CRC-16 of the PUS packet and will return an appropriate
     /// [PusError] if the check fails.
-    pub fn new(slice: &'raw_data [u8], timestamp_len: usize) -> Result<(Self, usize), PusError> {
+    pub fn new(slice: &'raw_data [u8], timestamp_len: usize) -> Result<Self, PusError> {
+        let tc = Self::new_no_crc_check(slice, timestamp_len)?;
+        verify_crc16_ccitt_false_from_raw_to_pus_error(tc.raw_data(), tc.crc16)?;
+        Ok(tc)
+    }
+
+    /// Like [PusTmReader::new] but uses a table-less CRC implementation.
+    pub fn new_crc_no_table(
+        slice: &'raw_data [u8],
+        timestamp_len: usize,
+    ) -> Result<Self, PusError> {
+        let tc = Self::new_no_crc_check(slice, timestamp_len)?;
+        verify_crc16_ccitt_false_from_raw_to_pus_error_no_table(tc.raw_data(), tc.crc16)?;
+        Ok(tc)
+    }
+
+    pub fn new_no_crc_check(
+        slice: &'raw_data [u8],
+        timestamp_len: usize,
+    ) -> Result<Self, PusError> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
             return Err(ByteConversionError::FromSliceTooSmall {
@@ -572,15 +745,13 @@ impl<'raw_data> PusTmReader<'raw_data> {
         };
         current_idx += timestamp_len;
         let raw_data = &slice[0..total_len];
-        let pus_tm = Self {
+        Ok(Self {
             sp_header,
             sec_header: PusTmSecondaryHeader::try_from(zc_sec_header_wrapper).unwrap(),
             raw_data: &slice[0..total_len],
             source_data: user_data_from_raw(current_idx, total_len, slice)?,
             crc16: crc_from_raw_data(raw_data)?,
-        };
-        verify_crc16_ccitt_false_from_raw_to_pus_error(raw_data, pus_tm.crc16)?;
-        Ok((pus_tm, total_len))
+        })
     }
 
     #[inline]
@@ -598,6 +769,11 @@ impl<'raw_data> PusTmReader<'raw_data> {
         self.sec_header.timestamp
     }
 
+    #[inline]
+    pub fn crc16(&self) -> u16 {
+        self.crc16
+    }
+
     /// This function will return the slice [Self] was constructed from.
     #[inline]
     pub fn raw_data(&self) -> &[u8] {
@@ -634,8 +810,8 @@ impl PusPacket for PusTmReader<'_> {
     }
 
     #[inline]
-    fn crc16(&self) -> Option<u16> {
-        Some(self.crc16)
+    fn opt_crc16(&self) -> Option<u16> {
+        Some(self.crc16())
     }
 }
 
