#define memorydepth 100
class MY_DATA{
  public:
    Double_t peak;
    Double_t wvf[memorydepth];
    Int_t selection;

    MY_DATA();
    string tobranch = "peak/D:wvf[" + to_string(memorydepth) + "]/D:selection/I";

    void setBranchName(Int_t n = memorydepth){
      tobranch = "peak/D:wvf[" + to_string(n) + "]/D:selection/I";
    }

};


MY_DATA::MY_DATA(){

  for(Int_t i = 0; i<memorydepth; i++){
    wvf[i]=0;
  }
  peak = 0;
  selection = 0;
}


void example_tree_write(){
  MY_DATA *data = new MY_DATA();
  Int_t npts = 10;
  data->setBranchName(npts);
  TFile *fnew = new TFile("example_tree.root","RECREATE");
  TTree *t1 = new TTree("t1","t1");
  t1->Branch("data",data,data->tobranch.c_str());
  for(Int_t i = 0; i < 5; i++){ // 5 entries only
      for(Int_t j = 0; j < npts; j++){
        data->wvf[j] = 0.5 + i;
      }
      data->peak = i;
      data->selection = i;
      t1->Fill();
  }
  fnew->WriteTObject(t1, "t1", "TObject::kOverwrite");
  fnew->Close();
}