Vulkan-Hpp/snippets/StructureChain.hpp

  template <typename X, typename Y>
  struct StructExtends
  {
    enum
    {
      value = false
    };
  };

  template <typename Type, class...>
  struct IsPartOfStructureChain
  {
    static const bool valid = false;
  };

  template <typename Type, typename Head, typename... Tail>
  struct IsPartOfStructureChain<Type, Head, Tail...>
  {
    static const bool valid = std::is_same<Type, Head>::value || IsPartOfStructureChain<Type, Tail...>::valid;
  };

  template <size_t Index, typename T, typename... ChainElements>
  struct StructureChainContains
  {
    static const bool value = std::is_same<T, typename std::tuple_element<Index, std::tuple<ChainElements...>>::type>::value ||
                              StructureChainContains<Index - 1, T, ChainElements...>::value;
  };

  template <typename T, typename... ChainElements>
  struct StructureChainContains<0, T, ChainElements...>
  {
    static const bool value = std::is_same<T, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value;
  };

  template <size_t Index, typename... ChainElements>
  struct StructureChainValidation
  {
    using TestType          = typename std::tuple_element<Index, std::tuple<ChainElements...>>::type;
    static const bool valid = StructExtends<TestType, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value &&
                              ( TestType::allowDuplicate || !StructureChainContains<Index - 1, TestType, ChainElements...>::value ) &&
                              StructureChainValidation<Index - 1, ChainElements...>::valid;
  };

  template <typename... ChainElements>
  struct StructureChainValidation<0, ChainElements...>
  {
    static const bool valid = true;
  };

  template <typename... ChainElements>
  class StructureChain : public std::tuple<ChainElements...>
  {
    // Note: StructureChain has no move constructor or move assignment operator, as it is not supposed to contain movable containers.
    //       In order to get a copy-operation on a move-operations, those functions are neither deleted nor defaulted.
  public:
    StructureChain() VULKAN_HPP_NOEXCEPT
    {
      static_assert( StructureChainValidation<sizeof...( ChainElements ) - 1, ChainElements...>::valid, "The structure chain is not valid!" );
      link<sizeof...( ChainElements ) - 1>();
    }

    StructureChain( StructureChain const & rhs ) VULKAN_HPP_NOEXCEPT : std::tuple<ChainElements...>( rhs )
    {
      static_assert( StructureChainValidation<sizeof...( ChainElements ) - 1, ChainElements...>::valid, "The structure chain is not valid!" );
      link( &std::get<0>( *this ),
            &std::get<0>( rhs ),
            reinterpret_cast<VkBaseOutStructure *>( &std::get<0>( *this ) ),
            reinterpret_cast<VkBaseInStructure const *>( &std::get<0>( rhs ) ) );
    }

    StructureChain( ChainElements const &... elems ) VULKAN_HPP_NOEXCEPT : std::tuple<ChainElements...>( elems... )
    {
      static_assert( StructureChainValidation<sizeof...( ChainElements ) - 1, ChainElements...>::valid, "The structure chain is not valid!" );
      link<sizeof...( ChainElements ) - 1>();
    }

    StructureChain & operator=( StructureChain const & rhs ) VULKAN_HPP_NOEXCEPT
    {
      std::tuple<ChainElements...>::operator=( rhs );
      link( &std::get<0>( *this ),
            &std::get<0>( rhs ),
            reinterpret_cast<VkBaseOutStructure *>( &std::get<0>( *this ) ),
            reinterpret_cast<VkBaseInStructure const *>( &std::get<0>( rhs ) ) );
      return *this;
    }

    template <typename T = typename std::tuple_element<0, std::tuple<ChainElements...>>::type, size_t Which = 0>
    T & get() VULKAN_HPP_NOEXCEPT
    {
      return std::get<ChainElementIndex<0, T, Which, void, ChainElements...>::value>( static_cast<std::tuple<ChainElements...> &>( *this ) );
    }

    template <typename T = typename std::tuple_element<0, std::tuple<ChainElements...>>::type, size_t Which = 0>
    T const & get() const VULKAN_HPP_NOEXCEPT
    {
      return std::get<ChainElementIndex<0, T, Which, void, ChainElements...>::value>( static_cast<std::tuple<ChainElements...> const &>( *this ) );
    }

    template <typename T0, typename T1, typename... Ts>
    std::tuple<T0 &, T1 &, Ts &...> get() VULKAN_HPP_NOEXCEPT
    {
      return std::tie( get<T0>(), get<T1>(), get<Ts>()... );
    }

    template <typename T0, typename T1, typename... Ts>
    std::tuple<T0 const &, T1 const &, Ts const &...> get() const VULKAN_HPP_NOEXCEPT
    {
      return std::tie( get<T0>(), get<T1>(), get<Ts>()... );
    }

    // assign a complete structure to the StructureChain without modifying the chaining
    template <typename T = typename std::tuple_element<0, std::tuple<ChainElements...>>::type, size_t Which = 0>
    StructureChain & assign( const T & rhs ) VULKAN_HPP_NOEXCEPT
    {
      T &  lhs   	= get<T, Which>();
      auto pNext = lhs.pNext;
      lhs        = rhs;
      lhs.pNext  = pNext;
      return *this;
    }

    template <typename ClassType, size_t Which = 0>
    typename std::enable_if<std::is_same<ClassType, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value && ( Which == 0 ), bool>::type
      isLinked() const VULKAN_HPP_NOEXCEPT
    {
      return true;
    }

