more granular error handling

Reviewed-on: #71

CHANGELOG.md

@@ -8,6 +8,57 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+Major API changes for the time API. If you are using the time API, it is strongly recommended
+to check all the API changes in the **Changed** chapter.
+
+## Fixed
+
+- CUC timestamp was fixed to include leap second corrections because it is based on the TAI
+  time reference. The default CUC time object do not implement `CcsdsTimeProvider` anymore
+  because the trait methods require cached leap second information. This task is now performed
+  by the `cuc::CucTimeWithLeapSecs` which implements the trait.
+
+## Added
+
+- `From<$EcssEnum$TY> from $TY` for the ECSS enum type definitions.
+- Added basic support conversions to the `time` library. Introduce new `chrono` and `timelib`
+  feature gate.
+- Added `CcsdsTimeProvider::timelib_date_time`.
+
+## Changed
+
+- Renamed `CcsdsTimeProvider::date_time` to `CcsdsTimeProvider::chrono_date_time`
+- Renamed `CcsdsTimeCodes` to `CcsdsTimeCode`
+- Renamed `cds::TimeProvider` to `cds::CdsTime`
+- Renamed `cuc::TimeProviderCcsdsEpoch` to `cuc::CucTime`
+- `UnixTimestamp` renamed to `UnixTime`
+- `UnixTime` seconds are now private and can be retrieved using the `secs` member method.
+- `UnixTime::new` renamed to `UnixTime::new_checked`.
+- `UnixTime` now has a nanosecond subsecond precision. The `new` constructor now expects
+   nanoseconds as the second argument.
+- Added new `UnixTime::new_subsec_millis` and `UnixTime::new_subsec_millis_checked` API
+  to still allow creating a timestamp with only millisecond subsecond resolution.
+- `CcsdsTimeProvider` now has a new `subsec_nanos` method in addition to a default
+  implementation for the `subsec_millis` method.
+- `CcsdsTimeProvider::date_time` renamed to `CcsdsTimeProvider::chrono_date_time`.
+- Added `UnixTime::MIN`, `UnixTime::MAX` and `UnixTime::EPOCH`.
+- Added `UnixTime::timelib_date_time`.
+- Error handling for ECSS and time module is more granular now, with a new
+  `DateBeforeCcsdsEpochError` error and a `DateBeforeCcsdsEpoch` enum variant for both
+  `CdsError` and `CucError`.
+
+# [v0.11.0-rc.0] 2024-03-04
+
+## Added
+
+- `From<$TY>` for the `EcssEnum$TY` ECSS enum type definitions.
+- `Sub` implementation for `UnixTimestamp` to calculate the duration between two timestamps.
+
+## Changed
+
+- `CcsdsTimeProvider` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+- `UnixTimestamp` `subsecond_millis` function now returns `u16` instead of `Option<u16>`.
+
 # [v0.10.0] 2024-02-17
 
 ## Added

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spacepackets"
-version = "0.10.0"
+version = "0.11.0-rc.0"
 edition = "2021"
 rust-version = "1.61"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
@@ -34,22 +34,31 @@ 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
 
-[dev-dependencies.postcard]
-version = "1"
+[dev-dependencies]
+postcard = "1"
+chrono = "0.4"
 
 [features]
 default = ["std"]
 std = ["chrono/std", "chrono/clock", "alloc", "thiserror"]
 serde = ["dep:serde", "chrono/serde"]
 alloc = ["postcard/alloc", "chrono/alloc"]
+chrono = ["dep:chrono"]
+timelib = ["dep:time"]
 
 [package.metadata.docs.rs]
 all-features = true

README.md

@@ -43,6 +43,8 @@ deserializing them with an appropriate `serde` provider like
 ## Optional Features
 
  - [`serde`](https://serde.rs/): Adds `serde` support for most types by adding `Serialize` and `Deserialize` `derive`s
+ - [`chrono`](https://crates.io/crates/chrono): Add basic support for the `chrono` time library.
+ - [`timelib`](https://crates.io/crates/time): Add basic support for the `time` time library.
 
 # Examples
 

src/ecss/mod.rs

@@ -205,13 +205,12 @@ pub trait PusPacket: CcsdsPacket {
     fn crc16(&self) -> Option<u16>;
 }
 
-pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, PusError> {
+pub(crate) fn crc_from_raw_data(raw_data: &[u8]) -> Result<u16, ByteConversionError> {
     if raw_data.len() < 2 {
         return Err(ByteConversionError::FromSliceTooSmall {
             found: raw_data.len(),
             expected: 2,
-        }
-        .into());
+        });
     }
     Ok(u16::from_be_bytes(
         raw_data[raw_data.len() - 2..raw_data.len()]
@@ -248,13 +247,12 @@ pub(crate) fn user_data_from_raw(
     current_idx: usize,
     total_len: usize,
     slice: &[u8],
-) -> Result<&[u8], PusError> {
+) -> Result<&[u8], ByteConversionError> {
     match current_idx {
         _ if current_idx > total_len - 2 => Err(ByteConversionError::FromSliceTooSmall {
             found: total_len - 2,
             expected: current_idx,
-        }
-        .into()),
+        }),
         _ => Ok(&slice[current_idx..total_len - 2]),
     }
 }
@@ -360,10 +358,34 @@ impl<TYPE: Debug + Copy + Clone + PartialEq + Eq + ToBeBytes + Into<u64>> EcssEn
 {
 }
 
