XrdClFwd.hh

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/*
 * XrdClFwd.hh
 *
 *  Created on: Oct 19, 2018
 *      Author: simonm
 */
 
#ifndef SRC_XRDCL_XRDCLFWD_HH_
#define SRC_XRDCL_XRDCLFWD_HH_
 
#include <memory>
#include <stdexcept>
 
namespace XrdCl
{
  //----------------------------------------------------------------------------
  //----------------------------------------------------------------------------
  template<typename T>
  struct FwdStorage
  {
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    FwdStorage() : ptr( nullptr ) { }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    FwdStorage( const T &value ) : ptr( new( &storage.memory ) T( value ) )
    {
    }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    FwdStorage& operator=( const T &value )
    {
      if( ptr ) throw std::logic_error( "XrdCl::Fwd already contains value." );
      ptr = new( &storage.memory ) T( value );
      return *this;
    }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    FwdStorage( T && value ) : ptr( new( &storage.memory ) T( std::move( value ) ) )
    {
    }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    FwdStorage& operator=( T && value )
    {
      if( ptr ) throw std::logic_error( "XrdCl::Fwd already contains value." );
      ptr = new( &storage.memory ) T( std::move( value ) );
      return *this;
    }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    ~FwdStorage()
    {
      if( ptr ) ptr->~T();
    }
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    union Memory
    {
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      Memory() { }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      ~Memory() { }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      T memory;
    };
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    Memory storage;
 
    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    T *ptr;
  };
 
  //----------------------------------------------------------------------------
  //----------------------------------------------------------------------------
  template<typename T>
  class Fwd : protected std::shared_ptr<FwdStorage<T>>
  {
    public:
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      Fwd() : std::shared_ptr<FwdStorage<T>>( new FwdStorage<T>() )
      {
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      Fwd( const Fwd &fwd ) : std::shared_ptr<FwdStorage<T>>( fwd )
      {
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      Fwd( Fwd && fwd ) : std::shared_ptr<FwdStorage<T>>( std::move( fwd ) )
      {
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      const Fwd& operator=( const T &value ) const
      {
        *this->get() = value;
        return *this;
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      const Fwd& operator=( T && value ) const
      {
        *this->get() = std::move( value );
        return *this;
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      T& operator*() const
      {
        if( !bool( this->get()->ptr ) ) throw std::logic_error( "XrdCl::Fwd contains no value!" );
        return *this->get()->ptr;
      }
 
      //------------------------------------------------------------------------
      //------------------------------------------------------------------------
      T* operator->() const
      {
        if( !bool( this->get()->ptr ) ) throw std::logic_error( "XrdCl::Fwd contains no value!" );
        return this->get()->ptr;
      }
 
  };
}
 
 
#endif /* SRC_XRDCL_XRDCLFWD_HH_ */