TCollectionProxyInfo.h

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// @(#)root/cont:$Id$
// Author: Markus Frank  28/10/04. Philippe Canal 02/01/2007
 
/*************************************************************************
 * Copyright (C) 1995-2004, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#ifndef ROOT_TCollectionProxyInfo
#define ROOT_TCollectionProxyInfo
 
//////////////////////////////////////////////////////////////////////////
//                                                                      //
//  Small helper to gather the information neede to generate a          //
//  Collection Proxy                                                    //
//
//////////////////////////////////////////////////////////////////////////
 
#include "RtypesCore.h"
#include "TError.h"
#include <vector>
#include <forward_list>
#include <typeinfo>
#include <type_traits>
#include <utility>
 
#if defined(_WIN32)
   #if _MSC_VER<1300
      #define TYPENAME
      #define R__VCXX6
   #else
      #define TYPENAME typename
   #endif
#else
   #define TYPENAME typename
#endif
 
class TVirtualCollectionProxy;
 
namespace ROOT {
namespace VecOps {
template <typename T>
class RVec;
}
 
namespace Internal {
template <typename T> class TStdBitsetHelper {
   // This class is intentionally empty, this is scaffolding to allow the equivalent
   // of 'template <int N> struct TCollectionProxyInfo::Type<std::bitset<N> >' which
   // is not effective in C++ (as of gcc 4.3.3).
};
}
 
namespace Detail {
 
   class TCollectionProxyInfo {
      // This class is a place holder for the information needed
      // to create the proper Collection Proxy.
      // This is similar to Reflex's CollFuncTable.
 
   public:
 
      // Same value as TVirtualCollectionProxy.
      static const UInt_t fgIteratorArenaSize = 16; // greater than sizeof(void*) + sizeof(UInt_t)
 
   /** @class ROOT::Detail::TCollectionProxyInfo::IteratorValue
    *
    * Small helper to encapsulate whether to return the value
    * pointed to by the iterator or its address.
    *
    **/
 
      template <typename Cont_t, typename value> struct IteratorValue {
         static void* get(typename Cont_t::iterator &iter) {
            return (void*)&(*iter);
         }
      };
 
      template <typename Cont_t, typename value_ptr> struct IteratorValue<Cont_t, value_ptr*> {
         static void* get(typename Cont_t::iterator &iter) {
            return (void*)(*iter);
         }
      };
 
      // Default std::vector uses a specialized raw-data iterator
      // representation. This is independent of the STL iterator ABI and is
      // also needed when an STL implementation makes vector::iterator large.
      template <typename T> struct IsStdVector : std::false_type {};
      template <typename T> struct IsStdVector<std::vector<T>> : std::true_type {};
 
   /** @class ROOT::Detail::TCollectionProxyInfo::Iterators
    *
    * Small helper to implement the function to create,access and destroy
    * iterators.
    *
    **/
 
      template <typename Cont_t, bool large = false>
      struct Iterators {
         typedef Cont_t *PCont_t;
         typedef typename Cont_t::iterator iterator;
 
         static void create(void *coll, void **begin_arena, void **end_arena, TVirtualCollectionProxy*) {
            PCont_t c = PCont_t(coll);
            new (*begin_arena) iterator(c->begin());
            new (*end_arena) iterator(c->end());
         }
         static void* copy(void *dest_arena, const void *source_ptr) {
            iterator *source = (iterator *)(source_ptr);
            new (dest_arena) iterator(*source);
            return dest_arena;
         }
         static void* next(void *iter_loc, const void *end_loc) {
            iterator *end = (iterator *)(end_loc);
            iterator *iter = (iterator *)(iter_loc);
            if (*iter != *end) {
               void *result = IteratorValue<Cont_t, typename Cont_t::value_type>::get(*iter);
               ++(*iter);
               return result;
            }
            return nullptr;
         }
         static void destruct1(void *iter_ptr) {
            iterator *start = (iterator *)(iter_ptr);
            start->~iterator();
         }
         static void destruct2(void *begin_ptr, void *end_ptr) {
            iterator *start = (iterator *)(begin_ptr);
            iterator *end = (iterator *)(end_ptr);
            start->~iterator();
            end->~iterator();
         }
      };
 
