chore: import upstream snapshot with attribution

cpp/include/ray/api/xlang_function.h

@@ -0,0 +1,85 @@
+// Copyright 2020-2021 The Ray Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <string>
+#include <string_view>
+
+namespace ray {
+
+template <typename R>
+struct PyFunction {
+  bool IsPython() { return true; }
+  R operator()() { return {}; }
+
+  std::string module_name;
+  std::string function_name;
+};
+
+struct PyActorClass {
+  bool IsPython() { return true; }
+  void operator()() {}
+
+  std::string module_name;
+  std::string class_name;
+  std::string function_name = "__init__";
+};
+
+template <typename R>
+struct PyActorMethod {
+  bool IsPython() { return true; }
+  R operator()() { return {}; }
+
+  std::string function_name;
+};
+
+struct JavaActorClass {
+  bool IsJava() { return true; }
+  void operator()() {}
+  std::string class_name;
+  std::string module_name = "";
+  std::string function_name = "<init>";
+};
+template <typename R>
+struct JavaActorMethod {
+  bool IsJava() { return true; }
+  R operator()() { return {}; }
+  std::string function_name;
+};
+
+template <typename R>
+struct JavaFunction {
+  bool IsJava() { return true; }
+  R operator()() { return {}; }
+  std::string class_name;
+  std::string function_name;
+};
+
+namespace internal {
+
+enum class LangType {
+  CPP,
+  PYTHON,
+  JAVA,
+};
+
+inline constexpr size_t XLANG_HEADER_LEN = 9;
+inline constexpr std::string_view METADATA_STR_DUMMY = "__RAY_DUMMY__";
+inline constexpr std::string_view METADATA_STR_RAW = "RAW";
+inline constexpr std::string_view METADATA_STR_XLANG = "XLANG";
+
+}  // namespace internal
+
+}  // namespace ray