Status.h

//
// Class Status
//   A communication status handle for non-blocking communication.
//
#ifndef IPPL_MPI_STATUS_H
#define IPPL_MPI_STATUS_H
 
#include <mpi.h>
#include <optional>
 
namespace ippl {
    namespace mpi {
 
        class Status {
        public:
            Status()
                : status_m()
                , count_m(-1){};
 
            Status(const Status&) = default;
 
            Status& operator=(Status& other) = default;
 
            int source() const noexcept { return status_m.MPI_SOURCE; }
 
            int tag() const noexcept { return status_m.MPI_TAG; }
 
            int error() const noexcept { return status_m.MPI_ERROR; }
 
            template <typename T>
            std::optional<int> count();
 
            // https://en.cppreference.com/w/cpp/language/cast_operator
            operator MPI_Status*() noexcept { return &status_m; }
 
            operator const MPI_Status*() const noexcept { return &status_m; }
 
        private:
            MPI_Status status_m;
            int count_m;
        };
 
        template <typename T>
        std::optional<int> Status::count() {
            if (count_m != -1) {
                return count_m;
            }
 
            int count             = MPI_UNDEFINED;
            MPI_Datatype datatype = get_mpi_datatype<T>(T());
            MPI_Get_count(&status_m, datatype, &count);
 
            if (count == MPI_UNDEFINED) {
                return std::optional<int>();
            }
            count_m = count;
            return count_m;
        }
    }  // namespace mpi
}  // namespace ippl
 
#endif