create release checklist

for UnixTimestamp

CHANGELOG.md

@@ -8,6 +8,85 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+# [v0.5.1] 2023-01-22
+
+## Added
+
+- `time::cds::TimeProvider`
+  - Add `Ord` and `PartialOrd`, use custom `PartialEq` impl to account for precision correctly.
+  - Add `precision_as_ns` function which converts microsecond and picosecond precision values
+    into nanoseconds.
+  - Add conversion trait to convert `cds::TimeProvider<DaysLen16Bits>` into
+    `cds::TimeProvider<DaysLen24Bits>` and vice-versa.
+- `time::UnixTimestamp`
+  - Add `Ord` and `PartialOrd` implementations.
+  - Add `Add<Duration>` and `AddAssign<Duration>` implementations.
+
+## Fixed
+
+- `time::cds::TimeProvider`: Fixed a big where subsecond milliseconds were not accounted for
+  when the provider has no submillisecond precision.
+
+# [v0.5.0] 2023-01-20
+
+The timestamp of `PusTm` is now optional. See Added and Changed section for details.
+
+## Added
+
+- `PusTmSecondaryHeader`: New `new_simple_no_timestamp` API to create secondary header without
+  timestamp.
+- `PusTm`: Add `new_simple_no_timestamp` method to create TM without timestamp
+- New `UnixTimestamp` abstraction which contains the unix seconds as an `i64`
+  and an optional subsecond millisecond counter (`u16`)
+- `MS_PER_DAY` constant.
+- CUC: Added `from_date_time` and `from_unix_stamp` constructors for time provider.
+- CUC: Add `Add<Duration>` and `AddAssign<Duration>` impl for time provider.
+
+### CDS time module
+
+- Implement `Add<Duration>` and `AddAssign<Duration>` for time providers, which allows
+  easily adding offsets to the providers.
+- Implement `TryFrom<DateTime<Utc>>` for time providers.
+- `get_dyn_time_provider_from_bytes`: Requires `alloc` support and returns
+  the correct `TimeProvider` instance wrapped as a boxed trait object
+  `Box<DynCdsTimeProvider>` by checking the length of days field.
+- Added constructor function to create the time provider
+  from `chrono::DateTime<Utc>` and a generic UNIX timestamp (`i64` seconds
+  and subsecond milliseconds).
+- `MAX_DAYS_24_BITS` which contains maximum value which can be supplied
+  to the days field of a CDS time provider with 24 bits days field width.
+- New `CdsTimestamp` trait which encapsulates common fields for all CDS time providers.
+- `from_unix_secs_with_u24_days` and `from_unix_secs_with_u16_days` which create
+   the time provider from a `UnixTimestamp` reference.
+- `from_dt_with_u16_days`, `from_dt_with_u24_days` and their `..._us_precision` and
+   `..._ps_precision` variants which allow to create time providers from
+   a `chrono::DateTime<Utc>`.
+- Add `from_bytes_with_u24_days` and `from_bytes_with_u16_days` associated methods
+
+## Changed
+
+
+- (breaking) `unix_epoch_to_ccsds_epoch`: Expect and return `i64` instead of `u64` now.
+- (breaking) `ccsds_epoch_to_unix_epoch`: Expect and return `i64` instead of `u64` now.
+- (breaking) `PusTmSecondaryHeader`: Timestamp is optional now, which translates to a
+  timestamp of size 0.
+- (breaking): `PusTm`: Renamed `time_stamp` method to `timestamp`, also returns
+  `Optional<&'src_data [u8]>` now.
+- (breaking): `PusTmSecondaryHeader`: Renamed `time_stamp` field to `timestamp` for consistency.
+- (breaking): Renamed `from_now_with_u24_days_and_us_prec` to `from_now_with_u24_days_us_precision`.
+  Also did the same for the `u16` variant.
+- (breaking): Renamed `from_now_with_u24_days_and_ps_prec` to `from_now_with_u24_days_ps_precision`.
+  Also did the same for the `u16` variant.
+- `CcsdsTimeProvider` trait (breaking):
+  - Add new `unix_stamp` method returning the new `UnixTimeStamp` struct.
+  - Add new  `subsecond_millis` method returning counter `Option<u16>`.
+  - Default impl for `unix_stamp` which re-uses `subsecond_millis` and
+    existing `unix_seconds` method.
+- `TimestampError` (breaking): Add `DateBeforeCcsdsEpoch` error type
+  because new CDS API allow supplying invalid date times before CCSDS epoch.
+  Make `TimestampError` with `#[non_exhaustive]` attribute to prevent
+  future breakages if new error variants are added.
+
 # [v0.4.2] 14.01.2023
 
 ## Fixed

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spacepackets"
-version = "0.4.2"
+version = "0.5.1"
 edition = "2021"
 rust-version = "1.60"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]

README.md

@@ -19,7 +19,7 @@ Currently, this includes the following components:
   [CCSDS 301.0-B-4 3.2](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 - CDS (CCSDS Day Segmented Time Code) implementation according to
   [CCSDS 301.0-B-4 3.3](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
-- Some helper types to support ASCII timecodes ad specified in
+- Some helper types to support ASCII timecodes as specified in
   [CCSDS 301.0-B-4 3.5](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 
 # Features

release_checklist.md

@@ -0,0 +1,18 @@
+Checklist for new releases
+=======
+
+# Pre-Release
+
+1. Make sure any new modules are documented sufficiently enough and check docs with
+   `cargo doc --all-features --open`.
+2. Bump version specifier in `Cargo.toml`.
+3. Update `CHANGELOG.md`: Convert `unreleased` section into version section with date and add new
+   `unreleased` section.
+4. Run `cargo test --all-features`.
+5. Run `cargo fmt` and `cargo clippy`. Check `cargo msrv` against MSRV in `Cargo.toml`.
+6. Wait for CI/CD results for EGit and Github. These also check cross-compilation for bare-metal
+   targets.
+
+# Post-Release
+
+1. Create a new release on `EGit` based on the release branch.

