openethereum/util/src/hashdb.rs

142 lines
4.3 KiB
Rust

// Copyright 2015-2017 Parity Technologies (UK) Ltd.
// This file is part of Parity.
// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity. If not, see <http://www.gnu.org/licenses/>.
//! Database of byte-slices keyed to their Keccak hash.
use hash::*;
use std::collections::HashMap;
use elastic_array::ElasticArray128;
/// `HashDB` value type.
pub type DBValue = ElasticArray128<u8>;
/// Trait modelling datastore keyed by a 32-byte Keccak hash.
pub trait HashDB: AsHashDB + Send + Sync {
/// Get the keys in the database together with number of underlying references.
fn keys(&self) -> HashMap<H256, i32>;
/// Look up a given hash into the bytes that hash to it, returning None if the
/// hash is not known.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let hello_bytes = "Hello world!".as_bytes();
/// let hash = m.insert(hello_bytes);
/// assert_eq!(m.get(&hash).unwrap(), hello_bytes);
/// }
/// ```
fn get(&self, key: &H256) -> Option<DBValue>;
/// Check for the existance of a hash-key.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::sha3::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let hello_bytes = "Hello world!".as_bytes();
/// assert!(!m.contains(&hello_bytes.sha3()));
/// let key = m.insert(hello_bytes);
/// assert!(m.contains(&key));
/// m.remove(&key);
/// assert!(!m.contains(&key));
/// }
/// ```
fn contains(&self, key: &H256) -> bool;
/// 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.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::hash::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let key = m.insert("Hello world!".as_bytes());
/// assert!(m.contains(&key));
/// }
/// ```
fn insert(&mut self, value: &[u8]) -> H256;
/// Like `insert()` , except you provide the key and the data is all moved.
fn emplace(&mut self, key: H256, value: DBValue);
/// 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.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::sha3::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let d = "Hello world!".as_bytes();
/// let key = &d.sha3();
/// m.remove(key); // OK - we now owe an insertion.
/// assert!(!m.contains(key));
/// m.remove(key); // OK - we now owe two insertions.
/// assert!(!m.contains(key));
/// m.insert(d); // OK - still owed.
/// assert!(!m.contains(key));
/// m.insert(d); // OK - now it's "empty" again.
/// assert!(!m.contains(key));
/// m.insert(d); // OK - now we've
/// assert_eq!(m.get(key).unwrap(), d);
/// }
/// ```
fn remove(&mut self, key: &H256);
}
/// Upcast trait.
pub trait AsHashDB {
/// Perform upcast to HashDB for anything that derives from HashDB.
fn as_hashdb(&self) -> &HashDB;
/// Perform mutable upcast to HashDB for anything that derives from HashDB.
fn as_hashdb_mut(&mut self) -> &mut HashDB;
}
impl<T: HashDB> AsHashDB for T {
fn as_hashdb(&self) -> &HashDB {
self
}
fn as_hashdb_mut(&mut self) -> &mut HashDB {
self
}
}
impl<'a> AsHashDB for &'a mut HashDB {
fn as_hashdb(&self) -> &HashDB {
&**self
}
fn as_hashdb_mut(&mut self) -> &mut HashDB {
&mut **self
}
}