Issue 151 - [Typed objects] Implement dynamically-sized array 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
@@ skipping 69 matching lines @@
     if (index < 0)
     {
       index = (viewTypes.push(viewType) | 0) - 1;
       views.push([]);
     }
     result.push(views[index]);
   }
   return result;
 };
 
+ /**
+ * Creates a wrapper function for a setter that will call the watcher function
+ * with the new value of the property before executing the actual setter.
+ */
+function watchSetter(/**Function*/ setter, /**Function*/ watcher) /**Function*/
+{
+  return function(value)
+  {
+    setter.call(this, watcher.call(this, value));
+  }
+}
+
+/**
+ * Creates a parameter-less wrapper function around a getter that will get
+ * bufferIndex and byteOffset parameters from object properties.
+ */
+function wrapGetter(/**Function*/ getter) /**Function*/
+{
+  return function()
+  {
+    return getter.call(this, this.bufferIndex, this.byteOffset);
+  }
+}
+
+/**
+ * Creates a wrapper function around a setter with value as the only parameter,
+ * the bufferIndex and byteOffset parameters will be retrieved from object
+ * properties.
+ */
+function wrapSetter(/**Function*/ setter) /**Function*/
+{
+  return function(value)
+  {
+    return setter.call(this, this.bufferIndex, this.byteOffset, value);
+  }
+}
+
 /**
  * Defines properties with given name and type on an object.
  *
  * @param obj object to define properties on
  * @param properties object mapping property names to their respective types
  * @param viewTypes see getViewsForType()
  * @param views see getViewsForType()
  * @param [offset] byte array offset at which the properties should start
+ * @param [watchers] map of watcher functions to be called when a particular property is being set
  * @param [cleanupValues] array of property/value combinations to be set when the object is created or destroyed
  * @return new start offset for additional properties
  */
-exports.defineProperties = function defineProperties(obj, properties, viewTypes, views, offset, cleanupValues)
+exports.defineProperties = function defineProperties(obj, properties, viewTypes, views, offset, watchers, cleanupValues)
 {
   offset = offset | 0;
 
   let propList = [];
   for (let name in properties)
     propList.push([name, properties[name]]);
 
   // 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)),
+      get: wrapGetter(type.createGetter.apply(type, [offset].concat(viewParams))),
+      set: wrapSetter(type.createSetter.apply(type, [offset].concat(viewParams))),
       configurable: false,
       enumerable: true
     };
+
+    if (watchers && typeof watchers[name] == "function")
+      descriptors[name].set = watchSetter(descriptors[name].set, watchers[name]);
+
     offset += type.referenceLength;
     if (cleanupValues && typeof type.cleanupValue != "undefined")
       cleanupValues.push([name, type.cleanupValue]);
   }
 
   // Define properties
   Object.defineProperties(obj, descriptors);
 
   return offset;
 };
+
+/**
+ * Creates a new array buffer and adds the necessary views.
+ *
+ * @param {Integer} byteSize  bytes to allocate for the buffer
+ * @param {Array} buffers  existing buffers (will be modified)
+ * @param {Array} viewTypes  view types for the buffers
+ * @param {Array} views  existing buffer views (will be modified)
+ * @result {Integer} index of the buffer created
+ */
+let addBuffer = exports.addBuffer = function(byteSize, buffers, viewTypes, views)
+{
+  let buffer = new ArrayBuffer(byteSize | 0);
+  buffers.push(buffer);
+  for (let i = 0, l = viewTypes.length | 0; i < l; i++)
+    views[i].push(new viewTypes[i](buffer));
+  return (buffers.length | 0) - 1;
+}
+
+/**
+ * Releases an array buffer.
+ *
+ * @param {Integer} bufferIndex  index of the buffer to be released.
+ * @param {Array} buffers  existing buffers (will be modified)
+ * @param {Array} views  existing buffer views (will be modified)
+ */
+exports.removeBuffer = function(bufferIndex, buffers, views)
+{
+  delete buffers[bufferIndex];
+  for (let i = 0, l = views.length | 0; i < l; i++)
+    delete views[i][bufferIndex];
+}
+
+/**
+ * Allocates a new fixed-size element. It will return the first available free
+ * block or create a new buffer if the existing ones have no space left.
+ *
+ * @param {TypedReference} firstFree  head of the linked list pointing to unallocated elements
+ * @param {Integer} byteLength  size of an element
+ * @param {Integer} bufferSize  number of elements in a buffer
+ * @param {Array} buffers  existing buffers (might be modified in necessary)
+ * @param {Array} viewTypes  view types for the buffers
+ * @param {Array} views  existing buffer views (might be modified if necessary)
+ * @result {Array} [bufferIndex, byteOffset] parameters of the newly allocated block
+ */
+exports.alloc = function(firstFree, byteLength, bufferSize, buffers, viewTypes, views)
+{
+  let bufferIndex = firstFree.bufferIndex | 0;
+  let byteOffset = firstFree.byteOffset | 0;
+  if (bufferIndex >= 0)
+  {
+    // There is still a free spot, simply move on firstFree reference
+    [firstFree.bufferIndex, firstFree.byteOffset] =
+        [firstFree.targetBufferIndex, firstFree.targetByteOffset];
+  }
+  else
+  {
+    byteLength = byteLength | 0;
+    bufferSize = bufferSize | 0;
+
+    // Create new buffer and use the first element of it
+    bufferIndex = addBuffer(byteLength * bufferSize, buffers, viewTypes, views);
+    byteOffset = 0;
+
+    // Mark last element of the new buffer as the last free spot
+    firstFree.bufferIndex = bufferIndex;
+    firstFree.byteOffset = (bufferSize - 1) * byteLength;
+    firstFree.targetBufferIndex = -1;
+
+    // Make each remaining element of the new buffer point to the next one
+    for (let i = bufferSize - 2; i >= 1; i--)
+    {
+      let nextByteOffset = firstFree.byteOffset;
+      firstFree.byteOffset = nextByteOffset - byteLength;
+      firstFree.targetBufferIndex = bufferIndex;
+      firstFree.targetByteOffset = nextByteOffset;
+    }
+  }
+  return [bufferIndex, byteOffset];
+};
+
+/**
+ * Releases the block at given offset so that it can be allocated again.
+ *
+ * @param {TypedReference} firstFree  head of the linked list pointing to unallocated elements
+ * @param {Integer} bufferIndex  buffer index of the block to be released
+ * @param {Integer} byteOffset  byte offset o fthe block to be released
+ */
+exports.dealloc = function(firstFree, bufferIndex, byteOffset)
+{
+  let oldFreeBufferIndex = firstFree.bufferIndex | 0;
+  let oldFreeByteOffset = firstFree.byteOffset | 0;
+
+  firstFree.bufferIndex = bufferIndex | 0;
+  firstFree.byteOffset = byteOffset | 0;
+  firstFree.targetBufferIndex = oldFreeBufferIndex;
+  firstFree.targetByteOffset = oldFreeByteOffset;
+}