CachedValue.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 CXXUTILS_CACHEDVALUE_H
#define CXXUTILS_CACHEDVALUE_H
 
 
#include "CxxUtils/checker_macros.h"
#include "CxxUtils/stall.h"
#include <atomic>
#include <utility>
 
 
namespace CxxUtils {
 
 
enum CacheState : unsigned char {
  INVALID = 0,
  UPDATING = 1,
  VALID = 2
};
 
 
template <class T>
class CachedValue
{
public:
  template <class U>
  friend class CachedValue;
 
       
  CachedValue();
 
 
  CachedValue (const T& val);
 
 
  CachedValue (T&& val) noexcept;
 
 
  CachedValue (const CachedValue& other);
 
 
  CachedValue (CachedValue&& other) noexcept;
 
 
  template <class U>
  CachedValue (const CachedValue<U>& other);
 
 
  CachedValue& operator= (const CachedValue& other);
 
    
  CachedValue& operator= (CachedValue&& other) noexcept;
 
    
  void set (const T& val) const;
 
 
  void set (T&& val) const noexcept;
 
 
  bool isValid() const;
    
 
  const T* ptr() const;
 
 
  void store (const T& val);
 
 
  void store (T&& val) noexcept;
 
 
  void reset();
 
    
private:
  mutable T m_val ATLAS_THREAD_SAFE;  
 
  mutable std::atomic<CacheState> m_cacheValid;  
};
 
 
} // namespace CxxUtils
 
 
#include "CxxUtils/CachedValue.icc"
 
 
#endif // not CXXUTILS_CACHEDVALUE_H