Struct trie_db::triedbmut::TrieDBMut

pub struct TrieDBMut<'a, H, C> where
    H: Hasher + 'a,
    C: NodeCodec<H>,  { /* private fields */ }

A Trie implementation using a generic HashDB backing database.

Use it as a TrieMut trait object. You can use db() to get the backing database object. Note that changes are not committed to the database until commit is called. Querying the root or dropping the trie will commit automatically.

Example

extern crate trie_db;
extern crate reference_trie;
extern crate hash_db;
extern crate keccak_hasher;
extern crate memory_db;

use hash_db::Hasher;
use reference_trie::{RefTrieDBMut, TrieMut};
use trie_db::DBValue;
use keccak_hasher::KeccakHasher;
use memory_db::*;

fn main() {
  let mut memdb = MemoryDB::default();
  let mut root = Default::default();
  let mut t = RefTrieDBMut::new(&mut memdb, &mut root);
  assert!(t.is_empty());
  assert_eq!(*t.root(), KeccakHasher::hash(&[0u8][..]));
  t.insert(b"foo", b"bar").unwrap();
  assert!(t.contains(b"foo").unwrap());
  assert_eq!(t.get(b"foo").unwrap().unwrap(), DBValue::from_slice(b"bar"));
  t.remove(b"foo").unwrap();
  assert!(!t.contains(b"foo").unwrap());
}

Implementations

impl<'a, H, C> TrieDBMut<'a, H, C> where
    H: Hasher,
    C: NodeCodec<H>, 

pub fn new(db: &'a mut dyn HashDB<H, DBValue>, root: &'a mut H::Out) -> Self

Create a new trie with backing database db and empty root.

pub fn from_existing(
    db: &'a mut dyn HashDB<H, DBValue>,
    root: &'a mut H::Out
) -> Result<Self, H::Out, C::Error>

Create a new trie with the backing database db and root. Returns an error if root` does not exist.

pub fn db(&self) -> &dyn HashDB<H, DBValue>

Get the backing database.

pub fn db_mut(&mut self) -> &mut dyn HashDB<H, DBValue>

Get the backing database mutably.

pub fn commit(&mut self)

Commit the in-memory changes to disk, freeing their storage and updating the state root.

Trait Implementations

impl<'a, H, C> Drop for TrieDBMut<'a, H, C> where
    H: Hasher,
    C: NodeCodec<H>, 

fn drop(&mut self)

Executes the destructor for this type.

impl<'a, H, C> TrieMut<H, C> for TrieDBMut<'a, H, C> where
    H: Hasher,
    C: NodeCodec<H>, 

fn root(&mut self) -> &H::Out

Return the root of the trie.

fn is_empty(&self) -> bool

Is the trie empty?

fn get<'x, 'key>(
    &'x self,
    key: &'key [u8]
) -> Result<Option<DBValue>, H::Out, C::Error> where
    'x: 'key, 

What is the value of the given key in this trie?

fn insert(
    &mut self,
    key: &[u8],
    value: &[u8]
) -> Result<Option<DBValue>, H::Out, C::Error>

Insert a key/value pair into the trie. An empty value is equivalent to removing key from the trie. Returns the old value associated with this key, if it existed.

fn remove(&mut self, key: &[u8]) -> Result<Option<DBValue>, H::Out, C::Error>

Remove a key from the trie. Equivalent to making it equal to the empty value. Returns the old value associated with this key, if it existed.

fn contains(&self, key: &[u8]) -> Result<bool, H::Out, C::Error>

Does the trie contain a given key?