// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.
// Parity Ethereum 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 Ethereum 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 Ethereum. If not, see .
use keccak::{keccak_256, H256};
use shared;
use std::cell::Cell;
#[derive(Default)]
pub struct SeedHashCompute {
prev_epoch: Cell,
prev_seedhash: Cell,
}
impl SeedHashCompute {
#[inline]
fn reset_cache(&self) {
self.prev_epoch.set(0);
self.prev_seedhash.set([0u8; 32]);
}
#[inline]
pub fn hash_block_number(&self, block_number: u64) -> H256 {
self.hash_epoch(shared::epoch(block_number))
}
#[inline]
pub fn hash_epoch(&self, epoch: u64) -> H256 {
if epoch < self.prev_epoch.get() {
// can't build on previous hash if requesting an older block
self.reset_cache();
}
if epoch > self.prev_epoch.get() {
let seed_hash = SeedHashCompute::resume_compute_seedhash(
self.prev_seedhash.get(),
self.prev_epoch.get(),
epoch,
);
self.prev_seedhash.set(seed_hash);
self.prev_epoch.set(epoch);
}
self.prev_seedhash.get()
}
#[inline]
pub fn resume_compute_seedhash(mut hash: H256, start_epoch: u64, end_epoch: u64) -> H256 {
for _ in start_epoch..end_epoch {
keccak_256::inplace(&mut hash);
}
hash
}
}
#[cfg(test)]
mod tests {
use super::SeedHashCompute;
#[test]
fn test_seed_compute_once() {
let seed_compute = SeedHashCompute::default();
let hash = [
241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253,
147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162,
];
assert_eq!(seed_compute.hash_block_number(486382), hash);
}
#[test]
fn test_seed_compute_zero() {
let seed_compute = SeedHashCompute::default();
assert_eq!(seed_compute.hash_block_number(0), [0u8; 32]);
}
#[test]
fn test_seed_compute_after_older() {
let seed_compute = SeedHashCompute::default();
// calculating an older value first shouldn't affect the result
let _ = seed_compute.hash_block_number(50000);
let hash = [
241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253,
147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162,
];
assert_eq!(seed_compute.hash_block_number(486382), hash);
}
#[test]
fn test_seed_compute_after_newer() {
let seed_compute = SeedHashCompute::default();
// calculating an newer value first shouldn't affect the result
let _ = seed_compute.hash_block_number(972764);
let hash = [
241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253,
147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162,
];
assert_eq!(seed_compute.hash_block_number(486382), hash);
}
}