openethereum/util/src/overlaydb.rs

308 lines
9.6 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/>.
//! Disk-backed `HashDB` implementation.
use std::sync::Arc;
use std::collections::HashMap;
use std::collections::hash_map::Entry;
use error::{Result, BaseDataError};
use bigint::hash::*;
use rlp::*;
use hashdb::*;
use memorydb::*;
use kvdb::{KeyValueDB, DBTransaction};
/// Implementation of the `HashDB` trait for a disk-backed database with a memory overlay.
///
/// The operations `insert()` and `remove()` take place on the memory overlay; batches of
/// such operations may be flushed to the disk-backed DB with `commit()` or discarded with
/// `revert()`.
///
/// `lookup()` and `contains()` maintain normal behaviour - all `insert()` and `remove()`
/// queries have an immediate effect in terms of these functions.
#[derive(Clone)]
pub struct OverlayDB {
overlay: MemoryDB,
backing: Arc<KeyValueDB>,
column: Option<u32>,
}
impl OverlayDB {
/// Create a new instance of OverlayDB given a `backing` database.
pub fn new(backing: Arc<KeyValueDB>, col: Option<u32>) -> OverlayDB {
OverlayDB{ overlay: MemoryDB::new(), backing: backing, column: col }
}
/// Create a new instance of OverlayDB with an anonymous temporary database.
#[cfg(test)]
pub fn new_temp() -> OverlayDB {
let backing = Arc::new(::kvdb::in_memory(0));
Self::new(backing, None)
}
/// Commit all operations in a single batch.
#[cfg(test)]
pub fn commit(&mut self) -> Result<u32> {
let mut batch = self.backing.transaction();
let res = self.commit_to_batch(&mut batch)?;
self.backing.write(batch).map(|_| res).map_err(|e| e.into())
}
/// Commit all operations to given batch.
pub fn commit_to_batch(&mut self, batch: &mut DBTransaction) -> Result<u32> {
let mut ret = 0u32;
let mut deletes = 0usize;
for i in self.overlay.drain() {
let (key, (value, rc)) = i;
if rc != 0 {
match self.payload(&key) {
Some(x) => {
let (back_value, back_rc) = x;
let total_rc: i32 = back_rc as i32 + rc;
if total_rc < 0 {
return Err(From::from(BaseDataError::NegativelyReferencedHash(key)));
}
deletes += if self.put_payload_in_batch(batch, &key, (back_value, total_rc as u32)) {1} else {0};
}
None => {
if rc < 0 {
return Err(From::from(BaseDataError::NegativelyReferencedHash(key)));
}
self.put_payload_in_batch(batch, &key, (value, rc as u32));
}
};
ret += 1;
}
}
trace!("OverlayDB::commit() deleted {} nodes", deletes);
Ok(ret)
}
/// Revert all operations on this object (i.e. `insert()`s and `remove()`s) since the
/// last `commit()`.
pub fn revert(&mut self) { self.overlay.clear(); }
/// Get the number of references that would be committed.
pub fn commit_refs(&self, key: &H256) -> i32 { self.overlay.raw(key).map_or(0, |(_, refs)| refs) }
/// Get the refs and value of the given key.
fn payload(&self, key: &H256) -> Option<(DBValue, u32)> {
self.backing.get(self.column, key)
.expect("Low-level database error. Some issue with your hard disk?")
.map(|d| {
let r = Rlp::new(&d);
(DBValue::from_slice(r.at(1).data()), r.at(0).as_val())
})
}
/// Put the refs and value of the given key, possibly deleting it from the db.
fn put_payload_in_batch(&self, batch: &mut DBTransaction, key: &H256, payload: (DBValue, u32)) -> bool {
if payload.1 > 0 {
let mut s = RlpStream::new_list(2);
s.append(&payload.1);
s.append(&&*payload.0);
batch.put(self.column, key, s.as_raw());
false
} else {
batch.delete(self.column, key);
true
}
}
}
impl HashDB for OverlayDB {
fn keys(&self) -> HashMap<H256, i32> {
let mut ret: HashMap<H256, i32> = self.backing.iter(self.column)
.map(|(key, _)| {
let h = H256::from_slice(&*key);
let r = self.payload(&h).unwrap().1;
(h, r as i32)
})
.collect();
for (key, refs) in self.overlay.keys() {
match ret.entry(key) {
Entry::Occupied(mut entry) => {
*entry.get_mut() += refs;
},
Entry::Vacant(entry) => {
entry.insert(refs);
}
}
}
ret
}
fn get(&self, key: &H256) -> Option<DBValue> {
// return ok if positive; if negative, check backing - might be enough references there to make
// it positive again.
let k = self.overlay.raw(key);
let memrc = {
if let Some((d, rc)) = k {
if rc > 0 { return Some(d); }
rc
} else {
0
}
};
match self.payload(key) {
Some(x) => {
let (d, rc) = x;
if rc as i32 + memrc > 0 {
Some(d)
}
else {
None
}
}
// Replace above match arm with this once https://github.com/rust-lang/rust/issues/15287 is done.
//Some((d, rc)) if rc + memrc > 0 => Some(d),
_ => None,
}
}
fn contains(&self, key: &H256) -> bool {
// return ok if positive; if negative, check backing - might be enough references there to make
// it positive again.
let k = self.overlay.raw(key);
match k {
Some((_, rc)) if rc > 0 => true,
_ => {
let memrc = k.map_or(0, |(_, rc)| rc);
match self.payload(key) {
Some(x) => {
let (_, rc) = x;
rc as i32 + memrc > 0
}
// Replace above match arm with this once https://github.com/rust-lang/rust/issues/15287 is done.
//Some((d, rc)) if rc + memrc > 0 => true,
_ => false,
}
}
}
}
fn insert(&mut self, value: &[u8]) -> H256 { self.overlay.insert(value) }
fn emplace(&mut self, key: H256, value: DBValue) { self.overlay.emplace(key, value); }
fn remove(&mut self, key: &H256) { self.overlay.remove(key); }
}
#[test]
#[cfg_attr(feature="dev", allow(blacklisted_name))]
fn overlaydb_revert() {
let mut m = OverlayDB::new_temp();
let foo = m.insert(b"foo"); // insert foo.
let mut batch = m.backing.transaction();
m.commit_to_batch(&mut batch).unwrap(); // commit - new operations begin here...
m.backing.write(batch).unwrap();
let bar = m.insert(b"bar"); // insert bar.
m.remove(&foo); // remove foo.
assert!(!m.contains(&foo)); // foo is gone.
assert!(m.contains(&bar)); // bar is here.
m.revert(); // revert the last two operations.
assert!(m.contains(&foo)); // foo is here.
assert!(!m.contains(&bar)); // bar is gone.
}
#[test]
fn overlaydb_overlay_insert_and_remove() {
let mut trie = OverlayDB::new_temp();
let h = trie.insert(b"hello world");
assert_eq!(trie.get(&h).unwrap(), DBValue::from_slice(b"hello world"));
trie.remove(&h);
assert_eq!(trie.get(&h), None);
}
#[test]
fn overlaydb_backing_insert_revert() {
let mut trie = OverlayDB::new_temp();
let h = trie.insert(b"hello world");
assert_eq!(trie.get(&h).unwrap(), DBValue::from_slice(b"hello world"));
trie.commit().unwrap();
assert_eq!(trie.get(&h).unwrap(), DBValue::from_slice(b"hello world"));
trie.revert();
assert_eq!(trie.get(&h).unwrap(), DBValue::from_slice(b"hello world"));
}
#[test]
fn overlaydb_backing_remove() {
let mut trie = OverlayDB::new_temp();
let h = trie.insert(b"hello world");
trie.commit().unwrap();
trie.remove(&h);
assert_eq!(trie.get(&h), None);
trie.commit().unwrap();
assert_eq!(trie.get(&h), None);
trie.revert();
assert_eq!(trie.get(&h), None);
}
#[test]
fn overlaydb_backing_remove_revert() {
let mut trie = OverlayDB::new_temp();
let h = trie.insert(b"hello world");
trie.commit().unwrap();
trie.remove(&h);
assert_eq!(trie.get(&h), None);
trie.revert();
assert_eq!(trie.get(&h).unwrap(), DBValue::from_slice(b"hello world"));
}
#[test]
fn overlaydb_negative() {
let mut trie = OverlayDB::new_temp();
let h = trie.insert(b"hello world");
trie.commit().unwrap();
trie.remove(&h);
trie.remove(&h); //bad - sends us into negative refs.
assert_eq!(trie.get(&h), None);
assert!(trie.commit().is_err());
}
#[test]
fn overlaydb_complex() {
let mut trie = OverlayDB::new_temp();
let hfoo = trie.insert(b"foo");
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
let hbar = trie.insert(b"bar");
assert_eq!(trie.get(&hbar).unwrap(), DBValue::from_slice(b"bar"));
trie.commit().unwrap();
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
assert_eq!(trie.get(&hbar).unwrap(), DBValue::from_slice(b"bar"));
trie.insert(b"foo"); // two refs
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
trie.commit().unwrap();
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
assert_eq!(trie.get(&hbar).unwrap(), DBValue::from_slice(b"bar"));
trie.remove(&hbar); // zero refs - delete
assert_eq!(trie.get(&hbar), None);
trie.remove(&hfoo); // one ref - keep
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
trie.commit().unwrap();
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
trie.remove(&hfoo); // zero ref - would delete, but...
assert_eq!(trie.get(&hfoo), None);
trie.insert(b"foo"); // one ref - keep after all.
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
trie.commit().unwrap();
assert_eq!(trie.get(&hfoo).unwrap(), DBValue::from_slice(b"foo"));
trie.remove(&hfoo); // zero ref - delete
assert_eq!(trie.get(&hfoo), None);
trie.commit().unwrap(); //
assert_eq!(trie.get(&hfoo), None);
}