HepMC3 event record library
class_example_read.cc

Basic example of use of root I/O: reading events from file

Author
Witold Pokorski
Date
16/10/14
// -*- C++ -*-
//
// This file is part of HepMC
// Copyright (C) 2014-2019 The HepMC collaboration (see AUTHORS for details)
//
/**
* @example class_example_read.cc
* @brief Basic example of use of root I/O: reading events from file
*
* @author Witold Pokorski
* @date 16/10/14
*/
#include "HepMC3/Print.h"
#include "MyClass.h"
#include "MyRunClass.h"
#include "TFile.h"
#include "TSystem.h"
#include "TKey.h"
#include <iostream>
using namespace HepMC3;
/** Main */
int main(int argc, char **argv) {
if( argc<3 ) {
std::cout << "Usage: " << argv[0] << " <input_root_file> <output_hepmc3_file>" << std::endl;
exit(-1);
}
TFile fo(argv[1]);
WriterAscii text_output(argv[2]);
MyClass* myevent;
int events_parsed = 0;
// Get GenRunInfo, if available
MyRunClass *my_run = (MyRunClass*)fo.Get("MyRunClass");
std::shared_ptr<GenRunInfo> run_info;
if( my_run ) run_info.reset(my_run->GetRunInfo());
fo.GetListOfKeys()->Print();
TIter next(fo.GetListOfKeys());
TKey *key;
while ((key=(TKey*)next()))
{
const char *cl = key->GetClassName();
if( strncmp(cl,"MyClass",7) != 0 ) continue;
fo.GetObject(key->GetName(), myevent);
std::cout << "Event: " << key->GetName() << std::endl;
if( events_parsed == 0 ) {
std::cout << "First event: " << std::endl;
Print::listing(*(myevent->GetEvent()));
}
if( run_info ) {
std::cout << "Setting run info" << std::endl;
myevent->GetEvent()->set_run_info(run_info);
run_info.reset();
}
text_output.write_event(*(myevent->GetEvent()));
++events_parsed;
if( events_parsed%100 == 0 ) {
std::cout << "Event: " << events_parsed << std::endl;
}
delete myevent->GetEvent();
delete myevent;
}
text_output.close();
std::cout << "Events parsed and written: " << events_parsed << std::endl;
return 0;
}