468 lines
13 KiB
Rust
468 lines
13 KiB
Rust
// Copyright 2017, 2018 Parity Technologies
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//! Reference-counted memory-based `HashDB` implementation.
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extern crate hash_db;
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extern crate parity_util_mem;
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#[cfg(test)]
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extern crate keccak_hasher;
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use hash_db::{AsHashDB, AsPlainDB, HashDB, HashDBRef, Hasher as KeyHasher, PlainDB, PlainDBRef};
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use parity_util_mem::MallocSizeOf;
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use std::{
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collections::{hash_map::Entry, HashMap},
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hash, mem,
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};
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// Backing `HashMap` parametrized with a `Hasher` for the keys `Hasher::Out` and the `Hasher::StdHasher`
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// as hash map builder.
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type FastMap<H, T> =
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HashMap<<H as KeyHasher>::Out, T, hash::BuildHasherDefault<<H as KeyHasher>::StdHasher>>;
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/// Reference-counted memory-based `HashDB` implementation.
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///
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/// Use `new()` to create a new database. Insert items with `insert()`, remove items
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/// with `remove()`, check for existence with `contains()` and lookup a hash to derive
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/// the data with `get()`. Clear with `clear()` and purge the portions of the data
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/// that have no references with `purge()`.
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///
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/// # Example
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/// ```rust
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/// extern crate hash_db;
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/// extern crate keccak_hasher;
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/// extern crate memory_db;
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///
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/// use hash_db::{Hasher, HashDB};
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/// use keccak_hasher::KeccakHasher;
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/// use memory_db::MemoryDB;
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/// fn main() {
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/// let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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/// let d = "Hello world!".as_bytes();
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///
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/// let k = m.insert(d);
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/// assert!(m.contains(&k));
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/// assert_eq!(m.get(&k).unwrap(), d);
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///
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/// m.insert(d);
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/// assert!(m.contains(&k));
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///
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/// m.remove(&k);
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/// assert!(m.contains(&k));
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///
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/// m.remove(&k);
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/// assert!(!m.contains(&k));
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///
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/// m.remove(&k);
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/// assert!(!m.contains(&k));
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///
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/// m.insert(d);
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/// assert!(!m.contains(&k));
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/// m.insert(d);
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/// assert!(m.contains(&k));
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/// assert_eq!(m.get(&k).unwrap(), d);
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///
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/// m.remove(&k);
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/// assert!(!m.contains(&k));
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/// }
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/// ```
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#[derive(Clone, PartialEq)]
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pub struct MemoryDB<H: KeyHasher, T> {
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data: FastMap<H, (T, i32)>,
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hashed_null_node: H::Out,
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null_node_data: T,
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}
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impl<'a, H, T> Default for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: From<&'a [u8]>,
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{
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fn default() -> Self {
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Self::from_null_node(&[0u8][..], [0u8][..].into())
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}
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}
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impl<H, T> MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default,
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{
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/// Remove an element and delete it from storage if reference count reaches zero.
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/// If the value was purged, return the old value.
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pub fn remove_and_purge(&mut self, key: &<H as KeyHasher>::Out) -> Option<T> {
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if key == &self.hashed_null_node {
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return None;
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}
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match self.data.entry(key.clone()) {
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Entry::Occupied(mut entry) => {
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if entry.get().1 == 1 {
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Some(entry.remove().0)
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} else {
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entry.get_mut().1 -= 1;
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None
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}
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}
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Entry::Vacant(entry) => {
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entry.insert((T::default(), -1)); // FIXME: shouldn't it be purged?
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None
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}
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}
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}
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}
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impl<'a, H: KeyHasher, T> MemoryDB<H, T>
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where
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T: From<&'a [u8]>,
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{
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/// Create a new `MemoryDB` from a given null key/data
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pub fn from_null_node(null_key: &'a [u8], null_node_data: T) -> Self {
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MemoryDB {
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data: FastMap::<H, _>::default(),
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hashed_null_node: H::hash(null_key),
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null_node_data,
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}
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}
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/// Create a new `MemoryDB` from a given null key/data
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pub fn new(data: &'a [u8]) -> Self {
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MemoryDB {
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data: FastMap::<H, _>::default(),
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hashed_null_node: H::hash(data),
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null_node_data: data.into(),
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}
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}
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/// Returns the number of elements in the map.
