openethereum/util/src/hashdb.rs

98 lines
3.1 KiB
Rust

//! Database of byte-slices keyed to their Keccak hash.
use hash::*;
use bytes::*;
use std::collections::HashMap;
/// Trait modelling datastore keyed by a 32-byte Keccak hash.
pub trait HashDB {
/// Get the keys in the database together with number of underlying references.
fn keys(&self) -> HashMap<H256, i32>;
/// Deprecated. use `get`.
fn lookup(&self, key: &H256) -> Option<&[u8]>; // TODO: rename to get.
/// 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.lookup(&hash).unwrap(), hello_bytes);
/// }
/// ```
fn get(&self, key: &H256) -> Option<&[u8]> { self.lookup(key) }
/// Deprecated. Use `contains`.
fn exists(&self, key: &H256) -> bool; // TODO: rename to contains.
/// 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.exists(&hello_bytes.sha3()));
/// let key = m.insert(hello_bytes);
/// assert!(m.exists(&key));
/// m.kill(&key);
/// assert!(!m.exists(&key));
/// }
/// ```
fn contains(&self, key: &H256) -> bool { self.exists(key) }
/// 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 `kill()`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.exists(&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: Bytes);
/// Deprecated - use `remove`.
fn kill(&mut self, key: &H256); // TODO: rename to remove.
/// 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.
///
/// # 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.kill(key); // OK - we now owe an insertion.
/// assert!(!m.exists(key));
/// m.insert(d); // OK - now it's "empty" again.
/// assert!(!m.exists(key));
/// m.insert(d); // OK - now we've
/// assert_eq!(m.lookup(key).unwrap(), d);
/// }
/// ```
fn remove(&mut self, key: &H256) { self.kill(key) }
}