Issue 151 - [Typed objects] Implement dynamically-sized array types

lib/typedObjects/arrayTypes.js

Index: lib/typedObjects/arrayTypes.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/typedObjects/arrayTypes.js
@@ -0,0 +1,267 @@
+/*
+ * 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";
+
+let {ilog2, nextPow2, alloc, dealloc, addBuffer, removeBuffer} = require("typedObjects/utils");
+
+function defaultArrayConstructor()
+{
+  this.arrayBufferIndex = -1;
+};
+
+function defaultArrayDestructor()
+{
+  this.length = 0;
+  this.size = 0;
+};
+
+function createGetter(elementGetter, elementShift)
+{
+  return function(index)
+  {
+    if (index < 0 || index >= this.length)
+      throw new Error("Array index out of bounds");
+    return elementGetter.call(this, this.arrayBufferIndex, this.arrayByteOffset + (index << elementShift));
+  };
+}
+
+function createSetter(elementSetter, elementShift)
+{
+  return function(index, value)
+  {
+    if (index < 0 || index >= this.length)
+      throw new Error("Array index out of bounds");
+    return elementSetter.call(this, this.arrayBufferIndex, this.arrayByteOffset + (index << elementShift), value);
+  }
+}
+
+function createCombinedConstructor(customConstructor)
+{
+  return function()
+  {
+    defaultArrayConstructor.apply(this);
+    customConstructor.apply(this, arguments);
+  }
+}
+
+function createCombinedDestructor(customDestructor)
+{
+  return function()
+  {
+    try
+    {
+      customDestructor.apply(this);
+    }
+    finally
+    {
+      defaultArrayDestructor.apply(this);
+    }
+  }
+}
+
+function createLengthWatcher(elementType, elementSetter)
+{
+  let {STATE_UNINITIALIZED} = require("typedObjects/objectTypes");
+  return function lengthWatcher(newLength)
+  {
+    newLength = newLength | 0;
+    if (newLength < 0)
+      newLength = 0;
+    if (newLength > this.size)
+      this.size = newLength;
+
+    let initialValue = elementType.initialValue;
+    if (typeof initialValue != "undefined")
+    {
+      let length = this.length;
+      if (newLength > length)
+      {
+        // We have to call element setter directly here, this.set() will
+        // complain because of writing out of bounds (new length isn't set yet).
+        // We also need to change state temporarily in order to avoid an attemt
+        // to release "existing" values.
+        let origState = this._state;
+        this._state = STATE_UNINITIALIZED;
+        try
+        {
+          let referenceLength = elementType.referenceLength | 0;
+          let bufferIndex = this.arrayBufferIndex | 0;
+          for (let i = length, offset = this.arrayByteOffset + length * referenceLength;
+              i < newLength;
+              i++, offset += referenceLength)
+          {
+            elementSetter.call(this, bufferIndex, offset, initialValue);
+          }
+        }
+        finally
+        {
+          this._state = origState;
+        }
+      }
+      else
+      {
+        for (let i = newLength; i < length; i++)
+          this.set(i, initialValue);
+      }
+    }
+
+    return newLength;
+  }
+}
+
+function createSizeWatcher(elementType, minElements, bufferSize, buffers, viewTypes, views, firstFree)
+{
+  let referenceLength = elementType.referenceLength | 0;
+  minElements = minElements | 0;
+  bufferSize = bufferSize | 0;
+  return function sizeWatcher(newSize)
+  {
+    newSize = newSize | 0;
+    let length = this.length | 0;
+    if (newSize < length)
+      newSize = length;
+    if (newSize > 0 && newSize < minElements)
+      newSize = minElements;
+    newSize = nextPow2(newSize);
+
+    let size = this.size;
+    if (size != newSize)
+    {
+      let origBufferIndex = this.arrayBufferIndex;
+      let origByteOffset = this.arrayByteOffset;
+      if (newSize > 0)
+      {
+        // Allocate new buffer
+        let bufferIndex, byteOffset;
+        let reference = firstFree[newSize];
+        if (typeof reference != "undefined")
+        {
+          [bufferIndex, byteOffset] = alloc(reference,
+              referenceLength * newSize, (bufferSize / newSize) | 0,
