storageSize.cc

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// -*- C++ -*-
//
// Package:     FWLite
// Class  :     storageSize
//
// Implementation:
//     [Notes on implementation]
//
// Original Author:  Chris Jones
//         Created:  Thu Jan 20 09:50:58 CST 2011
//

// system include files
#include <iostream>
#include <boost/program_options.hpp>
#include "TClass.h"
#include "TBufferFile.h"

// user include files
#include "FWCore/FWLite/interface/FWLiteEnabler.h"
#include "FWCore/Utilities/interface/Exception.h"

//
// constants, enums and typedefs
//
static char const* const kClassNameOpt = "className";
static char const* const kHelpOpt = "help";
static char const* const kHelpCommandOpt = "help,h";

int main(int argc, char* argv[]) try {
  std::string descString(argv[0]);
  descString += " [options] [--";
  descString += kClassNameOpt;
  descString +=
      "] class_name"
      "\n The program dumps information about how much storage space is needed to store the class"
      "\nAllowed options";
  boost::program_options::options_description desc(descString);
  desc.add_options()(kHelpCommandOpt, "show this help message")(kClassNameOpt, "name of class");

  boost::program_options::positional_options_description p;
  p.add(kClassNameOpt, 1);

  boost::program_options::variables_map vm;
  try {
    store(boost::program_options::command_line_parser(argc, argv).options(desc).positional(p).run(), vm);
    notify(vm);
  } catch (boost::program_options::error const& iException) {
    std::cerr << "failed to parse command line \n" << iException.what() << "\n";
    return 1;
  }

  if (vm.count(kHelpOpt)) {
    std::cout << desc << std::endl;
    return 0;
  }

  if (!vm.count(kClassNameOpt)) {
    std::cerr << "no class name given\n";
    return 1;
  }

  std::string className(vm[kClassNameOpt].as<std::string>());

  FWLiteEnabler::enable();

  TClass* cls = TClass::GetClass(className.c_str());
  if (nullptr == cls) {
    std::cerr << "class '" << className << "' is unknown by ROOT\n";
    return 1;
  }

  void* objInstance = cls->New();
  if (nullptr == objInstance) {
    std::cerr << "unable to create a default instance of the class " << className;
    return 1;
  }

  TBufferFile bf(TBuffer::kWrite);

  gDebug = 3;
  cls->WriteBuffer(bf, objInstance);

  gDebug = 0;
  std::cout << "Total amount stored: " << bf.Length() << " bytes" << std::endl;
  std::cout << "\nNOTE: add 4 bytes for each 'has written' value because of a bug in ROOT's printout of the accounting"
            << "\n  Each class (inheriting or as member data) has metadata an overhead of 10 bytes" << std::endl;
  return 0;
} catch (cms::Exception const& e) {
  std::cerr << e.explainSelf() << std::endl;
  return 1;
} catch (std::exception const& e) {
  std::cerr << e.what() << std::endl;
  return 1;
}