[boost] Re: [serialization] default-constructors (was Re[serialization]problem deserializing vectors)

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-01 12:16:34

Vladimir Prus <ghost_at_[hidden]> writes:

> David Abrahams wrote:
>> Samuel Krempp <krempp_at_[hidden]> writes:
>> > If I got it right, Robert is reluctant to have deserialization require
>> > default-constructability, even private
>>
>> I certainly agree that it's a nasty constraint.  I think I can see
>> only one way to achieve non-intrusive deserialization in portable C++:
>> the deserialization function gets an address into which the object
>> will be constructed with placement new.  
>
> I certainly miss something. You still have to either pass ctor parameters when 
> using placement new, or require the serialized type to have default ctor. Am 
> I wrong?

The serialization function writes the information neccessary to
reconstruct the ctor args.

The deserialization function deserializes that information from the stream
and then does the in-place construction.

This design is inspired by Python's __getinitargs__ interface to the
pickle module. http://www.python.org/doc/current/lib/module-pickle.html

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com