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pub fn len(&self) -> usize {
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self.data.len()
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}
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/// Shrinks the capacity of the map as much as possible.
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/// It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.
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pub fn shrink_to_fit(&mut self) {
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self.data.shrink_to_fit();
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}
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/// Clear all data from the database.
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///
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/// # Examples
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/// ```rust
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/// extern crate hash_db;
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/// extern crate keccak_hasher;
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/// extern crate memory_db;
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///
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/// use hash_db::{Hasher, HashDB};
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/// use keccak_hasher::KeccakHasher;
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/// use memory_db::MemoryDB;
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///
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/// fn main() {
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/// let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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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!(m.contains(&hash));
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/// m.clear();
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/// assert!(!m.contains(&hash));
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/// }
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/// ```
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pub fn clear(&mut self) {
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self.data.clear();
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}
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/// Purge all zero-referenced data from the database.
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pub fn purge(&mut self) {
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self.data.retain(|_, &mut (_, rc)| rc != 0);
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}
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/// Return the internal map of hashes to data, clearing the current state.
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pub fn drain(&mut self) -> FastMap<H, (T, i32)> {
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mem::replace(&mut self.data, FastMap::<H, _>::default())
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}
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/// Grab the raw information associated with a key. Returns None if the key
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/// doesn't exist.
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///
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/// Even when Some is returned, the data is only guaranteed to be useful
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/// when the refs > 0.
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pub fn raw(&self, key: &<H as KeyHasher>::Out) -> Option<(&T, i32)> {
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if key == &self.hashed_null_node {
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return Some((&self.null_node_data, 1));
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}
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self.data.get(key).map(|(value, count)| (value, *count))
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}
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/// Consolidate all the entries of `other` into `self`.
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pub fn consolidate(&mut self, mut other: Self) {
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for (key, (value, rc)) in other.drain() {
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match self.data.entry(key) {
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Entry::Occupied(mut entry) => {
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if entry.get().1 < 0 {
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entry.get_mut().0 = value;
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}
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entry.get_mut().1 += rc;
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}
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Entry::Vacant(entry) => {
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entry.insert((value, rc));
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}
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}
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}
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}
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/// Get the keys in the database together with number of underlying references.
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pub fn keys(&self) -> HashMap<H::Out, i32> {
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self.data
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.iter()
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.filter_map(|(k, v)| if v.1 != 0 { Some((*k, v.1)) } else { None })
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.collect()
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}
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}
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impl<H, T> MemoryDB<H, T>
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where
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H: KeyHasher,
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T: MallocSizeOf,
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{
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/// Returns the size of allocated heap memory
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pub fn mem_used(&self) -> usize {
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// TODO: figure out how to call malloc_size_of()
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//let mut ops = new_malloc_size_ops();
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//self.data.size_of(&mut ops)
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//self.data.malloc_size_of()
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0
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}
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}
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impl<H, T> PlainDB<H::Out, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn get(&self, key: &H::Out) -> Option<T> {
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match self.data.get(key) {
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Some(&(ref d, rc)) if rc > 0 => Some(d.clone()),
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_ => None,
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}
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}
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fn contains(&self, key: &H::Out) -> bool {
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match self.data.get(key) {
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Some(&(_, x)) if x > 0 => true,
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_ => false,
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}
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}
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fn emplace(&mut self, key: H::Out, value: T) {
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match self.data.entry(key) {
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Entry::Occupied(mut entry) => {
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let &mut (ref mut old_value, ref mut rc) = entry.get_mut();
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if *rc <= 0 {
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*old_value = value;
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}
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*rc += 1;
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}
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Entry::Vacant(entry) => {
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entry.insert((value, 1));
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}
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}
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}
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fn remove(&mut self, key: &H::Out) {
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match self.data.entry(*key) {
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Entry::Occupied(mut entry) => {
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let &mut (_, ref mut rc) = entry.get_mut();
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*rc -= 1;
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}
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Entry::Vacant(entry) => {
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entry.insert((T::default(), -1));
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}
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}
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}
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}
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impl<H, T> PlainDBRef<H::Out, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn get(&self, key: &H::Out) -> Option<T> {
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PlainDB::get(self, key)
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}
