Struct journaldb::overlaydb::OverlayDB

pub struct OverlayDB { /* fields omitted */ }

Implementation of the HashDB trait for a disk-backed database with a memory overlay.

The operations insert() and remove() take place on the memory overlay; batches of such operations may be flushed to the disk-backed DB with commit() or discarded with revert().

lookup() and contains() maintain normal behaviour - all insert() and remove() queries have an immediate effect in terms of these functions.

Methods

impl OverlayDB

pub fn new(backing: Arc<KeyValueDB>, col: Option<u32>) -> OverlayDB

Create a new instance of OverlayDB given a backing database.

pub fn commit_to_batch(&mut self, batch: &mut DBTransaction) -> Result<u32>

Commit all operations to given batch.

pub fn revert(&mut self)

Revert all operations on this object (i.e. insert()s and remove()s) since the last commit().

pub fn commit_refs(&self, key: &H256) -> i32

Get the number of references that would be committed.

Trait Implementations

impl AsHashDB<KeccakHasher> for OverlayDB

fn as_hashdb(&self) -> &HashDB<KeccakHasher>

Perform upcast to HashDB for anything that derives from HashDB.

fn as_hashdb_mut(&mut self) -> &mut HashDB<KeccakHasher>

Perform mutable upcast to HashDB for anything that derives from HashDB.

impl Clone for OverlayDB

fn clone(&self) -> OverlayDB

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl HashDB<KeccakHasher> for OverlayDB

fn keys(&self) -> HashMap<H256, i32>

Get the keys in the database together with number of underlying references.

fn get(&self, key: &H256) -> Option<DBValue>

Look up a given hash into the bytes that hash to it, returning None if the hash is not known.

fn contains(&self, key: &H256) -> bool

Check for the existance of a hash-key.

fn insert(&mut self, value: &[u8]) -> H256

Insert a datum item into the DB and return the datum's hash for a later lookup. Insertions are counted and the equivalent number of remove()s must be performed before the data is considered dead.

fn emplace(&mut self, key: H256, value: DBValue)

Like insert(), except you provide the key and the data is all moved.

fn remove(&mut self, key: &H256)

Remove a datum previously inserted. Insertions can be "owed" such that the same number of insert()s may happen without the data being eventually being inserted into the DB. It can be "owed" more than once.