Struct memory_db::MemoryDB

pub struct MemoryDB<H: KeyHasher, T> { /* fields omitted */ }

Reference-counted memory-based HashDB implementation.

Use new() to create a new database. Insert items with insert(), remove items with remove(), check for existence with contains() and lookup a hash to derive the data with get(). Clear with clear() and purge the portions of the data that have no references with purge().

Example

extern crate hash_db;
extern crate keccak_hasher;
extern crate memory_db;

use hash_db::*;
use keccak_hasher::KeccakHasher;
use memory_db::*;
fn main() {
  let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
  let d = "Hello world!".as_bytes();

  let k = m.insert(d);
  assert!(m.contains(&k));
  assert_eq!(m.get(&k).unwrap(), d);

  m.insert(d);
  assert!(m.contains(&k));

  m.remove(&k);
  assert!(m.contains(&k));

  m.remove(&k);
  assert!(!m.contains(&k));

  m.remove(&k);
  assert!(!m.contains(&k));

  m.insert(d);
  assert!(!m.contains(&k));
  m.insert(d);
  assert!(m.contains(&k));
  assert_eq!(m.get(&k).unwrap(), d);

  m.remove(&k);
  assert!(!m.contains(&k));
}

Methods

impl<H, T> MemoryDB<H, T> where     H: KeyHasher,     T: Default,

pub fn remove_and_purge(&mut self, key: &<H as KeyHasher>::Out) -> Option<T>

Remove an element and delete it from storage if reference count reaches zero. If the value was purged, return the old value.

impl<'a, H: KeyHasher, T> MemoryDB<H, T> where     T: From<&'a [u8]>,

pub fn from_null_node(null_key: &'a [u8], null_node_data: T) -> Self

Create a new MemoryDB from a given null key/data

pub fn new(data: &'a [u8]) -> Self

Create a new MemoryDB from a given null key/data

pub fn clear(&mut self)

Clear all data from the database.

Examples

extern crate hash_db;
extern crate keccak_hasher;
extern crate memory_db;

use hash_db::*;
use keccak_hasher::KeccakHasher;
use memory_db::*;

fn main() {
  let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
  let hello_bytes = "Hello world!".as_bytes();
  let hash = m.insert(hello_bytes);
  assert!(m.contains(&hash));
  m.clear();
  assert!(!m.contains(&hash));
}

pub fn purge(&mut self)

Purge all zero-referenced data from the database.

pub fn drain(     &mut self ) -> HashMap<<H as KeyHasher>::Out, (T, i32), BuildHasherDefault<<H as KeyHasher>::StdHasher>>

Return the internal map of hashes to data, clearing the current state.

pub fn raw(&self, key: &<H as KeyHasher>::Out) -> Option<(&T, i32)>

Grab the raw information associated with a key. Returns None if the key doesn't exist.

Even when Some is returned, the data is only guaranteed to be useful when the refs > 0.

pub fn consolidate(&mut self, other: Self)

Consolidate all the entries of other into self.

impl<H, T> MemoryDB<H, T> where     H: KeyHasher,     T: HeapSizeOf,

pub fn mem_used(&self) -> usize

Returns the size of allocated heap memory

Trait Implementations

impl<'a, H, T> Default for MemoryDB<H, T> where     H: KeyHasher,     T: From<&'a [u8]>,

fn default() -> Self

Returns the "default value" for a type.

impl<H: PartialEq + KeyHasher, T: PartialEq> PartialEq<MemoryDB<H, T>> for MemoryDB<H, T> where     H::Out: PartialEq,

fn eq(&self, other: &MemoryDB<H, T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &MemoryDB<H, T>) -> bool

This method tests for !=.

impl<H: Clone + KeyHasher, T: Clone> Clone for MemoryDB<H, T> where     H::Out: Clone,

fn clone(&self) -> MemoryDB<H, T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<H, T> HashDB<H, T> for MemoryDB<H, T> where     H: KeyHasher,     T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,

fn keys(&self) -> HashMap<H::Out, i32>

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

fn get(&self, key: &H::Out) -> Option<T>

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

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

Check for the existance of a hash-key.

fn emplace(&mut self, key: H::Out, value: T)

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

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

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 remove(&mut self, key: &H::Out)

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.

impl<H, T> AsHashDB<H, T> for MemoryDB<H, T> where     H: KeyHasher,     T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,

fn as_hash_db(&self) -> &dyn HashDB<H, T>

Perform upcast to HashDB for anything that derives from HashDB.

fn as_hash_db_mut(&mut self) -> &mut dyn HashDB<H, T>

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