Re: serialization, size errors... or something else.

  • From: Tyler Littlefield <tyler@xxxxxxxxxxxxx>
  • To: programmingblind@xxxxxxxxxxxxx
  • Date: Wed, 30 Jun 2010 16:40:13 -0600

I'm not passing pointers to classes though. the serialization function just 
does like s << level; etc. It only serializes fields in the class.
                Thanks,
Tyler Littlefield
        http://tds-solutions.net
        Twitter: sorressean

On Jun 30, 2010, at 4:30 PM, qubit wrote:

> what I'm trying to prevent with all these questions is the inadvertent 
> pointer shift that happens when you say B *bp = d; where d is of a type 
> derived from b, and there is multiple inheritance.
> It's a nasty gotcha that may have been eliminated in more recent definitions 
> of C++, but I don't know so am warning you.
> 
> Anyway, I also wanted to be sure you don't forget that things like virtual 
> pointers are embedded somewhere in the body of a class.  These take up 
> space, and if you write sizeof(T) bytes then you will include the virtual 
> pointers, but if you are expecting just to get visible data then the 
> calculation will be off.
> 
> Now if you don't do virtual functions, you'll have to think in another 
> direction.
> Any closer?
> 
> ----- Original Message ----- 
> From: "Tyler Littlefield" <tyler@xxxxxxxxxxxxx>
> To: <programmingblind@xxxxxxxxxxxxx>
> Sent: Wednesday, June 30, 2010 5:16 PM
> Subject: Re: serialization, size errors... or something else.
> 
> 
> What do you mean I'm passing it around as different types? Fwrite takes the 
> size of the block your writing, the number of blocks, and the file to write 
> to, as well as the block. so you supply 1 for the count, sizelf(T), and the 
> address of t. T is just the templated type. It looks something like:
> template <class T>
> void Write(const &T data)
> 
> Thanks,
> Tyler Littlefield
> http://tds-solutions.net
> Twitter: sorressean
> 
> On Jun 30, 2010, at 4:13 PM, qubit wrote:
> 
>> Ok, the plot thickens -- did you cast the address of the pointer to a 
>> char*
>> to pass to fwrite? Maybe a dumb question but I'm just feeling this out.
>> You have p being of some type T* and you say
>>   fwrite(fp, (char*)p, sizeof(T));
>> Is this done in a template function where you don't know the final type of
>> T?
>> What is T anyway?
>> I'm just hoping some funny pointer arithmetic is not getting done on p
>> because you are passing it around as different types.
>> Any progress?
>> --le
>> 
>> 
>> ----- Original Message ----- 
>> From: "Tyler Littlefield" <tyler@xxxxxxxxxxxxx>
>> To: <programmingblind@xxxxxxxxxxxxx>
>> Sent: Wednesday, June 30, 2010 4:55 PM
>> Subject: Re: serialization, size errors... or something else.
>> 
>> 
>> Basically what I did was used a templated function to write, then I write
>> the arg with fwrite, and use sizeof(T) to get the size. Reading does the
>> same thing, I also overloaded operators << and >> to read and write.
>> Thanks,
>> Tyler Littlefield
>> http://tds-solutions.net
>> Twitter: sorressean
>> 
>> On Jun 30, 2010, at 3:53 PM, qubit wrote:
>> 
>>> without knowing a little about your serialization strategy, it's hard to
>>> diagnose what might be wrong.
>>> Do you do something similar to Boost, or do you have some other 
>>> algorithm?
>>> --le
>>> 
>>> ----- Original Message ----- 
>>> From: "Tyler Littlefield" <tyler@xxxxxxxxxxxxx>
>>> To: <programmingblind@xxxxxxxxxxxxx>
>>> Sent: Wednesday, June 30, 2010 4:02 PM
>>> Subject: Re: serialization, size errors... or something else.
>>> 
>>> 
>>> I do know I'm reading to much because I get a size excception. I'm not
>>> sure
>>> how to cut this down because the serialization works through an
>>> inheritance
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