Add atomic insertion of transform batches

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+
+- `Registry::add_transforms`: insert a batch atomically. Any failed insertion
+  preserves the original topology and history, including samples that an
+  earlier insertion in the batch would have evicted.
+
 ## [2.2.0] - 2026-09-27
 
 ### Added

src/core/buffer/mod.rs

@@ -44,6 +44,7 @@ type NearestTransforms<'a, T> = (Option<(&'a T, &'a Isometry)>, Option<(&'a T, &
 /// than `max_age` relative to the latest inserted timestamp are removed
 /// automatically on insert. A buffer created with [`Buffer::dynamic`] never
 /// expires entries; use [`Buffer::remove_before`] for manual cleanup.
+#[derive(Clone)]
 pub(crate) struct Buffer<T = Timestamp>
 where
     T: TimePoint,
@@ -118,6 +119,7 @@ where
 /// a time series of dynamic samples. Keeping the kind structural — instead
 /// of a flag re-derived from the stored data — makes it impossible for a
 /// buffer to change kind when it is emptied and refilled.
+#[derive(Clone)]
 enum Kind<T>
 where
     T: TimePoint,

src/core/registry/mod.rs

@@ -159,6 +159,25 @@ where
         Self::process_add_transform(t, &mut self.data, self.max_age)
     }
 
+    /// Inserts a batch atomically. An invalid transform leaves the registry unchanged.
+    ///
+    /// # Errors
+    /// Returns the first error from [`Registry::add_transform`].
+    pub fn add_transforms(
+        &mut self,
+        transforms: impl IntoIterator<Item = Transform<T>>,
+    ) -> Result<(), RegistryError<T>> {
+        let mut next = Self {
+            data: self.data.clone(),
+            max_age: self.max_age,
+        };
+        for transform in transforms {
+            next.add_transform(transform)?;
+        }
+        *self = next;
+        Ok(())
+    }
+
     /// Maps `source`-frame coordinates into `target` at `timestamp`.
     ///
     /// The argument order matches tf2's `lookupTransform(target, source, time)`.

src/core/registry/tests.rs

@@ -3732,4 +3732,56 @@ mod registry_tests {
             "expected the moved frame to still be static, got {result:?}"
         );
     }
+    #[test]
+    fn a_failed_batch_does_not_leave_edges_or_evictions_behind() {
+        let mut registry = Registry::with_max_age(Duration::from_nanos(10));
+        let sample = |parent, child, ns, x| {
+            Transform::new(
+                parent,
+                child,
+                Vector3::new(x, 0.0, 0.0),
+                Quaternion::identity(),
+                Stamp::At(Timestamp::from_nanos(ns)),
+            )
+            .unwrap()
+        };
+        registry
+            .add_transform(sample("map", "base", 1, 1.0))
+            .unwrap();
+        let result = registry.add_transforms([
+            sample("map", "base", 100, 2.0),
+            sample("base", "camera", 100, 3.0),
+            sample("camera", "map", 100, 4.0),
+        ]);
+        assert!(matches!(result, Err(RegistryError::CycleDetected)));
+        assert_abs_diff_eq!(
+            registry
+                .get_transform("map", "base", Timestamp::from_nanos(1))
+                .unwrap()
+                .translation()
+                .x,
+            1.0,
+            epsilon = 1e-12
+        );
+        assert!(
+            registry
+                .get_transform("base", "camera", Timestamp::from_nanos(100))
+                .is_err()
+        );
+        registry
+            .add_transforms([
+                sample("map", "base", 2, 2.0),
+                sample("base", "camera", 2, 3.0),
+            ])
+            .unwrap();
+        assert_abs_diff_eq!(
+            registry
+                .get_transform("map", "camera", Timestamp::from_nanos(2))
+                .unwrap()
+                .translation()
+                .x,
+            5.0,
+            epsilon = 1e-12
+        );
+    }
 }