AuxDataSpan.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
#ifndef ATHCONTAINERSINTERFACES_AUXDATASPAN_H
#define ATHCONTAINERSINTERFACES_AUXDATASPAN_H
 
 
#include "CxxUtils/throw_out_of_range.h"
#include <cstddef>
#include <stdexcept>
 
 
namespace SG {
 
 
struct AuxDataSpanBase
{
  // cppcheck-suppress uninitMemberVar; false positive
  AuxDataSpanBase (void* the_beg = 0, size_t the_size = 0)
    : beg(the_beg), size(the_size)
  {
  }
 
 
  void* beg;
 
  size_t size;
};
 
 
namespace detail {
 
 
template <class T>
class AuxDataSpan
{
public:
  AuxDataSpan (const AuxDataSpanBase& span) : m_span (span) {}
 
 
  size_t size() const { return m_span.size; }
 
 
  bool empty() const { return m_span.size == 0; }
 
 
  T* data() { return reinterpret_cast<T*> (m_span.beg); }
 
 
  const T* data() const { return reinterpret_cast<T*> (m_span.beg); }
 
 
  T& operator[] (size_t index)
  {
    return data()[index];
  }
 
 
  const T& operator[] (size_t index) const
  {
    return data()[index];
  }
 
 
  T& at (size_t index)
  {
    if (index >= m_span.size) {
      CxxUtils::throw_out_of_range (__PRETTY_FUNCTION__, index, m_span.size, this);
    }
    return data()[index];
  }
 
 
  const T& at (size_t index) const
  {
    if (index >= m_span.size) {
      CxxUtils::throw_out_of_range (__PRETTY_FUNCTION__, index, m_span.size, this);
    }
    return data()[index];
  }
 
 
  T& front() { return data()[0]; }
 
 
  const T& front() const { return data()[0]; }
 
 
  T& back() { return data()[m_span.size-1]; }
 
 
  const T& back() const { return data()[m_span.size-1]; }
 
 
private:
  const AuxDataSpanBase& m_span;
};
 
 
template <class T>
class AuxDataConstSpan
{
public:
  AuxDataConstSpan (const AuxDataSpanBase& span)
    : m_span (span) {}
 
 
  size_t size() const { return m_span.size; }
 
 
  bool empty() const { return m_span.size == 0; }
 
 
  const T* data() const { return reinterpret_cast<const T*> (m_span.beg); }
 
 
  const T& operator[] (size_t index) const
  {
    return data()[index];
  }
 
 
  const T& at (size_t index) const
  {
    if (index >= m_span.size) {
      CxxUtils::throw_out_of_range (__PRETTY_FUNCTION__, index, m_span.size, this);
    }
    return data()[index];
  }
 
 
  const T& front() const { return data()[0]; }
 
 
  const T& back() const { return data()[m_span.size-1]; }
 
 
private:
  const AuxDataSpanBase& m_span;
};
 
 
} } // namespace SG::detail
 
 
#endif // not ATHCONTAINERSINTERFACES_AUXDATASPAN_H