src/lib.rs

@@ -13,7 +13,7 @@
 //!    [CCSDS 301.0-B-4 3.2](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 //!  - CDS (CCSDS Day Segmented Time Code) implementation according to
 //!    [CCSDS 301.0-B-4 3.3](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
-//!  - Some helper types to support ASCII timecodes ad specified in
+//!  - Some helper types to support ASCII timecodes as specified in
 //!    [CCSDS 301.0-B-4 3.5](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 //!
 //! ## Features

src/time/cuc.rs

@@ -3,7 +3,10 @@
 //!
 //! The core data structure to do this is the [TimeProviderCcsdsEpoch] struct.
 use super::*;
+use chrono::Datelike;
 use core::fmt::Debug;
+use core::ops::{Add, AddAssign};
+use core::time::Duration;
 
 const MIN_CUC_LEN: usize = 2;
 
@@ -42,12 +45,14 @@ impl TryFrom<u8> for FractionalResolution {
 /// Please note that this function will panic if the fractional value is not smaller than
 /// the maximum number of fractions allowed for the particular resolution.
 /// (e.g. passing 270 when the resolution only allows 255 values).
+#[inline]
 pub fn convert_fractional_part_to_ns(fractional_part: FractionalPart) -> u64 {
     let div = fractional_res_to_div(fractional_part.0);
     assert!(fractional_part.1 < div);
     10_u64.pow(9) * fractional_part.1 as u64 / div as u64
 }
 
+#[inline(always)]
 pub const fn fractional_res_to_div(res: FractionalResolution) -> u32 {
     2_u32.pow(8 * res as u32) - 1
 }
@@ -89,6 +94,7 @@ pub fn fractional_part_from_subsec_ns(
 pub enum CucError {
     InvalidCounterWidth(u8),
     InvalidFractionResolution(FractionalResolution),
+    /// Invalid counter supplied.
     InvalidCounter(u8, u64),
     InvalidFractions(FractionalResolution, u64),
 }
@@ -228,9 +234,10 @@ impl TimeProviderCcsdsEpoch {
     /// The counter width will always be set to 4 bytes because the normal CCSDS epoch will overflow
     /// when using less than that.
     #[cfg(feature = "std")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
     pub fn from_now(fraction_resolution: FractionalResolution) -> Result<Self, StdTimestampError> {
         let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
-        let ccsds_epoch = unix_epoch_to_ccsds_epoch(now.as_secs());
+        let ccsds_epoch = unix_epoch_to_ccsds_epoch(now.as_secs() as i64);
         if fraction_resolution == FractionalResolution::Seconds {
             return Ok(Self::new(ccsds_epoch as u32));
         }
@@ -243,9 +250,10 @@ impl TimeProviderCcsdsEpoch {
     /// Updates the current time stamp from the current time. The fractional field width remains
     /// the same and will be updated accordingly.
     #[cfg(feature = "std")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
     pub fn update_from_now(&mut self) -> Result<(), StdTimestampError> {
         let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
-        self.counter.1 = unix_epoch_to_ccsds_epoch(now.as_secs()) as u32;
+        self.counter.1 = unix_epoch_to_ccsds_epoch(now.as_secs() as i64) as u32;
         if self.fractions.is_some() {
             self.fractions = fractional_part_from_subsec_ns(
                 self.fractions.unwrap().0,
@@ -255,6 +263,42 @@ impl TimeProviderCcsdsEpoch {
         Ok(())
     }
 
+    pub fn from_date_time(
+        dt: &DateTime<Utc>,
+        res: FractionalResolution,
+    ) -> Result<Self, TimestampError> {
+        // Year before CCSDS epoch is invalid.
+        if dt.year() < 1958 {
+            return Err(TimestampError::DateBeforeCcsdsEpoch(*dt));
+        }
+        Self::new_generic(
+            WidthCounterPair(4, dt.timestamp() as u32),
+            fractional_part_from_subsec_ns(res, dt.timestamp_subsec_nanos() as u64),
+        )
+        .map_err(|e| e.into())
+    }
+
+    pub fn from_unix_stamp(
+        unix_stamp: &UnixTimestamp,
+        res: FractionalResolution,
+    ) -> Result<Self, TimestampError> {
+        let ccsds_epoch = unix_epoch_to_ccsds_epoch(unix_stamp.unix_seconds);
+        // Negative CCSDS epoch is invalid.
+        if ccsds_epoch < 0 {
+            return Err(TimestampError::DateBeforeCcsdsEpoch(
+                unix_stamp.as_date_time().unwrap(),
+            ));
+        }
+        if ccsds_epoch > u32::MAX as i64 {
+            return Err(CucError::InvalidCounter(4, ccsds_epoch as u64).into());
+        }
+        let mut fractions = None;
+        if let Some(subsec_millis) = unix_stamp.subsecond_millis {
+            fractions = fractional_part_from_subsec_ns(res, subsec_millis as u64 * 10_u64.pow(6));
+        }
+        Self::new_generic(WidthCounterPair(4, ccsds_epoch as u32), fractions).map_err(|e| e.into())
+    }
+
     pub fn new_u16_counter(counter: u16) -> Self {
         // These values are definitely valid, so it is okay to unwrap here.
         Self::new_generic(WidthCounterPair(2, counter as u32), None).unwrap()
@@ -351,6 +395,11 @@ impl TimeProviderCcsdsEpoch {
         pfield & 0b11
     }
 
+    #[inline]
+    fn unix_seconds(&self) -> i64 {
+        ccsds_epoch_to_unix_epoch(self.counter.1 as i64)
+    }
+
     /// This returns the length of the individual components of the CUC timestamp in addition
     /// to the total size.
     ///
@@ -543,10 +592,19 @@ impl CcsdsTimeProvider for TimeProviderCcsdsEpoch {
         CcsdsTimeCodes::CucCcsdsEpoch
     }
 
