daf truncation bugs

anise/src/naif/daf/daf.rs

@@ -500,7 +500,6 @@ impl<R: NAIFSummaryRecord> DAF<R> {
     }
 
     /// Writes the contents of this DAF file to a new location.
-    /// WARNING: BUGGY! https://github.com/nyx-space/anise/issues/262
     pub fn persist<P: AsRef<Path>>(&self, path: P) -> IoResult<()> {
         let mut fs = File::create(path)?;
 
@@ -525,7 +524,8 @@ impl<R: NAIFSummaryRecord> DAF<R> {
         name_rcrd.extend(vec![0x0; RCRD_LEN - name_rcrd.len()]);
         fs.write_all(&name_rcrd)?;
 
-        fs.write_all(&self.bytes[self.file_record().unwrap().fwrd_idx() * (2 * RCRD_LEN)..])
+        // Data starts right after the summary and name records in self.bytes
+        fs.write_all(&self.bytes[(self.file_record().unwrap().fwrd_idx() + 1) * RCRD_LEN..])
     }
 
     /// Returns an iterator over all summary data blocks.

anise/src/naif/daf/datatypes/chebyshev.rs

@@ -206,14 +206,18 @@ impl<'a> NAIFDataSet<'a> for Type2ChebyshevSet<'a> {
         };
 
         let end_idx = if let Some(end) = new_end {
-            self.spline_idx(end, summary)?
+            self.spline_idx(end, summary)? - 1
         } else {
             self.num_records - 1
         };
 
         self.record_data = &self.record_data[start_idx * self.rsize..(end_idx + 1) * self.rsize];
-        self.num_records = (self.record_data.len() / self.rsize) - 1;
-        self.init_epoch = self.nth_record(0).unwrap().midpoint_epoch() - 0.5 * self.interval_length;
+        self.num_records = self.record_data.len() / self.rsize;
+        self.init_epoch = self
+            .nth_record(0)
+            .context(InterpDecodingSnafu)?
+            .midpoint_epoch()
+            - 0.5 * self.interval_length;
 
         Ok(self)
     }

anise/src/naif/daf/datatypes/chebyshev3.rs

@@ -211,14 +211,18 @@ impl<'a> NAIFDataSet<'a> for Type3ChebyshevSet<'a> {
         };
 
         let end_idx = if let Some(end) = new_end {
-            self.spline_idx(end, summary)?
+            self.spline_idx(end, summary)? - 1
         } else {
             self.num_records - 1
         };
 
         self.record_data = &self.record_data[start_idx * self.rsize..(end_idx + 1) * self.rsize];
-        self.num_records = (self.record_data.len() / self.rsize) - 1;
-        self.init_epoch = self.nth_record(0).unwrap().midpoint_epoch() - 0.5 * self.interval_length;
+        self.num_records = self.record_data.len() / self.rsize;
+        self.init_epoch = self
+            .nth_record(0)
+            .context(InterpDecodingSnafu)?
+            .midpoint_epoch()
+            - 0.5 * self.interval_length;
 
         Ok(self)
     }

anise/tests/naif.rs

@@ -11,7 +11,7 @@
 use std::mem::size_of_val;
 
 use anise::{
-    constants::frames::EARTH_ITRF93,
+    constants::frames::{EARTH_ITRF93, EARTH_MOON_BARYCENTER_J2000, MOON_J2000},
     file2heap,
     math::rotation::Quaternion,
     naif::{
@@ -253,6 +253,17 @@ fn test_spk_truncate_cheby() {
     let summary = reloaded.data_summaries(None).unwrap()[idx];
     assert_eq!(summary.start_epoch(), new_start);
 
+    // Verify the persisted file has valid, queryable ephemeris data.
+    let almanac = Almanac::default().with_spk(reloaded);
+    let query_epoch = new_start + Unit::Day * 1;
+    let state = almanac
+        .translate_geometric(MOON_J2000, EARTH_MOON_BARYCENTER_J2000, query_epoch)
+        .unwrap();
+    assert!(
+        state.radius_km.norm() > 0.0,
+        "expected non-zero position from truncated+persisted BSP"
+    );
+
     // Test that we can remove segments all togethet
     let mut my_spk_rm = my_spk.clone();
     assert!(my_spk_rm.delete_nth_data(idx).is_ok());