Add a unit test Benchmark_UseDartApi to measure dart api overhead.

Sample output:

Benchmark_UseDartApi: 3.245700 us per iteration
Review URL: https://chromiumcodereview.appspot.com//9979016

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@6189 260f80e4-7a28-3924-810f-c04153c831b5

runtime/vm/dart_api_impl.cc

@@ -2919,6 +2919,11 @@ DART_EXPORT Dart_Handle Dart_GetNativeArgument(Dart_NativeArguments args,
                                                int index) {
   DARTSCOPE(Isolate::Current());
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
+  if (index < 0 || index >= arguments->Count()) {
+    return Api::NewError(
+        "%s: argument 'index' out of range. Expected 0..%d but saw %d.",
+        CURRENT_FUNC, arguments->Count() - 1, index);
+  }
   const Object& obj = Object::Handle(arguments->At(index));
   return Api::NewLocalHandle(obj);
 }

runtime/vm/dart_api_impl_test.cc

@@ -4740,6 +4740,111 @@ TEST_CASE(IsolateInterrupt) {
   Isolate::SetInterruptCallback(saved);
 }
 
+
+void InitNativeFields(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  int count = Dart_GetNativeArgumentCount(args);
+  EXPECT_EQ(1, count);
+
+  Dart_Handle recv = Dart_GetNativeArgument(args, 0);
+  EXPECT(!Dart_IsError(recv));
+  Dart_Handle result = Dart_SetNativeInstanceField(recv, 0, 7);
+  EXPECT(!Dart_IsError(result));
+
+  Dart_ExitScope();
+}
+
+
+// The specific api functions called here are a bit arbitrary.  We are
+// trying to get a sense of the overhead for using the dart api.
+void UseDartApi(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  int count = Dart_GetNativeArgumentCount(args);
+  EXPECT_EQ(3, count);
+
+  // Get the receiver.
+  Dart_Handle recv = Dart_GetNativeArgument(args, 0);
+  EXPECT(!Dart_IsError(recv));
+
+  // Get param1.
+  Dart_Handle param1 = Dart_GetNativeArgument(args, 1);
+  EXPECT(!Dart_IsError(param1));
+  EXPECT(Dart_IsInteger(param1));
+  bool fits = false;
+  Dart_Handle result = Dart_IntegerFitsIntoInt64(param1, &fits);
+  EXPECT(!Dart_IsError(result) && fits);
+  int64_t value1;
+  result = Dart_IntegerToInt64(param1, &value1);
+  EXPECT(!Dart_IsError(result));
+  EXPECT_LE(0, value1);
+  EXPECT_LE(value1, 1000000);
+
+  // Get native field from receiver.
+  intptr_t value2;
+  result = Dart_GetNativeInstanceField(recv, 0, &value2);
+  EXPECT(!Dart_IsError(result));
+  EXPECT_EQ(7, value2);
+
+  // Return param + receiver.field.
+  Dart_SetReturnValue(args, Dart_NewInteger(value1 * value2));
+  Dart_ExitScope();
+}
+
+
+static Dart_NativeFunction bm_uda_lookup(Dart_Handle name, int argument_count) {
+  const char* cstr = NULL;
+  Dart_Handle result = Dart_StringToCString(name, &cstr);
+  EXPECT(!Dart_IsError(result));
+  if (strcmp(cstr, "init") == 0) {
+    return InitNativeFields;
+  } else {
+    return UseDartApi;
+  }
+}
+
+
+TEST_CASE(Benchmark_UseDartApi) {
+  const char* kScriptChars =
+      "class Class extends NativeFieldsWrapper{\n"
+      "  int init() native 'init';\n"
+      "  int method(int param1, int param2) native 'method';\n"
+      "}\n"
+      "\n"
+      "double benchmark(int count) {\n"
+      "  Class c = new Class();\n"
+      "  c.init();\n"
+      "  Stopwatch sw = new Stopwatch.start();\n"
+      "  for (int i = 0; i < count; i++) {\n"
+      "    c.method(i,7);\n"
+      "  }\n"
+      "  sw.stop();\n"
+      "  return sw.elapsedInUs() / count;\n"
+      "}\n";
+
+  Dart_Handle lib = TestCase::LoadTestScript(
+      kScriptChars,
+      reinterpret_cast<Dart_NativeEntryResolver>(bm_uda_lookup));
+
+  // Create a native wrapper class with native fields.
+  Dart_Handle result = Dart_CreateNativeWrapperClass(
+      lib,
+      Dart_NewString("NativeFieldsWrapper"),
+      1);
+  EXPECT_VALID(result);
+
+  Dart_Handle args[1];
+  args[0] = Dart_NewInteger(100000);
+  result = Dart_Invoke(lib,
+                       Dart_NewString("benchmark"),
+                       1,
+                       args);
+  EXPECT_VALID(result);
+  EXPECT(Dart_IsDouble(result));
+  double out;
+  result = Dart_DoubleValue(result, &out);
+  fprintf(stderr, "Benchmark_UseDartApi: %f us per iteration\n", out);
+}
+
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart