Improve time module

CHANGELOG.md

@@ -8,6 +8,17 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
+## 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.
+
 # [v0.5.0] 2023-01-20
 
 The timestamp of `PusTm` is now optional. See Added and Changed section for details.

src/time/cds.rs

@@ -14,6 +14,7 @@ use core::any::Any;
 use core::fmt::Debug;
 use core::ops::{Add, AddAssign};
 use core::time::Duration;
+use core::cmp::Ordering;
 use delegate::delegate;
 
 /// Base value for the preamble field for a time field parser to determine the time field type.
@@ -158,7 +159,7 @@ pub fn precision_from_pfield(pfield: u8) -> SubmillisPrecision {
 /// let timestamp_in_5_minutes = timestamp_now + offset;
 /// assert_eq!(timestamp_in_5_minutes.unix_seconds(), former_unix_seconds + 5 * 60);
 /// ```
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct TimeProvider<DaysLen: ProvidesDaysLength = DaysLen16Bits> {
     pfield: u8,
@@ -459,6 +460,7 @@ impl<ProvidesDaysLen: ProvidesDaysLength> CdsCommon for TimeProvider<ProvidesDay
 }
 
 impl<ProvidesDaysLen: ProvidesDaysLength> TimeProvider<ProvidesDaysLen> {
+    /// Please note that a precision value of 0 will be converted to [None] (no precision).
     pub fn set_submillis_precision(&mut self, prec: SubmillisPrecision) {
         self.pfield &= !(0b11);
         if let SubmillisPrecision::Absent = prec {
@@ -486,6 +488,25 @@ impl<ProvidesDaysLen: ProvidesDaysLength> TimeProvider<ProvidesDaysLen> {
         self.ccsds_days
     }
 
+    /// Maps the submillisecond precision to a nanosecond value. This will reduce precision when
+    /// using picosecond resolution, but significantly simplifies comparison of timestamps.
+    pub fn precision_as_ns(&self) -> Option<u32> {
+        if let Some(prec) = self.submillis_precision {
+            match prec {
+                SubmillisPrecision::Microseconds(us) => {
+                    return Some(us as u32 * 1000);
+                }
+                SubmillisPrecision::Picoseconds(ps) => {
+                    return Some(ps / 1000);
+                }
+                _ => {
+                    return None;
+                }
+            }
+        }
+        None
+    }
+
     fn generic_raw_read_checks(
         buf: &[u8],
         days_len: LengthOfDaySegment,
@@ -1177,6 +1198,75 @@ impl TimeWriter for TimeProvider<DaysLen24Bits> {
     }
 }
 
