Issue 147 - [Typed objects] Implement object types

lib/typedObjects/utils.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";
+
+/**
+ * Calculates the binary logarithm (position of highest bit) of an integer.
+ * Source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogObvious
+ */
+exports.ilog2 = function ilog2(/**Integer*/ num) /**Integer*/
+{
+  num = num | 0;
+  let result = 0;
+  while ((num >>= 1) > 0)
+    result++;
+  return result;
+};
+
+/**
+ * Round up a 32-bit integer to the next power of two.
+ * Source: See http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+ */
+exports.nextPow2 = function nextPow2(/**Integer*/ num) /**Integer*/
+{
+  num = num | 0;
+  num--;
+  num |= num >> 1;
+  num |= num >> 2;
+  num |= num >> 4;
+  num |= num >> 8;
+  num |= num >> 16;
+  return num + 1;
+};
+
+/**
+ * Returns a property descriptor for an immutable property with given value.
+ */
+exports.fixedPropertyDescriptor = function fixedPropertyDescriptor(value) /**Object*/
+{
+  return {
+    value: value,
+    writable: false,
+    configurable: false,
+    enumerable: true
+  };
+};
+
+/**
+ * Generates the array of views that need to be passed as parameters for getters
+ * and setters of a given type.
+ *
+ * @param type
+ * @param viewTypes array of existing view types (will be extended if necessary)
+ * @param views array containing a views arrays for each view type (will be
+ *              extended if necessary)
+ * @return array of views required for the given type
+ */
+let getViewsForType = exports.getViewsForType = function getViewsForType(type, viewTypes, views)
+{
+  let requiredViews = type.viewTypes;
+  let result = [];
+  for (let i = 0, l = requiredViews.length | 0; i < l; i++)
+  {
+    let viewType = requiredViews[i];
+    let index = viewTypes.indexOf(viewType) | 0;
+    if (index < 0)
+    {
+      index = (viewTypes.push(viewType) | 0) - 1;
+      views.push([]);
+    }
+    result.push(views[index]);
+  }
+  return result;
+};
+
+/**
+ * Defines properties with given name and type on an object.
+ *
+ * @param obj object to define properties on
+ * @param propList array of properties where each property is represented by
+ *                 [name, type]
+ * @param viewTypes see getViewsForType()
+ * @param views see getViewsForType()
+ * @param [offset] byte array offset at which the properties should start
+ * @return new start offset for additional properties
+ */
+exports.defineProperties = function defineProperties(obj, propList, viewTypes, views, offset)
+{
+  offset = offset | 0;
+
+  // Put larger properties first to make sure alignment requirements are met.
+  propList.sort(function(a, b)
+  {
+    return b[1].referenceLength - a[1].referenceLength;
+  });
+
+  // Generates getters and setters for each property.
+  let descriptors = {};
+  for (let i = 0, l = propList.length | 0; i < l; i++)
+  {
+    let [name, type] = propList[i];
+
+    let viewParams = getViewsForType(type, viewTypes, views);
+    descriptors[name] = {
+      get: type.createGetter.apply(type, [offset].concat(viewParams)),
+      set: type.createSetter.apply(type, [offset].concat(viewParams)),
+      configurable: false,
+      enumerable: true
+    };
+    offset += type.referenceLength;
+  }
+
+  // Define properties
+  Object.defineProperties(obj, descriptors);
+
+  return offset;
+};