-pub type EcssEnumU8 = GenericEcssEnumWrapper<u8>;
-pub type EcssEnumU16 = GenericEcssEnumWrapper<u16>;
-pub type EcssEnumU32 = GenericEcssEnumWrapper<u32>;
-pub type EcssEnumU64 = GenericEcssEnumWrapper<u64>;
+impl<T: Copy + Into<u64>> From<T> for GenericEcssEnumWrapper<T> {
+    fn from(value: T) -> Self {
+        Self::new(value)
+    }
+}
+
+macro_rules! generic_ecss_enum_typedefs_and_from_impls {
+    ($($ty:ty => $Enum:ident),*) => {
+        $(
+            pub type $Enum = GenericEcssEnumWrapper<$ty>;
+
+            impl From<$Enum> for $ty {
+                fn from(value: $Enum) -> Self {
+                    value.value_typed()
+                }
+            }
+        )*
+    };
+}
+
+// Generates EcssEnum<$TY> type definitions as well as a From<$TY> for EcssEnum<$TY>
+// implementation.
+generic_ecss_enum_typedefs_and_from_impls! {
+    u8 => EcssEnumU8,
+    u16 => EcssEnumU16,
+    u32 => EcssEnumU32,
+    u64 => EcssEnumU64
+}
 
 /// Generic trait for PUS packet abstractions which can written to a raw slice as their raw
 /// byte representation. This is especially useful for generic abstractions which depend only
@@ -406,6 +428,8 @@ mod tests {
         assert_eq!(buf[1], 1);
         assert_eq!(my_enum.value(), 1);
         assert_eq!(my_enum.value_typed(), 1);
+        let enum_as_u8: u8 = my_enum.into();
+        assert_eq!(enum_as_u8, 1);
         let vec = my_enum.to_vec();
         assert_eq!(vec, buf[1..2]);
     }
@@ -423,6 +447,8 @@ mod tests {
         assert_eq!(buf[2], 0x2f);
         assert_eq!(my_enum.value(), 0x1f2f);
         assert_eq!(my_enum.value_typed(), 0x1f2f);
+        let enum_as_raw: u16 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f);
         let vec = my_enum.to_vec();
         assert_eq!(vec, buf[1..3]);
     }
@@ -458,6 +484,8 @@ mod tests {
         assert_eq!(buf[4], 0x4f);
         assert_eq!(my_enum.value(), 0x1f2f3f4f);
         assert_eq!(my_enum.value_typed(), 0x1f2f3f4f);
+        let enum_as_raw: u32 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f3f4f);
         let vec = my_enum.to_vec();
         assert_eq!(vec, buf[1..5]);
     }
@@ -494,6 +522,8 @@ mod tests {
         assert_eq!(buf[7], 0x5f);
         assert_eq!(my_enum.value(), 0x1f2f3f4f5f);
         assert_eq!(my_enum.value_typed(), 0x1f2f3f4f5f);
+        let enum_as_raw: u64 = my_enum.into();
+        assert_eq!(enum_as_raw, 0x1f2f3f4f5f);
         assert_eq!(u64::from_be_bytes(buf), 0x1f2f3f4f5f);
         let vec = my_enum.to_vec();
         assert_eq!(vec, buf);

src/ecss/tc.rs

@@ -654,8 +654,7 @@ impl<'raw_data> PusTcCreator<'raw_data> {
     }
 
     #[cfg(feature = "alloc")]
-    #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-    pub fn append_to_vec(&self, vec: &mut Vec<u8>) -> Result<usize, PusError> {
+    pub fn append_to_vec(&self, vec: &mut Vec<u8>) -> usize {
         let sph_zc = crate::zc::SpHeader::from(self.sp_header);
         let mut appended_len = PUS_TC_MIN_LEN_WITHOUT_APP_DATA;
         appended_len += self.app_data.len();
@@ -668,7 +667,7 @@ impl<'raw_data> PusTcCreator<'raw_data> {
         let mut digest = CRC_CCITT_FALSE.digest();
         digest.update(&vec[start_idx..start_idx + appended_len - 2]);
         vec.extend_from_slice(&digest.finalize().to_be_bytes());
-        Ok(appended_len)
+        appended_len
     }
 }
 
@@ -763,7 +762,8 @@ pub struct PusTcReader<'raw_data> {
 
 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.
+    /// 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> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TC_MIN_LEN_WITHOUT_APP_DATA {
@@ -1010,9 +1010,7 @@ mod tests {
     fn test_vec_ser_deser() {
         let pus_tc = base_ping_tc_simple_ctor();
         let mut test_vec = Vec::new();
-        let size = pus_tc
-            .append_to_vec(&mut test_vec)
-            .expect("Error writing TC to vector");
+        let size = pus_tc.append_to_vec(&mut test_vec);
         assert_eq!(size, 13);
         verify_test_tc_raw(&test_vec.as_slice());
         verify_crc_no_app_data(&test_vec.as_slice());
@@ -1058,9 +1056,7 @@ mod tests {
         let pus_tc = base_ping_tc_simple_ctor_with_app_data(&[1, 2, 3]);
         verify_test_tc(&pus_tc, true, 16);
         let mut test_vec = Vec::new();
-        let size = pus_tc
-            .append_to_vec(&mut test_vec)
-            .expect("Error writing TC to vector");
+        let size = pus_tc.append_to_vec(&mut test_vec);
         assert_eq!(test_vec[11], 1);
         assert_eq!(test_vec[12], 2);
         assert_eq!(test_vec[13], 3);

src/ecss/tm.rs

@@ -660,6 +660,37 @@ impl<'raw_data> PusTmCreator<'raw_data> {
         self.update_ccsds_data_len();
     }
 
+    /// 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() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: slice.len(),
+                expected: total_size,
+            });
+        }
+        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_bytes(&mut slice[curr_idx..curr_idx + sec_header_len])
+            .ok_or(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)
+    }
+
     /// Append the raw PUS byte representation to a provided [alloc::vec::Vec]
     #[cfg(feature = "alloc")]
     #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
@@ -689,34 +720,7 @@ impl WritablePusPacket for PusTmCreator<'_> {
     }
     /// 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 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(&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_bytes(&mut slice[curr_idx..curr_idx + sec_header_len])
-            .ok_or(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)
+        Ok(Self::write_to_bytes(self, slice)?)
     }
 }
 
