Release based on cl/313536507.

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I83ec7dee1a7ef6f4bdfd47482c94d03910525b7e

cpp/platform_v2/impl/shared/posix_mutex.cc

@@ -0,0 +1,40 @@
+// 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.
+
+#include "platform_v2/impl/shared/posix_mutex.h"
+
+namespace location {
+namespace nearby {
+namespace posix {
+
+Mutex::Mutex() : attr_(), mutex_() {
+  pthread_mutexattr_init(&attr_);
+  pthread_mutexattr_settype(&attr_, PTHREAD_MUTEX_RECURSIVE);
+
+  pthread_mutex_init(&mutex_, &attr_);
+}
+
+Mutex::~Mutex() {
+  pthread_mutex_destroy(&mutex_);
+
+  pthread_mutexattr_destroy(&attr_);
+}
+
+void Mutex::Lock() { pthread_mutex_lock(&mutex_); }
+
+void Mutex::Unlock() { pthread_mutex_unlock(&mutex_); }
+
+}  // namespace posix
+}  // namespace nearby
+}  // namespace location