// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! In-memory implementation of `Database`
use crate::{error, Change, ColumnId, Database, Transaction};
use parking_lot::RwLock;
use std::collections::{hash_map::Entry, HashMap};
#[derive(Default)]
/// This implements `Database` as an in-memory hash map. `commit` is not atomic.
pub struct MemDb(RwLock<HashMap<ColumnId, HashMap<Vec<u8>, (u32, Vec<u8>)>>>);
impl<H> Database<H> for MemDb
where
H: Clone + AsRef<[u8]>,
{
fn commit(&self, transaction: Transaction<H>) -> error::Result<()> {
let mut s = self.0.write();
for change in transaction.0.into_iter() {
match change {
Change::Set(col, key, value) => {
s.entry(col).or_default().insert(key, (1, value));
},
Change::Remove(col, key) => {
s.entry(col).or_default().remove(&key);
},
Change::Store(col, hash, value) => {
s.entry(col)
.or_default()
.entry(hash.as_ref().to_vec())
.and_modify(|(c, _)| *c += 1)
.or_insert_with(|| (1, value));
},
Change::Reference(col, hash) => {
if let Entry::Occupied(mut entry) =
s.entry(col).or_default().entry(hash.as_ref().to_vec())
{
entry.get_mut().0 += 1;
}
},
Change::Release(col, hash) => {
if let Entry::Occupied(mut entry) =
s.entry(col).or_default().entry(hash.as_ref().to_vec())
{
entry.get_mut().0 -= 1;
if entry.get().0 == 0 {
entry.remove();
}
}
},
}
}
Ok(())
}
fn get(&self, col: ColumnId, key: &[u8]) -> Option<Vec<u8>> {
let s = self.0.read();
s.get(&col).and_then(|c| c.get(key).map(|(_, v)| v.clone()))
}
}
impl MemDb {
/// Create a new instance
pub fn new() -> Self {
MemDb::default()
}
/// Count number of values in a column
pub fn count(&self, col: ColumnId) -> usize {
let s = self.0.read();
s.get(&col).map(|c| c.len()).unwrap_or(0)
}
}