Roll forward to cl/338482889

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I9850950db8bd84f0904ea1a413151887f52098cf

cpp/platform/public/condition_variable.h

@@ -0,0 +1,35 @@
+#ifndef PLATFORM_PUBLIC_CONDITION_VARIABLE_H_
+#define PLATFORM_PUBLIC_CONDITION_VARIABLE_H_
+
+#include "platform/api/condition_variable.h"
+#include "platform/api/platform.h"
+#include "platform/base/exception.h"
+#include "platform/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;
+
+  void Notify() { impl_->Notify(); }
+  Exception Wait() { return impl_->Wait(); }
+  Exception Wait(absl::Duration timeout) { return impl_->Wait(timeout); }
+
+ private:
+  std::unique_ptr<api::ConditionVariable> impl_;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_PUBLIC_CONDITION_VARIABLE_H_