Added a bloom filter to CSS selector matching.

components/util/fnv.rs

@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! This file stolen wholesale from rustc/src/librustc/util/nodemap.rs
+
+pub use std::hash::{Hash, Hasher, Writer};
+
+/// 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
+#[deriving(Clone)]
+pub struct FnvHasher;
+
+pub struct FnvState(u64);
+
+impl Hasher<FnvState> for FnvHasher {
+    fn hash<T: Hash<FnvState>>(&self, t: &T) -> u64 {
+        let mut state = FnvState(0xcbf29ce484222325);
+        t.hash(&mut state);
+        let FnvState(ret) = state;
+        return ret;
+    }
+}
+
+impl Writer for FnvState {
+    fn write(&mut self, bytes: &[u8]) {
+        let FnvState(mut hash) = *self;
+        for byte in bytes.iter() {
+            hash = hash ^ (*byte as u64);
+            hash = hash * 0x100000001b3;
+        }
+        *self = FnvState(hash);
+    }
+}
+
+#[inline(always)]
+pub fn hash<T: Hash<FnvState>>(t: &T) -> u64 {
+    let s = FnvHasher;
+    s.hash(t)
+}