Add Dart_IdentityHash to the embedding API.

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 581 matching lines @@
   }
   const Object& object1 = Object::Handle(isolate, Api::UnwrapHandle(obj1));
   const Object& object2 = Object::Handle(isolate, Api::UnwrapHandle(obj2));
   if (object1.IsInstance() && object2.IsInstance()) {
     return Instance::Cast(object1).IsIdenticalTo(Instance::Cast(object2));
   }
   return false;
 }
 
 
+DART_EXPORT uint64_t Dart_IdentityHash(Dart_Handle obj) {
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+
+  const Object& object = Object::Handle(isolate, Api::UnwrapHandle(obj));
+  if (!object.IsInstance() && !object.IsNull()) {
+    return 0;
+  }

[siva, 2014/05/02 17:29:59]

Maybe use the pattern:
  const Instance& obj = Api::UnwrapInstanceHandle(isolate, exception);
  if (obj.IsNull()) {
    RETURN_TYPE_ERROR(isolate, exception, Instance);
  }

+
+  const Library& libcore = Library::Handle(isolate, Library::CoreLibrary());
+  const String& function_name = String::Handle(isolate,
+                                               String::New("identityHashCode"));
+  const Function& function =
+      Function::Handle(isolate,
+                       libcore.LookupFunctionAllowPrivate(function_name));
+  if (function.IsNull()) {
+    UNREACHABLE();
+    return 0;
+  }
+
+  const Array& arguments = Array::Handle(isolate, Array::New(1));
+  arguments.SetAt(0, object);
+  const Object& result =
+      Object::Handle(isolate, DartEntry::InvokeFunction(function, arguments));
+
+  if (result.IsSmi()) {
+    return Smi::Cast(result).Value();
+  }
+  if (result.IsMint()) {
+    const Mint& mint = Mint::Cast(result);
+    if (!mint.IsNegative()) {
+      return mint.AsInt64Value();
+    }
+  }
+  if (result.IsBigint()) {
+    const Bigint& bigint = Bigint::Cast(result);
+    if (BigintOperations::FitsIntoUint64(bigint)) {
+      return BigintOperations::ToUint64(bigint);
+    }
+  }

[siva, 2014/05/02 17:29:59]

We have a similar pattern in Dart_NativeIntegerArgument maybe you could factor
this part out into a static function.

[rmacnak, 2014/05/02 21:19:13]

Given the lack of failure cases here I don't think there's a good refactoring.
But Dart_NativeIntegerArgument and Dart_IntegerToInt64 could share some code if
we're okay with slightly less specific error messages.

+  return 0;
+}
+
+
 DART_EXPORT Dart_Handle Dart_HandleFromPersistent(
     Dart_PersistentHandle object) {
   Isolate* isolate = Isolate::Current();
   CHECK_ISOLATE(isolate);
   ApiState* state = isolate->api_state();
   ASSERT(state != NULL);
   PersistentHandle* ref = PersistentHandle::Cast(object);
   return Api::NewHandle(isolate, ref->raw());
 }
 
@@ skipping 4127 matching lines @@
 
 
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data) {
   Service::RegisterRootEmbedderCallback(name, callback, user_data);
 }
 
 }  // namespace dart