Object.observe: generate change records for indexed properties.

src/elements.cc

Index: src/elements.cc
diff --git a/src/elements.cc b/src/elements.cc
index 3d188291030ddc66ec5ffc8828d59376dd666c31..771b0b6f01ad4559f7dc0b6269f3cb07fb2841e5 100644
--- a/src/elements.cc
+++ b/src/elements.cc
@@ -564,6 +564,28 @@ class ElementsAccessorBase : public ElementsAccessor {
            : backing_store->GetHeap()->the_hole_value();
   }
 
+  MUST_USE_RESULT virtual PropertyAttributes GetAttributes(
+      Object* receiver,
+      JSObject* holder,
+      uint32_t key,
+      FixedArrayBase* backing_store) {
+    if (backing_store == NULL) {
+      backing_store = holder->elements();
+    }
+    return ElementsAccessorSubclass::GetAttributesImpl(
+        receiver, holder, key, BackingStore::cast(backing_store));
+  }
+
+  MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
+        Object* receiver,
+        JSObject* obj,
+        uint32_t key,
+        BackingStore* backing_store) {
+    if (key >= ElementsAccessorSubclass::GetCapacityImpl(backing_store))

[Michael Starzinger, 2012/11/07 19:43:50]

Curly brackets around body.

[rossberg, 2012/11/08 11:22:56]

Done.

+      return ABSENT;
+    return backing_store->get(key)->IsTheHole() ? ABSENT : NONE;

[Toon Verwaest, 2012/11/08 10:01:31]

You can probably use is_the_hole(key) here.

[rossberg, 2012/11/08 11:22:56]

Done.

+  }
+
   MUST_USE_RESULT virtual MaybeObject* SetLength(JSArray* array,
                                                  Object* length) {
     return ElementsAccessorSubclass::SetLengthImpl(
@@ -1143,6 +1165,17 @@ class ExternalElementsAccessor
         : backing_store->GetHeap()->undefined_value();
   }
 
+

[Michael Starzinger, 2012/11/07 19:54:03]

Drop one of the two newlines.

[rossberg, 2012/11/08 11:22:56]

Done.

+  MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
+      Object* receiver,
+      JSObject* obj,
+      uint32_t key,
+      BackingStore* backing_store) {
+    return
+        key < ExternalElementsAccessorSubclass::GetCapacityImpl(backing_store)
+        ? NONE : ABSENT;
+  }
+
   MUST_USE_RESULT static MaybeObject* SetLengthImpl(
       JSObject* obj,
       Object* length,
@@ -1431,6 +1464,18 @@ class DictionaryElementsAccessor
     return obj->GetHeap()->the_hole_value();
   }
 
+  MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
+      Object* receiver,
+      JSObject* obj,
+      uint32_t key,
+      SeededNumberDictionary* backing_store) {
+    int entry = backing_store->FindEntry(key);
+    if (entry != SeededNumberDictionary::kNotFound) {
+      return backing_store->DetailsAt(entry).attributes();
+    }
+    return ABSENT;
+  }
+
   static bool HasElementImpl(Object* receiver,
                              JSObject* holder,
                              uint32_t key,
@@ -1490,6 +1535,25 @@ class NonStrictArgumentsElementsAccessor : public ElementsAccessorBase<
     }
   }
 
+  MUST_USE_RESULT static PropertyAttributes GetAttributesImpl(
+      Object* receiver,
+      JSObject* obj,
+      uint32_t key,
+      FixedArray* parameter_map) {
+    // Aliased parameters and non-aliased elements in a fast backing store

[Michael Starzinger, 2012/11/07 19:43:50]

I think we can drop all three lines of comments. It adds no valuable information
here. At least this is the wrong place to describe our crazy arguments object
layout.

[rossberg, 2012/11/08 11:22:56]

Done.

+    // behave as FAST_ELEMENT.  Non-aliased elements in a dictionary
+    // backing store behave as DICTIONARY_ELEMENT.
+    Object* probe = GetParameterMapArg(obj, parameter_map, key);
+    if (!probe->IsTheHole()) {
+      return NONE;
+    } else {
+      // If not aliased, check the arguments.
+      FixedArray* arguments = FixedArray::cast(parameter_map->get(1));

[Toon Verwaest, 2012/11/08 10:01:31]

Can we use a constant here? (kArgumentsIndex or so)

[rossberg, 2012/11/08 11:22:56]

Just mirrored this after GetImpl, which does the same thing. :)

+      return ElementsAccessor::ForArray(arguments)->GetAttributes(
+          receiver, obj, key, arguments);
+    }
+  }
+
   MUST_USE_RESULT static MaybeObject* SetLengthImpl(
       JSObject* obj,
       Object* length,