Function block_visit 

pub fn block_visit<R: Read + Seek>(
    reader: &mut BlockReader<R>,
    logical: u64,
    follow: bool,
    traversal: Traversal,
    visitor: &mut dyn FnMut(&TreeBlock),
) -> Result<()>

Read a single block and call visitor (and optionally walk children with follow).

Errors

Returns an error if any tree block cannot be read.