Roll forward to cl/338482889

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: Ic2bdb234e89f3c5860d1b483dd4bce689f13d057

cpp/platform/public/single_thread_executor.h

@@ -0,0 +1,41 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#ifndef PLATFORM_PUBLIC_SINGLE_THREAD_EXECUTOR_H_
+#define PLATFORM_PUBLIC_SINGLE_THREAD_EXECUTOR_H_
+
+#include "platform/public/submittable_executor.h"
+
+namespace location {
+namespace nearby {
+
+// An Executor that uses a single worker thread operating off an unbounded
+// queue.
+//
+// https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Executors.html#newSingleThreadExecutor--
+class SingleThreadExecutor final : public SubmittableExecutor {
+ public:
+  using Platform = api::ImplementationPlatform;
+  SingleThreadExecutor()
+      : SubmittableExecutor(Platform::CreateSingleThreadExecutor()) {}
+  ~SingleThreadExecutor() override = default;
+  SingleThreadExecutor(SingleThreadExecutor&&) = default;
+  SingleThreadExecutor& operator=(SingleThreadExecutor&&) = default;
+  int Tid() const { return GetTid(0); }
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_PUBLIC_SINGLE_THREAD_EXECUTOR_H_