#include "TTree.h"
#include "TObjArray.h"
#include "TBranchElement.h"
#include "TTreeFormula.h"
#include "TTreePlayer.h"

TTree *v520CopyTree(TTree *fTree, const char *selection, Option_t * = 0, Long64_t nentries = 1000000000,
                     Long64_t firstentry = 0)
{
   // we make a copy of the tree header
   TTree *tree = fTree->CloneTree(0);
   tree->Reset();
   if (tree == 0) return 0;

   // The clone should not delete any shared i/o buffers.
   TObjArray* branches = tree->GetListOfBranches();
   Int_t nb = branches->GetEntriesFast();
   for (Int_t i = 0; i < nb; ++i) {
      TBranch* br = (TBranch*) branches->UncheckedAt(i);
      if (br->InheritsFrom("TBranchElement")) {
         ((TBranchElement*) br)->ResetDeleteObject();
      }
   }

   Long64_t entry,entryNumber;
   nentries = ((TTreePlayer*)fTree->GetPlayer())->GetEntriesToProcess(firstentry, nentries);

   // Compile selection expression if there is one
   TTreeFormula *select = 0; // no need to interfer with fSelect since we
                             // handle the loop explicitly below and can call
                             // UpdateFormulaLeaves ourselves.
   if (strlen(selection)) {
      select = new TTreeFormula("Selection",selection,fTree);
      if (!select || !select->GetNdim()) { delete select; }
   }

   //loop on the specified entries
   Int_t tnumber = -1;
   for (entry=firstentry;entry<firstentry+nentries;entry++) {
      entryNumber = fTree->GetEntryNumber(entry);
      if (entryNumber < 0) break;
      Long64_t localEntry = fTree->LoadTree(entryNumber);
      if (localEntry < 0) break;
      if (tnumber != fTree->GetTreeNumber()) {
         tnumber = fTree->GetTreeNumber();
         if (select) select->UpdateFormulaLeaves();
      }
      if (select) {
         Int_t ndata = select->GetNdata();
         Bool_t keep = kFALSE;
         for(Int_t current = 0; current<ndata && !keep; current++) {
            keep |= (select->EvalInstance(current) != 0);
         }
         if (!keep) continue;
      }
      fTree->GetEntry(entryNumber);
      tree->Fill();
   }
   delete select;
   
   return tree;
}