openethereum/util/src/trie/journal.rs
2016-03-11 10:58:51 +01:00

104 lines
2.9 KiB
Rust

// 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/>.
use std::default::Default;
use sha3::*;
use hash::H256;
use bytes::*;
use rlp::*;
use hashdb::*;
/// Type of operation for the backing database - either a new node or a node deletion.
#[derive(Debug)]
enum Operation {
New(H256, Bytes),
Delete(H256),
}
/// How many insertions and removals were done in an `apply` operation.
pub struct Score {
/// Number of insertions.
pub inserts: usize,
/// Number of removals.
pub removes: usize,
}
/// A journal of operations on the backing database.
#[derive(Debug)]
pub struct Journal (Vec<Operation>);
impl Default for Journal {
fn default() -> Self {
Journal::new()
}
}
impl Journal {
/// Create a new, empty, object.
pub fn new() -> Journal { Journal(vec![]) }
/// Given the RLP that encodes a node, append a reference to that node `out` and leave `journal`
/// such that the reference is valid, once applied.
pub fn new_node(&mut self, rlp: Bytes, out: &mut RlpStream) {
if rlp.len() >= 32 {
let rlp_sha3 = rlp.sha3();
trace!("new_node: reference node {:?} => {:?}", rlp_sha3, rlp.pretty());
out.append(&rlp_sha3);
self.0.push(Operation::New(rlp_sha3, rlp));
}
else {
trace!("new_node: inline node {:?}", rlp.pretty());
out.append_raw(&rlp, 1);
}
}
/// Given the RLP that encodes a now-unused node, leave `journal` in such a state that it is noted.
pub fn delete_node_sha3(&mut self, old_sha3: H256) {
trace!("delete_node: {:?}", old_sha3);
self.0.push(Operation::Delete(old_sha3));
}
/// Register an RLP-encoded node for deletion (given a slice), if it needs to be deleted.
pub fn delete_node(&mut self, old: &[u8]) {
let r = Rlp::new(old);
if r.is_data() && r.size() == 32 {
self.delete_node_sha3(r.as_val());
}
}
/// Apply this journal to the HashDB `db` and return the number of insertions and removals done.
pub fn apply(self, db: &mut HashDB) -> Score {
trace!("applying {:?} changes", self.0.len());
let mut ret = Score{inserts: 0, removes: 0};
for d in self.0.into_iter() {
match d {
Operation::Delete(h) => {
trace!("TrieDBMut::apply --- {:?}", &h);
db.remove(&h);
ret.removes += 1;
},
Operation::New(h, d) => {
trace!("TrieDBMut::apply +++ {:?} -> {:?}", &h, d.pretty());
db.emplace(h, d);
ret.inserts += 1;
}
}
}
ret
}
}