77 lines
2.2 KiB
Rust
77 lines
2.2 KiB
Rust
// Copyright 2015-2018 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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#[macro_use]
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extern crate crunchy;
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extern crate ethereum_types;
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extern crate hashdb;
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use ethereum_types::H256;
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// use hashdb::Hasher;
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use std::hash;
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use std::collections::{HashMap, HashSet};
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/// Specialized version of `HashMap` with H256 keys and fast hashing function.
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pub type H256FastMap<T> = HashMap<H256, T, hash::BuildHasherDefault<PlainHasher>>;
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/// Specialized version of `HashSet` with H256 keys and fast hashing function.
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pub type H256FastSet = HashSet<H256, hash::BuildHasherDefault<PlainHasher>>;
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/// Hasher that just takes 8 bytes of the provided value.
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/// May only be used for keys which are 32 bytes.
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#[derive(Default)]
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pub struct PlainHasher {
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prefix: u64,
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}
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impl hash::Hasher for PlainHasher {
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#[inline]
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fn finish(&self) -> u64 {
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self.prefix
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}
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#[inline]
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#[allow(unused_assignments)]
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fn write(&mut self, bytes: &[u8]) {
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debug_assert!(bytes.len() == 32);
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let mut bytes_ptr = bytes.as_ptr();
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let mut prefix_ptr = &mut self.prefix as *mut u64 as *mut u8;
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unroll! {
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for _i in 0..8 {
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unsafe {
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*prefix_ptr ^= (*bytes_ptr ^ *bytes_ptr.offset(8)) ^ (*bytes_ptr.offset(16) ^ *bytes_ptr.offset(24));
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bytes_ptr = bytes_ptr.offset(1);
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prefix_ptr = prefix_ptr.offset(1);
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}
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}
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use std::hash::Hasher;
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use super::PlainHasher;
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#[test]
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fn it_works() {
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let mut bytes = [32u8; 32];
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bytes[0] = 15;
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let mut hasher = PlainHasher::default();
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hasher.write(&bytes);
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assert_eq!(hasher.prefix, 47);
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}
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}
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