-    /// Please note that this function only works as intended if the time counter resolution
-    /// is one second.
     fn unix_seconds(&self) -> i64 {
-        ccsds_epoch_to_unix_epoch(self.counter.1 as u64) as i64
+        self.unix_seconds()
+    }
+
+    fn subsecond_millis(&self) -> Option<u16> {
+        if let Some(fractions) = self.fractions {
+            if fractions.0 == FractionalResolution::Seconds {
+                return None;
+            }
+            // Rounding down here is the correct approach.
+            return Some((convert_fractional_part_to_ns(fractions) / 10_u32.pow(6) as u64) as u16);
+        }
+        None
     }
 
     fn date_time(&self) -> Option<DateTime<Utc>> {
@@ -563,6 +621,95 @@ impl CcsdsTimeProvider for TimeProviderCcsdsEpoch {
     }
 }
 
+fn get_provider_values_after_duration_addition(
+    provider: &TimeProviderCcsdsEpoch,
+    duration: Duration,
+) -> (u32, Option<FractionalPart>) {
+    let mut new_counter = provider.counter.1;
+    let subsec_nanos = duration.subsec_nanos();
+    let mut increment_counter = |amount: u32| {
+        let mut sum: u64 = 0;
+        let mut counter_inc_handler = |max_val: u64| {
+            sum = new_counter as u64 + amount as u64;
+            if sum >= max_val {
+                new_counter = (sum % max_val) as u32;
+                return;
+            }
+            new_counter = sum as u32;
+        };
+        match provider.counter.0 {
+            1 => counter_inc_handler(u8::MAX as u64),
+            2 => counter_inc_handler(u16::MAX as u64),
+            3 => counter_inc_handler((2_u32.pow(24) - 1) as u64),
+            4 => counter_inc_handler(u32::MAX as u64),
+            _ => {
+                // Should never happen
+                panic!("invalid counter width")
+            }
+        }
+    };
+    let fractional_part = if let Some(fractional_part) = &provider.fractions {
+        let fractional_increment =
+            fractional_part_from_subsec_ns(fractional_part.0, subsec_nanos as u64).unwrap();
+        let mut increment_fractions = |resolution| {
+            let mut new_fractions = fractional_part.1 + fractional_increment.1;
+            let max_fractions = fractional_res_to_div(resolution);
+            if new_fractions > max_fractions {
+                increment_counter(1);
+                new_fractions -= max_fractions;
+            }
+            Some(FractionalPart(resolution, new_fractions))
+        };
+        match fractional_increment.0 {
+            FractionalResolution::Seconds => None,
+            _ => increment_fractions(fractional_increment.0),
+        }
+    } else {
+        None
+    };
+    increment_counter(duration.as_secs() as u32);
+    (new_counter, fractional_part)
+}
+
+impl AddAssign<Duration> for TimeProviderCcsdsEpoch {
+    fn add_assign(&mut self, duration: Duration) {
+        let (new_counter, new_fractional_part) =
+            get_provider_values_after_duration_addition(self, duration);
+        self.counter.1 = new_counter;
+        if self.fractions.is_some() {
+            self.fractions = new_fractional_part;
+        }
+    }
+}
+
+impl Add<Duration> for TimeProviderCcsdsEpoch {
+    type Output = Self;
+
+    fn add(self, duration: Duration) -> Self::Output {
+        let (new_counter, new_fractional_part) =
+            get_provider_values_after_duration_addition(&self, duration);
+        if let Some(fractional_part) = new_fractional_part {
+            // The generated fractional part should always be valid, so its okay to unwrap here.
+            return Self::new_with_fractions(new_counter, fractional_part).unwrap();
+        }
+        Self::new(new_counter)
+    }
+}
+
+impl Add<Duration> for &TimeProviderCcsdsEpoch {
+    type Output = TimeProviderCcsdsEpoch;
+
+    fn add(self, duration: Duration) -> Self::Output {
+        let (new_counter, new_fractional_part) =
+            get_provider_values_after_duration_addition(self, duration);
+        if let Some(fractional_part) = new_fractional_part {
+            // The generated fractional part should always be valid, so its okay to unwrap here.
+            return Self::Output::new_with_fractions(new_counter, fractional_part).unwrap();
+        }
+        Self::Output::new(new_counter)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -599,6 +746,7 @@ mod tests {
         let zero_cuc = zero_cuc.unwrap();
         let res = zero_cuc.write_to_bytes(&mut buf);
         assert!(res.is_ok());
+        assert!(zero_cuc.subsecond_millis().is_none());
         assert_eq!(zero_cuc.len_as_bytes(), 5);
         assert_eq!(pfield_len(buf[0]), 1);
         let written = res.unwrap();
@@ -947,4 +1095,31 @@ mod tests {
         // Assert that the maximum resolution can be reached
         assert_eq!(fractions.1, 2_u32.pow(3 * 8) - 2);
     }
+
+    #[test]
+    fn add_duration_basic() {
+        let mut cuc_stamp = TimeProviderCcsdsEpoch::new(200);
+        cuc_stamp.set_fractional_resolution(FractionalResolution::FifteenUs);
+        let duration = Duration::from_millis(2500);
+        cuc_stamp += duration;
+        assert_eq!(cuc_stamp.width_counter_pair().1, 202);
+        let fractions = cuc_stamp.width_fractions_pair().unwrap().1;
+        let expected_val =
+            (0.5 * fractional_res_to_div(FractionalResolution::FifteenUs) as f64).floor() as u32;
+        assert_eq!(fractions, expected_val);
+        let cuc_stamp2 = cuc_stamp + Duration::from_millis(501);
+        // What I would roughly expect
+        assert_eq!(cuc_stamp2.counter.1, 203);
+        assert!(cuc_stamp2.fractions.unwrap().1 < 100);
+        assert!(cuc_stamp2.subsecond_millis().unwrap() <= 1);
+    }
+
+    #[test]
+    fn add_duration_overflow() {
+        let mut cuc_stamp =
+            TimeProviderCcsdsEpoch::new_generic(WidthCounterPair(1, 255), None).unwrap();
+        let duration = Duration::from_secs(10);
+        cuc_stamp += duration;
+        assert_eq!(cuc_stamp.counter.1, 10);
+    }
 }

src/time/mod.rs

@@ -1,7 +1,10 @@
 //! CCSDS Time Code Formats according to [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 use crate::{ByteConversionError, SizeMissmatch};
 use chrono::{DateTime, LocalResult, TimeZone, Utc};
+use core::cmp::Ordering;
 use core::fmt::{Display, Formatter};
+use core::ops::{Add, AddAssign};
+use core::time::Duration;
 