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fn contains(&self, key: &H::Out) -> bool {
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PlainDB::contains(self, key)
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}
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}
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impl<H, T> HashDB<H, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn get(&self, key: &H::Out) -> Option<T> {
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if key == &self.hashed_null_node {
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return Some(self.null_node_data.clone());
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}
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PlainDB::get(self, key)
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}
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fn contains(&self, key: &H::Out) -> bool {
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if key == &self.hashed_null_node {
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return true;
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}
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PlainDB::contains(self, key)
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}
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fn emplace(&mut self, key: H::Out, value: T) {
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if value == self.null_node_data {
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return;
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}
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PlainDB::emplace(self, key, value)
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}
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fn insert(&mut self, value: &[u8]) -> H::Out {
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if T::from(value) == self.null_node_data {
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return self.hashed_null_node.clone();
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}
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let key = H::hash(value);
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PlainDB::emplace(self, key.clone(), value.into());
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key
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}
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fn remove(&mut self, key: &H::Out) {
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if key == &self.hashed_null_node {
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return;
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}
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PlainDB::remove(self, key)
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}
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}
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impl<H, T> HashDBRef<H, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn get(&self, key: &H::Out) -> Option<T> {
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HashDB::get(self, key)
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}
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fn contains(&self, key: &H::Out) -> bool {
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HashDB::contains(self, key)
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}
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}
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impl<H, T> AsPlainDB<H::Out, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn as_plain_db(&self) -> &dyn PlainDB<H::Out, T> {
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self
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}
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fn as_plain_db_mut(&mut self) -> &mut dyn PlainDB<H::Out, T> {
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self
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}
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}
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impl<H, T> AsHashDB<H, T> for MemoryDB<H, T>
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where
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H: KeyHasher,
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T: Default + PartialEq<T> + for<'a> From<&'a [u8]> + Clone + Send + Sync,
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{
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fn as_hash_db(&self) -> &dyn HashDB<H, T> {
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self
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}
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fn as_hash_db_mut(&mut self) -> &mut dyn HashDB<H, T> {
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self
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}
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}
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#[cfg(test)]
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mod tests {
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use super::{HashDB, KeyHasher, MemoryDB};
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use keccak_hasher::KeccakHasher;
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#[test]
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fn memorydb_remove_and_purge() {
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let hello_bytes = b"Hello world!";
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let hello_key = KeccakHasher::hash(hello_bytes);
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let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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m.remove(&hello_key);
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assert_eq!(m.raw(&hello_key).unwrap().1, -1);
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m.purge();
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assert_eq!(m.raw(&hello_key).unwrap().1, -1);
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m.insert(hello_bytes);
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assert_eq!(m.raw(&hello_key).unwrap().1, 0);
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m.purge();
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assert_eq!(m.raw(&hello_key), None);
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let mut m = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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assert!(m.remove_and_purge(&hello_key).is_none());
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assert_eq!(m.raw(&hello_key).unwrap().1, -1);
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m.insert(hello_bytes);
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m.insert(hello_bytes);
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assert_eq!(m.raw(&hello_key).unwrap().1, 1);
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assert_eq!(&*m.remove_and_purge(&hello_key).unwrap(), hello_bytes);
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assert_eq!(m.raw(&hello_key), None);
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assert!(m.remove_and_purge(&hello_key).is_none());
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}
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#[test]
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fn consolidate() {
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let mut main = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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let mut other = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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let remove_key = other.insert(b"doggo");
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main.remove(&remove_key);
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let insert_key = other.insert(b"arf");
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main.emplace(insert_key, "arf".as_bytes().to_vec());
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let negative_remove_key = other.insert(b"negative");
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other.remove(&negative_remove_key); // ref cnt: 0
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other.remove(&negative_remove_key); // ref cnt: -1
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main.remove(&negative_remove_key); // ref cnt: -1
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main.consolidate(other);
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let overlay = main.drain();
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assert_eq!(
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overlay.get(&remove_key).unwrap(),
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&("doggo".as_bytes().to_vec(), 0)
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);
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assert_eq!(
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overlay.get(&insert_key).unwrap(),
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&("arf".as_bytes().to_vec(), 2)
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);
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assert_eq!(
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overlay.get(&negative_remove_key).unwrap(),
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&("negative".as_bytes().to_vec(), -2)
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);
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}
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#[test]
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fn default_works() {
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let mut db = MemoryDB::<KeccakHasher, Vec<u8>>::default();
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let hashed_null_node = KeccakHasher::hash(&[0u8][..]);
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assert_eq!(db.insert(&[0u8][..]), hashed_null_node);
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}
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}
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