Roll forward to cl/314747126

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: Ie19e006429b138b3768e97dae971a43fdc5ef8bf

cpp/platform_v2/public/condition_variable.h

@@ -0,0 +1,50 @@
+// 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_V2_PUBLIC_CONDITION_VARIABLE_H_
+#define PLATFORM_V2_PUBLIC_CONDITION_VARIABLE_H_
+
+#include "platform_v2/api/condition_variable.h"
+#include "platform_v2/api/platform.h"
+#include "platform_v2/base/exception.h"
+#include "platform_v2/public/mutex.h"
+
+namespace location {
+namespace nearby {
+
+// The ConditionVariable class is a synchronization primitive that can be used
+// to block a thread, or multiple threads at the same time, until another thread
+// both modifies a shared variable (the condition), and notifies the
+// ConditionVariable.
+class ConditionVariable final {
+ public:
+  using Platform = api::ImplementationPlatform;
+  explicit ConditionVariable(Mutex* mutex)
+      : impl_(Platform::CreateConditionVariable(mutex->impl_.get())) {}
+  ConditionVariable(ConditionVariable&&) = default;
+  ConditionVariable& operator=(ConditionVariable&&) = default;
+
+  // https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#notify--
+  void Notify() { impl_->Notify(); }
+  // https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--
+  Exception Wait() { return impl_->Wait(); }
+
+ private:
+  std::unique_ptr<api::ConditionVariable> impl_;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_V2_PUBLIC_CONDITION_VARIABLE_H_