PackedArray.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef CXXUTILS_PACKEDARRAY_H
#define CXXUTILS_PACKEDARRAY_H
 
 
#include <vector>
#include <cstddef>
 
 
namespace CxxUtils {
 

class PackedArray
{
private:
  // Type of the underlying vector holding the data.
  typedef std::vector<unsigned int> basetype;
 
public:
  // Standard STL container typedefs.
  typedef size_t                   size_type;
  typedef unsigned int             value_type;
  typedef basetype::allocator_type allocator_type;

  class proxy
  {
  public:
    proxy (PackedArray& arr, size_type n) : m_arr (arr), m_n (n) {}

    operator value_type() const { return m_arr.get (m_n); }

    proxy& operator= (value_type v) { m_arr.set (m_n, v); return *this; }
 
  private:
    PackedArray& m_arr;

    size_type m_n;
  };
 

  PackedArray (int bitsize = 8,
               const allocator_type& allocator = allocator_type());

  PackedArray (int bitsize,
               size_type n,
               value_type val = 0,
               const allocator_type& allocator = allocator_type());

  void assign (size_type n, value_type u);

  allocator_type get_allocator() const;

  size_type size() const;

  size_type max_size() const;

  size_type capacity() const;

  void resize (size_type sz, value_type c = 0);

  bool empty() const;

  void reserve (size_type n);

  value_type get(size_type n) const;

  void set(size_type n, value_type val);

  value_type operator[](size_type n) const;

  proxy operator[](size_type n);

  value_type at(size_type n) const;

  proxy at(size_type n);

  value_type front() const;

  value_type back() const;

  proxy front();

  proxy back();

  void push_back (value_type x);

  void pop_back();

  void swap (PackedArray& other);

  void clear();

  void set_bitsize (int bitsize);

  int bitsize () const;
 
 
private:
  int m_bitsize = 0;

  size_type m_size = 0;

  value_type m_mask = 0;

  basetype m_vec;

  size_t nbase (size_type n) const;

  size_t tondx (size_type n) const;

  int tooff (size_type n) const;

  value_type doget (size_type ndx, int off) const;

  void doset (size_type ndx, int off, value_type v);

  void range_check (size_type n) const;
};
 
 
} // namespace CxxUtils
 
 
#endif // not CXXUTILS_PACKEDARRAY_H