60 lines
1.8 KiB
Rust
60 lines
1.8 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::collections::{HashMap, HashSet};
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use std::default::Default;
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use std::hash::{Hasher, Hash, BuildHasherDefault};
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pub type FnvHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FnvHasher>>;
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pub type FnvHashSet<V> = HashSet<V, BuildHasherDefault<FnvHasher>>;
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#[allow(non_snake_case)]
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pub fn FnvHashMap<K: Hash + Eq, V>() -> FnvHashMap<K, V> {
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HashMap::default()
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}
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#[allow(non_snake_case)]
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pub fn FnvHashSet<V: Hash + Eq>() -> FnvHashSet<V> {
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HashSet::default()
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}
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/// A speedy hash algorithm for node ids and def ids. The hashmap in
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/// libcollections by default uses SipHash which isn't quite as speedy as we
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/// want. In the compiler we're not really worried about DOS attempts, so we
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/// just default to a non-cryptographic hash.
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///
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/// This uses FNV hashing, as described here:
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/// http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
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pub struct FnvHasher(u64);
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impl Default for FnvHasher {
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#[inline]
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fn default() -> FnvHasher {
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FnvHasher(0xcbf29ce484222325)
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}
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}
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impl Hasher for FnvHasher {
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#[inline]
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fn write(&mut self, bytes: &[u8]) {
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let FnvHasher(mut hash) = *self;
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for byte in bytes {
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hash = hash ^ (*byte as u64);
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hash = hash.wrapping_mul(0x100000001b3);
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}
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*self = FnvHasher(hash);
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}
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#[inline]
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fn finish(&self) -> u64 {
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self.0
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}
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}
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