Say, I've got a library which initializes an object like this:
Type *object;
lib_init(&object); // lib_init takes Type **object as the parameter
So, what if I want to use the library with my code which uses smart pointers? Is this a proper way?
Type *pObject;
lib_init(&pObject);
unique_ptr<Type> object(nullptr);
object.reset(pObject);
Or is there a smart way to do this?
You could wrap the initialization into a function that returns a unique pointer:
std::unique_ptr<Type> init_type()
{
Type* p;
lib_init(&p);
return std::unique_ptr<Type>(p);
}
Then
std::unique_ptr<Type> object(init_type());
Bear in mind that, unless the pointer is to be de-allocated with delete, you'll need to provide a custom deleter too. For example, assuming the de-allocation function is void lib_dispose(Type*), then
std::unique_ptr<Type, void (*)(Type*)> init_type()
{
Type* p;
lib_init(&p);
return std::unique_ptr<Type, void (*)(Type*)>(p, lib_dispose);
}
unique_ptr ? (and so that handles also case with custom deleter)
make_unique is suitable here, because the legacy API requires initializes a pointer.I don't think you need smart pointer here, you can take the standard library approach for std::string/std::vector etc. - wrap the pointer in RAII mechanism
class CType{
Type* m_Ptr;
public:
CType(){
lib_init(&m_Ptr);
}
~Ctype(){
lib_dispose(&m_Ptr);
}
//TODO: Copy constructor, move constructor assignment operators..
operator Type&(){
return *m_Ptr;
}
operator const Type&() const{
return *m_Ptr;
}
operator Type*(){
return m_Ptr;
}
operator const Type*() const{
return m_Ptr;
}
Type* asPointer(){
return m_Ptr;
}
};
now use Ctype anywhere you would use regular Type, the polymorphism will kick in when you try to use CType as Type* or Type&..
lib_init? I would expect there to be a correspondinglib_destroyor something along these lines. It's unlikely thatdelete objectis the right way to dispose of an object allocated by a C language library - but that's whatunique_ptrwould do unless told otherwise.lib_disposeand I understand that there must be a custom deleter in order to call that function. Actually, the answer to my question is here stackoverflow.com/a/24543176/135749. Exactly the behavior that I was looking for. Thank you, everybody.