@@ -822,7 +998,7 @@ impl PusPacket for PusTmZeroCopyWriter<'_> {
     }
 
     #[inline]
-    fn crc16(&self) -> Option<u16> {
+    fn opt_crc16(&self) -> Option<u16> {
         Some(u16::from_be_bytes(
             self.raw_tm[self.sp_header().total_len() - 2..self.sp_header().total_len()]
                 .try_into()
@@ -918,7 +1094,66 @@ mod tests {
             .write_to_bytes(&mut buf)
             .expect("Serialization failed");
         assert_eq!(ser_len, 22);
-        verify_raw_ping_reply(pus_tm.crc16().unwrap(), &buf);
+        verify_raw_ping_reply(pus_tm.opt_crc16(), &buf);
+    }
+
+    #[test]
+    fn test_serialization_no_source_data_alt_ctor() {
+        let timestamp = dummy_timestamp();
+        let sph = SpHeader::new_for_unseg_tm_checked(0x123, 0x234, 0).unwrap();
+        let tm_header = PusTmSecondaryHeader::new_simple(17, 2, timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let mut pus_tm =
+            PusTmCreatorWithReservedSourceData::new(&mut buf, sph, tm_header, 0).unwrap();
+        assert_eq!(pus_tm.source_data_len(), 0);
+        assert_eq!(pus_tm.source_data(), &[]);
+        assert_eq!(pus_tm.source_data_mut(), &[]);
+        let ser_len = pus_tm.finalize();
+        assert_eq!(ser_len, 22);
+        verify_raw_ping_reply(None, &buf);
+    }
+
+    #[test]
+    fn test_serialization_no_source_data_alt_ctor_no_crc() {
+        let timestamp = dummy_timestamp();
+        let sph = SpHeader::new_for_unseg_tm_checked(0x123, 0x234, 0).unwrap();
+        let tm_header = PusTmSecondaryHeader::new_simple(17, 2, timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let mut pus_tm =
+            PusTmCreatorWithReservedSourceData::new(&mut buf, sph, tm_header, 0).unwrap();
+        assert_eq!(pus_tm.source_data_len(), 0);
+        assert_eq!(pus_tm.source_data(), &[]);
+        assert_eq!(pus_tm.source_data_mut(), &[]);
+        let ser_len = pus_tm.finalize_no_crc();
+        assert_eq!(ser_len, 20);
+        verify_raw_ping_reply_no_crc(&buf);
+        assert_eq!(buf[20], 0);
+        assert_eq!(buf[21], 0);
+    }
+
+    #[test]
+    fn test_serialization_no_source_data_no_table() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let ser_len = pus_tm
+            .write_to_bytes_crc_no_table(&mut buf)
+            .expect("Serialization failed");
+        assert_eq!(ser_len, 22);
+        verify_raw_ping_reply(pus_tm.opt_crc16(), &buf);
+    }
+
+    #[test]
+    fn test_serialization_no_source_data_no_crc() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let ser_len = pus_tm
+            .write_to_bytes_no_crc(&mut buf)
+            .expect("Serialization failed");
+        assert_eq!(ser_len, 20);
+        assert_eq!(buf[20], 0);
+        assert_eq!(buf[21], 0);
     }
 
     #[test]
@@ -935,6 +1170,46 @@ mod tests {
         assert_eq!(buf[22], 3);
     }
 