      // For Vector we take an extra short cut to avoid derefencing
      // the iterator all the time and redefine the 'address' of the
      // iterator as the iterator itself.  This requires special handling
      // in the looper (see TStreamerInfoAction) but is much faster.
      template <typename T> struct Iterators<std::vector<T>, false> {
         typedef std::vector<T> Cont_t;
         typedef Cont_t *PCont_t;
         typedef typename Cont_t::iterator iterator;
 
         static void create(void *coll, void **begin_arena, void **end_arena, TVirtualCollectionProxy*) {
            PCont_t c = PCont_t(coll);
            if (c->empty()) {
               *begin_arena = nullptr;
               *end_arena = nullptr;
               return;
            }
            *begin_arena = c->data();
            *end_arena = c->data() + c->size(); // We can not dereference the end iterator at all.
         }
         static void* copy(void *dest, const void *source) {
            *(void**)dest = *(void**)(const_cast<void*>(source));
            return dest;
         }
         static void* next(void * /* iter_loc */, const void * /* end_loc */) {
            // Should not be used.
            // In the case of vector, so that the I/O can perform better,
            // the begin_arena and the end_arena are *not* set to the
            // address of any iterator rather they are set to the value of
            // the beginning (and end) address of the vector's data.
            // Hence this routine (which takes the value of fBegin) can
            // *not* update where its points to (which in the case of vector
            // would require update the value of fBegin).
            R__ASSERT(0 && "Intentionally not implemented, do not use.");
            return nullptr;
         }
         static void destruct1(void  * /* iter_ptr */) {
            // Nothing to do
         }
         static void destruct2(void * /* begin_ptr */, void * /* end_ptr */) {
            // Nothing to do
         }
      };
 
      template <typename Cont_t> struct Iterators<Cont_t, /* large= */ true > {
         typedef Cont_t *PCont_t;
         typedef typename Cont_t::iterator iterator;
 
         static void create(void *coll, void **begin_arena, void **end_arena, TVirtualCollectionProxy*) {
            PCont_t  c = PCont_t(coll);
            if constexpr (IsStdVector<Cont_t>::value) {
               if (c->empty()) {
                  *begin_arena = nullptr;
                  *end_arena = nullptr;
                  return;
               }
               *begin_arena = c->data();
               *end_arena = c->data() + c->size();
            } else {
               *begin_arena = new iterator(c->begin());
               *end_arena = new iterator(c->end());
            }
         }
         static void* copy(void *dest_arena, const void *source_ptr) {
            if constexpr (IsStdVector<Cont_t>::value) {
               *(void**)dest_arena = *(void**)(const_cast<void*>(source_ptr));
               return dest_arena;
            } else {
               iterator *source = (iterator *)(source_ptr);
               void *iter = new iterator(*source);
               return iter;
            }
         }
         static void* next(void *iter_loc, const void *end_loc) {
            if constexpr (IsStdVector<Cont_t>::value) {
               // The vector raw-data iterator is advanced by the dedicated
               // vector looper, not through this callback.
               R__ASSERT(0 && "Intentionally not implemented, do not use.");
               return nullptr;
            } else {
               iterator *end = (iterator *)(end_loc);
               iterator *iter = (iterator *)(iter_loc);
               if (*iter != *end) {
                  void *result = IteratorValue<Cont_t, typename Cont_t::value_type>::get(*iter);
                  ++(*iter);
                  return result;
               }
               return nullptr;
            }
         }
         static void destruct1(void *begin_ptr) {
            if constexpr (!IsStdVector<Cont_t>::value) {
               iterator *start = (iterator *)(begin_ptr);
               delete start;
            }
         }
         static void destruct2(void *begin_ptr, void *end_ptr) {
            if constexpr (!IsStdVector<Cont_t>::value) {
               iterator *start = (iterator *)(begin_ptr);
               iterator *end = (iterator *)(end_ptr);
               delete start;
               delete end;
            }
         }
      };
 
