Initial public release of nearby library

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I85d490e448375aa4eb7b09680757c02fff1420b4

cpp/platform/api/system_clock.h

@@ -0,0 +1,36 @@
+// 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_API_SYSTEM_CLOCK_H_
+#define PLATFORM_API_SYSTEM_CLOCK_H_
+
+#include <cstdint>
+
+namespace location {
+namespace nearby {
+
+class SystemClock {
+ public:
+  virtual ~SystemClock() {}
+
+  // Returns the time (in milliseconds) since the system was booted, and
+  // includes deep sleep. This clock should be guaranteed to be monotonic, and
+  // should continue to tick even when the CPU is in power saving modes.
+  virtual std::int64_t elapsedRealtime() = 0;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_API_SYSTEM_CLOCK_H_