Function compute_state_after_unrecord

atomic-repository/src/unrecord.rs:568–601

Compute the new Merkle state after unrecording changes. This recomputes the state by re-hashing the remaining changes. # Arguments `txn` - Read transaction `view` - View being modified `removed` - Set of change hashes being removed # Returns The new Merkle state after removal.

(
    txn: &T,
    view: &ViewState,
    removed: &HashSet<Hash>,
)

///
/// The new Merkle state after removal.
pub fn compute_state_after_unrecord<T: ViewTxnT>(
    txn: &T,
    view: &ViewState,
    removed: &HashSet<Hash>,
) -> UnrecordResult<Merkle> {
    let mut state = Merkle::ZERO;

    // Iterate through all changes and recompute state without the removed ones
    let iter = txn
        .iter_changes(view, 0)
        .map_err(|e| UnrecordError::Database(e.to_string()))?;

    for result in iter {
        let (_, change_id, _) = result.map_err(|e| UnrecordError::Database(e.to_string()))?;

        // Get external hash
        let hash = txn
            .get_external(change_id)
            .map_err(|e| UnrecordError::Database(e.to_string()))?
            .ok_or_else(|| UnrecordError::ChangeNotFound {
                hash: format!("{:?}", change_id),
            })?;

        // Skip removed changes
        if removed.contains(&hash) {
            continue;
        }

        // Update state
        state = state.next(&hash);
    }

    Ok(state)
}

/// Preview what would be unrecorded without actually doing it.
///