more granular error handling

CHANGELOG.md

@@ -43,6 +43,9 @@ to check all the API changes in the **Changed** chapter.
 - `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
 

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]),
     }
 }

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 {
@@ -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);
         }
     }
 

src/time/cds.rs

@@ -34,8 +34,9 @@ use core::any::Any;
 use serde::{Deserialize, Serialize};
 
 use super::{
-    ccsds_to_unix_days, unix_to_ccsds_days, CcsdsTimeCode, CcsdsTimeProvider, TimeReader,
-    TimeWriter, TimestampError, UnixTime, MS_PER_DAY, SECONDS_PER_DAY,
+    ccsds_to_unix_days, unix_to_ccsds_days, CcsdsTimeCode, CcsdsTimeProvider,
+    DateBeforeCcsdsEpochError, TimeReader, TimeWriter, TimestampError, UnixTime, MS_PER_DAY,
+    SECONDS_PER_DAY,
 };
 
 /// Base value for the preamble field for a time field parser to determine the time field type.
@@ -99,6 +100,7 @@ pub enum CdsError {
     /// There are distinct constructors depending on the days field width detected in the preamble
     /// field. This error will be returned if there is a missmatch.
     InvalidCtorForDaysOfLenInPreamble(LengthOfDaySegment),
+    DateBeforeCcsdsEpoch(DateBeforeCcsdsEpochError),
 }
 
 impl Display for CdsError {
@@ -113,12 +115,27 @@ impl Display for CdsError {
                     "wrong constructor for length of day {length_of_day:?} detected in preamble",
                 )
             }
+            CdsError::DateBeforeCcsdsEpoch(e) => write!(f, "date before CCSDS epoch: {e}"),
         }
     }
 }
 
 #[cfg(feature = "std")]
-impl Error for CdsError {}
+impl Error for CdsError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            CdsError::DateBeforeCcsdsEpoch(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
+impl From<DateBeforeCcsdsEpochError> for CdsError {
+    fn from(value: DateBeforeCcsdsEpochError) -> Self {
+        Self::DateBeforeCcsdsEpoch(value)
+    }
+}
+
 pub fn length_of_day_segment_from_pfield(pfield: u8) -> LengthOfDaySegment {
     if (pfield >> 2) & 0b1 == 1 {
         return LengthOfDaySegment::Long24Bits;
@@ -226,11 +243,11 @@ impl ConversionFromUnix {
         unix_seconds: i64,
         subsec_nanos: u32,
         precision: SubmillisPrecision,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, DateBeforeCcsdsEpochError> {
         let (unix_days, secs_of_day) = calc_unix_days_and_secs_of_day(unix_seconds);
         let ccsds_days = unix_to_ccsds_days(unix_days);
         if ccsds_days == 0 && (secs_of_day > 0 || subsec_nanos > 0) || ccsds_days < 0 {
-            return Err(TimestampError::DateBeforeCcsdsEpoch(
+            return Err(DateBeforeCcsdsEpochError(
                 UnixTime::new_checked(unix_seconds, subsec_nanos)
                     .expect("unix timestamp creation failed"),
             ));
@@ -318,19 +335,19 @@ fn calc_unix_days_and_secs_of_day(unix_seconds: i64) -> (i64, u32) {
 
 #[cfg(feature = "chrono")]
 impl ConversionFromChronoDatetime {
-    fn new(dt: &chrono::DateTime<chrono::Utc>) -> Result<Self, TimestampError> {
+    fn new(dt: &chrono::DateTime<chrono::Utc>) -> Result<Self, DateBeforeCcsdsEpochError> {
         Self::new_generic(dt, SubmillisPrecision::Absent)
     }
 
     fn new_with_submillis_us_prec(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, DateBeforeCcsdsEpochError> {
         Self::new_generic(dt, SubmillisPrecision::Microseconds)
     }
 
     fn new_with_submillis_ps_prec(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, DateBeforeCcsdsEpochError> {
         Self::new_generic(dt, SubmillisPrecision::Picoseconds)
     }
 
