openethereum/util/src/memorydb.rs
Gav Wood 8404edb656 Fix whitespace (#4299)
* Fix whitespace.

* Update copyright years/owner.

* Push release only for tags.
2017-01-25 18:51:41 +01:00

298 lines
7.6 KiB
Rust

// Copyright 2015-2017 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/>.
//! Reference-counted memory-based `HashDB` implementation.
use hash::*;
use rlp::*;
use sha3::*;
use hashdb::*;
use heapsize::*;
use std::mem;
use std::collections::HashMap;
use std::collections::hash_map::Entry;
/// Reference-counted memory-based `HashDB` implementation.
///
/// Use `new()` to create a new database. Insert items with `insert()`, remove items
/// with `remove()`, check for existence with `containce()` and lookup a hash to derive
/// the data with `get()`. Clear with `clear()` and purge the portions of the data
/// that have no references with `purge()`.
///
/// # Example
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let d = "Hello world!".as_bytes();
///
/// let k = m.insert(d);
/// assert!(m.contains(&k));
/// assert_eq!(m.get(&k).unwrap(), d);
///
/// m.insert(d);
/// assert!(m.contains(&k));
///
/// m.remove(&k);
/// assert!(m.contains(&k));
///
/// m.remove(&k);
/// assert!(!m.contains(&k));
///
/// m.remove(&k);
/// assert!(!m.contains(&k));
///
/// m.insert(d);
/// assert!(!m.contains(&k));
/// m.insert(d);
/// assert!(m.contains(&k));
/// assert_eq!(m.get(&k).unwrap(), d);
///
/// m.remove(&k);
/// assert!(!m.contains(&k));
/// }
/// ```
#[derive(Default, Clone, PartialEq)]
pub struct MemoryDB {
data: H256FastMap<(DBValue, i32)>,
}
impl MemoryDB {
/// Create a new instance of the memory DB.
pub fn new() -> MemoryDB {
MemoryDB {
data: H256FastMap::default(),
}
}
/// Clear all data from the database.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let hello_bytes = "Hello world!".as_bytes();
/// let hash = m.insert(hello_bytes);
/// assert!(m.contains(&hash));
/// m.clear();
/// assert!(!m.contains(&hash));
/// }
/// ```
pub fn clear(&mut self) {
self.data.clear();
}
/// Purge all zero-referenced data from the database.
pub fn purge(&mut self) {
let empties: Vec<_> = self.data.iter()
.filter(|&(_, &(_, rc))| rc == 0)
.map(|(k, _)| k.clone())
.collect();
for empty in empties { self.data.remove(&empty); }
}
/// Return the internal map of hashes to data, clearing the current state.
pub fn drain(&mut self) -> H256FastMap<(DBValue, i32)> {
mem::replace(&mut self.data, H256FastMap::default())
}
/// Grab the raw information associated with a key. Returns None if the key
/// doesn't exist.
///
/// Even when Some is returned, the data is only guaranteed to be useful
/// when the refs > 0.
pub fn raw(&self, key: &H256) -> Option<(DBValue, i32)> {
if key == &SHA3_NULL_RLP {
return Some((DBValue::from_slice(&NULL_RLP_STATIC), 1));
}
self.data.get(key).cloned()
}
/// Returns the size of allocated heap memory
pub fn mem_used(&self) -> usize {
self.data.heap_size_of_children()
}
/// Remove an element and delete it from storage if reference count reaches zero.
/// If the value was purged, return the old value.
pub fn remove_and_purge(&mut self, key: &H256) -> Option<DBValue> {
if key == &SHA3_NULL_RLP {
return None;
}
match self.data.entry(key.clone()) {
Entry::Occupied(mut entry) =>
if entry.get().1 == 1 {
Some(entry.remove().0)
} else {
entry.get_mut().1 -= 1;
None
},
