Method get_vertex_content

atomic-core/src/merge/engine.rs:222–244

Read the content bytes for a graph vertex from the change store. Returns an empty `Vec` for root or empty (structural) vertices.

(&self, vertex: &GraphNode<NodeId>)

    ///
    /// Returns an empty `Vec` for root or empty (structural) vertices.
    fn get_vertex_content(&self, vertex: &GraphNode<NodeId>) -> Result<Vec<u8>, PristineError> {
        if vertex.is_root() || vertex.start == vertex.end {
            return Ok(Vec::new());
        }

        let len = vertex.end.get().saturating_sub(vertex.start.get()) as usize;
        if len == 0 {
            return Ok(Vec::new());
        }

        let mut buf = vec![0u8; len];

        let txn = self.txn;
        let hash_fn = |id: NodeId| -> Option<Hash> { txn.get_external(id).ok().flatten() };

        self.changes
            .get_contents(hash_fn, *vertex, &mut buf)
            .map_err(|e| PristineError::Inconsistent {
                message: format!("ChangeStore::get_contents failed for {}: {}", vertex, e),
            })?;

        Ok(buf)
    }

    /// Walk deleted forward edges from `parent` to find a dead vertex that
    /// was deleted by both `left_change` and `right_change`.