+    #[test]
+    fn test_serialization_with_source_data_alt_ctor() {
+        let src_data = &[1, 2, 3];
+        let mut buf: [u8; 32] = [0; 32];
+        let sph = SpHeader::new_for_unseg_tm_checked(0x123, 0x234, 0).unwrap();
+        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, dummy_timestamp());
+        let mut hk_reply_unwritten =
+            PusTmCreatorWithReservedSourceData::new(&mut buf, sph, tc_header, 3).unwrap();
+        assert_eq!(hk_reply_unwritten.source_data_len(), 3);
+        assert_eq!(hk_reply_unwritten.source_data(), &[0, 0, 0]);
+        assert_eq!(hk_reply_unwritten.source_data_mut(), &[0, 0, 0]);
+        let source_data_mut = hk_reply_unwritten.source_data_mut();
+        source_data_mut.copy_from_slice(src_data);
+        let ser_len = hk_reply_unwritten.finalize();
+        assert_eq!(ser_len, 25);
+        assert_eq!(buf[20], 1);
+        assert_eq!(buf[21], 2);
+        assert_eq!(buf[22], 3);
+    }
+
+    #[test]
+    fn test_serialization_with_source_data_alt_ctor_no_table() {
+        let src_data = &[1, 2, 3];
+        let mut buf: [u8; 32] = [0; 32];
+        let sph = SpHeader::new_for_unseg_tm_checked(0x123, 0x234, 0).unwrap();
+        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, dummy_timestamp());
+        let mut hk_reply_unwritten =
+            PusTmCreatorWithReservedSourceData::new(&mut buf, sph, tc_header, 3).unwrap();
+        assert_eq!(hk_reply_unwritten.source_data_len(), 3);
+        assert_eq!(hk_reply_unwritten.source_data(), &[0, 0, 0]);
+        assert_eq!(hk_reply_unwritten.source_data_mut(), &[0, 0, 0]);
+        let source_data_mut = hk_reply_unwritten.source_data_mut();
+        source_data_mut.copy_from_slice(src_data);
+        let ser_len = hk_reply_unwritten.finalize_crc_no_table();
+        assert_eq!(ser_len, 25);
+        assert_eq!(buf[20], 1);
+        assert_eq!(buf[21], 2);
+        assert_eq!(buf[22], 3);
+    }
+
     #[test]
     fn test_setters() {
         let timestamp = dummy_timestamp();
@@ -955,11 +1230,12 @@ mod tests {
         let pus_tm = base_ping_reply_full_ctor(timestamp);
         let tm_vec = pus_tm.to_vec().expect("Serialization failed");
         assert_eq!(tm_vec.len(), 22);
-        let (tm_deserialized, size) =
+        let tm_deserialized =
             PusTmReader::new(tm_vec.as_slice(), 7).expect("Deserialization failed");
-        assert_eq!(tm_vec.len(), size);
+        assert_eq!(tm_vec.len(), tm_deserialized.total_len());
         verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
     }
+
     #[test]
     fn test_deserialization_no_source_data() {
         let timestamp = dummy_timestamp();
@@ -969,13 +1245,48 @@ mod tests {
             .write_to_bytes(&mut buf)
             .expect("Serialization failed");
         assert_eq!(ser_len, 22);
-        let (tm_deserialized, size) = PusTmReader::new(&buf, 7).expect("Deserialization failed");
-        assert_eq!(ser_len, size);
+        let tm_deserialized = PusTmReader::new(&buf, 7).expect("Deserialization failed");
+        assert_eq!(ser_len, tm_deserialized.total_len());
         assert_eq!(tm_deserialized.user_data(), tm_deserialized.source_data());
         assert_eq!(tm_deserialized.raw_data(), &buf[..ser_len]);
-        assert_eq!(tm_deserialized.crc16().unwrap(), pus_tm.crc16().unwrap());
+        assert_eq!(tm_deserialized.crc16(), pus_tm.opt_crc16().unwrap());
         verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
     }
+
+    #[test]
+    fn test_deserialization_no_source_data_with_trait() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let ser_len =
+            WritablePusPacket::write_to_bytes(&pus_tm, &mut buf).expect("Serialization failed");
+        assert_eq!(ser_len, 22);
+        let tm_deserialized = PusTmReader::new(&buf, 7).expect("Deserialization failed");
+        assert_eq!(ser_len, tm_deserialized.total_len());
+        assert_eq!(tm_deserialized.user_data(), tm_deserialized.source_data());
+        assert_eq!(tm_deserialized.raw_data(), &buf[..ser_len]);
+        assert_eq!(tm_deserialized.crc16(), pus_tm.opt_crc16().unwrap());
+        verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
+    }
+
+    #[test]
+    fn test_deserialization_no_table() {
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(timestamp);
+        let mut buf: [u8; 32] = [0; 32];
+        let ser_len = pus_tm
+            .write_to_bytes(&mut buf)
+            .expect("Serialization failed");
+        assert_eq!(ser_len, 22);
+        let tm_deserialized =
+            PusTmReader::new_crc_no_table(&buf, 7).expect("Deserialization failed");
+        assert_eq!(ser_len, tm_deserialized.total_len());
+        assert_eq!(tm_deserialized.user_data(), tm_deserialized.source_data());
+        assert_eq!(tm_deserialized.raw_data(), &buf[..ser_len]);
+        assert_eq!(tm_deserialized.crc16(), pus_tm.opt_crc16().unwrap());
+        verify_ping_reply_with_reader(&tm_deserialized, false, 22, dummy_timestamp());
+    }
+
     #[test]
     fn test_deserialization_faulty_crc() {
         let timestamp = dummy_timestamp();
@@ -1042,7 +1353,7 @@ mod tests {
         let res = pus_tm.append_to_vec(&mut vec);
         assert!(res.is_ok());
         assert_eq!(res.unwrap(), 22);
-        verify_raw_ping_reply(pus_tm.crc16().unwrap(), vec.as_slice());
+        verify_raw_ping_reply(pus_tm.opt_crc16(), vec.as_slice());
     }
 
