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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)
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