+              buffers, viewTypes, views);
+        }
+        else
+        {
+          // This array is too large, it needs an individual buffer
+          bufferIndex = addBuffer(referenceLength * newSize, buffers, viewTypes, views);
+          bufferOffset = 0;
+        }
+
+        if (size > 0)
+        {
+          let copyBytes = length * referenceLength;
+          let src = new Uint8Array(buffers[this.arrayBufferIndex], this.arrayByteOffset, copyBytes);
+          let dst = new Uint8Array(buffers[bufferIndex], byteOffset, copyBytes);
+          dst.set(src);
+        }
+
+        this.arrayBufferIndex = bufferIndex;
+        this.arrayByteOffset = byteOffset;
+      }
+      else
+        this.arrayBufferIndex = -1;
+
+      if (size > 0)
+      {
+        // Release old buffer
+        let reference = firstFree[size];
+        if (typeof reference != "undefined")
+          dealloc(reference, origBufferIndex, origByteOffset);
+        else
+          removeBuffer(origBufferIndex, buffers, views);
+      }
+    }
+
+    return newSize;
+  }
+}
+
+function createArrayType(elementType, typeDescriptor, meta)
+{
+  if (typeof meta != "object" || meta == null)
+    meta = {};
+
+  // We need to make sure that all buffer chunks are big enough to hold a
+  // reference in order to manage the free chunks as a linked list. Each array
+  // buffer should be dedicated to arrays of particular size - the number of
+  // possible sizes is limited as the sizes can only be powers of two.
+  let {TypedReference} = require("typedObjects/references");
+  let minElements = nextPow2(Math.max(Math.ceil(TypedReference.byteLength / elementType.referenceLength) | 0, 1));
+  let bufferSize = ("arrayBufferSize" in meta ? meta.arrayBufferSize | 0 : 1024);
+  bufferSize = nextPow2(Math.max(bufferSize, minElements * 2)) | 0;
+
+  let buffers = [];
+  let viewTypes = elementType.viewTypes.slice();
+  let views = [];
+  for (let i = 0, l = viewTypes.length | 0; i < l; i++)
+    views.push([]);
+
+  let elementGetter = elementType.createGetter.apply(elementType, [0].concat(views));
+  let elementSetter = elementType.createSetter.apply(elementType, [0].concat(views));
+
+  let typedReferenceTypes = TypedReference.viewTypes;
+  let typedReferenceViews = [];
+  for (let i = 0, l = typedReferenceTypes.length | 0; i < l; i++)
+  {
+    let type = typedReferenceTypes[i];
+    let index = viewTypes.indexOf(type);
+    if (index < 0)
+    {
+      viewTypes.push(type);
+      views.push([]);
+      index = viewTypes.length - 1;
+    }
+    typedReferenceViews.push(views[index]);
+  }
+
+  let firstFree = [];
+  for (let i = minElements; i < bufferSize; i <<= 1)
+    firstFree[i] = new TypedReference(-1, typedReferenceViews);
+
+  let {int16, uint32} = require("typedObjects/primitiveTypes");
+  typeDescriptor = Object.create(typeDescriptor || {});
+  typeDescriptor.arrayBufferIndex = int16;
+  typeDescriptor.arrayByteOffset = uint32;
+  typeDescriptor.length = uint32;
+  typeDescriptor.size = uint32;
+
+  let elementShift = ilog2(elementType.referenceLength | 0);
+  typeDescriptor.get = createGetter(elementGetter, elementShift);
+  typeDescriptor.set = createSetter(elementSetter, elementShift);
+
+  if (meta.hasOwnProperty("constructor") && typeof meta.constructor == "function")
+    meta.constructor = createCombinedConstructor(meta.constructor);
+  else
+    meta.constructor = defaultArrayConstructor;
+
+  if (meta.hasOwnProperty("destructor") && typeof meta.destructor == "function")
+    meta.destructor = createCombinedDestructor(meta.destructor);
+  else
+    meta.destructor = defaultArrayDestructor;
+
+  if (!meta.watch || typeof meta.watch != "object")
+    meta.watch = {};
+
+  meta.watch.length = createLengthWatcher(elementType, elementSetter);
+  meta.watch.size = createSizeWatcher(elementType, minElements, bufferSize, buffers, viewTypes, views, firstFree);
+
+  let {ObjectBase} = require("typedObjects/objectTypes");
+  return ObjectBase.extend(typeDescriptor, meta);
+}
+
+exports.createArrayType = createArrayType;