     #[test]
@@ -1058,7 +1369,7 @@ mod tests {
         assert_eq!(vec.len(), 26);
     }
 
-    fn verify_raw_ping_reply(crc16: u16, buf: &[u8]) {
+    fn verify_raw_ping_reply_no_crc(buf: &[u8]) {
         // Secondary header is set -> 0b0000_1001 , APID occupies last bit of first byte
         assert_eq!(buf[0], 0x09);
         // Rest of APID 0x123
@@ -1079,12 +1390,19 @@ mod tests {
         assert_eq!(buf[12], 0x00);
         // Timestamp
         assert_eq!(&buf[13..20], dummy_timestamp());
+    }
+
+    fn verify_raw_ping_reply(crc16: Option<u16>, buf: &[u8]) {
+        verify_raw_ping_reply_no_crc(buf);
         let mut digest = CRC_CCITT_FALSE.digest();
         digest.update(&buf[0..20]);
         let crc16_calced = digest.finalize();
-        assert_eq!(((crc16 >> 8) & 0xff) as u8, buf[20]);
-        assert_eq!((crc16 & 0xff) as u8, buf[21]);
-        assert_eq!(crc16, crc16_calced);
+        let crc16_read = u16::from_be_bytes([buf[20], buf[21]]);
+        assert_eq!(crc16_read, crc16_calced);
+        if let Some(crc16) = crc16 {
+            assert_eq!(((crc16 >> 8) & 0xff) as u8, buf[20]);
+            assert_eq!((crc16 & 0xff) as u8, buf[21]);
+        }
     }
 
     fn verify_ping_reply(
@@ -1111,7 +1429,7 @@ mod tests {
     }
 
     fn verify_ping_reply_generic(
-        tm: &(impl CcsdsPacket + GenericPusTmSecondaryHeader + PusPacket),
+        tm: &(impl GenericPusTmSecondaryHeader + PusPacket),
         has_user_data: bool,
         exp_full_len: usize,
     ) {
@@ -1152,7 +1470,7 @@ mod tests {
         let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut buf = [0; 32];
         pus_tm.write_to_bytes(&mut buf).unwrap();
-        assert_eq!(pus_tm, PusTmReader::new(&buf, timestamp.len()).unwrap().0);
+        assert_eq!(pus_tm, PusTmReader::new(&buf, timestamp.len()).unwrap());
     }
 
