instant to ntp timestamp

crates/rist-rs-bits/src/rtcp/mod.rs

@@ -297,7 +297,7 @@ impl<'a> Iterator for RTCPPacketViewIterator<'a> {
 mod test {
     use core::ops::Sub;
 
-    use rist_rs_types::traits::time::clock::StdSystemClock;
+    use rist_rs_types::{time::ntp, traits::time::clock::StdSystemClock};
 
     use super::RTCPPacketView;
     use crate::rtcp::RTCPPacketViewIterator;

crates/rist-rs-types/src/time/ntp.rs

@@ -1,7 +1,7 @@
 use core::fmt::Display;
 use std::{ops::Add, time::Duration};
 
-use crate::traits::time::clock::Clock;
+use crate::traits::time::clock::{Clock, TimePoint};
 
 #[derive(Debug, Clone, Copy)]
 pub struct Timestamp {
@@ -17,12 +17,20 @@ impl Display for Timestamp {
 
 impl Timestamp {
     const FRAC: f64 = std::u32::MAX as f64;
-    const EPOCH_DELTA: u64 = 2_208_988_800;
 
     pub fn new(sec: u32, frac: u32) -> Timestamp {
         Timestamp { sec, frac }
     }
 
+    pub fn from_time_point<C: Clock>(
+        tp: C::TimePoint,
+    ) -> Result<Timestamp, <C::TimePoint as TimePoint>::Error> {
+        let ep = tp.duration_since(C::epoch())?;
+        let ns = (ep.subsec_nanos() as f64 * Self::FRAC * 1.0e-9) as u32;
+        let s = (ep.as_secs() as i64 + C::ntp_epoch_offset()) as u32;
+        Ok(Self::new(s, ns))
+    }
+
     pub fn seconds(&self) -> u32 {
         self.sec
     }
@@ -45,7 +53,7 @@ impl Timestamp {
 
     pub fn to_instant<C: Clock>(&self) -> C::TimePoint {
         C::epoch().add(Duration::new(
-            self.sec as u64 - Self::EPOCH_DELTA,
+            (self.sec as i64 - C::ntp_epoch_offset()) as u64,
             self.frac_ns() as u32,
         ))
     }

crates/rist-rs-types/src/traits/time/clock/mod.rs

@@ -64,7 +64,11 @@ pub trait Clock: Clone + Send + 'static {
     /// Returns true if the clocks time is monotonically increasing
     fn is_monotonic(&self) -> bool;
 
+    // This clocks epoch as a point in time
     fn epoch() -> Self::TimePoint;
+
+    // Offset of this clocks epoch to the NTP epoch in seconds
+    fn ntp_epoch_offset() -> i64;
 }
 
 cfg_std! {
@@ -94,6 +98,10 @@ cfg_std! {
         fn epoch() -> Self::TimePoint {
             std::time::UNIX_EPOCH
         }
+
+        fn ntp_epoch_offset() -> i64 {
+            2208988800
+        }
     }
 
     impl TimePoint for SystemTime {