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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.
4 //
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.
10
11 use std::collections::{HashMap, HashSet};
12 use std::default::Default;
13 use std::hash::{Hasher, Hash, BuildHasherDefault};
14
15 pub type FnvHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FnvHasher>>;
16 pub type FnvHashSet<V> = HashSet<V, BuildHasherDefault<FnvHasher>>;
17
18 #[allow(non_snake_case)]
19 pub fn FnvHashMap<K: Hash + Eq, V>() -> FnvHashMap<K, V> {
20 HashMap::default()
21 }
22
23 #[allow(non_snake_case)]
24 pub fn FnvHashSet<V: Hash + Eq>() -> FnvHashSet<V> {
25 HashSet::default()
26 }
27
28 /// A speedy hash algorithm for node ids and def ids. The hashmap in
29 /// libcollections by default uses SipHash which isn't quite as speedy as we
30 /// want. In the compiler we're not really worried about DOS attempts, so we
31 /// just default to a non-cryptographic hash.
32 ///
33 /// This uses FNV hashing, as described here:
34 /// http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
35 pub struct FnvHasher(u64);
36
37 impl Default for FnvHasher {
38 #[inline]
39 fn default() -> FnvHasher {
40 FnvHasher(0xcbf29ce484222325)
41 }
42 }
43
44 impl Hasher for FnvHasher {
45 #[inline]
46 fn write(&mut self, bytes: &[u8]) {
47 let FnvHasher(mut hash) = *self;
48 for byte in bytes {
49 hash = hash ^ (*byte as u64);
50 hash = hash.wrapping_mul(0x100000001b3);
51 }
52 *self = FnvHasher(hash);
53 }
54
55 #[inline]
56 fn finish(&self) -> u64 {
57 self.0
58 }
59 }