@@ -788,6 +792,9 @@ impl<'raw_data> PusTmReader<'raw_data> {
     /// Create a [PusTmReader] instance from a raw slice. On success, it returns a tuple containing
     /// the instance and the found byte length of the packet. The timestamp length needs to be
     /// known beforehand.
+    ///
+    /// 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> {
         let raw_data_len = slice.len();
         if raw_data_len < PUS_TM_MIN_LEN_WITHOUT_SOURCE_DATA {
@@ -1097,7 +1104,7 @@ mod tests {
 
     use super::*;
     use crate::ecss::PusVersion::PusC;
-    use crate::time::cds::TimeProvider;
+    use crate::time::cds::CdsTime;
     #[cfg(feature = "serde")]
     use crate::time::CcsdsTimeProvider;
     use crate::SpHeader;
@@ -1136,7 +1143,7 @@ mod tests {
     #[test]
     fn test_basic_simple_api() {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let time_provider = CdsTime::new_with_u16_days(0, 0);
         let mut stamp_buf: [u8; 8] = [0; 8];
         let pus_tm =
             PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)
@@ -1260,18 +1267,11 @@ mod tests {
         let res = pus_tm.write_to_bytes(&mut buf);
         assert!(res.is_err());
         let error = res.unwrap_err();
-        assert!(matches!(error, PusError::ByteConversion { .. }));
-        match error {
-            PusError::ByteConversion(err) => match err {
-                ByteConversionError::ToSliceTooSmall { found, expected } => {
-                    assert_eq!(expected, 22);
-                    assert_eq!(found, 16);
-                }
-                _ => panic!("Invalid PUS error {:?}", err),
-            },
-            _ => {
-                panic!("Invalid error {:?}", error);
-            }
+        if let ByteConversionError::ToSliceTooSmall { found, expected } = error {
+            assert_eq!(expected, 22);
+            assert_eq!(found, 16);
+        } else {
+            panic!("Invalid error {:?}", error);
         }
     }
 
@@ -1534,7 +1534,7 @@ mod tests {
     #[cfg(feature = "serde")]
     fn test_serialization_creator_serde() {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let time_provider = CdsTime::new_with_u16_days(0, 0);
         let mut stamp_buf: [u8; 8] = [0; 8];
         let pus_tm =
             PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)
@@ -1549,7 +1549,7 @@ mod tests {
     #[cfg(feature = "serde")]
     fn test_serialization_reader_serde() {
         let mut sph = SpHeader::tm_unseg(0x123, 0x234, 0).unwrap();
-        let time_provider = TimeProvider::new_with_u16_days(0, 0);
+        let time_provider = CdsTime::new_with_u16_days(0, 0);
         let mut stamp_buf: [u8; 8] = [0; 8];
         let pus_tm =
             PusTmCreator::new_simple(&mut sph, 17, 2, &time_provider, &mut stamp_buf, None, true)

src/time/ascii.rs

@@ -2,11 +2,8 @@
 //! [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf) section 3.5 .
 //! See [chrono::DateTime::format] for a usage example of the generated
 //! [chrono::format::DelayedFormat] structs.
-#[cfg(feature = "alloc")]
-use chrono::{
-    format::{DelayedFormat, StrftimeItems},
-    DateTime, Utc,
-};
+#[cfg(all(feature = "alloc", feature = "chrono"))]
+pub use alloc_mod_chrono::*;
 
 /// Tuple of format string and formatted size for time code A.
 ///
@@ -34,36 +31,41 @@ pub const FMT_STR_CODE_B_WITH_SIZE: (&str, usize) = ("%Y-%jT%T%.3f", 21);
 /// Three digits are used for the decimal fraction and a terminator is added at the end.
 pub const FMT_STR_CODE_B_TERMINATED_WITH_SIZE: (&str, usize) = ("%Y-%jT%T%.3fZ", 22);
 
-/// Generates a time code formatter using the [FMT_STR_CODE_A_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_a(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_A_WITH_SIZE.0)
-}
+#[cfg(all(feature = "alloc", feature = "chrono"))]
+pub mod alloc_mod_chrono {
+    use super::*;
+    use chrono::{
+        format::{DelayedFormat, StrftimeItems},
+        DateTime, Utc,
+    };
 
-/// Generates a time code formatter using the [FMT_STR_CODE_A_TERMINATED_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_a_terminated(
-    date: &DateTime<Utc>,
-) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_A_TERMINATED_WITH_SIZE.0)
-}
+    /// Generates a time code formatter using the [FMT_STR_CODE_A_WITH_SIZE] format.
+    #[cfg_attr(doc_cfg, doc(cfg(all(feature = "alloc", feature = "chrono"))))]
+    pub fn generate_time_code_a(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_A_WITH_SIZE.0)
+    }
 
-/// Generates a time code formatter using the [FMT_STR_CODE_B_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_b(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_B_WITH_SIZE.0)
-}
+    /// Generates a time code formatter using the [FMT_STR_CODE_A_TERMINATED_WITH_SIZE] format.
+    #[cfg_attr(doc_cfg, doc(cfg(all(feature = "alloc", feature = "chrono"))))]
+    pub fn generate_time_code_a_terminated(
+        date: &DateTime<Utc>,
+    ) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_A_TERMINATED_WITH_SIZE.0)
+    }
 
-/// Generates a time code formatter using the [FMT_STR_CODE_B_TERMINATED_WITH_SIZE] format.
-#[cfg(feature = "alloc")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-pub fn generate_time_code_b_terminated(
-    date: &DateTime<Utc>,
-) -> DelayedFormat<StrftimeItems<'static>> {
-    date.format(FMT_STR_CODE_B_TERMINATED_WITH_SIZE.0)
+    /// Generates a time code formatter using the [FMT_STR_CODE_B_WITH_SIZE] format.
+    #[cfg_attr(doc_cfg, doc(cfg(all(feature = "alloc", feature = "chrono"))))]
+    pub fn generate_time_code_b(date: &DateTime<Utc>) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_B_WITH_SIZE.0)
+    }
+
+    /// Generates a time code formatter using the [FMT_STR_CODE_B_TERMINATED_WITH_SIZE] format.
+    #[cfg_attr(doc_cfg, doc(cfg(all(feature = "alloc", feature = "chrono"))))]
+    pub fn generate_time_code_b_terminated(
+        date: &DateTime<Utc>,
+    ) -> DelayedFormat<StrftimeItems<'static>> {
+        date.format(FMT_STR_CODE_B_TERMINATED_WITH_SIZE.0)
+    }
 }
 
