Question

Assume I have a class

class A
{
 char *attr1,*attr2;
public:
 . . .
};

How to save the object of this class to file in a binary format and read it back?

Thanks.

Answer 1

Read about serialization. For example the Boost serialization library. They have a nice definition:

Here, we use the term “serialization”
to mean the reversible deconstruction
of an arbitrary set of C++ data
structures to a sequence of bytes.
Such a system can be used to
reconstitute an equivalent structure
in another program context. Depending
on the context, this might used
implement object persistence, remote
parameter passing or other facility.
In this system we use the term
“archive” to refer to a specific
rendering of this stream of bytes.
This could be a file of binary data,
text data, XML, or some other created
by the user of this library.

That said, such a solution is the 5-kg hammer that solves most serialization problems. It may be the case that you need something far simpler. For example, if you object only consists of a few char* attributes you can save it in a simpler way. A general solution, however, would allow you flexibility in case your object gets more complex in the future.