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