     #[test]
@@ -1172,9 +1490,8 @@ mod tests {
         assert!(!writer.set_apid(MAX_SEQ_COUNT + 1));
         writer.finish();
         // This performs all necessary checks, including the CRC check.
-        let (tm_read_back, tm_size_read_back) =
-            PusTmReader::new(&buf, 7).expect("Re-creating PUS TM failed");
-        assert_eq!(tm_size_read_back, tm_size);
+        let tm_read_back = PusTmReader::new(&buf, 7).expect("Re-creating PUS TM failed");
+        assert_eq!(tm_read_back.total_len(), tm_size);
         assert_eq!(tm_read_back.msg_counter(), 100);
         assert_eq!(tm_read_back.dest_id(), 55);
         assert_eq!(tm_read_back.seq_count(), MAX_SEQ_COUNT);
@@ -1222,7 +1539,7 @@ mod tests {
         assert_eq!(writer.sec_header_without_timestamp().msg_counter(), 100);
         assert_eq!(writer.user_data(), DUMMY_DATA);
         // Need to check crc16 before finish, because finish will update the CRC.
-        let crc16 = writer.crc16();
+        let crc16 = writer.opt_crc16();
         assert!(crc16.is_some());
         assert_eq!(crc16.unwrap(), crc16_raw);
         writer.finish();
@@ -1240,8 +1557,8 @@ mod tests {
         let pus_tm = base_ping_reply_full_ctor(timestamp);
         let mut buf = [0; 32];
         pus_tm.write_to_bytes(&mut buf).unwrap();
-        let (tm_0, _) = PusTmReader::new(&buf, timestamp.len()).unwrap();
-        let (tm_1, _) = PusTmReader::new(&buf, timestamp.len()).unwrap();
+        let tm_0 = PusTmReader::new(&buf, timestamp.len()).unwrap();
+        let tm_1 = PusTmReader::new(&buf, timestamp.len()).unwrap();
         assert_eq!(tm_0, tm_1);
     }
     #[test]
@@ -1313,7 +1630,7 @@ mod tests {
             PusTmCreator::new_simple(sph, 17, 2, &time_provider, &mut stamp_buf, &[], true)
                 .unwrap();
         let pus_tm_vec = pus_tm.to_vec().unwrap();
-        let (tm_reader, _) = PusTmReader::new(&pus_tm_vec, time_provider.len_as_bytes()).unwrap();
+        let tm_reader = PusTmReader::new(&pus_tm_vec, time_provider.len_as_bytes()).unwrap();
         let output = to_allocvec(&tm_reader).unwrap();
         let output_converted_back: PusTmReader = from_bytes(&output).unwrap();
         assert_eq!(output_converted_back, tm_reader);

src/lib.rs

@@ -26,8 +26,8 @@
 //!
 //!  - [`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.
+//!    like [`alloc::vec::Vec`](https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html).
+//!    Enabled by the `std` feature.
 //!
 //! ### Optional features
 //!
@@ -62,7 +62,6 @@ extern crate alloc;
 extern crate std;
 
 use core::{fmt::Debug, hash::Hash};
-use crc::{Crc, CRC_16_IBM_3740};
 use delegate::delegate;
 use zerocopy::{FromBytes, IntoBytes};
 
@@ -70,6 +69,7 @@ use zerocopy::{FromBytes, IntoBytes};
 use serde::{Deserialize, Serialize};
 
 pub mod cfdp;
+pub mod crc;
 pub mod ecss;
 pub mod seq_count;
 pub mod time;
@@ -81,9 +81,6 @@ mod private {
 
 pub const CCSDS_HEADER_LEN: usize = core::mem::size_of::<crate::zc::SpHeader>();
 
-/// CRC algorithm used by the PUS standard, the CCSDS TC standard and the CFDP standard.
-pub const CRC_CCITT_FALSE: Crc<u16> = Crc::<u16>::new(&CRC_16_IBM_3740);
-
 pub const MAX_APID: u16 = 2u16.pow(11) - 1;
 pub const MAX_SEQ_COUNT: u16 = 2u16.pow(14) - 1;
 
@@ -452,9 +449,9 @@ pub trait CcsdsPrimaryHeader {
 /// # Arguments
 ///
 /// * `version` - CCSDS version field, occupies the first 3 bits of the raw header. Will generally
-///    be set to 0b000 in all constructors provided by this crate.
+///   be set to 0b000 in all constructors provided by this crate.
 /// * `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
+///   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(Debug, PartialEq, Eq, Copy, Clone)]

src/time/cds.rs

@@ -569,7 +569,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
             ));
         }
         let pfield = buf[0];
-        match CcsdsTimeCode::try_from(pfield >> 4 & 0b111) {
+        match CcsdsTimeCode::try_from((pfield >> 4) & 0b111) {
             Ok(cds_type) => match cds_type {
                 CcsdsTimeCode::Cds => (),
                 _ => {
@@ -582,7 +582,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
             _ => {
                 return Err(TimestampError::InvalidTimeCode {
                     expected: CcsdsTimeCode::Cds,
-                    found: pfield >> 4 & 0b111,
+                    found: (pfield >> 4) & 0b111,
                 });
             }
         };