@@ -338,10 +355,10 @@ impl ConversionFromChronoDatetime {
     fn new_generic(
         dt: &chrono::DateTime<chrono::Utc>,
         prec: SubmillisPrecision,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, DateBeforeCcsdsEpochError> {
         // The CDS timestamp does not support timestamps before the CCSDS epoch.
         if dt.year() < 1958 {
-            return Err(TimestampError::DateBeforeCcsdsEpoch(UnixTime::from(*dt)));
+            return Err(DateBeforeCcsdsEpochError(UnixTime::from(*dt)));
         }
         // The contained values in the conversion should be all positive now
         let unix_conversion =
@@ -680,7 +697,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
     fn from_dt_generic(
         dt: &chrono::DateTime<chrono::Utc>,
         days_len: LengthOfDaySegment,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         let conv_from_dt = ConversionFromChronoDatetime::new(dt)?;
         Self::generic_from_conversion(days_len, conv_from_dt)
     }
@@ -689,7 +706,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
     fn from_dt_generic_us_prec(
         dt: &chrono::DateTime<chrono::Utc>,
         days_len: LengthOfDaySegment,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         let conv_from_dt = ConversionFromChronoDatetime::new_with_submillis_us_prec(dt)?;
         Self::generic_from_conversion(days_len, conv_from_dt)
     }
@@ -698,7 +715,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
     fn from_dt_generic_ps_prec(
         dt: &chrono::DateTime<chrono::Utc>,
         days_len: LengthOfDaySegment,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         let conv_from_dt = ConversionFromChronoDatetime::new_with_submillis_ps_prec(dt)?;
         Self::generic_from_conversion(days_len, conv_from_dt)
     }
@@ -707,7 +724,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
         unix_stamp: &UnixTime,
         days_len: LengthOfDaySegment,
         submillis_prec: SubmillisPrecision,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         let conv_from_dt =
             ConversionFromUnix::new(unix_stamp.secs, unix_stamp.subsec_nanos, submillis_prec)?;
         Self::generic_from_conversion(days_len, conv_from_dt)
@@ -717,33 +734,31 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsTime<ProvidesDaysLen> {
     fn from_now_generic(days_len: LengthOfDaySegment) -> Result<Self, StdTimestampError> {
         let conversion_from_now = ConversionFromNow::new()?;
         Self::generic_from_conversion(days_len, conversion_from_now)
-            .map_err(StdTimestampError::Timestamp)
+            .map_err(|e| StdTimestampError::Timestamp(TimestampError::from(e)))
     }
 
     #[cfg(feature = "std")]
     fn from_now_generic_us_prec(days_len: LengthOfDaySegment) -> Result<Self, StdTimestampError> {
         let conversion_from_now = ConversionFromNow::new_with_submillis_us_prec()?;
         Self::generic_from_conversion(days_len, conversion_from_now)
-            .map_err(StdTimestampError::Timestamp)
+            .map_err(|e| StdTimestampError::Timestamp(TimestampError::from(e)))
     }
 
     #[cfg(feature = "std")]
     fn from_now_generic_ps_prec(days_len: LengthOfDaySegment) -> Result<Self, StdTimestampError> {
         let conversion_from_now = ConversionFromNow::new_with_submillis_ps_prec()?;
         Self::generic_from_conversion(days_len, conversion_from_now)
-            .map_err(StdTimestampError::Timestamp)
+            .map_err(|e| StdTimestampError::Timestamp(TimestampError::from(e)))
     }
 
