Index: lib/hash.js
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+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present 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/>.
+ */
+
+/** @module hash */
+
+"use strict";
+
+// This is an implementation of the SuperFastHash algorithm.
+// See http://www.azillionmonkeys.com/qed/hash.html
+function SuperFastHash(message)
+{
+  let {length} = message;
+
+  if (length == 0)
+    return 0;
+
+  let index = 0;
+
+  let nextUint8 = () => message[index++];
+  let nextUint16 = () => nextUint8() | nextUint8() << 8;
+
+  let digest = length;
+
+  for (let n = length >> 2; n > 0; n--)
+  {
+    digest = digest + nextUint16() >>> 0;
+    digest ^= digest << 16 >>> 0 ^ nextUint16() << 11;
+    digest = digest + (digest >>> 11) >>> 0;
+  }
+
+  switch (length & 3)
+  {
+    case 3:
+      digest = digest + nextUint16() >>> 0;
+      digest ^= digest << 16 >>> 0;
+      digest ^= nextUint8() << 18;
+      digest = digest + (digest >>> 11) >>> 0;
+      break;
+    case 2:
+      digest = digest + nextUint16() >>> 0;
+      digest ^= digest << 11 >>> 0;
+      digest = digest + (digest >>> 17) >>> 0;
+      break;
+    case 1:
+      digest = digest + nextUint8() >>> 0;
+      digest ^= digest << 10 >>> 0;
+      digest = digest + (digest >>> 1) >>> 0;
+  }
+
+  digest ^= digest << 3 >>> 0;
+  digest = digest + (digest >>> 5) >>> 0;
+  digest ^= digest << 4 >>> 0;
+  digest = digest + (digest >>> 17) >>> 0;
+  digest ^= digest << 25 >>> 0;
+  digest = digest + (digest >>> 6) >>> 0;
+
+  return digest;
+}
+
+/**
+ * Calculates the digest for a message.
+ *
+ * The hashing algorithm used is "SuperFastHash"
+ * (see http://www.azillionmonkeys.com/qed/hash.html). If no encoding is
+ * specified, the return value is a 32-bit unsigned integer.
+ *
+ * @param {number[]} message The message. This must be an array-like object of
+ *        "bytes" (i.e. only the lowest 8 bits are relevant). In order to hash
+ *        a string, it must be converted into UTF-8 or some other 8-bit
+ *        encoding first.
+ * @param {Object} [options]
+ * @param {string} [options.encoding] The encoding of the digest. This may be
+ *        set to "hex". If no encoding is specified, the preferred default
+ *        encoding for the hashing algorithm is used.
+ * @return {number|string} The digest.
+ */
+function hash(message, {encoding} = {})
+{
+  let digest = SuperFastHash(message);
+
+  if (encoding == "hex")
+    return digest.toString(16);
+
+  return digest;
+}
+
+exports.hash = hash;