%%cpp -d

#include "TROOT.h"
#include "TKey.h"
#include "TFile.h"
#include "TSystem.h"
#include "TTree.h"

void CopyDir(TDirectory *source) {
   //copy all objects and subdirs of directory source as a subdir of the current directory
   source->ls();
   TDirectory *savdir = gDirectory;
   TDirectory *adir = savdir->mkdir(source->GetName());
   adir->cd();
   //loop on all entries of this directory
   TKey *key;
   //Loop in reverse order to make sure that the order of cycles is
   //preserved.
   TIter nextkey(source->GetListOfKeys(),kIterBackward);
   while ((key = (TKey*)nextkey())) {
      const char *classname = key->GetClassName();
      TClass *cl = gROOT->GetClass(classname);
      if (!cl) continue;
      if (cl->InheritsFrom(TDirectory::Class())) {
         source->cd(key->GetName());
         TDirectory *subdir = gDirectory;
         adir->cd();
         CopyDir(subdir);
         adir->cd();
      } else if (cl->InheritsFrom(TTree::Class())) {
         TTree *T = (TTree*)source->Get(key->GetName());
         // Avoid writing the data of a TTree more than once.
         // Note this assume that older cycles are (as expected) older
         // snapshots of the TTree meta data.
         if (!adir->FindObject(key->GetName())) {
            adir->cd();
            TTree *newT = T->CloneTree(-1,"fast");
            newT->Write();
         }
      } else {
         source->cd();
         TObject *obj = key->ReadObj();
         adir->cd();
         obj->Write();
         delete obj;
     }
  }
  adir->SaveSelf(kTRUE);
  savdir->cd();
}

%%cpp -d
void CopyFile(const char *fname) {
   //Copy all objects and subdirs of file fname as a subdir of the current directory
   TDirectory *target = gDirectory;
   TFile *f = TFile::Open(fname);
   if (!f || f->IsZombie()) {
      printf("Cannot copy file: %s\n",fname);
      target->cd();
      return;
   }
   target->cd();
   CopyDir(f);
   delete f;
   target->cd();
}

if(gSystem->AccessPathName("tot100.root")) {
   gSystem->CopyFile("hsimple.root", "tot100.root");
   gSystem->CopyFile("hsimple.root", "hs1.root");
   gSystem->CopyFile("hsimple.root", "hs2.root");
}

TFile *f = new TFile("result.root","recreate");
CopyFile("tot100.root");
CopyFile("hsimple.root");
CopyFile("hs1.root");
CopyFile("hs2.root");
f->ls();
delete f;