+impl<DaysLenProvider: ProvidesDaysLength> PartialEq for TimeProvider<DaysLenProvider> {
+    fn eq(&self, other: &Self) -> bool {
+        if self.ccsds_days == other.ccsds_days
+            && self.ms_of_day == other.ms_of_day
+            && self.precision_as_ns().unwrap_or(0) == other.precision_as_ns().unwrap_or(0)
+        {
+            return true;
+        }
+        false
+    }
+}
+
+impl<DaysLenProvider: ProvidesDaysLength> PartialOrd for TimeProvider<DaysLenProvider> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if self == other {
+            return Some(Ordering::Equal);
+        }
+        match self.ccsds_days_as_u32().cmp(&other.ccsds_days_as_u32()) {
+            Ordering::Less => return Some(Ordering::Less),
+            Ordering::Greater => return Some(Ordering::Greater),
+            _ => (),
+        }
+        match self.ms_of_day().cmp(&other.ms_of_day()) {
+            Ordering::Less => return Some(Ordering::Less),
+            Ordering::Greater => return Some(Ordering::Greater),
+            _ => (),
+        }
+        match self
+            .precision_as_ns()
+            .unwrap_or(0)
+            .cmp(&other.precision_as_ns().unwrap_or(0))
+        {
+            Ordering::Less => return Some(Ordering::Less),
+            Ordering::Greater => return Some(Ordering::Greater),
+            _ => (),
+        }
+        Some(Ordering::Equal)
+    }
+}
+
+impl<DaysLenProvider: ProvidesDaysLength + Eq> Ord for TimeProvider<DaysLenProvider> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        PartialOrd::partial_cmp(self, other).unwrap()
+    }
+}
+
+impl From<TimeProvider<DaysLen16Bits>> for TimeProvider<DaysLen24Bits> {
+    fn from(value: TimeProvider<DaysLen16Bits>) -> Self {
+        // This function only fails if the days value exceeds 24 bits, which is not possible here,
+        // so it is okay to unwrap.
+        Self::new_with_u24_days(value.ccsds_days_as_u32(), value.ms_of_day()).unwrap()
+    }
+}
+
+/// This conversion can fail if the days value exceeds 16 bits.
+impl TryFrom<TimeProvider<DaysLen24Bits>> for TimeProvider<DaysLen16Bits> {
+    type Error = CdsError;
+    fn try_from(value: TimeProvider<DaysLen24Bits>) -> Result<Self, CdsError> {
+        let ccsds_days = value.ccsds_days_as_u32();
+        if ccsds_days > u16::MAX as u32 {
+            return Err(CdsError::InvalidCcsdsDays(ccsds_days as i64));
+        }
+        Ok(Self::new_with_u16_days(
+            ccsds_days as u16,
+            value.ms_of_day(),
+        ))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -2066,6 +2156,43 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_eq() {
+        let stamp0 = TimeProvider::new_with_u16_days(0, 0);
+        let mut buf: [u8; 7] = [0; 7];
+        stamp0.write_to_bytes(&mut buf).unwrap();
+        let stamp1 = TimeProvider::from_bytes_with_u16_days(&buf).unwrap();
+        assert_eq!(stamp0, stamp1);
+        assert!(!(stamp0 < stamp1));
+        assert!(!(stamp1 > stamp0));
+    }
+
+    #[test]
+    fn test_ord() {
+        let stamp0 = TimeProvider::new_with_u24_days(0, 0).unwrap();
+        let stamp1 = TimeProvider::new_with_u24_days(0, 50000).unwrap();
+        let mut stamp2 = TimeProvider::new_with_u24_days(0, 50000).unwrap();
+        stamp2.set_submillis_precision(SubmillisPrecision::Microseconds(500));
+        let stamp3 = TimeProvider::new_with_u24_days(1, 0).unwrap();
+        assert!(stamp1 > stamp0);
+        assert!(stamp2 > stamp0);
+        assert!(stamp2 > stamp1);
+        assert!(stamp3 > stamp0);
+        assert!(stamp3 > stamp1);
+        assert!(stamp3 > stamp2);
+    }
+
+    #[test]
+    fn test_conversion() {
+        let mut stamp_small = TimeProvider::new_with_u16_days(u16::MAX, 500);
+        let stamp_larger: TimeProvider<DaysLen24Bits> = stamp_small.into();
+        assert_eq!(stamp_larger.ccsds_days_as_u32(), u16::MAX as u32);
+        assert_eq!(stamp_larger.ms_of_day(), 500);
+        stamp_small = stamp_larger.try_into().unwrap();
+        assert_eq!(stamp_small.ccsds_days_as_u32(), u16::MAX as u32);
+        assert_eq!(stamp_small.ms_of_day(), 500);
+    }
+
     #[test]
     #[cfg(feature = "serde")]
     fn test_serialization() {

src/time/mod.rs

@@ -2,6 +2,7 @@
 use crate::{ByteConversionError, SizeMissmatch};
 use chrono::{DateTime, LocalResult, TimeZone, Utc};
 use core::fmt::{Display, Formatter};
+use core::cmp::Ordering;
 
 #[allow(unused_imports)]
 #[cfg(not(feature = "std"))]
@@ -232,7 +233,8 @@ pub trait CcsdsTimeProvider {
 
 /// UNIX timestamp: Elapsed seconds since 01-01-1970 00:00:00.
 ///
-/// Also can optionally include subsecond millisecond for greater accuracy.
+/// 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 {
@@ -241,24 +243,28 @@ pub struct UnixTimestamp {
 }
 
 impl UnixTimestamp {
-    /// Returns none if the subsecond millisecond value is larger than 999.
+    /// 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 {
-            unix_seconds,
-            subsecond_millis: Some(subsec_millis),
-        })
+        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: Some(subsec_millis),
+            subsecond_millis,
         }
     }
 
@@ -310,6 +316,48 @@ impl From<DateTime<Utc>> for UnixTimestamp {
     }
 }
 
+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()
+    }
+}
+
 #[cfg(all(test, feature = "std"))]
 mod tests {
     use super::*;
@@ -358,4 +406,59 @@ mod tests {
         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));
+    }
 }