openethereum/src/hashdb.rs
2015-11-28 01:38:36 +01:00

83 lines
2.4 KiB
Rust

use hash::*;
use bytes::Bytes;
pub trait HashDB {
/// 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 lookup(&self, key: &H256) -> Option<&Bytes>;
/// 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 exists(&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 `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;
/// 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 kill(&mut self, key: &H256);
}