#include <iostream>
#include <fstream>
#include <sstream>

#include <TFile.h>
#include <TTree.h>
#include <TProcessID.h>
#include <TROOT.h>

using namespace std;
  
void process_mem_usage(double& vm_usage, double& resident_set)
{
   using std::ios_base;
   using std::ifstream;
   using std::string;

   vm_usage     = 0.0;
   resident_set = 0.0;

   // 'file' stat seems to give the most reliable results
   //
   ifstream stat_stream("/proc/self/stat",ios_base::in);

   // dummy vars for leading entries in stat that we don't care about
   //
   string pid, comm, state, ppid, pgrp, session, tty_nr;
   string tpgid, flags, minflt, cminflt, majflt, cmajflt;
   string utime, stime, cutime, cstime, priority, nice;
   string O, itrealvalue, starttime;

   // the two fields we want
   //
   unsigned long vsize;
   long rss;

   stat_stream >> pid >> comm >> state >> ppid >> pgrp >> session >> tty_nr
               >> tpgid >> flags >> minflt >> cminflt >> majflt >> cmajflt
               >> utime >> stime >> cutime >> cstime >> priority >> nice
               >> O >> itrealvalue >> starttime >> vsize >> rss; // don't care about the rest

   stat_stream.close();

   long page_size_kb = sysconf(_SC_PAGE_SIZE) / 1024; // in case x86-64 is configured to use 2MB pages
   vm_usage     = vsize / 1024.0;
   resident_set = rss * page_size_kb;
}

int main() {
  
  double vm2,rss2;
  
  process_mem_usage(vm2, rss2);
  
  cout << "At the very beginning: VM: " << vm2 << "; RSS: " << rss2 << endl;
  
  
  const int nSamples=5;
  
  string samples[nSamples]={"fill","in","your","samples","here"};
  
  TFile *f[nSamples];
  TTree *events[nSamples];
  
  for(int i=0;i<nSamples;i++) {
    f[i] = new TFile(samples[i%5].c_str());
    // events[i] = (TTree*)f[i]->Get("events");
    process_mem_usage(vm2, rss2);
    cout << "After loading file " << i << " VM: " << vm2 << "; RSS: " << rss2 << endl;  
  }
  
  for(int i=0;i<nSamples;i++) {
    f[i]->Close();
    delete f[i];
    process_mem_usage(vm2, rss2);
    cout << "After unloading file " << i << " VM: " << vm2 << "; RSS: " << rss2 << endl;  
  }
  
  return 0;
}