зеркало из https://github.com/mozilla/gecko-dev.git
46 строки
1.4 KiB
Rust
46 строки
1.4 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! This file stolen wholesale from rustc/src/librustc/util/nodemap.rs
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pub use std::hash::{Hash, Hasher, Writer};
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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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#[deriving(Clone)]
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pub struct FnvHasher;
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pub struct FnvState(u64);
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impl Hasher<FnvState> for FnvHasher {
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fn hash<Sized? T: Hash<FnvState>>(&self, t: &T) -> u64 {
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let mut state = FnvState(0xcbf29ce484222325);
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t.hash(&mut state);
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let FnvState(ret) = state;
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return ret;
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}
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}
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impl Writer for FnvState {
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fn write(&mut self, bytes: &[u8]) {
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let FnvState(mut hash) = *self;
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for byte in bytes.iter() {
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hash = hash ^ (*byte as u64);
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hash = hash * 0x100000001b3;
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}
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*self = FnvState(hash);
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}
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}
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#[inline(always)]
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pub fn hash<T: Hash<FnvState>>(t: &T) -> u64 {
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let s = FnvHasher;
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s.hash(t)
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}
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