forest: clone correctly

Now the forest can detect if a node is packed or cloned, and correctly
clones a node in those circumstances.  But it still needs to be
tested.

2 files changed, 19 insertions, 0 deletions

diff --git a/graph/src/builder.rs b/graph/src/builder.rs
index b04e7f6..c5f9252 100644
--- a/graph/src/builder.rs
+++ b/graph/src/builder.rs
@@ -82,6 +82,9 @@ pub trait BuilderMut {
     /// Add an edge from the source to the target.
     fn add_edge(&mut self, source: usize, target: usize, label: Self::Label) -> Result<(), Error>;
 
+    /// Set the label of an existing node to a new label.
+    fn set_label(&mut self, node_id: usize, label: Self::Label) -> Result<(), Error>;
+
     /// Remove an edge from the source to the target.
     ///
     /// Since some graphs are labelled, the users are allowed to pass
diff --git a/graph/src/labelled/binary.rs b/graph/src/labelled/binary.rs
index e3e1943..201dda2 100644
--- a/graph/src/labelled/binary.rs
+++ b/graph/src/labelled/binary.rs
@@ -551,6 +551,22 @@ impl<'a, T: GraphLabel> BuilderMut for PLGBuilderMut<'a, T> {
 
         Ok(())
     }
+
+    #[inline]
+    fn set_label(&mut self, node_id: usize, label: Self::Label) -> Result<(), Error> {
+        if !self.graph.has_node(node_id) {
+            return Err(Error::IndexOutOfBounds(node_id, self.nodes_len()));
+        }
+
+        // node_id is now guaranteed to be valid.
+
+        self.graph.nodes.get_mut(node_id).unwrap().label = label;
+
+        self.graph.label_index_map.remove(&label);
+        self.graph.label_index_map.insert(label, node_id);
+
+        Ok(())
+    }
 }
 
 #[cfg(test)]