     fn generic_from_conversion<C: CdsConverter>(
         days_len: LengthOfDaySegment,
         converter: C,
-    ) -> Result<Self, TimestampError> {
-        let ccsds_days: ProvidesDaysLen::FieldType =
-            converter.ccsds_days_as_u32().try_into().map_err(|_| {
-                TimestampError::Cds(CdsError::InvalidCcsdsDays(
-                    converter.ccsds_days_as_u32().into(),
-                ))
-            })?;
+    ) -> Result<Self, CdsError> {
+        let ccsds_days: ProvidesDaysLen::FieldType = converter
+            .ccsds_days_as_u32()
+            .try_into()
+            .map_err(|_| CdsError::InvalidCcsdsDays(converter.ccsds_days_as_u32().into()))?;
         let mut provider = Self {
             pfield: Self::generate_p_field(days_len, converter.submillis_precision()),
             ccsds_days,
@@ -825,9 +840,7 @@ impl CdsTime<DaysLen24Bits> {
     /// [TimestampError::Cds] if the time is before the CCSDS epoch (1958-01-01T00:00:00+00:00)
     /// or the CCSDS days value exceeds the allowed bit width (24 bits).
     #[cfg(feature = "chrono")]
-    pub fn from_dt_with_u24_days(
-        dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    pub fn from_dt_with_u24_days(dt: &chrono::DateTime<chrono::Utc>) -> Result<Self, CdsError> {
         Self::from_dt_generic(dt, LengthOfDaySegment::Long24Bits)
     }
 
@@ -841,7 +854,7 @@ impl CdsTime<DaysLen24Bits> {
     pub fn from_unix_stamp_with_u24_days(
         unix_stamp: &UnixTime,
         submillis_prec: SubmillisPrecision,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_unix_generic(unix_stamp, LengthOfDaySegment::Long24Bits, submillis_prec)
     }
 
@@ -849,7 +862,7 @@ impl CdsTime<DaysLen24Bits> {
     #[cfg(feature = "chrono")]
     pub fn from_dt_with_u24_days_us_precision(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_dt_generic_us_prec(dt, LengthOfDaySegment::Long24Bits)
     }
 
@@ -857,7 +870,7 @@ impl CdsTime<DaysLen24Bits> {
     #[cfg(feature = "chrono")]
     pub fn from_dt_with_u24_days_ps_precision(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_dt_generic_ps_prec(dt, LengthOfDaySegment::Long24Bits)
     }
 
@@ -915,9 +928,7 @@ impl CdsTime<DaysLen16Bits> {
     /// [TimestampError::Cds] if the time is before the CCSDS epoch (01-01-1958 00:00:00) or
     /// the CCSDS days value exceeds the allowed bit width (16 bits).
     #[cfg(feature = "chrono")]
-    pub fn from_dt_with_u16_days(
-        dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    pub fn from_dt_with_u16_days(dt: &chrono::DateTime<chrono::Utc>) -> Result<Self, CdsError> {
         Self::from_dt_generic(dt, LengthOfDaySegment::Short16Bits)
     }
 
@@ -938,7 +949,7 @@ impl CdsTime<DaysLen16Bits> {
     pub fn from_unix_stamp_with_u16_days(
         unix_stamp: &UnixTime,
         submillis_prec: SubmillisPrecision,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_unix_generic(unix_stamp, LengthOfDaySegment::Short16Bits, submillis_prec)
     }
 
@@ -946,7 +957,7 @@ impl CdsTime<DaysLen16Bits> {
     #[cfg(feature = "chrono")]
     pub fn from_dt_with_u16_days_us_precision(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_dt_generic_us_prec(dt, LengthOfDaySegment::Short16Bits)
     }
 
@@ -954,7 +965,7 @@ impl CdsTime<DaysLen16Bits> {
     #[cfg(feature = "chrono")]
     pub fn from_dt_with_u16_days_ps_precision(
         dt: &chrono::DateTime<chrono::Utc>,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CdsError> {
         Self::from_dt_generic_ps_prec(dt, LengthOfDaySegment::Short16Bits)
     }
 
