SelectionLoader.cc

/* 
Beam Delivery Simulation (BDSIM) Copyright (C) BDSIM Collaboration, 2001 - 2026.
 
This file is part of BDSIM.
 
BDSIM is free software: you can redistribute it and/or modify 
it under the terms of the GNU General Public License as published 
by the Free Software Foundation version 3 of the License.
 
BDSIM is distributed in the hope that it will be useful, but 
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with BDSIM.  If not, see <http://www.gnu.org/licenses/>.
*/
#include "SelectionLoader.hh"
 
#include <algorithm>
#include <fstream>
#include <iostream>
#include <regex>
#include <stdexcept>
#include <string>
#include <vector>
 
std::string RBDS::LoadSelection(const std::string& selectionFile)
{
  std::ifstream f(selectionFile.c_str());
  if(!f)
    {throw std::invalid_argument("LoadSelection> could not open file " + selectionFile);}
 
  int lineCounter = 0;
  std::string line;
 
  // unique patterns to match
  // match a line starting with #
  std::regex comment("^\\#.*");
 
  std::string selection;  
  while(std::getline(f, line))
    {
      lineCounter++;
      if (std::all_of(line.begin(), line.end(), isspace))
        {continue;} // skip empty lines
      else if (std::regex_search(line, comment))
        {continue;} // skip lines starting with '#'
      else
        
      {
        if (!selection.empty())
          {throw std::invalid_argument("Multiple selections (non-empty lines) found in file - only one should be specified.");}
          std::vector<std::string> results;
          std::regex wspace("\\s+"); // any whitespace
          // -1 here makes it point to the suffix, ie the word rather than the wspace
          std::sregex_token_iterator iter(line.begin(), line.end(), wspace, -1);
          std::sregex_token_iterator end;
          for (; iter != end; ++iter)
            {
              std::string res = (*iter).str();
              if (res.empty())
                {continue;}
              results.push_back(res);
            }
          if (results.size() != 1)
            {
              std::cerr << "Error on line " << lineCounter << "\"" << line << "\"" << std::endl;
              throw std::invalid_argument("More than one word on line -> no white space allowed");
            }
          else
            {selection = results[0];}
        }
    }
  
  f.close();
 
  return selection;
}