nearby: snapshot as of cl/296436629

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I2cf5bf225b76f4c1541954651f3a7544a14e0cec

cpp/platform/api/count_down_latch.h

@@ -0,0 +1,28 @@
+#ifndef PLATFORM_API_COUNT_DOWN_LATCH_H_
+#define PLATFORM_API_COUNT_DOWN_LATCH_H_
+
+#include <cstdint>
+
+#include "platform/exception.h"
+
+namespace location {
+namespace nearby {
+
+// A synchronization aid that allows one or more threads to wait until a set of
+// operations being performed in other threads completes.
+//
+// https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CountDownLatch.html
+class CountDownLatch {
+ public:
+  virtual ~CountDownLatch() {}
+
+  virtual Exception::Value await() = 0;  // throws Exception::INTERRUPTED
+  virtual ExceptionOr<bool> await(
+      std::int32_t timeout_millis) = 0;  // throws Exception::INTERRUPTED
+  virtual void countDown() = 0;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_API_COUNT_DOWN_LATCH_H_