 #[cfg(test)]
@@ -77,7 +79,7 @@ mod tests {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_a(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 10);
         assert_eq!(stamp.len(), FMT_STR_CODE_A_WITH_SIZE.1);
@@ -88,10 +90,10 @@ mod tests {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_a_terminated(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 10);
-        let z_terminator = stamp.find("Z");
+        let z_terminator = stamp.find('Z');
         assert!(z_terminator.is_some());
         assert_eq!(
             z_terminator.unwrap(),
@@ -105,7 +107,7 @@ mod tests {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_b(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 8);
         assert_eq!(stamp.len(), FMT_STR_CODE_B_WITH_SIZE.1);
@@ -116,10 +118,10 @@ mod tests {
         let date = Utc::now();
         let stamp_formatter = generate_time_code_b_terminated(&date);
         let stamp = format!("{}", stamp_formatter);
-        let t_sep = stamp.find("T");
+        let t_sep = stamp.find('T');
         assert!(t_sep.is_some());
         assert_eq!(t_sep.unwrap(), 8);
-        let z_terminator = stamp.find("Z");
+        let z_terminator = stamp.find('Z');
         assert!(z_terminator.is_some());
         assert_eq!(
             z_terminator.unwrap(),

src/time/mod.rs

@@ -1,9 +1,10 @@
 //! CCSDS Time Code Formats according to [CCSDS 301.0-B-4](https://public.ccsds.org/Pubs/301x0b4e1.pdf)
 use crate::ByteConversionError;
-use chrono::{DateTime, LocalResult, TimeZone, Utc};
+#[cfg(feature = "chrono")]
+use chrono::{TimeZone, Utc};
 use core::cmp::Ordering;
 use core::fmt::{Display, Formatter};
-use core::ops::{Add, AddAssign};
+use core::ops::{Add, AddAssign, Sub};
 use core::time::Duration;
 use core::u8;
 
@@ -13,6 +14,7 @@ use num_traits::float::FloatCore;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+
 #[cfg(feature = "std")]
 use std::error::Error;
 #[cfg(feature = "std")]
@@ -27,10 +29,11 @@ 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;
+pub const NANOS_PER_SECOND: u32 = 1_000_000_000;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub enum CcsdsTimeCodes {
+pub enum CcsdsTimeCode {
     CucCcsdsEpoch = 0b001,
     CucAgencyEpoch = 0b010,
     Cds = 0b100,
@@ -38,16 +41,16 @@ pub enum CcsdsTimeCodes {
     AgencyDefined = 0b110,
 }
 
-impl TryFrom<u8> for CcsdsTimeCodes {
+impl TryFrom<u8> for CcsdsTimeCode {
     type Error = ();
 
     fn try_from(value: u8) -> Result<Self, Self::Error> {
         match value {
-            x if x == CcsdsTimeCodes::CucCcsdsEpoch as u8 => Ok(CcsdsTimeCodes::CucCcsdsEpoch),
-            x if x == CcsdsTimeCodes::CucAgencyEpoch as u8 => Ok(CcsdsTimeCodes::CucAgencyEpoch),
-            x if x == CcsdsTimeCodes::Cds as u8 => Ok(CcsdsTimeCodes::Cds),
-            x if x == CcsdsTimeCodes::Ccs as u8 => Ok(CcsdsTimeCodes::Ccs),
-            x if x == CcsdsTimeCodes::AgencyDefined as u8 => Ok(CcsdsTimeCodes::AgencyDefined),
+            x if x == CcsdsTimeCode::CucCcsdsEpoch as u8 => Ok(CcsdsTimeCode::CucCcsdsEpoch),
+            x if x == CcsdsTimeCode::CucAgencyEpoch as u8 => Ok(CcsdsTimeCode::CucAgencyEpoch),
+            x if x == CcsdsTimeCode::Cds as u8 => Ok(CcsdsTimeCode::Cds),
+            x if x == CcsdsTimeCode::Ccs as u8 => Ok(CcsdsTimeCode::Ccs),
+            x if x == CcsdsTimeCode::AgencyDefined as u8 => Ok(CcsdsTimeCode::AgencyDefined),
             _ => Err(()),
         }
     }
@@ -55,20 +58,32 @@ impl TryFrom<u8> for CcsdsTimeCodes {
 
 /// Retrieve the CCSDS time code from the p-field. If no valid time code identifier is found, the
 /// value of the raw time code identification field is returned.
-pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCodes, u8> {
+pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCode, u8> {
     let raw_bits = (pfield >> 4) & 0b111;
-    CcsdsTimeCodes::try_from(raw_bits).map_err(|_| raw_bits)
+    CcsdsTimeCode::try_from(raw_bits).map_err(|_| raw_bits)
 }
 
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct DateBeforeCcsdsEpochError(UnixTime);
+
+impl Display for DateBeforeCcsdsEpochError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        write!(f, "date before ccsds epoch: {:?}", self.0)
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for DateBeforeCcsdsEpochError {}
+
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[non_exhaustive]
 pub enum TimestampError {
-    InvalidTimeCode { expected: CcsdsTimeCodes, found: u8 },
+    InvalidTimeCode { expected: CcsdsTimeCode, found: u8 },
     ByteConversion(ByteConversionError),
     Cds(cds::CdsError),
     Cuc(cuc::CucError),
-    DateBeforeCcsdsEpoch(DateTime<Utc>),
     CustomEpochNotSupported,
 }
 
