openethereum/ethcore/src/db.rs

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// Copyright 2015, 2016 Ethcore (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/>.
//! Extras db utils.
use std::ops::Deref;
use std::hash::Hash;
use std::collections::HashMap;
use util::{DBTransaction, Database, RwLock};
use util::rlp::{encode, Encodable, decode, Decodable};
#[derive(Clone, Copy)]
pub enum CacheUpdatePolicy {
Overwrite,
Remove,
}
pub trait Cache<K, V> {
fn insert(&mut self, k: K, v: V) -> Option<V>;
fn remove(&mut self, k: &K) -> Option<V>;
fn get(&self, k: &K) -> Option<&V>;
}
impl<K, V> Cache<K, V> for HashMap<K, V> where K: Hash + Eq {
fn insert(&mut self, k: K, v: V) -> Option<V> {
HashMap::insert(self, k, v)
}
fn remove(&mut self, k: &K) -> Option<V> {
HashMap::remove(self, k)
}
fn get(&self, k: &K) -> Option<&V> {
HashMap::get(self, k)
}
}
/// Should be used to get database key associated with given value.
pub trait Key<T> {
type Target: Deref<Target = [u8]>;
/// Returns db key.
fn key(&self) -> Self::Target;
}
/// Should be used to write value into database.
pub trait Writable {
/// Writes the value into the database.
fn write<T, R>(&self, key: &Key<T, Target = R>, value: &T) where T: Encodable, R: Deref<Target = [u8]>;
/// Writes the value into the database and updates the cache.
fn write_with_cache<K, T, R>(&self, cache: &mut Cache<K, T>, key: K, value: T, policy: CacheUpdatePolicy) where
K: Key<T, Target = R> + Hash + Eq,
T: Encodable,
R: Deref<Target = [u8]> {
self.write(&key, &value);
match policy {
CacheUpdatePolicy::Overwrite => {
cache.insert(key, value);
},
CacheUpdatePolicy::Remove => {
cache.remove(&key);
}
}
}
/// Writes the values into the database and updates the cache.
fn extend_with_cache<K, T, R>(&self, cache: &mut Cache<K, T>, values: HashMap<K, T>, policy: CacheUpdatePolicy) where
K: Key<T, Target = R> + Hash + Eq,
T: Encodable,
R: Deref<Target = [u8]> {
match policy {
CacheUpdatePolicy::Overwrite => {
for (key, value) in values.into_iter() {
self.write(&key, &value);
cache.insert(key, value);
}
},
CacheUpdatePolicy::Remove => {
for (key, value) in &values {
self.write(key, value);
cache.remove(key);
}
},
}
}
}
/// Should be used to read values from database.
pub trait Readable {
/// Returns value for given key.
fn read<T, R>(&self, key: &Key<T, Target = R>) -> Option<T> where
T: Decodable,
R: Deref<Target = [u8]>;
/// Returns value for given key either in cache or in database.
fn read_with_cache<K, T, C>(&self, cache: &RwLock<C>, key: &K) -> Option<T> where
K: Key<T> + Eq + Hash + Clone,
T: Clone + Decodable,
C: Cache<K, T> {
{
let read = cache.read();
if let Some(v) = read.get(key) {
return Some(v.clone());
}
}
self.read(key).map(|value: T|{
let mut write = cache.write();
write.insert(key.clone(), value.clone());
value
})
}
/// Returns true if given value exists.
fn exists<T, R>(&self, key: &Key<T, Target = R>) -> bool where R: Deref<Target= [u8]>;
/// Returns true if given value exists either in cache or in database.
fn exists_with_cache<K, T, R, C>(&self, cache: &RwLock<C>, key: &K) -> bool where
K: Eq + Hash + Key<T, Target = R>,
R: Deref<Target = [u8]>,
C: Cache<K, T> {
{
let read = cache.read();
if read.get(key).is_some() {
return true;
}
}
self.exists::<T, R>(key)
}
}
impl Writable for DBTransaction {
fn write<T, R>(&self, key: &Key<T, Target = R>, value: &T) where T: Encodable, R: Deref<Target = [u8]> {
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let result = self.put(&key.key(), &encode(value));
if let Err(err) = result {
panic!("db put failed, key: {:?}, err: {:?}", &key.key() as &[u8], err);
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}
}
}
impl Readable for Database {
fn read<T, R>(&self, key: &Key<T, Target = R>) -> Option<T> where T: Decodable, R: Deref<Target = [u8]> {
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let result = self.get(&key.key());
match result {
Ok(option) => option.map(|v| decode(&v)),
Err(err) => {
panic!("db get failed, key: {:?}, err: {:?}", &key.key() as &[u8], err);
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}
}
}
fn exists<T, R>(&self, key: &Key<T, Target = R>) -> bool where R: Deref<Target = [u8]> {
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let result = self.get(&key.key());
match result {
Ok(v) => v.is_some(),
Err(err) => {
panic!("db get failed, key: {:?}, err: {:?}", &key.key() as &[u8], err);
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}
}
}
}