 #[allow(unused_imports)]
 #[cfg(not(feature = "std"))]
@@ -20,6 +23,7 @@ pub mod cuc;
 
 pub const DAYS_CCSDS_TO_UNIX: i32 = -4383;
 pub const SECONDS_PER_DAY: u32 = 86400;
+pub const MS_PER_DAY: u32 = SECONDS_PER_DAY * 1000;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -55,6 +59,7 @@ pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCodes, u8> {
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[non_exhaustive]
 pub enum TimestampError {
     /// Contains tuple where first value is the expected time code and the second
     /// value is the found raw value
@@ -62,6 +67,7 @@ pub enum TimestampError {
     ByteConversionError(ByteConversionError),
     CdsError(cds::CdsError),
     CucError(cuc::CucError),
+    DateBeforeCcsdsEpoch(DateTime<Utc>),
     CustomEpochNotSupported,
 }
 
@@ -118,6 +124,9 @@ impl Display for TimestampError {
             TimestampError::ByteConversionError(e) => {
                 write!(f, "byte conversion error {}", e)
             }
+            TimestampError::DateBeforeCcsdsEpoch(e) => {
+                write!(f, "datetime with date before ccsds epoch: {}", e)
+            }
             TimestampError::CustomEpochNotSupported => {
                 write!(f, "custom epochs are not supported")
             }
@@ -164,12 +173,12 @@ pub const fn ccsds_to_unix_days(ccsds_days: i64) -> i64 {
 
 /// Similar to [unix_to_ccsds_days] but converts the epoch instead, which is the number of elpased
 /// seconds since the CCSDS and UNIX epoch times.
-pub const fn unix_epoch_to_ccsds_epoch(unix_epoch: u64) -> u64 {
-    (unix_epoch as i64 - (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)) as u64
+pub const fn unix_epoch_to_ccsds_epoch(unix_epoch: i64) -> i64 {
+    unix_epoch - (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)
 }
 
-pub const fn ccsds_epoch_to_unix_epoch(ccsds_epoch: u64) -> u64 {
-    (ccsds_epoch as i64 + (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)) as u64
+pub const fn ccsds_epoch_to_unix_epoch(ccsds_epoch: i64) -> i64 {
+    ccsds_epoch + (DAYS_CCSDS_TO_UNIX as i64 * SECONDS_PER_DAY as i64)
 }
 
 #[cfg(feature = "std")]
@@ -199,6 +208,9 @@ pub trait TimeReader {
 }
 
 /// Trait for generic CCSDS time providers.
+///
+/// The UNIX helper methods and the [Self::date_time] method are not strictly necessary but extremely
+/// practical because they are a very common and simple exchange format for time information.
 pub trait CcsdsTimeProvider {
     fn len_as_bytes(&self) -> usize;
 
@@ -208,10 +220,209 @@ pub trait CcsdsTimeProvider {
     /// in big endian format.
     fn p_field(&self) -> (usize, [u8; 2]);
     fn ccdsd_time_code(&self) -> CcsdsTimeCodes;
+
     fn unix_seconds(&self) -> i64;
+    fn subsecond_millis(&self) -> Option<u16>;
+    fn unix_stamp(&self) -> UnixTimestamp {
+        UnixTimestamp {
+            unix_seconds: self.unix_seconds(),
+            subsecond_millis: self.subsecond_millis(),
+        }
+    }
+
     fn date_time(&self) -> Option<DateTime<Utc>>;
 }
 