@@ -90,9 +105,6 @@ impl Display for TimestampError {
             TimestampError::ByteConversion(e) => {
                 write!(f, "time stamp: {e}")
             }
-            TimestampError::DateBeforeCcsdsEpoch(e) => {
-                write!(f, "datetime with date before ccsds epoch: {e}")
-            }
             TimestampError::CustomEpochNotSupported => {
                 write!(f, "custom epochs are not supported")
             }
@@ -111,6 +123,7 @@ impl Error for TimestampError {
         }
     }
 }
+
 impl From<cds::CdsError> for TimestampError {
     fn from(e: cds::CdsError) -> Self {
         TimestampError::Cds(e)
@@ -196,6 +209,7 @@ pub trait TimeWriter {
     fn write_to_bytes(&self, bytes: &mut [u8]) -> Result<usize, TimestampError>;
 
     #[cfg(feature = "alloc")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
     fn to_vec(&self) -> Result<alloc::vec::Vec<u8>, TimestampError> {
         let mut vec = alloc::vec![0; self.len_written()];
         self.write_to_bytes(&mut vec)?;
@@ -203,16 +217,15 @@ pub trait TimeWriter {
     }
 }
 
-pub trait TimeReader {
-    fn from_bytes(buf: &[u8]) -> Result<Self, TimestampError>
-    where
-        Self: Sized;
+pub trait TimeReader: Sized {
+    fn from_bytes(buf: &[u8]) -> Result<Self, TimestampError>;
 }
 
 /// Trait for generic CCSDS time providers.
 ///
-/// The UNIX helper methods and the [Self::date_time] method are not strictly necessary but extremely
+/// The UNIX helper methods and the helper method are not strictly necessary but extremely
 /// practical because they are a very common and simple exchange format for time information.
+/// Therefore, it was decided to keep them in this trait as well.
 pub trait CcsdsTimeProvider {
     fn len_as_bytes(&self) -> usize;
 
@@ -221,66 +234,120 @@ pub trait CcsdsTimeProvider {
     /// entry denotes the length of the pfield and the second entry is the value of the pfield
     /// in big endian format.
     fn p_field(&self) -> (usize, [u8; 2]);
-    fn ccdsd_time_code(&self) -> CcsdsTimeCodes;
+    fn ccdsd_time_code(&self) -> CcsdsTimeCode;
 
-    fn unix_seconds(&self) -> i64;
-    fn subsecond_millis(&self) -> Option<u16>;
-    fn unix_stamp(&self) -> UnixTimestamp {
-        if self.subsecond_millis().is_none() {
-            return UnixTimestamp::new_only_seconds(self.unix_seconds());
-        }
-        UnixTimestamp::const_new(self.unix_seconds(), self.subsecond_millis().unwrap())
+    fn unix_secs(&self) -> i64;
+    fn subsec_nanos(&self) -> u32;
+
+    fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos() / 1_000_000) as u16
     }
 
-    fn date_time(&self) -> Option<DateTime<Utc>>;
+    fn unix_time(&self) -> UnixTime {
+        UnixTime::new(self.unix_secs(), self.subsec_nanos())
+    }
+
+    #[cfg(feature = "chrono")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "chrono")))]
+    fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        chrono::Utc.timestamp_opt(self.unix_secs(), self.subsec_nanos())
+    }
+
+    #[cfg(feature = "timelib")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "timelib")))]
+    fn timelib_date_time(&self) -> Result<time::OffsetDateTime, time::error::ComponentRange> {
+        Ok(time::OffsetDateTime::from_unix_timestamp(self.unix_secs())?
+            + time::Duration::nanoseconds(self.subsec_nanos().into()))
+    }
 }
 
-/// UNIX timestamp: Elapsed seconds since 1970-01-01T00:00:00+00:00.
+/// UNIX time: Elapsed non-leap seconds since 1970-01-01T00:00:00+00:00 UTC.
 ///
-/// Also can optionally include subsecond millisecond for greater accuracy. Please note that a
-/// subsecond millisecond value of 0 gets converted to [None].
+/// This is a commonly used time format and can therefore also be used as a generic format to
+/// convert other CCSDS time formats to and from. The subsecond precision is in nanoseconds
+/// similarly to other common time formats and libraries.
 #[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>,
+pub struct UnixTime {
+    secs: i64,
+    subsec_nanos: u32,
 }
 
-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 {
+impl UnixTime {
+    /// The UNIX epoch time: 1970-01-01T00:00:00+00:00 UTC.
+    pub const EPOCH: Self = Self {
+        secs: 0,
+        subsec_nanos: 0,
+    };
+
+    /// The minimum possible `UnixTime`.
+    pub const MIN: Self = Self {
+        secs: i64::MIN,
+        subsec_nanos: 0,
+    };
+
+    /// The maximum possible `UnixTime`.
+    pub const MAX: Self = Self {
+        secs: i64::MAX,
+        subsec_nanos: NANOS_PER_SECOND - 1,
+    };
+
+    /// Returns [None] if the subsecond nanosecond value is invalid (larger than fraction of a
+    /// second)
+    pub fn new_checked(unix_seconds: i64, subsec_nanos: u32) -> Option<Self> {
+        if subsec_nanos >= NANOS_PER_SECOND {
             return None;
         }
-        Some(Self::const_new(unix_seconds, subsec_millis))
+        Some(Self::new(unix_seconds, subsec_nanos))
     }
 