@@ -1168,7 +1179,7 @@ impl AddAssign<Duration> for CdsTime<DaysLen24Bits> {
 
 #[cfg(feature = "chrono")]
 impl TryFrom<chrono::DateTime<chrono::Utc>> for CdsTime<DaysLen16Bits> {
-    type Error = TimestampError;
+    type Error = CdsError;
 
     fn try_from(dt: chrono::DateTime<chrono::Utc>) -> Result<Self, Self::Error> {
         let conversion = ConversionFromChronoDatetime::new(&dt)?;
@@ -1178,8 +1189,7 @@ impl TryFrom<chrono::DateTime<chrono::Utc>> for CdsTime<DaysLen16Bits> {
 
 #[cfg(feature = "chrono")]
 impl TryFrom<chrono::DateTime<chrono::Utc>> for CdsTime<DaysLen24Bits> {
-    type Error = TimestampError;
-
+    type Error = CdsError;
     fn try_from(dt: chrono::DateTime<chrono::Utc>) -> Result<Self, Self::Error> {
         let conversion = ConversionFromChronoDatetime::new(&dt)?;
         Self::generic_from_conversion(LengthOfDaySegment::Long24Bits, conversion)
@@ -1991,12 +2001,12 @@ mod tests {
                 panic!("creation should not succeed")
             }
             Err(e) => {
-                if let TimestampError::Cds(CdsError::InvalidCcsdsDays(days)) = e {
+                if let CdsError::InvalidCcsdsDays(days) = e {
                     assert_eq!(
                         days,
                         unix_to_ccsds_days(invalid_unix_secs / SECONDS_PER_DAY as i64)
                     );
-                    assert_eq!(e.to_string(), "cds error: invalid ccsds days 69919");
+                    assert_eq!(e.to_string(), "invalid ccsds days 69919");
                 } else {
                     panic!("unexpected error {}", e)
                 }
@@ -2018,8 +2028,8 @@ mod tests {
                 panic!("creation should not succeed")
             }
             Err(e) => {
-                if let TimestampError::DateBeforeCcsdsEpoch(dt) = e {
-                    let dt = dt.chrono_date_time();
+                if let CdsError::DateBeforeCcsdsEpoch(DateBeforeCcsdsEpochError(unix_dt)) = e {
+                    let dt = unix_dt.chrono_date_time();
                     if let chrono::LocalResult::Single(dt) = dt {
                         assert_eq!(dt.year(), 1957);
                         assert_eq!(dt.month(), 12);
@@ -2249,7 +2259,9 @@ mod tests {
             .unwrap();
         let time_provider = CdsTime::from_dt_with_u24_days(&datetime_utc);
         assert!(time_provider.is_err());
-        if let TimestampError::DateBeforeCcsdsEpoch(dt) = time_provider.unwrap_err() {
+        if let CdsError::DateBeforeCcsdsEpoch(DateBeforeCcsdsEpochError(dt)) =
+            time_provider.unwrap_err()
+        {
             assert_eq!(dt, datetime_utc.into());
         }
     }

src/time/cuc.rs

@@ -17,7 +17,8 @@ use crate::ByteConversionError;
 use super::StdTimestampError;
 use super::{
     ccsds_epoch_to_unix_epoch, ccsds_time_code_from_p_field, unix_epoch_to_ccsds_epoch,
-    CcsdsTimeCode, CcsdsTimeProvider, TimeReader, TimeWriter, TimestampError, UnixTime,
+    CcsdsTimeCode, CcsdsTimeProvider, DateBeforeCcsdsEpochError, TimeReader, TimeWriter,
+    TimestampError, UnixTime,
 };
 #[cfg(feature = "std")]
 use std::error::Error;
@@ -116,6 +117,7 @@ pub enum CucError {
         value: u64,
     },
     LeapSecondCorrectionError,
+    DateBeforeCcsdsEpoch(DateBeforeCcsdsEpochError),
 }
 
 impl Display for CucError {
@@ -136,12 +138,28 @@ impl Display for CucError {
             CucError::LeapSecondCorrectionError => {
                 write!(f, "error while correcting for leap seconds")
             }
+            CucError::DateBeforeCcsdsEpoch(e) => {
+                write!(f, "date before ccsds epoch: {e}")
+            }
         }
     }
 }
 
