Add 'hashdb/' from commit '8b968c0609746cc2369966cd02f21fe298d51b03'
git-subtree-dir: hashdb git-subtree-mainline:652774a6d7
git-subtree-split:8b968c0609
This commit is contained in:
commit
ed4aa8c4c6
|
@ -0,0 +1,10 @@
|
||||||
|
[package]
|
||||||
|
name = "hashdb"
|
||||||
|
version = "0.2.0"
|
||||||
|
authors = ["Parity Technologies <admin@parity.io>"]
|
||||||
|
description = "trait for hash-keyed databases."
|
||||||
|
license = "GPL-3.0"
|
||||||
|
|
||||||
|
[dependencies]
|
||||||
|
elastic-array = "0.10"
|
||||||
|
heapsize = "0.4"
|
|
@ -0,0 +1,83 @@
|
||||||
|
// Copyright 2015-2018 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 hash.
|
||||||
|
extern crate elastic_array;
|
||||||
|
extern crate heapsize;
|
||||||
|
|
||||||
|
use elastic_array::ElasticArray128;
|
||||||
|
use heapsize::HeapSizeOf;
|
||||||
|
use std::collections::HashMap;
|
||||||
|
use std::{fmt::Debug, hash::Hash};
|
||||||
|
|
||||||
|
/// Trait describing an object that can hash a slice of bytes. Used to abstract
|
||||||
|
/// other types over the hashing algorithm. Defines a single `hash` method and an
|
||||||
|
/// `Out` associated type with the necessary bounds.
|
||||||
|
pub trait Hasher: Sync + Send {
|
||||||
|
/// The output type of the `Hasher`
|
||||||
|
type Out: AsRef<[u8]> + AsMut<[u8]> + Default + HeapSizeOf + Debug + PartialEq + Eq + Hash + Send + Sync + Clone + Copy;
|
||||||
|
/// What to use to build `HashMap`s with this `Hasher`
|
||||||
|
type StdHasher: Sync + Send + Default + std::hash::Hasher;
|
||||||
|
/// The length in bytes of the `Hasher` output
|
||||||
|
const LENGTH: usize;
|
||||||
|
|
||||||
|
/// Compute the hash of the provided slice of bytes returning the `Out` type of the `Hasher`
|
||||||
|
fn hash(x: &[u8]) -> Self::Out;
|
||||||
|
}
|
||||||
|
|
||||||
|
/// `HashDB` value type.
|
||||||
|
pub type DBValue = ElasticArray128<u8>;
|
||||||
|
|
||||||
|
/// Trait modelling datastore keyed by a hash defined by the `Hasher`.
|
||||||
|
pub trait HashDB<H: Hasher>: Send + Sync + AsHashDB<H> {
|
||||||
|
/// Get the keys in the database together with number of underlying references.
|
||||||
|
fn keys(&self) -> HashMap<H::Out, i32>;
|
||||||
|
|
||||||
|
/// Look up a given hash into the bytes that hash to it, returning None if the
|
||||||
|
/// hash is not known.
|
||||||
|
fn get(&self, key: &H::Out) -> Option<DBValue>;
|
||||||
|
|
||||||
|
/// Check for the existance of a hash-key.
|
||||||
|
fn contains(&self, key: &H::Out) -> 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.
|
||||||
|
fn insert(&mut self, value: &[u8]) -> H::Out;
|
||||||
|
|
||||||
|
/// Like `insert()`, except you provide the key and the data is all moved.
|
||||||
|
fn emplace(&mut self, key: H::Out, 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.
|
||||||
|
fn remove(&mut self, key: &H::Out);
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Upcast trait.
|
||||||
|
pub trait AsHashDB<H: Hasher> {
|
||||||
|
/// Perform upcast to HashDB for anything that derives from HashDB.
|
||||||
|
fn as_hashdb(&self) -> &HashDB<H>;
|
||||||
|
/// Perform mutable upcast to HashDB for anything that derives from HashDB.
|
||||||
|
fn as_hashdb_mut(&mut self) -> &mut HashDB<H>;
|
||||||
|
}
|
||||||
|
|
||||||
|
// NOTE: There used to be a `impl<T> AsHashDB for T` but that does not work with generics. See https://stackoverflow.com/questions/48432842/implementing-a-trait-for-reference-and-non-reference-types-causes-conflicting-im
|
||||||
|
// This means we need concrete impls of AsHashDB in several places, which somewhat defeats the point of the trait.
|
||||||
|
impl<'a, H: Hasher> AsHashDB<H> for &'a mut HashDB<H> {
|
||||||
|
fn as_hashdb(&self) -> &HashDB<H> { &**self }
|
||||||
|
fn as_hashdb_mut(&mut self) -> &mut HashDB<H> { &mut **self }
|
||||||
|
}
|
||||||
|
|
Loading…
Reference in New Issue