+/// UNIX timestamp: Elapsed seconds since 01-01-1970 00:00:00.
+///
+/// Also can optionally include subsecond millisecond for greater accuracy. Please note that a
+/// subsecond millisecond value of 0 gets converted to [None].
+#[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct UnixTimestamp {
+    pub unix_seconds: i64,
+    subsecond_millis: Option<u16>,
+}
+
+impl UnixTimestamp {
+    /// Returns none if the subsecond millisecond value is larger than 999. 0 is converted to
+    /// a [None] value.
+    pub fn new(unix_seconds: i64, subsec_millis: u16) -> Option<Self> {
+        if subsec_millis > 999 {
+            return None;
+        }
+        Some(Self::const_new(unix_seconds, subsec_millis))
+    }
+
+    /// Like [Self::new] but const. Panics if the subsecond value is larger than 999.
+    pub const fn const_new(unix_seconds: i64, subsec_millis: u16) -> Self {
+        if subsec_millis > 999 {
+            panic!("subsec milliseconds exceeds 999");
+        }
+        let subsecond_millis = if subsec_millis == 0 {
+            None
+        } else {
+            Some(subsec_millis)
+        };
+        Self {
+            unix_seconds,
+            subsecond_millis,
+        }
+    }
+
+    pub fn new_only_seconds(unix_seconds: i64) -> Self {
+        Self {
+            unix_seconds,
+            subsecond_millis: None,
+        }
+    }
+
+    pub fn subsecond_millis(&self) -> Option<u16> {
+        self.subsecond_millis
+    }
+
+    #[cfg(feature = "std")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+    pub fn from_now() -> Result<Self, SystemTimeError> {
+        let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
+        let epoch = now.as_secs();
+        Ok(UnixTimestamp {
+            unix_seconds: epoch as i64,
+            subsecond_millis: Some(now.subsec_millis() as u16),
+        })
+    }
+
+    #[inline]
+    pub fn unix_seconds_f64(&self) -> f64 {
+        let mut secs = self.unix_seconds as f64;
+        if let Some(subsec_millis) = self.subsecond_millis {
+            secs += subsec_millis as f64 / 1000.0;
+        }
+        secs
+    }
+
+    pub fn as_date_time(&self) -> LocalResult<DateTime<Utc>> {
+        Utc.timestamp_opt(
+            self.unix_seconds,
+            self.subsecond_millis.unwrap_or(0) as u32 * 10_u32.pow(6),
+        )
+    }
+}
+
+impl From<DateTime<Utc>> for UnixTimestamp {
+    fn from(value: DateTime<Utc>) -> Self {
+        Self {
+            unix_seconds: value.timestamp(),
+            subsecond_millis: Some(value.timestamp_subsec_millis() as u16),
+        }
+    }
+}
+
+impl PartialOrd for UnixTimestamp {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if self == other {
+            return Some(Ordering::Equal);
+        }
+        match self.unix_seconds.cmp(&other.unix_seconds) {
+            Ordering::Less => return Some(Ordering::Less),
+            Ordering::Greater => return Some(Ordering::Greater),
+            _ => (),
+        }
+
+        match self
+            .subsecond_millis()
+            .unwrap_or(0)
+            .cmp(&other.subsecond_millis().unwrap_or(0))
+        {
+            Ordering::Less => {
+                return if self.unix_seconds < 0 {
+                    Some(Ordering::Greater)
+                } else {
+                    Some(Ordering::Less)
+                }
+            }
+            Ordering::Greater => {
+                return if self.unix_seconds < 0 {
+                    Some(Ordering::Less)
+                } else {
+                    Some(Ordering::Greater)
+                }
+            }
+            Ordering::Equal => (),
+        }
+        Some(Ordering::Equal)
+    }
+}
+
+impl Ord for UnixTimestamp {
+    fn cmp(&self, other: &Self) -> Ordering {
+        PartialOrd::partial_cmp(self, other).unwrap()
+    }
+}
+
+fn get_new_stamp_after_addition(
+    current_stamp: &UnixTimestamp,
+    duration: Duration,
+) -> UnixTimestamp {
+    let mut new_subsec_millis =
+        current_stamp.subsecond_millis().unwrap_or(0) + duration.subsec_millis() as u16;
+    let mut new_unix_seconds = current_stamp.unix_seconds;
+    let mut increment_seconds = |value: u32| {
+        if new_unix_seconds < 0 {
+            new_unix_seconds = new_unix_seconds
+                .checked_sub(value.into())
+                .expect("new unix seconds would exceed i64::MIN");
+        } else {
+            new_unix_seconds = new_unix_seconds
+                .checked_add(value.into())
+                .expect("new unix seconds would exceed i64::MAX");
+        }
+    };
+    if new_subsec_millis >= 1000 {
+        new_subsec_millis -= 1000;
+        increment_seconds(1);
+    }
+    increment_seconds(
+        duration
+            .as_secs()
+            .try_into()
+            .expect("duration seconds exceeds u32::MAX"),
+    );
+    UnixTimestamp::const_new(new_unix_seconds, new_subsec_millis)
+}
+
+/// Please note that this operation will panic on the following conditions:
+///
+/// - Unix seconds after subtraction for stamps before the unix epoch exceeds [i64::MIN].
+/// - Unix seconds after addition  exceeds [i64::MAX].
+/// - Seconds from duration to add exceeds [u32::MAX].
+impl AddAssign<Duration> for UnixTimestamp {
+    fn add_assign(&mut self, duration: Duration) {
+        *self = get_new_stamp_after_addition(self, duration);
+    }
+}
+
+/// Please note that this operation will panic for the following conditions:
+///
+/// - Unix seconds after subtraction for stamps before the unix epoch exceeds [i64::MIN].
+/// - Unix seconds after addition  exceeds [i64::MAX].
+/// - Unix seconds exceeds [u32::MAX].
+impl Add<Duration> for UnixTimestamp {
+    type Output = Self;
+
+    fn add(self, duration: Duration) -> Self::Output {
+        get_new_stamp_after_addition(&self, duration)
+    }
+}
+
+impl Add<Duration> for &UnixTimestamp {
+    type Output = UnixTimestamp;
+
+    fn add(self, duration: Duration) -> Self::Output {
+        get_new_stamp_after_addition(self, duration)
+    }
+}
+
 #[cfg(all(test, feature = "std"))]
 mod tests {
     use super::*;
@@ -234,10 +445,116 @@ mod tests {
             .duration_since(SystemTime::UNIX_EPOCH)
             .unwrap();
         let unix_epoch = now.as_secs();
-        let ccsds_epoch = unix_epoch_to_ccsds_epoch(now.as_secs());
+        let ccsds_epoch = unix_epoch_to_ccsds_epoch(now.as_secs() as i64) as u64;
         assert!(ccsds_epoch > unix_epoch);
         assert_eq!((ccsds_epoch - unix_epoch) % SECONDS_PER_DAY as u64, 0);
         let days_diff = (ccsds_epoch - unix_epoch) / SECONDS_PER_DAY as u64;
         assert_eq!(days_diff, -DAYS_CCSDS_TO_UNIX as u64);
     }
+
+    #[test]
+    fn basic_unix_stamp_test() {
+        let stamp = UnixTimestamp::new_only_seconds(-200);
+        assert_eq!(stamp.unix_seconds, -200);
+        assert!(stamp.subsecond_millis().is_none());
+        let stamp = UnixTimestamp::new_only_seconds(250);
+        assert_eq!(stamp.unix_seconds, 250);
+        assert!(stamp.subsecond_millis().is_none());
+    }
+
+    #[test]
+    fn basic_float_unix_stamp_test() {
+        let stamp = UnixTimestamp::new(500, 600).unwrap();
+        assert!(stamp.subsecond_millis.is_some());
+        assert_eq!(stamp.unix_seconds, 500);
+        let subsec_millis = stamp.subsecond_millis().unwrap();
+        assert_eq!(subsec_millis, 600);
+        assert!((500.6 - stamp.unix_seconds_f64()).abs() < 0.0001);
+    }
+
+    #[test]
+    fn test_ord_larger() {
+        let stamp0 = UnixTimestamp::new_only_seconds(5);
+        let stamp1 = UnixTimestamp::new(5, 500).unwrap();
+        let stamp2 = UnixTimestamp::new_only_seconds(6);
+        assert!(stamp1 > stamp0);
+        assert!(stamp2 > stamp0);
+        assert!(stamp2 > stamp1);
+    }
+
+    #[test]
+    fn test_ord_smaller() {
+        let stamp0 = UnixTimestamp::new_only_seconds(5);
+        let stamp1 = UnixTimestamp::new(5, 500).unwrap();
+        let stamp2 = UnixTimestamp::new_only_seconds(6);
+        assert!(stamp0 < stamp1);
+        assert!(stamp0 < stamp2);
+        assert!(stamp1 < stamp2);
+    }
+
+    #[test]
+    fn test_ord_larger_neg_numbers() {
+        let stamp0 = UnixTimestamp::new_only_seconds(-5);
+        let stamp1 = UnixTimestamp::new(-5, 500).unwrap();
+        let stamp2 = UnixTimestamp::new_only_seconds(-6);
+        assert!(stamp0 > stamp1);
+        assert!(stamp0 > stamp2);
+        assert!(stamp1 > stamp2);
+        assert!(stamp1 >= stamp2);
+        assert!(stamp0 >= stamp1);
+    }
+
+    #[test]
+    fn test_ord_smaller_neg_numbers() {
+        let stamp0 = UnixTimestamp::new_only_seconds(-5);
+        let stamp1 = UnixTimestamp::new(-5, 500).unwrap();
+        let stamp2 = UnixTimestamp::new_only_seconds(-6);
+        assert!(stamp2 < stamp1);
+        assert!(stamp2 < stamp0);
+        assert!(stamp1 < stamp0);
+        assert!(stamp1 <= stamp0);
+        assert!(stamp2 <= stamp1);
+    }
+
+    #[test]
+    fn test_eq() {
+        let stamp0 = UnixTimestamp::new(5, 0).unwrap();
+        let stamp1 = UnixTimestamp::new_only_seconds(5);
+        assert_eq!(stamp0, stamp1);
+        assert!(stamp0 <= stamp1);
+        assert!(stamp0 >= stamp1);
+        assert!(!(stamp0 < stamp1));
+        assert!(!(stamp0 > stamp1));
+    }
+
+    #[test]
+    fn test_addition() {
+        let mut stamp0 = UnixTimestamp::new_only_seconds(1);
+        stamp0 += Duration::from_secs(5);
+        assert_eq!(stamp0.unix_seconds, 6);
+        assert!(stamp0.subsecond_millis().is_none());
+        let stamp1 = stamp0 + Duration::from_millis(500);
+        assert_eq!(stamp1.unix_seconds, 6);
+        assert!(stamp1.subsecond_millis().is_some());
+        assert_eq!(stamp1.subsecond_millis().unwrap(), 500);
+    }
+
+    #[test]
+    fn test_addition_on_ref() {
+        let stamp0 = &UnixTimestamp::new(20, 500).unwrap();
+        let stamp1 = stamp0 + Duration::from_millis(2500);
+        assert_eq!(stamp1.unix_seconds, 23);
+        assert!(stamp1.subsecond_millis().is_none());
+    }
+
+    #[test]
+    fn test_addition_spillover() {
+        let mut stamp0 = UnixTimestamp::new(1, 900).unwrap();
+        stamp0 += Duration::from_millis(100);
+        assert_eq!(stamp0.unix_seconds, 2);
+        assert!(stamp0.subsecond_millis().is_none());
+        stamp0 += Duration::from_millis(1100);
+        assert_eq!(stamp0.unix_seconds, 3);
+        assert_eq!(stamp0.subsecond_millis().unwrap(), 100);
+    }
 }

src/tm.rs

@@ -48,7 +48,7 @@ pub mod zc {
 
     pub struct PusTmSecHeader<'slice> {
         pub(crate) zc_header: PusTmSecHeaderWithoutTimestamp,
-        pub(crate) timestamp: &'slice [u8],
+        pub(crate) timestamp: Option<&'slice [u8]>,
     }
 
     impl TryFrom<crate::tm::PusTmSecondaryHeader<'_>> for PusTmSecHeaderWithoutTimestamp {
@@ -115,20 +115,17 @@ pub struct PusTmSecondaryHeader<'stamp> {
     pub subservice: u8,
     pub msg_counter: u16,
     pub dest_id: u16,
-    pub time_stamp: &'stamp [u8],
+    pub timestamp: Option<&'stamp [u8]>,
 }
 
 impl<'stamp> PusTmSecondaryHeader<'stamp> {
-    pub fn new_simple(service: u8, subservice: u8, time_stamp: &'stamp [u8]) -> Self {
-        PusTmSecondaryHeader {
-            pus_version: PusVersion::PusC,
-            sc_time_ref_status: 0,
-            service,
-            subservice,
-            msg_counter: 0,
-            dest_id: 0,
-            time_stamp,
-        }
+    pub fn new_simple(service: u8, subservice: u8, timestamp: &'stamp [u8]) -> Self {
+        Self::new(service, subservice, 0, 0, Some(timestamp))
+    }
+
+    /// Like [Self::new_simple] but without a timestamp.
+    pub fn new_simple_no_timestamp(service: u8, subservice: u8) -> Self {
+        Self::new(service, subservice, 0, 0, None)
     }
 