  /** @class ROOT::Detail::TCollectionProxyInfo::Environ
    *
    * Small helper to save proxy environment in the event of
    * recursive calls.
    *
    * @author  M.Frank
    * @version 1.0
    * @date    10/10/2004
    */
   struct EnvironBase {
   private:
      EnvironBase(const EnvironBase&); // Intentionally not implement, copy is not supported
      EnvironBase &operator=(const EnvironBase&); // Intentionally not implement, copy is not supported
   public:
      EnvironBase() : fIdx(0), fSize(0), fObject(nullptr), fStart(nullptr), fTemp(nullptr), fUseTemp(kFALSE), fRefCount(1), fSpace(0)
      {
      }
      virtual ~EnvironBase() {}
      size_t              fIdx;
      size_t              fSize;
      void*               fObject;
      void*               fStart;
      void*               fTemp;
      union {
         Bool_t fUseTemp;
         Bool_t fLastValueVecBool;
      };
      int                 fRefCount;
      size_t              fSpace;
   };
   template <typename T> struct Environ : public EnvironBase {
      Environ() : fIterator() {}
      typedef T           Iter_t;
      Iter_t              fIterator;
      T& iter() { return fIterator; }
      static void        *Create() {
         return new Environ();
      }
   };
 
   template <class T, class Q> struct PairHolder {
      T first;
      Q second;
      PairHolder() {}
      PairHolder(const PairHolder& c) : first(c.first), second(c.second) {}
      virtual ~PairHolder() {}
   private:
      PairHolder& operator=(const PairHolder&) = delete;
   };
 
   template <class T> struct Address {
      virtual ~Address() {}
      static void* address(T ref) {
         return const_cast<void*>(reinterpret_cast<const void*>(&ref));
      }
   };
 
   struct SfinaeHelper {
      // Use SFINAE to get the size of the container
 
      // In general we get the size of the container with the size method
      template <class T>
      static size_t GetContainerSize(const T& c) {return c.size();}
 
      // Since forward_list does not provide a size operator, we have to
      // use an alternative. This has a cost of course.
      template <class T, class ALLOCATOR>
      static size_t GetContainerSize(const std::forward_list<T,ALLOCATOR>& c) {return std::distance(c.begin(),c.end());}
   };
 
   /** @class ROOT::Detail::TCollectionProxyInfo::Type
    *
    * Small helper to encapsulate basic data accesses for
    * all STL continers.
    *
    * @author  M.Frank
    * @version 1.0
    * @date    10/10/2004
    */
   template <class T> struct Type
      : public Address<TYPENAME T::const_reference>
   {
      typedef T                      Cont_t;
      typedef typename T::iterator   Iter_t;
      typedef typename T::value_type Value_t;
      typedef Environ<Iter_t>        Env_t;
      typedef Env_t                 *PEnv_t;
      typedef Cont_t                *PCont_t;
      typedef Value_t               *PValue_t;
 
      virtual ~Type() {}
 
      static inline PCont_t object(void* ptr)   {
         return PCont_t(PEnv_t(ptr)->fObject);
      }
      static void* size(void* env)  {
         PEnv_t  e = PEnv_t(env);
         e->fSize   = SfinaeHelper::GetContainerSize(*PCont_t(e->fObject));
         return &e->fSize;
      }
      static void* clear(void* env)  {
         object(env)->clear();
         return nullptr;
      }
      static void* first(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
#if 0
         // Assume iterators do not need destruction
         ::new(e->buff) Iter_t(c->begin());
#endif
         e->fIterator = c->begin();
         e->fSize  = SfinaeHelper::GetContainerSize(*c);
         if ( 0 == e->fSize ) return e->fStart = nullptr;
         TYPENAME T::const_reference ref = *(e->iter());
         return e->fStart = Type<T>::address(ref);
      }
      static void* next(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
         for (; e->fIdx > 0 && e->iter() != c->end(); ++(e->iter()), --e->fIdx){ }
         // TODO: Need to find something for going backwards....
         if ( e->iter() == c->end() ) return nullptr;
         TYPENAME T::const_reference ref = *(e->iter());
         return Type<T>::address(ref);
      }
      static void* construct(void *what, size_t size)  {
         PValue_t m = PValue_t(what);
         for (size_t i=0; i<size; ++i, ++m)
            ::new(m) Value_t();
         return nullptr;
      }
      static void* collect(void *coll, void *array)  {
         PCont_t  c = PCont_t(coll);
         PValue_t m = PValue_t(array);
         for (Iter_t i=c->begin(); i != c->end(); ++i, ++m )
            ::new(m) Value_t(*i);
         return nullptr;
      }
      static void destruct(void *what, size_t size)  {
         PValue_t m = PValue_t(what);
         for (size_t i=0; i < size; ++i, ++m )
            m->~Value_t();
      }
 
      static const bool fgLargeIterator = sizeof(typename Cont_t::iterator) > fgIteratorArenaSize;
      typedef Iterators<Cont_t,fgLargeIterator> Iterators_t;
 
