AuxDataTraits.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
 
/*
  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
*/
#ifndef ATHCONTAINERS_AUXDATATRAITS_H
#define ATHCONTAINERS_AUXDATATRAITS_H
 
 
#include "CxxUtils/span.h"
#include <vector>
#include <cstdlib>
 
 
namespace SG {
 
 
template <class T>
using AuxAllocator_t = std::allocator<T>;
constexpr const char* auxAllocatorNamePrefix = "std::allocator<";
 
 
template <class T, class ALLOC = AuxAllocator_t<T> >
class AuxDataTraits
{
public:
  using element_type = T;
 
  using reference_type = element_type&;
  using const_reference_type =  const element_type&;
 
  using allocator_type = ALLOC;
 
  using vector_type = std::vector<T, allocator_type>;
  using container_value_type = typename vector_type::value_type;
 
  using container_pointer_type = typename vector_type::pointer;
  using const_container_pointer_type = typename vector_type::const_pointer;
 
  static reference_type index (void* ptr, size_t ndx)
  {
    return reinterpret_cast<container_pointer_type>(ptr)[ndx];
  }
    
  static const_reference_type index (const void* ptr, size_t ndx)
  {
    return reinterpret_cast<const_container_pointer_type>(ptr)[ndx];
  }
 
  using span = CxxUtils::span<container_value_type>;
  using const_span = CxxUtils::span<const container_value_type>;
};
 
 
template <class ALLOC>
class AuxDataTraits<bool, ALLOC>
{
public:
  using element_type = bool;
 
  using reference_type = element_type&;
  using const_reference_type =  const element_type&;
 
  using allocator_type = typename std::allocator_traits<ALLOC>::template rebind_alloc<char>;
 
  using vector_type = std::vector<char, allocator_type>;
  using container_value_type = typename vector_type::value_type;
 
  using container_pointer_type = typename vector_type::pointer;
  using const_container_pointer_type = typename vector_type::const_pointer;
 
  static reference_type index (void* ptr, size_t ndx)
  {
    return reinterpret_cast<bool*>(ptr)[ndx];
  }
    
  static const_reference_type index (const void* ptr, size_t ndx)
  {
    return reinterpret_cast<const bool*>(ptr)[ndx];
  }
 
  using span = CxxUtils::span<container_value_type>;
  using const_span = CxxUtils::span<const container_value_type>;
};
 
 
template <class T>
struct Zero
{
  static T zero()
  {
    return T();
  }
};
 
 
} // namespace SG
 
 
#endif // not ATHCONTAINERS_AUXDATATRAITS_H