[ROOT] Fixing automatic streamers

From: Salvatore Rappoccio (rappoccio@heplcdf2.harvard.edu)
Date: Sun Jun 06 2004 - 13:39:16 MEST 

Hi, All,

I have a class that I have been allowing ROOT to generate Streamers for:

class X {

  X();
  X( const X & );

private:
  TH1F * x;
  TH1F * y;

  ClassDef(X,1)
};


Now, I need to extend the class to have an array for "x" and "y":

class X {

  X();
  X( const X &);

  enum Number_t { N=0, N_NUMBER_TYPES };

private:
  TH1F* x[N];
  TH1F* y[N];

  ClassDef(X,2)
};

Will the automatic Streamer generator be able to pick up this change? I 
imagine not. So if not, what is the order of the variables streamed in the 
automatic Streamer? Is there a version number written out? I imagine it to 
be:

  version >> x >> y;

but I can't really be sure. The automatic generation looks like:

void X::Streamer( TBuffer &R__b)
{
   // Stream an object of class X.

   if (R__b.IsReading()) {
      X::Class()->ReadBuffer(R__b, this);
   } else {
      X::Class()->WriteBuffer(R__b, this);
   }
}

so I can't figure out the order of the objects read in and out are. After 
I know the order, it is of course trivial to write a streamer to handle 
both versions, but I can't figure out what the order is.

Thanks,
Sal Rappoccio

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