Add fast path to ListGetAsBytes for byte-size ExternalTypedData.

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
@@ skipping 2668 matching lines @@
                                                                                \
       }                                                                        \
       const Integer& integer = Integer::Cast(element);                         \
       native_array[i] = static_cast<uint8_t>(integer.AsInt64Value() & 0xff);   \
       ASSERT(integer.AsInt64Value() <= 0xff);                                  \
     }                                                                          \
     return Api::Success();                                                     \
   }                                                                            \
   return Api::NewError("Invalid length passed in to access array elements");   \
 
-
-static Dart_Handle CopyBytes(const TypedData& array,
+template<typename T>
+static Dart_Handle CopyBytes(const T& array,
                              intptr_t offset,
                              uint8_t* native_array,
                              intptr_t length) {
-  ASSERT(array.IsTypedData());
   ASSERT(array.ElementSizeInBytes() == 1);
   NoGCScope no_gc;
   memmove(native_array,
           reinterpret_cast<uint8_t*>(array.DataAddr(offset)),
           length);
   return Api::Success();
 }
 
 
 DART_EXPORT Dart_Handle Dart_ListGetAsBytes(Dart_Handle list,
                                             intptr_t offset,
                                             uint8_t* native_array,
                                             intptr_t length) {
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   const Object& obj = Object::Handle(isolate, Api::UnwrapHandle(list));
   if (obj.IsTypedData()) {
     const TypedData& array = TypedData::Cast(obj);
     if (array.ElementSizeInBytes() == 1) {
       if (!Utils::RangeCheck(offset, length, array.Length())) {
         return Api::NewError(
             "Invalid length passed in to access list elements");
       }
       return CopyBytes(array, offset, native_array, length);
     }
   }
+  if (obj.IsExternalTypedData()) {
+    const ExternalTypedData& external_array = ExternalTypedData::Cast(obj);
+    if (external_array.ElementSizeInBytes() == 1) {
+      if (!Utils::RangeCheck(offset, length, external_array.Length())) {
+        return Api::NewError(
+            "Invalid length passed in to access list elements");
+      }
+      return CopyBytes(external_array, offset, native_array, length);
+    }
+  }
   if (RawObject::IsTypedDataViewClassId(obj.GetClassId())) {
     const Instance& view = Instance::Cast(obj);
     if (TypedDataView::ElementSizeInBytes(view) == 1) {
       intptr_t view_length = Smi::Value(TypedDataView::Length(view));
       if (!Utils::RangeCheck(offset, length, view_length)) {
         return Api::NewError(
             "Invalid length passed in to access list elements");
       }
       const Instance& data = Instance::Handle(TypedDataView::Data(view));
       if (data.IsTypedData()) {
@@ skipping 2341 matching lines @@
 
 
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data) {
   Service::RegisterRootEmbedderCallback(name, callback, user_data);
 }
 
 }  // namespace dart