-    /// 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");
+    /// Returns [None] if the subsecond millisecond value is invalid (larger than fraction of a
+    /// second)
+    pub fn new_subsec_millis_checked(unix_seconds: i64, subsec_millis: u16) -> Option<Self> {
+        if subsec_millis >= 1000 {
+            return None;
+        }
+        Self::new_checked(unix_seconds, subsec_millis as u32 * 1_000_000)
+    }
+
+    /// This function will panic if the subsecond value is larger than the fraction of a second.
+    /// Use [Self::new_checked] if you want to handle this case without a panic.
+    pub const fn new(unix_seconds: i64, subsecond_nanos: u32) -> Self {
+        if subsecond_nanos >= NANOS_PER_SECOND {
+            panic!("invalid subsecond nanos value");
         }
-        let subsecond_millis = if subsec_millis == 0 {
-            None
-        } else {
-            Some(subsec_millis)
-        };
         Self {
-            unix_seconds,
-            subsecond_millis,
+            secs: unix_seconds,
+            subsec_nanos: subsecond_nanos,
         }
     }
 
-    pub fn new_only_seconds(unix_seconds: i64) -> Self {
+    /// This function will panic if the subsecond value is larger than the fraction of a second.
+    /// Use [Self::new_subsec_millis_checked] if you want to handle this case without a panic.
+    pub const fn new_subsec_millis(unix_seconds: i64, subsecond_millis: u16) -> Self {
+        if subsecond_millis >= 1000 {
+            panic!("invalid subsecond millisecond value");
+        }
         Self {
-            unix_seconds,
-            subsecond_millis: None,
+            secs: unix_seconds,
+            subsec_nanos: subsecond_millis as u32 * 1_000_000,
         }
     }
 
-    pub fn subsecond_millis(&self) -> Option<u16> {
-        self.subsecond_millis
+    pub fn new_only_secs(unix_seconds: i64) -> Self {
+        Self {
+            secs: unix_seconds,
+            subsec_nanos: 0,
+        }
+    }
+
+    #[inline]
+    pub fn subsec_millis(&self) -> u16 {
+        (self.subsec_nanos / 1_000_000) as u16
+    }
+
+    pub fn subsec_nanos(&self) -> u32 {
+        self.subsec_nanos
     }
 
     #[cfg(feature = "std")]
@@ -288,63 +355,88 @@ impl UnixTimestamp {
     pub fn from_now() -> Result<Self, SystemTimeError> {
         let now = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
         let epoch = now.as_secs();
-        Ok(Self::const_new(epoch as i64, now.subsec_millis() as u16))
+        Ok(Self::new(epoch as i64, now.subsec_nanos()))
     }
 
     #[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 unix_secs_f64(&self) -> f64 {
+        self.secs as f64 + (self.subsec_nanos as f64 / 1_000_000_000.0)
     }
 
-    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),
-        )
+    pub fn secs(&self) -> i64 {
+        self.secs
+    }
+
+    #[cfg(feature = "chrono")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "chrono")))]
+    pub fn chrono_date_time(&self) -> chrono::LocalResult<chrono::DateTime<chrono::Utc>> {
+        Utc.timestamp_opt(self.secs, self.subsec_nanos)
+    }
+
+    #[cfg(feature = "timelib")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "timelib")))]
+    pub fn timelib_date_time(&self) -> Result<time::OffsetDateTime, time::error::ComponentRange> {
+        Ok(time::OffsetDateTime::from_unix_timestamp(self.secs())?
+            + time::Duration::nanoseconds(self.subsec_nanos().into()))
+    }
+
+    // Calculate the difference in milliseconds between two UnixTimestamps
+    pub fn diff_in_millis(&self, other: &UnixTime) -> Option<i64> {
+        let seconds_difference = self.secs.checked_sub(other.secs)?;
+        // Convert seconds difference to milliseconds
+        let milliseconds_difference = seconds_difference.checked_mul(1000)?;
+
+        // Calculate the difference in subsecond milliseconds directly
+        let subsecond_difference_nanos = self.subsec_nanos as i64 - other.subsec_nanos as i64;
+
+        // Combine the differences
+        Some(milliseconds_difference + (subsecond_difference_nanos / 1_000_000))
     }
 }
 
-impl From<DateTime<Utc>> for UnixTimestamp {
-    fn from(value: DateTime<Utc>) -> Self {
-        Self::const_new(value.timestamp(), value.timestamp_subsec_millis() as u16)
+#[cfg(feature = "chrono")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "chrono")))]
+impl From<chrono::DateTime<chrono::Utc>> for UnixTime {
+    fn from(value: chrono::DateTime<chrono::Utc>) -> Self {
+        Self::new(value.timestamp(), value.timestamp_subsec_nanos())
     }
 }
 
-impl PartialOrd for UnixTimestamp {
+#[cfg(feature = "timelib")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "timelib")))]
+impl From<time::OffsetDateTime> for UnixTime {
+    fn from(value: time::OffsetDateTime) -> Self {
+        Self::new(value.unix_timestamp(), value.nanosecond())
+    }
+}
+
+impl PartialOrd for UnixTime {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
         Some(self.cmp(other))
     }
 }
 
-impl Ord for UnixTimestamp {
+impl Ord for UnixTime {
     fn cmp(&self, other: &Self) -> Ordering {
         if self == other {
             return Ordering::Equal;
         }
-        match self.unix_seconds.cmp(&other.unix_seconds) {
+        match self.secs.cmp(&other.secs) {
             Ordering::Less => return Ordering::Less,
             Ordering::Greater => return Ordering::Greater,
             _ => (),
         }
 
-        match self
-            .subsecond_millis()
-            .unwrap_or(0)
-            .cmp(&other.subsecond_millis().unwrap_or(0))
-        {
+        match self.subsec_millis().cmp(&other.subsec_millis()) {
             Ordering::Less => {
-                return if self.unix_seconds < 0 {
+                return if self.secs < 0 {
                     Ordering::Greater
                 } else {
                     Ordering::Less
                 }
             }
             Ordering::Greater => {
-                return if self.unix_seconds < 0 {
+                return if self.secs < 0 {
                     Ordering::Less
                 } else {
                     Ordering::Greater
@@ -356,13 +448,36 @@ impl Ord for UnixTimestamp {
     }
 }
 