 #[cfg(feature = "std")]
-impl Error for CucError {}
+impl Error for CucError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            CucError::DateBeforeCcsdsEpoch(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
+impl From<DateBeforeCcsdsEpochError> for CucError {
+    fn from(e: DateBeforeCcsdsEpochError) -> Self {
+        Self::DateBeforeCcsdsEpoch(e)
+    }
+}
 
 /// Tuple object where the first value is the width of the counter and the second value
 /// is the counter value.
@@ -398,20 +416,19 @@ impl CucTime {
         dt: &chrono::DateTime<chrono::Utc>,
         res: FractionalResolution,
         leap_seconds: u32,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CucError> {
         // Year before CCSDS epoch is invalid.
         if dt.year() < 1958 {
-            return Err(TimestampError::DateBeforeCcsdsEpoch(UnixTime::from(*dt)));
+            return Err(DateBeforeCcsdsEpochError(UnixTime::from(*dt)).into());
         }
         let counter = dt
             .timestamp()
             .checked_add(i64::from(leap_seconds))
-            .ok_or(TimestampError::Cuc(CucError::LeapSecondCorrectionError))?;
+            .ok_or(CucError::LeapSecondCorrectionError)?;
         Self::new_generic(
             WidthCounterPair(4, counter as u32),
             fractional_part_from_subsec_ns(res, dt.timestamp_subsec_nanos() as u64),
         )
-        .map_err(|e| e.into())
     }
 
     /// Generates a CUC timestamp from a UNIX timestamp with a width of 4. This width is able
@@ -420,11 +437,11 @@ impl CucTime {
         unix_stamp: &UnixTime,
         res: FractionalResolution,
         leap_seconds: u32,
-    ) -> Result<Self, TimestampError> {
+    ) -> Result<Self, CucError> {
         let counter = unix_epoch_to_ccsds_epoch(unix_stamp.secs);
         // Negative CCSDS epoch is invalid.
         if counter < 0 {
-            return Err(TimestampError::DateBeforeCcsdsEpoch(*unix_stamp));
+            return Err(DateBeforeCcsdsEpochError(*unix_stamp).into());
         }
         // We already excluded negative values, so the conversion to u64 should always work.
         let mut counter = u32::try_from(counter).map_err(|_| CucError::InvalidCounter {
@@ -433,10 +450,10 @@ impl CucTime {
         })?;
         counter = counter
             .checked_add(leap_seconds)
-            .ok_or(TimestampError::Cuc(CucError::LeapSecondCorrectionError))?;
+            .ok_or(CucError::LeapSecondCorrectionError)?;
         let fractions =
             fractional_part_from_subsec_ns(res, unix_stamp.subsec_millis() as u64 * 10_u64.pow(6));
-        Self::new_generic(WidthCounterPair(4, counter as u32), fractions).map_err(|e| e.into())
+        Self::new_generic(WidthCounterPair(4, counter as u32), fractions)
     }
 
     /// Most generic constructor which allows full configurability for the counter and for the

src/time/mod.rs

@@ -63,6 +63,19 @@ pub fn ccsds_time_code_from_p_field(pfield: u8) -> Result<CcsdsTimeCode, u8> {
     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]
@@ -71,7 +84,6 @@ pub enum TimestampError {
     ByteConversion(ByteConversionError),
     Cds(cds::CdsError),
     Cuc(cuc::CucError),
-    DateBeforeCcsdsEpoch(UnixTime),
     CustomEpochNotSupported,
 }
 
@@ -93,9 +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")
             }
@@ -114,6 +123,7 @@ impl Error for TimestampError {
         }
     }
 }
+
 impl From<cds::CdsError> for TimestampError {
     fn from(e: cds::CdsError) -> Self {
         TimestampError::Cds(e)