Entry::Vacant(entry) => {
entry.insert((DBValue::new(), -1));
None
}
}
}
/// Consolidate all the entries of `other` into `self`.
pub fn consolidate(&mut self, mut other: Self) {
for (key, (value, rc)) in other.drain() {
match self.data.entry(key) {
Entry::Occupied(mut entry) => {
if entry.get().1 < 0 {
entry.get_mut().0 = value;
}
entry.get_mut().1 += rc;
}
Entry::Vacant(entry) => {
entry.insert((value, rc));
}
}
}
}
}
static NULL_RLP_STATIC: [u8; 1] = [0x80; 1];
impl HashDB for MemoryDB {
fn get(&self, key: &H256) -> Option<DBValue> {
if key == &SHA3_NULL_RLP {
return Some(DBValue::from_slice(&NULL_RLP_STATIC));
}
match self.data.get(key) {
Some(&(ref d, rc)) if rc > 0 => Some(d.clone()),
_ => None
}
}
fn keys(&self) -> HashMap<H256, i32> {
self.data.iter().filter_map(|(k, v)| if v.1 != 0 {Some((k.clone(), v.1))} else {None}).collect()
}
fn contains(&self, key: &H256) -> bool {
if key == &SHA3_NULL_RLP {
return true;
}
match self.data.get(key) {
Some(&(_, x)) if x > 0 => true,
_ => false
}
}
fn insert(&mut self, value: &[u8]) -> H256 {
if value == &NULL_RLP {
return SHA3_NULL_RLP.clone();
}
let key = value.sha3();
if match self.data.get_mut(&key) {
Some(&mut (ref mut old_value, ref mut rc @ -0x80000000i32 ... 0)) => {
*old_value = DBValue::from_slice(value);
*rc += 1;
false
},
Some(&mut (_, ref mut x)) => { *x += 1; false } ,
None => true,
}{ // ... None falls through into...
self.data.insert(key.clone(), (DBValue::from_slice(value), 1));
}
key
}
fn emplace(&mut self, key: H256, value: DBValue) {
if &*value == &NULL_RLP {
return;
}
match self.data.get_mut(&key) {
Some(&mut (ref mut old_value, ref mut rc @ -0x80000000i32 ... 0)) => {
*old_value = value;
*rc += 1;
return;
},
Some(&mut (_, ref mut x)) => { *x += 1; return; } ,
None => {},
}
// ... None falls through into...
self.data.insert(key, (value, 1));
}
fn remove(&mut self, key: &H256) {
if key == &SHA3_NULL_RLP {
return;
}
if match self.data.get_mut(key) {
Some(&mut (_, ref mut x)) => { *x -= 1; false }
None => true
}{ // ... None falls through into...
self.data.insert(key.clone(), (DBValue::new(), -1));
}
}
}
#[test]
fn memorydb_remove_and_purge() {
let hello_bytes = b"Hello world!";
let hello_key = hello_bytes.sha3();
let mut m = MemoryDB::new();
m.remove(&hello_key);
assert_eq!(m.raw(&hello_key).unwrap().1, -1);
m.purge();
assert_eq!(m.raw(&hello_key).unwrap().1, -1);
m.insert(hello_bytes);
assert_eq!(m.raw(&hello_key).unwrap().1, 0);
m.purge();
assert_eq!(m.raw(&hello_key), None);
let mut m = MemoryDB::new();
assert!(m.remove_and_purge(&hello_key).is_none());
assert_eq!(m.raw(&hello_key).unwrap().1, -1);
m.insert(hello_bytes);
m.insert(hello_bytes);
assert_eq!(m.raw(&hello_key).unwrap().1, 1);
assert_eq!(&*m.remove_and_purge(&hello_key).unwrap(), hello_bytes);
assert_eq!(m.raw(&hello_key), None);
assert!(m.remove_and_purge(&hello_key).is_none());
}
#[test]
fn consolidate() {
let mut main = MemoryDB::new();
let mut other = MemoryDB::new();
let remove_key = other.insert(b"doggo");
main.remove(&remove_key);
let insert_key = other.insert(b"arf");
main.emplace(insert_key, DBValue::from_slice(b"arf"));
main.consolidate(other);
let overlay = main.drain();
assert_eq!(overlay.get(&remove_key).unwrap(), &(DBValue::from_slice(b"doggo"), 0));
assert_eq!(overlay.get(&insert_key).unwrap(), &(DBValue::from_slice(b"arf"), 2));
}