Roll forward to cl/314747126

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

cpp/platform_v2/impl/g3/condition_variable.h

@@ -0,0 +1,47 @@
+// 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_IMPL_G3_CONDITION_VARIABLE_H_
+#define PLATFORM_V2_IMPL_G3_CONDITION_VARIABLE_H_
+
+#include "platform_v2/api/condition_variable.h"
+#include "platform_v2/base/exception.h"
+#include "platform_v2/impl/g3/mutex.h"
+#include "absl/synchronization/mutex.h"
+
+namespace location {
+namespace nearby {
+namespace g3 {
+
+class ConditionVariable : public api::ConditionVariable {
+ public:
+  explicit ConditionVariable(g3::Mutex* mutex) : mutex_(&mutex->mutex_) {}
+  ~ConditionVariable() override = default;
+
+  Exception Wait() override {
+    cond_var_.Wait(mutex_);
+    return {Exception::kSuccess};
+  }
+  void Notify() override { cond_var_.SignalAll(); }
+
+ private:
+  absl::Mutex* mutex_;
+  absl::CondVar cond_var_;
+};
+
+}  // namespace g3
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_V2_IMPL_G3_CONDITION_VARIABLE_H_