Factory.h

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// --------------------------------------------------------------------------
//                   OpenMS -- Open-Source Mass Spectrometry
// --------------------------------------------------------------------------
// Copyright The OpenMS Team -- Eberhard Karls University Tuebingen,
// ETH Zurich, and Freie Universitaet Berlin 2002-2023.
//
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//    may be used to endorse or promote products derived from this software
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// $Maintainer: Chris Bielow $
// $Authors: Chris Bielow $
// --------------------------------------------------------------------------
 
#pragma once
 
#include <OpenMS/CONCEPT/Exception.h>
#include <OpenMS/CONCEPT/FactoryBase.h>
#include <OpenMS/CONCEPT/SingletonRegistry.h>
#include <OpenMS/DATASTRUCTURES/String.h>
 
#include <mutex>
#include <map>
#include <typeinfo>
 
namespace OpenMS
{
  class String;
 
  template <typename FactoryProduct>
  class Factory :
    public FactoryBase
  {
    friend class singletonsNeedNoFriends; //some versions of gcc would warn otherwise
 
private:
    typedef FactoryProduct * (*FunctionType)();
    typedef std::map<String, FunctionType> Map;
    typedef typename Map::const_iterator MapIterator;
    typedef Factory<FactoryProduct> FactoryType;
 
    ~Factory() override{}
 
    Factory()
    {
    }
 
    static Factory * instance_()
    {
      if (!instance_ptr_)
      {
        // name of this Factory
        String myName = typeid(FactoryType).name();
 
        //check if an instance of this kind of Factory already registered
        if (!SingletonRegistry::isRegistered(myName))
        {
          // if not registered yet ... add it
          instance_ptr_ = new Factory();
          // now, attention as ORDER of commands is important here:
          // first register the Factory
          SingletonRegistry::registerFactory(myName, instance_ptr_);
          // because this call, might use another instance of this factory, but we want the other instance to register the children with "US"
          FactoryProduct::registerChildren();
        }
        else
        {
          // get instance of this factory from registry
          instance_ptr_ = static_cast<FactoryType *>(SingletonRegistry::getFactory(myName));
        }
      }
      return instance_ptr_;
    }
 
public:
 
    static FactoryProduct * create(const String & name)
    {
 
      // unique lock (make sure we only create one instance)
      //  -> Since we may call Factory<FactoryProduct>::create for another
      //     FactoryProduct during initialization, we have to implement locking
      //     per template class specialization.
      static std::mutex factory_create_mutex;
      std::lock_guard<std::mutex> lock(factory_create_mutex);
 
      MapIterator it = instance_()->inventory_.find(name);
      if (it != instance_()->inventory_.end())
      {
        return (*(it->second))();
      }
      else
      {
        throw Exception::InvalidValue(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION, "This FactoryProduct is not registered!", name.c_str());
      }
    }
 
    static void registerProduct(const String & name, const FunctionType creator)
    {
      instance_()->inventory_[name] = creator;
    }
 
    static bool isRegistered(const String & name)
    {
      if (instance_()->inventory_.find(name) != instance_()->inventory_.end())
      {
        return true;
      }
      return false;
    }
 
    static std::vector<String> registeredProducts()
    {
      std::vector<String> list;
      for (MapIterator it = instance_()->inventory_.begin(); it != instance_()->inventory_.end(); ++it)
      {
        list.push_back(it->first);
      }
      return list;
    }
 
private:
 
    Map inventory_;
    static Factory * instance_ptr_;
  };
 
  template <typename FactoryProduct>
  Factory<FactoryProduct> * Factory<FactoryProduct>::instance_ptr_ = nullptr;
 
}