Re: [ROOT] How to convert Object to char[] and backwards?

From: Mario Schubert (Mario.Schubert@Physik.uni-muenchen.de)
Date: Mon Sep 02 2002 - 18:18:42 MEST 

Hello Maarten,

how do I have to write it correctly with the following class:

class c_MsgSimple : public TObject {
public:
  c_MsgSimple() {};
  ~c_MsgSimple() {};

  Int_t iValue;
  Long_t lValue;
  Double_t dValue;
  TString txt;

  ClassDef(c_MsgSimple, 1)
};

I have the 
   ClassImp(c_MsgSimple)
and a LinkDef.h like:

#pragma link off all typedefs;
#pragma link off all globals;
#pragma link off all classes;
#pragma link off all functions;

#pragma link C++ nestedclass;
#pragma link C++ nestedtypedef;

#pragma link C++ class c_MsgSimple+;

My program is the following:

  TBuffer a(TBuffer::kWrite);

  c_MsgSimple MsgSimple_in;
  MsgSimple_in.iValue=123456780;
  MsgSimple_in.lValue=(Long_t)2076543219;
  MsgSimple_in.dValue=3.1415;
  MsgSimple_in.txt="test text";
  
  B << "i=" << MsgSimple_in.iValue
    << " l=" << MsgSimple_in.lValue
    << " d=" << MsgSimple_in.dValue
    << " txt=" << MsgSimple_in.txt
    << E;
  
  a.WriteObject(&MsgSimple_in);
  
  char *buf = new char(a.Length());
  Int_t len = a.Length();
  
  // send and receive char array
  memcpy(buf, a.Buffer(), len);
  
  TBuffer b(TBuffer::kRead);
  b.SetBuffer( buf, len, kFALSE );
  
  c_MsgSimple* MsgSimple_out;
  
  MsgSimple_out = (c_MsgSimple*)b.ReadObject(gROOT->GetClass("c_MsgSimple"));
  
  B << "i=" << MsgSimple_out->iValue
    << " l=" << MsgSimple_out->lValue
    << " d=" << MsgSimple_out->dValue
    << " txt=" << MsgSimple_out->txt
    << E;
  
  return 0;

But the output is: (!!!!??????????)

i=123456780 l=2076543219 d=3.1415 txt=test text
i=123456780 l=0 d=3.1415 txt=test text

What I am doing wrong?

Thank you for your help.

Ciao,
    Mario Schubert
---------------------------------------------
Beschleunigerlabor der LMU und TU München
Dipl. Phys. Mario Schubert
EMail: mario.schubert@physik.uni-muenchen.de
Phone: (+49 89)289 14283
FAX:   (+49 89)289 14280
Am Coulombwall 6, D-85748 Garching, Germany

On Friday 30 August 2002 18:42, Maarten Ballintijn wrote:
> Hi Mario,
>
> TBuffer is the way to go. Please attached simple example.
> The tricky part might be the ownership of the buffer.
> (see the comments in the source for details)
>
> If you still have problems, please provide the ROOT version
> you are using, the platform you are running on and a simplified
> example of your problem.
>
> 		Cheers,
> 			Maarten.
>
> On Fri, 2002-08-30 at 11:46, Mario Schubert wrote:
> > Hello,
> >
> > I need to convert/serialize/marshal an object (in derived from TObject,
> > with dictionary generated) to a simmple char[] array.
> > Then it will be sent over and received by the MPICH library.
> > After this I want to generate this object from the char[] array.
> >
> > How to do this?
> >
> > My experiments with TMessage/TBuffer ended in segmentation faults. :-|
> > Thank you very much for your help.
> >
> > Ciao,
> >     Mario Schubert

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