C++中的二进制封装？

Question

1) What is binary encapsulation in c++, and does c++ support binary encapsulation?

I did some searching but all that I found was just encapsulation, which roughly is nothing but wrapping of data and methods in a class.

2) So what is the difference between encapsulation and binary encapsulation?

Answer 1

A quote from this text should clear things up:

Whereas C++ does support syntactic encapsulation via its private and protected keywords, the C++ draft standard has no notion of binary encapsulation. This is because the compilation model of C++ requires the client's compiler to have access to all information regarding object layout in order to instantiate an instance of a class or to make nonvirtual method calls. This includes information about the size and order of the object's private and protected data members.

To clarify: Syntactic encapsulation is when you use the language syntax to encapsulate. In C++ this would be the private/protected keywords.

I found the text throughthis thread which has a short explanation of the concept as well.

Edit:

As pointed out below there can exist binary encapsulation in C++. See this wiki page on Opaque pointers for more info.

Answer 2

1. There are 2 types of Encapsulation Syntactical Encapsulation & Binary Encapsulation.
2. C ++ Doesn't support Binary Encapsulation.It only supports Syntactical Encapsulation.
3. Binary Encapsulation is supported by COM.
4. Best example of Binary Encapsulation is QueryInterface(void **) method of COM.
5. As this method takes one output parameter as void **. So it's double redirection as pointer is void **.
6. To get more details on this read Inside COM by Don Bix.