     pub fn new(
@@ -136,7 +133,7 @@ impl<'stamp> PusTmSecondaryHeader<'stamp> {
         subservice: u8,
         msg_counter: u16,
         dest_id: u16,
-        time_stamp: &'stamp [u8],
+        timestamp: Option<&'stamp [u8]>,
     ) -> Self {
         PusTmSecondaryHeader {
             pus_version: PusVersion::PusC,
@@ -145,7 +142,7 @@ impl<'stamp> PusTmSecondaryHeader<'stamp> {
             subservice,
             msg_counter,
             dest_id,
-            time_stamp,
+            timestamp,
         }
     }
 }
@@ -187,7 +184,7 @@ impl<'slice> TryFrom<zc::PusTmSecHeader<'slice>> for PusTmSecondaryHeader<'slice
             subservice: sec_header.zc_header.subservice(),
             msg_counter: sec_header.zc_header.msg_counter(),
             dest_id: sec_header.zc_header.dest_id(),
-            time_stamp: sec_header.timestamp,
+            timestamp: sec_header.timestamp,
         })
     }
 }
@@ -257,15 +254,17 @@ impl<'src_data> PusTm<'src_data> {
 
     pub fn len_packed(&self) -> usize {
         let mut length = PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA;
-        length += self.sec_header.time_stamp.len();
+        if let Some(timestamp) = self.sec_header.timestamp {
+            length += timestamp.len();
+        }
         if let Some(src_data) = self.source_data {
             length += src_data.len();
         }
         length
     }
 
-    pub fn time_stamp(&self) -> &'src_data [u8] {
-        self.sec_header.time_stamp
+    pub fn timestamp(&self) -> Option<&'src_data [u8]> {
+        self.sec_header.timestamp
     }
 
     pub fn source_data(&self) -> Option<&'src_data [u8]> {
@@ -304,7 +303,9 @@ impl<'src_data> PusTm<'src_data> {
         digest.update(sph_zc.as_bytes());
         let pus_tc_header = zc::PusTmSecHeaderWithoutTimestamp::try_from(self.sec_header).unwrap();
         digest.update(pus_tc_header.as_bytes());
-        digest.update(self.sec_header.time_stamp);
+        if let Some(stamp) = self.sec_header.timestamp {
+            digest.update(stamp);
+        }
         if let Some(src_data) = self.source_data {
             digest.update(src_data);
         }
@@ -337,9 +338,11 @@ impl<'src_data> PusTm<'src_data> {
             .write_to_bytes(&mut slice[curr_idx..curr_idx + sec_header_len])
             .ok_or(ByteConversionError::ZeroCopyToError)?;
         curr_idx += sec_header_len;
-        let timestamp_len = self.sec_header.time_stamp.len();
-        slice[curr_idx..curr_idx + timestamp_len].copy_from_slice(self.sec_header.time_stamp);
-        curr_idx += timestamp_len;
+        if let Some(timestamp) = self.sec_header.timestamp {
+            let timestamp_len = timestamp.len();
+            slice[curr_idx..curr_idx + timestamp_len].copy_from_slice(timestamp);
+            curr_idx += timestamp_len;
+        }
         if let Some(src_data) = self.source_data {
             slice[curr_idx..curr_idx + src_data.len()].copy_from_slice(src_data);
             curr_idx += src_data.len();
@@ -361,8 +364,10 @@ impl<'src_data> PusTm<'src_data> {
     #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
     pub fn append_to_vec(&self, vec: &mut Vec<u8>) -> Result<usize, PusError> {
         let sph_zc = crate::zc::SpHeader::from(self.sp_header);
-        let mut appended_len =
-            PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA + self.sec_header.time_stamp.len();
+        let mut appended_len = PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA;
+        if let Some(timestamp) = self.sec_header.timestamp {
+            appended_len += timestamp.len();
+        }
         if let Some(src_data) = self.source_data {
             appended_len += src_data.len();
         };
@@ -374,8 +379,10 @@ impl<'src_data> PusTm<'src_data> {
         let sec_header = zc::PusTmSecHeaderWithoutTimestamp::try_from(self.sec_header).unwrap();
         vec.extend_from_slice(sec_header.as_bytes());
         ser_len += sec_header.as_bytes().len();
-        vec.extend_from_slice(self.sec_header.time_stamp);
-        ser_len += self.sec_header.time_stamp.len();
+        if let Some(timestamp) = self.sec_header.timestamp {
+            ser_len += timestamp.len();
+            vec.extend_from_slice(timestamp);
+        }
         if let Some(src_data) = self.source_data {
             vec.extend_from_slice(src_data);
             ser_len += src_data.len();
@@ -414,9 +421,13 @@ impl<'src_data> PusTm<'src_data> {
         )
         .ok_or(ByteConversionError::ZeroCopyFromError)?;
         current_idx += PUC_TM_MIN_SEC_HEADER_LEN;
+        let mut timestamp = None;
+        if timestamp_len > 0 {
+            timestamp = Some(&slice[current_idx..current_idx + timestamp_len]);
+        }
         let zc_sec_header_wrapper = zc::PusTmSecHeader {
             zc_header: sec_header_zc,
-            timestamp: &slice[current_idx..current_idx + timestamp_len],
+            timestamp,
         };
         current_idx += timestamp_len;
         let raw_data = &slice[0..total_len];
@@ -473,33 +484,33 @@ mod tests {
     use crate::ecss::PusVersion::PusC;
     use crate::SpHeader;
 
-    fn base_ping_reply_full_ctor(time_stamp: &[u8]) -> PusTm {
+    fn base_ping_reply_full_ctor(timestamp: &[u8]) -> PusTm {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let tc_header = PusTmSecondaryHeader::new_simple(17, 2, &time_stamp);
+        let tc_header = PusTmSecondaryHeader::new_simple(17, 2, &timestamp);
         PusTm::new(&mut sph, tc_header, None, true)
     }
 
