Function get_last_change

atomic-repository/src/unrecord.rs:687–708

Get the hash of the last change in a view. # Arguments `txn` - Read transaction `view` - View to query # Returns The hash of the last change, or None if view is empty.

(_txn: &T, view: &ViewState)

///
/// The hash of the last change, or None if view is empty.
pub fn get_last_change<T: ViewTxnT>(_txn: &T, view: &ViewState) -> UnrecordResult<Option<Hash>> {
    if view.change_count == 0 {
        return Ok(None);
    }

    let last_seq = view.change_count - 1;
    let node_id = _txn
        .get_change_at_seq(view, last_seq)
        .map_err(|e| UnrecordError::Database(e.to_string()))?
        .ok_or_else(|| UnrecordError::Inconsistent {
            reason: format!("No change at sequence {}", last_seq),
        })?;

    let hash = _txn
        .get_external(node_id)
        .map_err(|e| UnrecordError::Database(e.to_string()))?
        .ok_or_else(|| UnrecordError::ChangeNotFound {
            hash: format!("{:?}", node_id),
        })?;

    Ok(Some(hash))
}

// Tests