C++ member-to-object for classes with standard layout

container_of.hh

// All rights reserved,
// Derrick Pallas
// License: zlib

#ifndef CONTAINER_OF
#define CONTAINER_OF

#include <cstddef>

template <class T, typename M>
T & container_of(M & m, const M T::*mp) {
  static const T * null = reinterpret_cast<const T *>(NULL);
  const ptrdiff_t offset = reinterpret_cast<const ptrdiff_t>(&(null->*mp));
  return *reinterpret_cast<T*>(reinterpret_cast<char*>(&m) - offset);
}

#endif//CONTAINER_OF