Initial JS stub implementation of Object.observe. Adds support for .object/.unobserve/.notify/.deli…

src/object-observe.js

+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"use strict";
+
+var InternalObjectIsFrozen = $Object.isFrozen;
+var InternalObjectFreeze = $Object.freeze;
+
+var InternalWeakMapProto = {
+  __proto__: null,
+  set: $WeakMap.prototype.set,
+  get: $WeakMap.prototype.get,
+  has: $WeakMap.prototype.has
+}
+
+function createInternalWeakMap() {
+  var map = new $WeakMap;
+  map.__proto__ = InternalWeakMapProto;
+  return map;
+}
+
+var observerInfoMap = createInternalWeakMap();
+var objectInfoMap = createInternalWeakMap();
+
+$Object.observe = function(object, callback) {
+  if (!IS_SPEC_OBJECT(object))
+    throw MakeTypeError("observe_non_object", ["observe"]);
+  if (!IS_SPEC_FUNCTION(callback))
+    throw MakeTypeError("observe_non_function", ["observe"]);
+  if (InternalObjectIsFrozen(callback))
+    throw MakeTypeError("observe_callback_frozen");
+
+  if (!observerInfoMap.has(callback)) {
+    // TODO: setup observerInfo.priority.
+    observerInfoMap.set(callback, {
+      pendingChangeRecords: null
+    });
+  }
+
+  var objectInfo = objectInfoMap.get(object);
+  if (IS_UNDEFINED(objectInfo)) {
+    // TODO: setup objectInfo.notifier
+    objectInfo = {
+      changeObservers: new InternalArray(callback)
+    };
+    objectInfoMap.set(object, objectInfo);
+    return;
+  }
+
+  var changeObservers = objectInfo.changeObservers;
+  if (changeObservers.indexOf(callback) >= 0)
+    return;
+
+  changeObservers.push(callback);
+}
+
+$Object.unobserve = function(object, callback) {
+  if (!IS_SPEC_OBJECT(object))
+    throw MakeTypeError("observe_non_object", ["unobserve"]);
+
+  var objectInfo = objectInfoMap.get(object);
+  if (IS_UNDEFINED(objectInfo))
+    return;
+
+  var changeObservers = objectInfo.changeObservers;
+  var index = changeObservers.indexOf(callback);
+  if (index < 0)
+    return;
+
+  changeObservers.splice(index, 1);
+}
+
+function EnqueueChangeRecord(changeRecord, observers) {
+  for (var i = 0; i < observers.length; i++) {
+    var observer = observers[i];
+    var observerInfo = observerInfoMap.get(observer);
+
+    // TODO: "activate" the observer
+
+    if (IS_NULL(observerInfo.pendingChangeRecords)) {
+      observerInfo.pendingChangeRecords = new InternalArray(changeRecord);
+    } else {
+      observerInfo.pendingChangeRecords.push(changeRecord);
+    }
+  }
+}
+
+$Object.notify = function(object, changeRecord) {
+  // TODO: notifier needs to be [[THIS]]
+  if (!IS_STRING(changeRecord.type))
+    throw MakeTypeError("observe_type_non_string");
+
+  var objectInfo = objectInfoMap.get(object);
+  if (IS_UNDEFINED(objectInfo))
+    return;
+
+  var newRecord = {
+    object: object  // TODO: Needs to be 'object' retreived from notifier
+  };
+  for (var prop in changeRecord) {
+    if (prop === 'object')
+      continue;
+    newRecord[prop] = changeRecord[prop];
+  }
+  InternalObjectFreeze(newRecord);
+
+  EnqueueChangeRecord(newRecord, objectInfo.changeObservers);
+}
+
+$Object.deliverChangeRecords = function(callback) {
+  if (!IS_SPEC_FUNCTION(callback))
+    throw MakeTypeError("observe_non_function", ["deliverChangeRecords"]);
+
+  var observerInfo = observerInfoMap.get(callback);
+  if (IS_UNDEFINED(observerInfo))
+    return;
+
+  var pendingChangeRecords = observerInfo.pendingChangeRecords;
+  if (IS_NULL(pendingChangeRecords))
+    return;
+
+  observerInfo.pendingChangeRecords = null;
+  var delivered = [];
+  %MoveArrayContents(pendingChangeRecords, delivered);
+  callback(delivered);
+}