    template <typename ClassType, size_t Which = 0>
    typename std::enable_if<!std::is_same<ClassType, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value || ( Which != 0 ), bool>::type
      isLinked() const VULKAN_HPP_NOEXCEPT
    {
      static_assert( IsPartOfStructureChain<ClassType, ChainElements...>::valid, "Can't unlink Structure that's not part of this StructureChain!" );
      return isLinked( reinterpret_cast<VkBaseInStructure const *>( &get<ClassType, Which>() ) );
    }

    template <typename ClassType, size_t Which = 0>
    typename std::enable_if<!std::is_same<ClassType, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value || ( Which != 0 ), void>::type
      relink() VULKAN_HPP_NOEXCEPT
    {
      static_assert( IsPartOfStructureChain<ClassType, ChainElements...>::valid, "Can't relink Structure that's not part of this StructureChain!" );
      auto pNext = reinterpret_cast<VkBaseInStructure *>( &get<ClassType, Which>() );
      VULKAN_HPP_ASSERT( !isLinked( pNext ) );
      auto & headElement = std::get<0>( static_cast<std::tuple<ChainElements...> &>( *this ) );
      pNext->pNext       = reinterpret_cast<VkBaseInStructure const *>( headElement.pNext );
      headElement.pNext  = pNext;
    }

    template <typename ClassType, size_t Which = 0>
    typename std::enable_if<!std::is_same<ClassType, typename std::tuple_element<0, std::tuple<ChainElements...>>::type>::value || ( Which != 0 ), void>::type
      unlink() VULKAN_HPP_NOEXCEPT
    {
      static_assert( IsPartOfStructureChain<ClassType, ChainElements...>::valid, "Can't unlink Structure that's not part of this StructureChain!" );
      unlink( reinterpret_cast<VkBaseOutStructure const *>( &get<ClassType, Which>() ) );
    }

  private:
    template <int Index, typename T, int Which, typename, class First, class... Types>
    struct ChainElementIndex : ChainElementIndex<Index + 1, T, Which, void, Types...>
    {
    };

    template <int Index, typename T, int Which, class First, class... Types>
    struct ChainElementIndex<Index, T, Which, typename std::enable_if<!std::is_same<T, First>::value, void>::type, First, Types...>
      : ChainElementIndex<Index + 1, T, Which, void, Types...>
    {
    };

    template <int Index, typename T, int Which, class First, class... Types>
    struct ChainElementIndex<Index, T, Which, typename std::enable_if<std::is_same<T, First>::value, void>::type, First, Types...>
      : ChainElementIndex<Index + 1, T, Which - 1, void, Types...>
    {
    };

    template <int Index, typename T, class First, class... Types>
    struct ChainElementIndex<Index, T, 0, typename std::enable_if<std::is_same<T, First>::value, void>::type, First, Types...>
      : std::integral_constant<int, Index>
    {
    };

    bool isLinked( VkBaseInStructure const * pNext ) const VULKAN_HPP_NOEXCEPT
    {
      VkBaseInStructure const * elementPtr =
        reinterpret_cast<VkBaseInStructure const *>( &std::get<0>( static_cast<std::tuple<ChainElements...> const &>( *this ) ) );
      while ( elementPtr )
      {
        if ( elementPtr->pNext == pNext )
        {
          return true;
        }
        elementPtr = elementPtr->pNext;
      }
      return false;
    }

    template <size_t Index>
    typename std::enable_if<Index != 0, void>::type link() VULKAN_HPP_NOEXCEPT
    {
      auto & x = std::get<Index - 1>( static_cast<std::tuple<ChainElements...> &>( *this ) );
      x.pNext  = &std::get<Index>( static_cast<std::tuple<ChainElements...> &>( *this ) );
      link<Index - 1>();
    }

    template <size_t Index>
    typename std::enable_if<Index == 0, void>::type link() VULKAN_HPP_NOEXCEPT
    {
    }

    void link( void * dstBase, void const * srcBase, VkBaseOutStructure * dst, VkBaseInStructure const * src )
    {
      while ( src->pNext )
      {
        std::ptrdiff_t offset = reinterpret_cast<char const *>( src->pNext ) - reinterpret_cast<char const *>( srcBase );
        dst->pNext            = reinterpret_cast<VkBaseOutStructure *>( reinterpret_cast<char *>( dstBase ) + offset );
        dst                   = dst->pNext;
        src                   = src->pNext;
      }
      dst->pNext = nullptr;
    }

    void unlink( VkBaseOutStructure const * pNext ) VULKAN_HPP_NOEXCEPT
    {
      VkBaseOutStructure * elementPtr = reinterpret_cast<VkBaseOutStructure *>( &std::get<0>( static_cast<std::tuple<ChainElements...> &>( *this ) ) );
      while ( elementPtr && ( elementPtr->pNext != pNext ) )
      {
        elementPtr = elementPtr->pNext;
      }
      if ( elementPtr )
      {
        elementPtr->pNext = pNext->pNext;
      }
      else
      {
        VULKAN_HPP_ASSERT( false );  // fires, if the ClassType member has already been unlinked !
      }
    }
  };
  // interupt the VULKAN_HPP_NAMESPACE for a moment to add specializations of std::tuple_size and std::tuple_element for the StructureChain!
}

namespace std
{
  template <typename... Elements>
  struct tuple_size<VULKAN_HPP_NAMESPACE::StructureChain<Elements...>>
  {
    static constexpr size_t value = std::tuple_size<std::tuple<Elements...>>::value;
  };

  template <std::size_t Index, typename... Elements>
  struct tuple_element<Index, VULKAN_HPP_NAMESPACE::StructureChain<Elements...>>
  {
    using type = typename std::tuple_element<Index, std::tuple<Elements...>>::type;
  };
}  // namespace std

namespace VULKAN_HPP_NAMESPACE
{