Re: [Boost-users] [serialization] transparently treating a class like a built-in type

Subject: Re: [Boost-users] [serialization] transparently treating a class like a built-in type
From: Stefan Strasser (strasser_at_[hidden])
Date: 2010-07-27 11:22:56

Zitat von Kenneth Riddile <kfriddile_at_[hidden]>:

> I have some xml archives that store a lot of floating point values.   
> I would like to read these into a program that is designed to easily  
> switch between using floats and a custom fixed-point type via a  
> typedef.  The way that would be easiest would be to add a  
> serialize() method to the fixed-point class definition.  However,  
> the xml archive requires that I use an nvp wrapper.  Since the data  
> was originally serialized out as plain floats, the data looks  
> something like this:
>
> <x>0.95260203</x>
> <y>0.87517798</y>
> <z>0.54323343</z>

I'm not sure if it was intended to be used that way, but you could use  
Boost.Serialization's versioning.

namespace serialization{
struct version<your_type>
   : mpl::integral_c<unsigned int,mpl::if_int_then_0_else_1>{};
}

void load(Archive &ar,unsigned int version){
   if(version == 0) load fixed point...
   else load floating point...
   ...into whatever type is currently typedef'ed
}

wrt to your "value" "indirection", just load the float directly, or if  
that's not an option because of encapsulation use a temporary and  
initialize "x" later on.

ar >> make_nvp("x",x.value);

instead of

ar & NVP(x);