107 lines
3.2 KiB
Rust
107 lines
3.2 KiB
Rust
// Copyright 2015-2019 Parity Technologies (UK) Ltd.
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// This file is part of Parity Ethereum.
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// Parity Ethereum 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 Ethereum 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 Ethereum. If not, see <http://www.gnu.org/licenses/>.
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//! Database cache manager
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use std::{
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collections::{HashSet, VecDeque},
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hash::Hash,
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};
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const COLLECTION_QUEUE_SIZE: usize = 8;
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/// DB cache manager
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pub struct CacheManager<T> {
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pref_cache_size: usize,
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max_cache_size: usize,
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bytes_per_cache_entry: usize,
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cache_usage: VecDeque<HashSet<T>>,
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}
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impl<T> CacheManager<T>
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where
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T: Eq + Hash,
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{
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/// Create new cache manager with preferred (heap) sizes.
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pub fn new(
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pref_cache_size: usize,
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max_cache_size: usize,
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bytes_per_cache_entry: usize,
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) -> Self {
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CacheManager {
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pref_cache_size: pref_cache_size,
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max_cache_size: max_cache_size,
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bytes_per_cache_entry: bytes_per_cache_entry,
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cache_usage: (0..COLLECTION_QUEUE_SIZE)
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.into_iter()
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.map(|_| Default::default())
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.collect(),
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}
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}
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/// Mark element as used.
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pub fn note_used(&mut self, id: T) {
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if !self.cache_usage[0].contains(&id) {
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if let Some(c) = self
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.cache_usage
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.iter_mut()
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.skip(1)
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.find(|e| e.contains(&id))
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{
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c.remove(&id);
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}
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self.cache_usage[0].insert(id);
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}
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}
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/// Collects unused objects from cache.
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/// First params is the current size of the cache.
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/// Second one is an with objects to remove. It should also return new size of the cache.
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pub fn collect_garbage<F>(&mut self, current_size: usize, mut notify_unused: F)
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where
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F: FnMut(HashSet<T>) -> usize,
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{
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if current_size < self.pref_cache_size {
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self.rotate_cache_if_needed();
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return;
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}
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for _ in 0..COLLECTION_QUEUE_SIZE {
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if let Some(back) = self.cache_usage.pop_back() {
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let current_size = notify_unused(back);
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self.cache_usage.push_front(Default::default());
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if current_size < self.max_cache_size {
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break;
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}
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}
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}
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}
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fn rotate_cache_if_needed(&mut self) {
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if self.cache_usage.is_empty() {
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return;
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}
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if self.cache_usage[0].len() * self.bytes_per_cache_entry
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> self.pref_cache_size / COLLECTION_QUEUE_SIZE
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{
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if let Some(cache) = self.cache_usage.pop_back() {
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self.cache_usage.push_front(cache);
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}
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}
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}
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}
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