-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;
+/// Difference between two UNIX timestamps. The [Duration] type can not contain negative durations,
+/// so the sign information is supplied separately.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct StampDiff {
+    pub positive_duration: bool,
+    pub duration_absolute: Duration,
+}
+
+impl Sub for UnixTime {
+    type Output = Option<StampDiff>;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        let difference = self.diff_in_millis(&rhs)?;
+        Some(if difference < 0 {
+            StampDiff {
+                positive_duration: false,
+                duration_absolute: Duration::from_millis(-difference as u64),
+            }
+        } else {
+            StampDiff {
+                positive_duration: true,
+                duration_absolute: Duration::from_millis(difference as u64),
+            }
+        })
+    }
+}
+
+fn get_new_stamp_after_addition(current_stamp: &UnixTime, duration: Duration) -> UnixTime {
+    let mut new_subsec_nanos = current_stamp.subsec_nanos() + duration.subsec_nanos();
+    let mut new_unix_seconds = current_stamp.secs;
     let mut increment_seconds = |value: u32| {
         if new_unix_seconds < 0 {
             new_unix_seconds = new_unix_seconds
@@ -374,8 +489,8 @@ fn get_new_stamp_after_addition(
                 .expect("new unix seconds would exceed i64::MAX");
         }
     };
-    if new_subsec_millis >= 1000 {
-        new_subsec_millis -= 1000;
+    if new_subsec_nanos >= 1_000_000_000 {
+        new_subsec_nanos -= 1_000_000_000;
         increment_seconds(1);
     }
     increment_seconds(
@@ -384,7 +499,7 @@ fn get_new_stamp_after_addition(
             .try_into()
             .expect("duration seconds exceeds u32::MAX"),
     );
-    UnixTimestamp::const_new(new_unix_seconds, new_subsec_millis)
+    UnixTime::new(new_unix_seconds, new_subsec_nanos)
 }
 
 /// Please note that this operation will panic on the following conditions:
@@ -392,7 +507,7 @@ fn get_new_stamp_after_addition(
 /// - 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 {
+impl AddAssign<Duration> for UnixTime {
     fn add_assign(&mut self, duration: Duration) {
         *self = get_new_stamp_after_addition(self, duration);
     }
@@ -403,7 +518,7 @@ impl AddAssign<Duration> for UnixTimestamp {
 /// - 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 {
+impl Add<Duration> for UnixTime {
     type Output = Self;
 
     fn add(self, duration: Duration) -> Self::Output {
@@ -411,8 +526,8 @@ impl Add<Duration> for UnixTimestamp {
     }
 }
 
-impl Add<Duration> for &UnixTimestamp {
-    type Output = UnixTimestamp;
+impl Add<Duration> for &UnixTime {
+    type Output = UnixTime;
 
     fn add(self, duration: Duration) -> Self::Output {
         get_new_stamp_after_addition(self, duration)
@@ -423,10 +538,15 @@ impl Add<Duration> for &UnixTimestamp {
 mod tests {
     use alloc::string::ToString;
     use chrono::{Datelike, Timelike};
-    use std::format;
+    use std::{format, println};
 
     use super::{cuc::CucError, *};
 
+    #[allow(dead_code)]
+    const UNIX_STAMP_CONST: UnixTime = UnixTime::new(5, 999_999_999);
+    #[allow(dead_code)]
+    const UNIX_STAMP_CONST_2: UnixTime = UnixTime::new_subsec_millis(5, 999);
+
     #[test]
     fn test_days_conversion() {
         assert_eq!(unix_to_ccsds_days(DAYS_CCSDS_TO_UNIX.into()), 0);
@@ -462,29 +582,29 @@ mod tests {
 
     #[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());
+        let stamp = UnixTime::new_only_secs(-200);
+        assert_eq!(stamp.secs, -200);
+        assert_eq!(stamp.subsec_millis(), 0);
+        let stamp = UnixTime::new_only_secs(250);
+        assert_eq!(stamp.secs, 250);
+        assert_eq!(stamp.subsec_millis(), 0);
     }
 
     #[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();
+        let stamp = UnixTime::new_subsec_millis_checked(500, 600).unwrap();
+        assert_eq!(stamp.secs, 500);
+        let subsec_millis = stamp.subsec_millis();
         assert_eq!(subsec_millis, 600);
-        assert!((500.6 - stamp.unix_seconds_f64()).abs() < 0.0001);
+        println!("{:?}", (500.6 - stamp.unix_secs_f64()).to_string());
+        assert!((500.6 - stamp.unix_secs_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);
+        let stamp0 = UnixTime::new_only_secs(5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(6);
         assert!(stamp1 > stamp0);
         assert!(stamp2 > stamp0);
         assert!(stamp2 > stamp1);
@@ -492,9 +612,9 @@ mod tests {
 
     #[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);
+        let stamp0 = UnixTime::new_only_secs(5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(6);
         assert!(stamp0 < stamp1);
         assert!(stamp0 < stamp2);
         assert!(stamp1 < stamp2);
@@ -502,9 +622,9 @@ mod tests {
 
     #[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);
+        let stamp0 = UnixTime::new_only_secs(-5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(-5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(-6);
         assert!(stamp0 > stamp1);
         assert!(stamp0 > stamp2);
         assert!(stamp1 > stamp2);
@@ -514,9 +634,9 @@ mod tests {
 
     #[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);
+        let stamp0 = UnixTime::new_only_secs(-5);
+        let stamp1 = UnixTime::new_subsec_millis_checked(-5, 500).unwrap();
+        let stamp2 = UnixTime::new_only_secs(-6);
         assert!(stamp2 < stamp1);
         assert!(stamp2 < stamp0);
         assert!(stamp1 < stamp0);
@@ -524,10 +644,11 @@ mod tests {
         assert!(stamp2 <= stamp1);
     }
 
