Method find_block

atomic-core/src/pristine/txn/read.rs:139–198

(&self, pos: Position<NodeId>)

    }

    fn find_block(&self, pos: Position<NodeId>) -> PristineResult<GraphNode<NodeId>> {
        // Handle ROOT position specially - ROOT is a virtual span that doesn't
        // exist in the database. It represents the repository root and is the
        // parent of all top-level files and directories.
        if pos.change.is_root() {
            return Ok(GraphNode::ROOT);
        }

        let table = self.txn.open_multimap_table(GRAPH)?;

        let change_id = pos.change.get();
        let target_pos = pos.pos.get();

        let start_key = encode_vertex(change_id, 0, 0);
        let end_key = encode_vertex(change_id, u64::MAX, u64::MAX);

        // Track empty span match as fallback
        let mut empty_vertex_match: Option<GraphNode<NodeId>> = None;

        for result in table.range::<&[u8; 24]>(&start_key..=&end_key)? {
            let (key, _values) = result?;
            let (v_change, v_start, v_end) = decode_vertex(key.value());

            if v_change != change_id {
                continue;
            }

            // Check for non-empty span containing this position.
            // For edges pointing to content, we want to find the content span
            // even if there's an empty inode span at the same start position.
            // This is critical for graph traversal: an edge to position 9 should
            // find content span V[9:23], not inode span V[9:9].
            if v_start != v_end && v_start <= target_pos && target_pos < v_end {
                return Ok(GraphNode {
                    change: NodeId::new(v_change),
                    start: ChangePosition::new(v_start),
                    end: ChangePosition::new(v_end),
                });
            }

            // Track empty span at exact position as fallback
            if v_start == v_end && v_start == target_pos && empty_vertex_match.is_none() {
                empty_vertex_match = Some(GraphNode {
                    change: NodeId::new(v_change),
                    start: ChangePosition::new(v_start),
                    end: ChangePosition::new(v_end),
                });
            }
        }

        // Return empty span if no non-empty span matched
        if let Some(found) = empty_vertex_match {
            return Ok(found);
        }

        Err(PristineError::BlockNotFound {
            change: change_id,
            pos: target_pos,