InstanceLimit.h

/********************************************************************************
 *    Copyright (C) 2019 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH    *
 *                                                                              *
 *              This software is distributed under the terms of the             *
 *              GNU Lesser General Public Licence (LGPL) version 3,             *
 *                  copied verbatim in the file "LICENSE"                       *
 ********************************************************************************/
 
#ifndef FAIR_MQ_TOOLS_INSTANCELIMIT_H
#define FAIR_MQ_TOOLS_INSTANCELIMIT_H
 
#include "Strings.h"
 
namespace fair::mq::tools
{
 
template<typename Tag, int Max>
struct InstanceLimiter
{
    InstanceLimiter() { Increment(); }
    explicit InstanceLimiter(const InstanceLimiter&) = delete;
    explicit InstanceLimiter(InstanceLimiter&&) = delete;
    InstanceLimiter& operator=(const InstanceLimiter&) = delete;
    InstanceLimiter& operator=(InstanceLimiter&&) = delete;
    ~InstanceLimiter() { Decrement(); }
    auto GetCount() -> int { return fCount; }
 
  private:
    auto Increment() -> void
    {
        if (fCount < Max) {
            ++fCount;
        } else {
            throw std::runtime_error(
                ToString("More than ", Max, " instances of ", Tag(), " in parallel not supported"));
        }
    }
 
    auto Decrement() -> void
    {
        if (fCount > 0) {
            --fCount;
        }
    }
 
    static int fCount;
};
 
template<typename Tag, int Max>
int InstanceLimiter<Tag, Max>::fCount(0);
 
} // namespace fair::mq::tools
 
#endif /* FAIR_MQ_TOOLS_INSTANCELIMIT_H */