   };
 
   /** @class ROOT::Detail::TCollectionProxyInfo::Pushback
    *
    * Small helper to encapsulate all necessary data accesses for
    * containers like vector, list, deque
    *
    * @author  M.Frank
    * @version 1.0
    * @date    10/10/2004
    */
   template <class T> struct Pushback : public Type<T> {
      typedef T                      Cont_t;
      typedef typename T::iterator   Iter_t;
      typedef typename T::value_type Value_t;
      typedef Environ<Iter_t>        Env_t;
      typedef Env_t                 *PEnv_t;
      typedef Cont_t                *PCont_t;
      typedef Value_t               *PValue_t;
      static void resize(void* obj, size_t n) {
         PCont_t c = PCont_t(obj);
         c->resize(n);
      }
      static void* feed(void *from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         PValue_t m = PValue_t(from);
         for (size_t i=0; i<size; ++i, ++m)
            c->push_back(*m);
         return nullptr;
      }
      static int value_offset()  {
         return 0;
      }
   };
 
   /** @class ROOT::Detail::TCollectionProxyInfo::Pushfront
    *
    * Small helper to encapsulate all necessary data accesses for
    * containers like forward_list
    *
    * @author  D.Piparo
    * @version 1.0
    * @date    26/02/2015
    */
   template <class T> struct Pushfront : public Type<T> {
      typedef T                      Cont_t;
      typedef typename T::iterator   Iter_t;
      typedef typename T::value_type Value_t;
      typedef Environ<Iter_t>        Env_t;
      typedef Env_t                 *PEnv_t;
      typedef Cont_t                *PCont_t;
      typedef Value_t               *PValue_t;
      static void resize(void* obj, size_t n) {
         PCont_t c = PCont_t(obj);
         c->resize(n);
      }
      static void* feed(void *from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         if (size==0) return nullptr;
         PValue_t m = &(PValue_t(from)[size-1]); // Take the last item
         // Iterate backwards not to revert ordering
         for (size_t i=0; i<size; ++i, --m){
            c->push_front(*m);
         }
         return nullptr;
      }
      static int value_offset()  {
         return 0;
      }
   };
 
   /** @class ROOT::Detail::TCollectionProxyInfo::Insert
    *
    * Small helper to encapsulate all necessary data accesses for
    * containers like set, multiset etc.
    *
    * @author  M.Frank
    * @version 1.0
    * @date    10/10/2004
    */
   template <class T> struct Insert : public Type<T> {
      typedef T                      Cont_t;
      typedef typename T::iterator   Iter_t;
      typedef typename T::value_type Value_t;
      typedef Environ<Iter_t>        Env_t;
      typedef Env_t                 *PEnv_t;
      typedef Cont_t                *PCont_t;
      typedef Value_t               *PValue_t;
      static void* feed(void *from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         PValue_t m = PValue_t(from);
         for (size_t i=0; i<size; ++i, ++m)
            c->insert(*m);
         return nullptr;
      }
      static void resize(void* /* obj */, size_t )  {
         ;
      }
      static int value_offset()  {
         return 0;
      }
   };
 
   /** @class ROOT::Detail::TCollectionProxyInfo::MapInsert
    *
    * Small helper to encapsulate all necessary data accesses for
    * containers like set, multiset etc.
    *
    * @author  M.Frank
    * @version 1.0
    * @date    10/10/2004
    */
   template <class T> struct MapInsert : public Type<T> {
      typedef T                      Cont_t;
      typedef typename T::iterator   Iter_t;
      typedef typename T::value_type Value_t;
      typedef Environ<Iter_t>        Env_t;
      typedef Env_t                 *PEnv_t;
      typedef Cont_t                *PCont_t;
      typedef Value_t               *PValue_t;
      static void* feed(void *from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         PValue_t m = PValue_t(from);
         for (size_t i=0; i<size; ++i, ++m)
            c->insert(*m);
         return nullptr;
      }
      static void resize(void* /* obj */, size_t )  {
         ;
      }
      static int value_offset()  {
         return ((char*)&((PValue_t(0x1000))->second)) - ((char*)PValue_t(0x1000));
      }
   };
 
 
   public:
      const std::type_info &fInfo;
      size_t fIterSize;
      size_t fValueDiff;
      int    fValueOffset;
      void*  (*fSizeFunc)(void*);
      void   (*fResizeFunc)(void*,size_t);
      void*  (*fClearFunc)(void*);
      void*  (*fFirstFunc)(void*);
      void*  (*fNextFunc)(void*);
      void*  (*fConstructFunc)(void*,size_t);
      void   (*fDestructFunc)(void*,size_t);
      void*  (*fFeedFunc)(void*,void*,size_t);
      void*  (*fCollectFunc)(void*,void*);
      void*  (*fCreateEnv)();
 
      // Set of function of direct iteration of the collections.
      void (*fCreateIterators)(void *collection, void **begin_arena, void **end_arena, TVirtualCollectionProxy *proxy);
      // begin_arena and end_arena should contain the location of memory arena  of size fgIteratorSize.
      // If the collection iterator are of that size or less, the iterators will be constructed in place in those location (new with placement)
      // Otherwise the iterators will be allocated via a regular new and their address returned by modifying the value of begin_arena and end_arena.
 
      void* (*fCopyIterator)(void *dest, const void *source);
      // Copy the iterator source, into dest.   dest should contain should contain the location of memory arena  of size fgIteratorSize.
      // If the collection iterator are of that size or less, the iterator will be constructed in place in this location (new with placement)
      // Otherwise the iterator will be allocated via a regular new and its address returned by modifying the value of dest.
 
      void* (*fNext)(void *iter, const void *end);
      // iter and end should be pointer to respectively an iterator to be incremented and the result of colleciton.end()
      // 'Next' will increment the iterator 'iter' and return 0 if the iterator reached the end.
      // If the end is not reached, 'Next' will return the address of the content unless the collection contains pointers in
      // which case 'Next' will return the value of the pointer.
 
      void (*fDeleteSingleIterator)(void *iter);
      void (*fDeleteTwoIterators)(void *begin, void *end);
      // If the sizeof iterator is greater than fgIteratorArenaSize, call delete on the addresses,
      // Otherwise just call the iterator's destructor.
 
   public:
      TCollectionProxyInfo(const std::type_info& info,
                           size_t iter_size,
                           size_t value_diff,
                           int    value_offset,
                           void*  (*size_func)(void*),
                           void   (*resize_func)(void*,size_t),
                           void*  (*clear_func)(void*),
                           void*  (*first_func)(void*),
                           void*  (*next_func)(void*),
                           void*  (*construct_func)(void*,size_t),
                           void   (*destruct_func)(void*,size_t),
                           void*  (*feed_func)(void*,void*,size_t),
                           void*  (*collect_func)(void*,void*),
                           void*  (*create_env)(),
                           void   (*getIterators)(void *collection, void **begin_arena, void **end_arena, TVirtualCollectionProxy *proxy) = nullptr,
                           void*  (*copyIterator)(void *dest, const void *source) = nullptr,
                           void*  (*next)(void *iter, const void *end) = nullptr,
                           void   (*deleteSingleIterator)(void *iter) = nullptr,
                           void   (*deleteTwoIterators)(void *begin, void *end) = nullptr
                           ) :
         fInfo(info), fIterSize(iter_size), fValueDiff(value_diff),
         fValueOffset(value_offset),
         fSizeFunc(size_func),fResizeFunc(resize_func),fClearFunc(clear_func),
         fFirstFunc(first_func),fNextFunc(next_func),fConstructFunc(construct_func),
         fDestructFunc(destruct_func),fFeedFunc(feed_func),fCollectFunc(collect_func),
         fCreateEnv(create_env),
         fCreateIterators(getIterators),fCopyIterator(copyIterator),fNext(next),
         fDeleteSingleIterator(deleteSingleIterator),fDeleteTwoIterators(deleteTwoIterators)
      {
      }
 
      /// Generate proxy from template
      template <class T> static TCollectionProxyInfo* Generate(const T&)  {
         // Generate a TCollectionProxyInfo given a TCollectionProxyInfo::Type
         // template (used to described the behavior of the stl collection.
         // Typical use looks like:
         //      ::ROOT::Detail::TCollectionProxyInfo::Generate(TCollectionProxyInfo::Pushback< std::vector<string> >()));
 
         PairHolder<TYPENAME T::Value_t, TYPENAME T::Value_t>* p =
            (PairHolder<TYPENAME T::Value_t, TYPENAME T::Value_t>*)0x1000;
         return new TCollectionProxyInfo(typeid(TYPENAME T::Cont_t),
                                               sizeof(TYPENAME T::Iter_t),
                                               (((char*)&p->second)-((char*)&p->first)),
                                               T::value_offset(),
                                               T::size,
                                               T::resize,
                                               T::clear,
                                               T::first,
                                               T::next,
                                               T::construct,
                                               T::destruct,
                                               T::feed,
                                               T::collect,
                                               T::Env_t::Create,
                                               T::Iterators_t::create,
                                               T::Iterators_t::copy,
                                               T::Iterators_t::next,
                                               T::Iterators_t::destruct1,
                                               T::Iterators_t::destruct2);
      }
 
      template <class T> static TCollectionProxyInfo Get(const T&)  {
 
         // Generate a TCollectionProxyInfo given a TCollectionProxyInfo::Type
         // template (used to described the behavior of the stl collection.
         // Typical use looks like:
         //      ::ROOT::Detail::TCollectionProxyInfo::Get(TCollectionProxyInfo::Pushback< std::vector<string> >()));
 
         PairHolder<TYPENAME T::Value_t, TYPENAME T::Value_t>* p =
            (PairHolder<TYPENAME T::Value_t, TYPENAME T::Value_t>*)0x1000;
         return TCollectionProxyInfo(typeid(TYPENAME T::Cont_t),
                                           sizeof(TYPENAME T::Iter_t),
                                           (((char*)&p->second)-((char*)&p->first)),
                                           T::value_offset(),
                                           T::size,
                                           T::resize,
                                           T::clear,
                                           T::first,
                                           T::next,
                                           T::construct,
                                           T::destruct,
                                           T::feed,
                                           T::collect,
                                           T::Env_t::Create);
      }
 
   };
 
   // This specialization is chosen if T is a vector<bool, A>, irrespective of the nature
   // of the allocator A represents.
   template <class A> struct TCollectionProxyInfo::Type<std::vector<Bool_t, A>>
   : public TCollectionProxyInfo::Address<typename std::vector<Bool_t, A>::const_reference>
   {
      typedef std::vector<Bool_t, A>       Cont_t;
      typedef typename Cont_t::iterator    Iter_t;
      typedef typename Cont_t::value_type  Value_t;
      typedef Environ<Iter_t>              Env_t;
      typedef Env_t                       *PEnv_t;
      typedef Cont_t                      *PCont_t;
      typedef Value_t                     *PValue_t;
 
      virtual ~Type() {}
 
      static inline PCont_t object(void* ptr)   {
         return PCont_t(PEnv_t(ptr)->fObject);
      }
      static void* size(void* env)  {
         PEnv_t  e = PEnv_t(env);
         e->fSize   = PCont_t(e->fObject)->size();
         return &e->fSize;
      }
      static void* clear(void* env)  {
         object(env)->clear();
         return nullptr;
      }
      static void* first(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
#if 0
         // Assume iterators do not need destruction
         ::new(e->buff) Iter_t(c->begin());
#endif
         e->fIterator = c->begin();
         e->fSize  = c->size();
         return nullptr;
      }
      static void* next(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
         for (; e->fIdx > 0 && e->iter() != c->end(); ++(e->iter()), --e->fIdx){ }
         // TODO: Need to find something for going backwards....
         return nullptr;
      }
      static void* construct(void*,size_t)  {
         // Nothing to construct.
         return nullptr;
      }
      static void* collect(void *coll, void *array)  {
         PCont_t  c = PCont_t(coll);
         PValue_t m = PValue_t(array); // 'start' is a buffer outside the container.
         for (Iter_t i=c->begin(); i != c->end(); ++i, ++m )
            ::new(m) Value_t(*i);
         return nullptr;
      }
      static void destruct(void*,size_t)  {
         // Nothing to destruct.
      }
 
      //static const bool fgLargeIterator = sizeof(Cont_t::iterator) > fgIteratorArenaSize;
      //typedef Iterators<Cont_t,fgLargeIterator> Iterators_t;
 
      struct Iterators {
         typedef typename Cont_t::iterator iterator;
 
         static void create(void *coll, void **begin_arena, void **end_arena, TVirtualCollectionProxy*) {
            PCont_t c = PCont_t(coll);
            new (*begin_arena) iterator(c->begin());
            new (*end_arena) iterator(c->end());
         }
         static void* copy(void *dest_arena, const void *source_ptr) {
            const iterator *source = (const iterator *)(source_ptr);
            new (dest_arena) iterator(*source);
            return dest_arena;
         }
         static void* next(void *, const void *) {
            R__ASSERT(false && "Intentionally not implemented, should use VectorLooper or similar for vector<bool>.");
            return {};
         }
         static void destruct1(void *iter_ptr) {
            iterator *start = (iterator *)(iter_ptr);
            start->~iterator();
         }
         static void destruct2(void *begin_ptr, void *end_ptr) {
            iterator *start = (iterator *)(begin_ptr);
            iterator *end = (iterator *)(end_ptr);
            start->~iterator();
            end->~iterator();
         }
      };
      typedef Iterators Iterators_t;
 
   };
 
   template <class A> struct TCollectionProxyInfo::Pushback<std::vector<Bool_t, A> > : public TCollectionProxyInfo::Type<std::vector<Bool_t, A> > {
      typedef std::vector<Bool_t, A>       Cont_t;
      typedef typename Cont_t::iterator    Iter_t;
      typedef typename Cont_t::value_type  Value_t;
      typedef Environ<Iter_t>              Env_t;
      typedef Env_t                       *PEnv_t;
      typedef Cont_t                      *PCont_t;
      typedef Value_t                     *PValue_t;
 
      static void resize(void* obj,size_t n) {
         PCont_t c = PCont_t(obj);
         c->resize(n);
      }
      static void* feed(void* from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         PValue_t m = PValue_t(from);
         for (size_t i=0; i<size; ++i, ++m)
            c->push_back(*m);
         return nullptr;
      }
      static int value_offset()  {
         return 0;
      }
   };
 
   // Need specialization for boolean references due to stupid STL std::vector<bool>
   template <class A> struct TCollectionProxyInfo::Address<std::vector<Bool_t, A>> {
      virtual ~Address() {}
      static void* address(typename std::vector<Bool_t, A>::const_reference) {
         R__ASSERT(false && "Intentionally not implemented, should use VectorLooper or other functions specialized for "
                            "vector<bool> instead");
         return {};
      }
   };
 
   template <typename Bitset_t> struct TCollectionProxyInfo::Type<Internal::TStdBitsetHelper<Bitset_t> > : public TCollectionProxyInfo::Address<const Bool_t &>
   {
      typedef Bitset_t                 Cont_t;
      typedef std::pair<size_t,Bool_t> Iter_t;
      typedef Bool_t                   Value_t;
      typedef Environ<Iter_t>          Env_t;
      typedef Env_t                   *PEnv_t;
      typedef Cont_t                  *PCont_t;
      typedef Value_t                 *PValue_t;
 
