- Create an all static TypedDataView class which uses implicit field offset

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 20947)
+++ runtime/vm/object.h	(working copy)
@@ -3432,6 +3432,7 @@
   HEAP_OBJECT_IMPLEMENTATION(Instance, Object);
   friend class Class;
   friend class Closure;
+  friend class TypedDataView;
 };
 
 
@@ -5092,6 +5093,12 @@
                    intptr_t src_offset_in_bytes,
                    intptr_t length_in_bytes);
 
+  static bool IsTypedData(const Instance& obj) {
+    ASSERT(!obj.IsNull());
+    intptr_t cid = obj.raw()->GetClassId();
+    return RawObject::IsTypedDataClassId(cid);
+  }
+
  protected:
   void SetLength(intptr_t value) const {
     raw_ptr()->length_ = Smi::New(value);
@@ -5103,6 +5110,7 @@
   FINAL_HEAP_OBJECT_IMPLEMENTATION(TypedData, Instance);
   friend class Class;
   friend class ExternalTypedData;
+  friend class TypedDataView;
 };
 
 
@@ -5187,6 +5195,12 @@
                    intptr_t src_offset_in_bytes,
                    intptr_t length_in_bytes);
 
+  static bool IsExternalTypedData(const Instance& obj) {
+    ASSERT(!obj.IsNull());
+    intptr_t cid = obj.raw()->GetClassId();
+    return RawObject::IsExternalTypedDataClassId(cid);
+  }
+
  protected:
   void SetLength(intptr_t value) const {
     raw_ptr()->length_ = Smi::New(value);
@@ -5206,6 +5220,71 @@
 };
 
 
+class TypedDataView : public AllStatic {
+ public:
+  static intptr_t ElementSizeInBytes(const Instance& view_obj) {
+    ASSERT(!view_obj.IsNull());
+    intptr_t cid = view_obj.raw()->GetClassId();
+    return ElementSizeInBytes(cid);
+  }
+
+  static RawInstance* Data(const Instance& view_obj) {
+    ASSERT(!view_obj.IsNull());
+    return *reinterpret_cast<RawInstance**>(view_obj.raw_ptr() + kDataOffset);
+  }
+
+  static RawSmi* OffsetInBytes(const Instance& view_obj) {
+    ASSERT(!view_obj.IsNull());
+    return *reinterpret_cast<RawSmi**>(
+        view_obj.raw_ptr() + kOffsetInBytesOffset);
+  }
+
+  static RawSmi* Length(const Instance& view_obj) {
+    ASSERT(!view_obj.IsNull());
+    return *reinterpret_cast<RawSmi**>(view_obj.raw_ptr() + kLengthOffset);
+  }
+
+  static bool IsExternalTypedDataView(const Instance& view_obj) {
+    const Instance& data = Instance::Handle(Data(view_obj));
+    intptr_t cid = data.raw()->GetClassId();
+    ASSERT(RawObject::IsTypedDataClassId(cid) ||
+           RawObject::IsExternalTypedDataClassId(cid));
+    return RawObject::IsExternalTypedDataClassId(cid);
+  }
+
+  static intptr_t NumberOfFields() {
+    return (kLengthOffset - kTypeArguments);
+  }
+
+  static intptr_t data_offset() {
+    return kWordSize * kDataOffset;
+  }
+
+  static intptr_t offset_in_bytes_offset() {
+    return kWordSize * kOffsetInBytesOffset;
+  }
+
+  static intptr_t length_offset() {
+    return kWordSize * kLengthOffset;
+  }
+
+  static intptr_t ElementSizeInBytes(intptr_t class_id) {
+    ASSERT(RawObject::IsTypedDataViewClassId(class_id));
+    return (class_id == kByteDataViewCid) ?
+        TypedData::element_size[kTypedDataInt8ArrayCid] :
+        TypedData::element_size[class_id - kTypedDataInt8ArrayViewCid];
+  }
+
+ private:
+  enum {
+    kTypeArguments = 1,
+    kDataOffset = 2,
+    kOffsetInBytesOffset = 3,
+    kLengthOffset = 4,
+  };
+};
+
+
 // DartFunction represents the abstract Dart class 'Function'.
 class DartFunction : public Instance {
  private: