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