      virtual ~Type() {}
 
      static inline PCont_t object(void* ptr)   {
         return PCont_t(PEnv_t(ptr)->fObject);
      }
      static void* size(void* env)  {
         PEnv_t  e = PEnv_t(env);
         e->fSize   = PCont_t(e->fObject)->size();
         return &e->fSize;
      }
      static void* clear(void* env)  {
         object(env)->reset();
         return nullptr;
      }
      static void* first(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
         e->fIterator.first = 0;
         e->fIterator.second = c->size() > 0 ? c->test(e->fIterator.first) : false ;  // Iterator actually hold the value.
         e->fSize  = c->size();
         return &(e->fIterator.second);
      }
      static void* next(void* env)  {
         PEnv_t  e = PEnv_t(env);
         PCont_t c = PCont_t(e->fObject);
         for (; e->fIdx > 0 && e->fIterator.first != c->size(); ++(e->fIterator.first), --e->fIdx){ }
         e->fIterator.second = (e->fIterator.first != c->size()) ? c->test(e->fIterator.first) : false;
         return &(e->fIterator.second);
      }
      static void* construct(void*,size_t)  {
         // Nothing to construct.
         return nullptr;
      }
      static void* collect(void *coll, void *array)  {
         PCont_t  c = PCont_t(coll);
         PValue_t m = PValue_t(array); // 'start' is a buffer outside the container.
         for (size_t i=0; i != c->size(); ++i, ++m )
            *m = c->test(i);
         return nullptr;
      }
      static void destruct(void*,size_t)  {
         // Nothing to destruct.
      }
 
      //static const bool fgLargeIterator = sizeof(typename Cont_t::iterator) > fgIteratorArenaSize;
      //typedef Iterators<Cont_t,fgLargeIterator> Iterators_t;
 
      struct Iterators {
         union PtrSize_t { size_t fIndex; void *fAddress; };
         typedef std::pair<PtrSize_t,Bool_t> iterator;
         // In the end iterator we store the bitset pointer
         // and do not use the 'second' part of the pair.
         // In the other iterator we store the index
         // and the value.
 
         static void create(void *coll, void **begin_arena, void **end_arena, TVirtualCollectionProxy*) {
            iterator *begin = new (*begin_arena) iterator;
            begin->first.fIndex = 0;
            begin->second = false;
            iterator *end = new (*end_arena) iterator;
            end->first.fAddress = coll;
            end->second = false;
         }
         static void* copy(void *dest_arena, const void *source_ptr) {
            const iterator *source = (const iterator *)(source_ptr);
            new (dest_arena) iterator(*source);
            return dest_arena;
         }
         static void* next(void *iter_loc, const void *end_loc) {
            const iterator *end = (const iterator *)(end_loc);
            PCont_t c = (PCont_t)end->first.fAddress;
            iterator *iter = (iterator *)(iter_loc);
            if (iter->first.fIndex != c->size()) {
               iter->second = c->test(iter->first.fIndex);
               ++(iter->first.fIndex);
               return &(iter->second);
            } else {
               return nullptr;
            }
         }
         static void destruct1(void *iter_ptr) {
            iterator *start = (iterator *)(iter_ptr);
            start->~iterator();
         }
         static void destruct2(void *begin_ptr, void *end_ptr) {
            iterator *start = (iterator *)(begin_ptr);
            iterator *end = (iterator *)(end_ptr);
            start->~iterator();
            end->~iterator();
         }
      };
      typedef Iterators Iterators_t;
   };
 
   template <typename Bitset_t>
   struct TCollectionProxyInfo::Pushback<Internal::TStdBitsetHelper<Bitset_t>  > : public TCollectionProxyInfo::Type<Internal::TStdBitsetHelper<Bitset_t> > {
      using InfoBase_t = TCollectionProxyInfo::Type<Internal::TStdBitsetHelper<Bitset_t> >;
      using typename InfoBase_t::Cont_t;
      using typename InfoBase_t::Iter_t;
      using typename InfoBase_t::Value_t;
      using typename InfoBase_t::Env_t;
      using typename InfoBase_t::PEnv_t;
      using typename InfoBase_t::PCont_t;
      using typename InfoBase_t::PValue_t;
 
      static void resize(void*,size_t)  {
      }
      static void* feed(void *from, void *to, size_t size)  {
         PCont_t  c = PCont_t(to);
         PValue_t m = PValue_t(from);
         for (size_t i=0; i<size; ++i, ++m)
            c->set(i,*m);
         return nullptr;
      }
      static int value_offset()  {
         return 0;
      }
   };
 
} // namespace Detail
 
// For (reasonable) backward compatibility:
using namespace Detail;
} // namespace ROOT
 
#endif