1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use std::collections::{HashMap, HashSet};
12 use std::collections::hash_state::DefaultState;
13 use std::default::Default;
14 use std::hash::{Hasher, Hash};
16 pub type FnvHashMap<K, V> = HashMap<K, V, DefaultState<FnvHasher>>;
17 pub type FnvHashSet<V> = HashSet<V, DefaultState<FnvHasher>>;
19 #[allow(non_snake_case)]
20 pub fn FnvHashMap<K: Hash + Eq, V>() -> FnvHashMap<K, V> {
24 #[allow(non_snake_case)]
25 pub fn FnvHashSet<V: Hash + Eq>() -> FnvHashSet<V> {
29 /// A speedy hash algorithm for node ids and def ids. The hashmap in
30 /// libcollections by default uses SipHash which isn't quite as speedy as we
31 /// want. In the compiler we're not really worried about DOS attempts, so we
32 /// just default to a non-cryptographic hash.
34 /// This uses FNV hashing, as described here:
35 /// http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
36 pub struct FnvHasher(u64);
38 impl Default for FnvHasher {
39 fn default() -> FnvHasher { FnvHasher(0xcbf29ce484222325) }
42 impl Hasher for FnvHasher {
43 fn write(&mut self, bytes: &[u8]) {
44 let FnvHasher(mut hash) = *self;
46 hash = hash ^ (*byte as u64);
47 hash = hash.wrapping_mul(0x100000001b3);
49 *self = FnvHasher(hash);
51 fn finish(&self) -> u64 { self.0 }