WIP - Dictionary types implementation

lib/typedObjects/hash.js

+/*
+ * This file is part of Adblock Plus <http://adblockplus.org/>,
+ * Copyright (C) 2006-2014 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+/*
+ * Note: This implements the hash function by Paul Hsieh, see
+ * http://www.azillionmonkeys.com/qed/hash.html. The code below is based on Paul
+ * Hsieh's code which is licensed under LGPL 2.1.
+ */
+
+exports.calculateHash = function calculateHash(/**string*/ str)
+{
+  let length = str.length | 0;
+  let hash = length << 1;
+
+  for (let i = 0; i < length - 1; i += 2)
+  {
+    // Main loop, process two characters at a time
+    hash += str.get(i);
+    let tmp = (str.get(i + 1) << 11) ^ hash;
+    hash = (hash << 16) ^ tmp;
+    hash += hash >>> 11;
+  }
+
+  if (length & 1)
+  {
+    // Process remaining character
+    hash += str.get(length - 1);
+    hash ^= hash << 11;
+    hash += hash >>> 17;
+  }
+
+  // "Avalanching" of final 127 bits
+  hash ^= hash << 3;
+  hash += hash >>> 5;
+  hash ^= hash << 4;
+  hash += hash >>> 17;
+  hash ^= hash << 25;
+  hash += hash >>> 6;
+  return hash >>> 0;
+}