+    #[allow(clippy::nonminimal_bool)]
     #[test]
     fn test_eq() {
-        let stamp0 = UnixTimestamp::new(5, 0).unwrap();
-        let stamp1 = UnixTimestamp::new_only_seconds(5);
+        let stamp0 = UnixTime::new(5, 0);
+        let stamp1 = UnixTime::new_only_secs(5);
         assert_eq!(stamp0, stamp1);
         assert!(stamp0 <= stamp1);
         assert!(stamp0 >= stamp1);
@@ -537,28 +658,27 @@ mod tests {
 
     #[test]
     fn test_addition() {
-        let mut stamp0 = UnixTimestamp::new_only_seconds(1);
+        let mut stamp0 = UnixTime::new_only_secs(1);
         stamp0 += Duration::from_secs(5);
-        assert_eq!(stamp0.unix_seconds, 6);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.secs(), 6);
+        assert_eq!(stamp0.subsec_millis(), 0);
         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);
+        assert_eq!(stamp1.secs, 6);
+        assert_eq!(stamp1.subsec_millis(), 500);
     }
 
     #[test]
     fn test_addition_on_ref() {
-        let stamp0 = &UnixTimestamp::new(20, 500).unwrap();
+        let stamp0 = &UnixTime::new_subsec_millis_checked(20, 500).unwrap();
         let stamp1 = stamp0 + Duration::from_millis(2500);
-        assert_eq!(stamp1.unix_seconds, 23);
-        assert!(stamp1.subsecond_millis().is_none());
+        assert_eq!(stamp1.secs, 23);
+        assert_eq!(stamp1.subsec_millis(), 0);
     }
 
     #[test]
     fn test_as_dt() {
-        let stamp = UnixTimestamp::new_only_seconds(0);
-        let dt = stamp.as_date_time().unwrap();
+        let stamp = UnixTime::new_only_secs(0);
+        let dt = stamp.chrono_date_time().unwrap();
         assert_eq!(dt.year(), 1970);
         assert_eq!(dt.month(), 1);
         assert_eq!(dt.day(), 1);
@@ -569,20 +689,55 @@ mod tests {
 
     #[test]
     fn test_from_now() {
-        let stamp_now = UnixTimestamp::from_now().unwrap();
-        let dt_now = stamp_now.as_date_time().unwrap();
+        let stamp_now = UnixTime::from_now().unwrap();
+        let dt_now = stamp_now.chrono_date_time().unwrap();
         assert!(dt_now.year() >= 2020);
     }
 
+    #[test]
+    fn test_stamp_diff_positive_0() {
+        let stamp_later = UnixTime::new(2, 0);
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_later - UnixTime::new(1, 0)).expect("stamp diff error");
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_secs(1));
+    }
+
+    #[test]
+    fn test_stamp_diff_positive_1() {
+        let stamp_later = UnixTime::new(3, 800 * 1_000_000);
+        let stamp_earlier = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_later - stamp_earlier).expect("stamp diff error");
+        assert!(positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
+    }
+
+    #[test]
+    fn test_stamp_diff_negative() {
+        let stamp_later = UnixTime::new_subsec_millis_checked(3, 800).unwrap();
+        let stamp_earlier = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
+        let StampDiff {
+            positive_duration,
+            duration_absolute,
+        } = (stamp_earlier - stamp_later).expect("stamp diff error");
+        assert!(!positive_duration);
+        assert_eq!(duration_absolute, Duration::from_millis(1900));
+    }
+
     #[test]
     fn test_addition_spillover() {
-        let mut stamp0 = UnixTimestamp::new(1, 900).unwrap();
+        let mut stamp0 = UnixTime::new_subsec_millis_checked(1, 900).unwrap();
         stamp0 += Duration::from_millis(100);
-        assert_eq!(stamp0.unix_seconds, 2);
-        assert!(stamp0.subsecond_millis().is_none());
+        assert_eq!(stamp0.secs, 2);
+        assert_eq!(stamp0.subsec_millis(), 0);
         stamp0 += Duration::from_millis(1100);
-        assert_eq!(stamp0.unix_seconds, 3);
-        assert_eq!(stamp0.subsecond_millis().unwrap(), 100);
+        assert_eq!(stamp0.secs, 3);
+        assert_eq!(stamp0.subsec_millis(), 100);
     }
 
     #[test]
@@ -591,4 +746,26 @@ mod tests {
         let stamp_error = TimestampError::from(cuc_error);
         assert_eq!(stamp_error.to_string(), format!("cuc error: {cuc_error}"));
     }
+
+    #[test]
+    #[cfg(feature = "timelib")]
+    fn test_unix_stamp_as_timelib_datetime() {
+        let stamp_epoch = UnixTime::EPOCH;
+        let timelib_dt = stamp_epoch.timelib_date_time().unwrap();
+        assert_eq!(timelib_dt.year(), 1970);
+        assert_eq!(timelib_dt.month(), time::Month::January);
+        assert_eq!(timelib_dt.day(), 1);
+        assert_eq!(timelib_dt.hour(), 0);
+        assert_eq!(timelib_dt.minute(), 0);
+        assert_eq!(timelib_dt.second(), 0);
+    }
+
+    #[test]
+    #[cfg(feature = "timelib")]
+    fn test_unix_stamp_from_timelib_datetime() {
+        let timelib_dt = time::OffsetDateTime::UNIX_EPOCH;
+        let unix_time = UnixTime::from(timelib_dt);
+        let timelib_converted_back = unix_time.timelib_date_time().unwrap();
+        assert_eq!(timelib_dt, timelib_converted_back);
+    }
 }

src/util.rs

@@ -77,6 +77,7 @@ pub trait UnsignedEnum {
     fn value(&self) -> u64;
 
     #[cfg(feature = "alloc")]
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
     fn to_vec(&self) -> alloc::vec::Vec<u8> {
         let mut buf = alloc::vec![0; self.size()];
         self.write_to_be_bytes(&mut buf).unwrap();