Macro to generate a Tree skeleton function

Int_t MakeCode(TTree *t, const char *filename=0)
{
//_________________________________________________________________________
//   generate skeleton function for a TNtuple or TTree pointed by t
//   The function code is written on filename
//   if filename is NULL, filename will be nameoftree.C
//
//   The generated code includes the following:
//      - Identification of the original Tree and Input file name
//      - Connection of the Tree file
//      - Declaration of Tree variables
//      - Declaration of pointers to leaves and setting of leaves addresses
//      - a skeleton for the event loop
//
//   To use this function:
//      - connect your Tree file (eg: TFile f("myfile.root");)
//      - .L MakeCode.C
//      - MakeCode(T,"anal.C")
//    where T is the name of the Tree in file myfile.root
//    and anal.C the name of the file created by this function.
//
//   Use this macro with ROOT version 0.90
//   In ROOT version 1.0 the TTree class includes a new function
//       TTree::MakeCode(const char *filename)
//   that generates the skeleton code for a TTree object.
//
//          Author: Rene Brun
//_________________________________________________________________________

// Check against an invalid Tree pointer
   if (!t) return 1;
   if (!t->IsA()->InheritsFrom("TTree")) {
      printf("Attempt to makecode for a non-TTree object\n");
      return 2;
   }
// Connect output file
   char tfile[64];
   if (filename) strcpy(tfile,filename);
   else          sprintf(tfile,"%s.C",t->GetName());
   FILE *fp = fopen(tfile,"w");
   if (!fp) {
      printf("Cannot open output file:%s\n",tfile);
      return 3;
   }
// Print header
   TObjArray *leaves = t->GetListOfLeaves();
   Int_t nleaves = leaves->GetEntriesFast();
   TDatime td;
   fprintf(fp,"{\n");
   fprintf(fp,"//////////////////////////////////////////////////////////\n");
   fprintf(fp,"//   This file has been automatically generated \n");
   fprintf(fp,"//     (%s by ROOT version%s)\n",td.AsString(),gROOT->GetVersion());
   fprintf(fp,"//   from TTree %s/%s\n",t->GetName(),t->GetTitle());
   fprintf(fp,"//   found on file: %s\n",gFile->GetName());
   fprintf(fp,"//////////////////////////////////////////////////////////\n");
   fprintf(fp,"\n");
   fprintf(fp,"\n");


// Reset and file connect
   fprintf(fp,"//Reset ROOT and connect tree file\n");
   fprintf(fp,"   gROOT->Reset();\n");
   fprintf(fp,"   TFile *f = new TFile(\"%s\");\n\n",gFile->GetName());

// First loop on all leaves to generate type declarations
   fprintf(fp,"//Declaration of leaves types\n");
   Int_t len, nl, l;
   TLeaf *leafcount;
   char *bname;
   char branchname[64];
   for (l=0;l<nleaves;l++) {
      TLeaf *leaf = (TLeaf*)leaves->UncheckedAt(l);
      TBranch *branch = leaf->GetBranch();
      nl = branch->GetListOfLeaves()->GetEntriesFast();
      if (nl > 1) strcpy(branchname,leaf->GetName());
      else        strcpy(branchname,branch->GetName());
      bname = branchname;
      while (*bname) {if (*bname == '.') *bname='_'; bname++;}
      if (!strcmp(branch->ClassName(),"TBranchObject")) {
         TLeafObject *leafobj = (TLeafObject*)leaf;
         fprintf(fp,"   %-15s *%s;\n",leafobj->GetTypeName(), leafobj->GetName());
         continue;
      }
      len = leaf->GetLen();
      leafcount =leaf->GetLeafCount();
      if (leafcount) len = leafcount->GetMaximum()+1;
      if (len > 1) fprintf(fp,"   %-15s %s[%d];\n",leaf->GetTypeName(), branchname,len);
      else         fprintf(fp,"   %-15s %s;\n",leaf->GetTypeName(), branchname);
   }

// Second loop on all leaves to set the leaf addresses
   fprintf(fp,"\n//Get a pointer to individual leaves and set their addresses\n");
   fprintf(fp,"   TObjArray *leaves = %s->GetListOfLeaves();\n",t->GetName());
   for (l=0;l<nleaves;l++) {
      TLeaf *leaf = (TLeaf*)leaves->UncheckedAt(l);
      TBranch *branch = leaf->GetBranch();
      nl = branch->GetListOfLeaves()->GetEntriesFast();
      if (nl > 1) strcpy(branchname,leaf->GetName());
      else        strcpy(branchname,branch->GetName());
      bname = branchname;
      while (*bname) {if (*bname == '.') *bname='_'; bname++;}
      if (!strcmp(branch->ClassName(),"TBranchObject")) { 
         fprintf(fp,"   TLeaf *l_%-15s = (TLeaf*)leaves->At(%d);\n",branchname,l);
      } else {
         len = leaf->GetLen();
         leafcount =leaf->GetLeafCount();
         if (leafcount) len = leafcount->GetMaximum()+1;
         if (len > 1) fprintf(fp,"   TLeaf *l_%-15s = (TLeaf*)leaves->At(%d);   l_%s->SetAddress(&%s[0]);\n",branchname,l,branchname,branchname);
         else         fprintf(fp,"   TLeaf *l_%-15s = (TLeaf*)leaves->At(%d);   l_%s->SetAddress(&%s);\n",branchname,l,branchname,branchname);
      }
   }

//Generate instructions to make the loop on events
   fprintf(fp,"\n//This is the loop skeleton\n");
   fprintf(fp,"//To read only selected branches, Insert a statement like:\n");
   fprintf(fp,"//          leafname->GetBranch()->GetEvent(i); instead of %s->GetEvent(i);\n",t->GetName());
   fprintf(fp,"\n   Int_t nentries = %s->GetEntries();\n",t->GetName());
   fprintf(fp,"   for (Int_t i=0; i<nentries;i++) {\n");
   fprintf(fp,"      %s->GetEvent(i);\n",t->GetName());
   fprintf(fp,"   }\n");
   fprintf(fp,"}\n");

   fclose(fp);
   printf("Macro: %s generated from Tree: %s\n",tfile,t->GetName());

   return 0;
}