stl-ex-2d.cpp

u_int32_t CarSize(const Car &car)			// (3)
{
  return sizeof(length) * 3 + model.length() + 1 + 
    sizeof(*engine); 					// (4)
}

void CopyCar(void *dest, const Car&car)			// (5)
{
  // Copy all bytes of the car object into memory chunk M 
  // referenced by dest.
  // M is preallocated and just big enough because our CarSize is used
  // to measure the object size. Note the bytes
  // of the Engine object E referenced by car.engine should be copied
  // into this M, rather than the car.engine pointer value,
  // in order to deep copy E.

  char *p = (char *)dest;

  memcpy(p, car.length, sizeof(size_t));
  p += sizeof(size_t);
  memcpy(p, car.width, sizeof(size_t));
  p += sizeof(size_t);
  memcpy(p, car.height, sizeof(size_t));
  p += sizeof(size_t);

  memcpy(p, car.model.c_str(), car.model.length() + 1); // (6)
  p += car.model.length() + 1;				// (6)

  memcpy(p, car.engine, sizeof(*car.engine);		// (7)
}

void RestoreCar(Car &car, const void* src)		// (8)
{
  // src references the memory chunk M which contains the bytes of a Car
  // object previously marshalled by CopyCar function, so we know
  // the data structure and composition of M. Thus here we can
  // un-marshal bytes stored in M to assign to each member of car.
  // Since we have data of the Engine member in M, we should create an
  // Engine object E using 'new' operator, and assign to its members 
  // using bytes in M, and assign E's pointer to car.engine.

  char *p = src;

  memcpy(car.length, p, sizeof(size_t));
  p += sizeof(size_t);
  memcpy(car.width, p, sizeof(size_t));
  p += sizeof(size_t);
  memcpy(car.height, p, sizeof(size_t));
  p += sizeof(size_t);

  car.model = p; 					// (9)
  p += car.model.length() + 1;				// (9)

  memcpy(car.engine, p, sizeof(*car.engine);
  
}

dbstl::DbstlElemTraits<Car> *pCarTraits = 
  dbstl::DbstlElemTraits<Car>::instance();		// (10)
pCarTraits->set_size_function(CarSize);			// (11)
pCarTraits->set_copy_function(CopyCar);			// (12)
pCarTraits->set_restore_function(RestoreCar);		// (13)