-    fn base_hk_reply<'a>(time_stamp: &'a [u8], src_data: &'a [u8]) -> PusTm<'a> {
+    fn base_hk_reply<'a>(timestamp: &'a [u8], src_data: &'a [u8]) -> PusTm<'a> {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, &time_stamp);
+        let tc_header = PusTmSecondaryHeader::new_simple(3, 5, &timestamp);
         PusTm::new(&mut sph, tc_header, Some(src_data), true)
     }
 
-    fn dummy_time_stamp() -> &'static [u8] {
+    fn dummy_timestamp() -> &'static [u8] {
         return &[0, 1, 2, 3, 4, 5, 6];
     }
 
     #[test]
     fn test_basic() {
-        let time_stamp = dummy_time_stamp();
-        let pus_tm = base_ping_reply_full_ctor(&time_stamp);
-        verify_ping_reply(&pus_tm, false, 22, dummy_time_stamp());
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(&timestamp);
+        verify_ping_reply(&pus_tm, false, 22, dummy_timestamp());
     }
 
     #[test]
     fn test_serialization_no_source_data() {
-        let time_stamp = dummy_time_stamp();
-        let pus_tm = base_ping_reply_full_ctor(&time_stamp);
+        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)
@@ -511,7 +522,7 @@ mod tests {
     #[test]
     fn test_serialization_with_source_data() {
         let src_data = [1, 2, 3];
-        let hk_reply = base_hk_reply(dummy_time_stamp(), &src_data);
+        let hk_reply = base_hk_reply(dummy_timestamp(), &src_data);
         let mut buf: [u8; 32] = [0; 32];
         let ser_len = hk_reply
             .write_to_bytes(&mut buf)
@@ -524,8 +535,8 @@ mod tests {
 
     #[test]
     fn test_setters() {
-        let time_stamp = dummy_time_stamp();
-        let mut pus_tm = base_ping_reply_full_ctor(&time_stamp);
+        let timestamp = dummy_timestamp();
+        let mut pus_tm = base_ping_reply_full_ctor(&timestamp);
         pus_tm.set_sc_time_ref_status(0b1010);
         pus_tm.set_dest_id(0x7fff);
         pus_tm.set_msg_counter(0x1f1f);
@@ -538,8 +549,8 @@ mod tests {
 
     #[test]
     fn test_deserialization_no_source_data() {
-        let time_stamp = dummy_time_stamp();
-        let pus_tm = base_ping_reply_full_ctor(&time_stamp);
+        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)
@@ -547,13 +558,13 @@ mod tests {
         assert_eq!(ser_len, 22);
         let (tm_deserialized, size) = PusTm::from_bytes(&buf, 7).expect("Deserialization failed");
         assert_eq!(ser_len, size);
-        verify_ping_reply(&tm_deserialized, false, 22, dummy_time_stamp());
+        verify_ping_reply(&tm_deserialized, false, 22, dummy_timestamp());
     }
 
     #[test]
     fn test_manual_field_update() {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let tc_header = PusTmSecondaryHeader::new_simple(17, 2, dummy_time_stamp());
+        let tc_header = PusTmSecondaryHeader::new_simple(17, 2, dummy_timestamp());
         let mut tm = PusTm::new(&mut sph, tc_header, None, false);
         tm.calc_crc_on_serialization = false;
         assert_eq!(tm.data_len(), 0x00);
@@ -573,8 +584,8 @@ mod tests {
 
     #[test]
     fn test_target_buf_too_small() {
-        let time_stamp = dummy_time_stamp();
-        let pus_tm = base_ping_reply_full_ctor(&time_stamp);
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(&timestamp);
         let mut buf: [u8; 16] = [0; 16];
         let res = pus_tm.write_to_bytes(&mut buf);
         assert!(res.is_err());
@@ -597,8 +608,8 @@ mod tests {
     #[test]
     #[cfg(feature = "alloc")]
     fn test_append_to_vec() {
-        let time_stamp = dummy_time_stamp();
-        let pus_tm = base_ping_reply_full_ctor(&time_stamp);
+        let timestamp = dummy_timestamp();
+        let pus_tm = base_ping_reply_full_ctor(&timestamp);
         let mut vec = Vec::new();
         let res = pus_tm.append_to_vec(&mut vec);
         assert!(res.is_ok());
@@ -610,7 +621,7 @@ mod tests {
     #[cfg(feature = "alloc")]
     fn test_append_to_vec_with_src_data() {
         let src_data = [1, 2, 3];
-        let hk_reply = base_hk_reply(dummy_time_stamp(), &src_data);
+        let hk_reply = base_hk_reply(dummy_timestamp(), &src_data);
         let mut vec = Vec::new();
         vec.push(4);
         let res = hk_reply.append_to_vec(&mut vec);
@@ -639,7 +650,7 @@ mod tests {
         assert_eq!(buf[11], 0x00);
         assert_eq!(buf[12], 0x00);
         // Timestamp
-        assert_eq!(&buf[13..20], dummy_time_stamp());
+        assert_eq!(&buf[13..20], dummy_timestamp());
         let mut digest = CRC_CCITT_FALSE.digest();
         digest.update(&buf[0..20]);
         let crc16 = digest.finalize();
@@ -651,14 +662,14 @@ mod tests {
         tm: &PusTm,
         has_user_data: bool,
         exp_full_len: usize,
-        exp_time_stamp: &[u8],
+        exp_timestamp: &[u8],
     ) {
         assert!(tm.is_tm());
         assert_eq!(PusPacket::service(tm), 17);
         assert_eq!(PusPacket::subservice(tm), 2);
         assert!(tm.sec_header_flag());
         assert_eq!(tm.len_packed(), exp_full_len);
-        assert_eq!(tm.time_stamp(), exp_time_stamp);
+        assert_eq!(tm.timestamp().unwrap(), exp_timestamp);
         if has_user_data {
             assert!(!tm.user_data().is_none());
         }