Function join_arguments

lib/tiny-process/process_win.cpp:57–103

// Based on blog post https://learn.microsoft.com/en-us/archive/blogs/twistylittlepassagesallalike/everyone-quotes-command-line-arguments-the-wrong-way
template <class Char>
static std::basic_string<Char> join_arguments(const std::vector<std::basic_string<Char>> &args) {
  using charset = CharSet<Char>;

  std::basic_string<Char> ret;

  for(const auto &arg : args) {
    if(!ret.empty())
      ret.push_back(charset::space);

    if(!arg.empty() && arg.find_first_of(charset::whitespace) == arg.npos) {
      ret.append(arg);
      continue;
    }

    ret.push_back(charset::doublequote);

    for(auto it = arg.begin();; ++it) {
      size_t n_backslashes = 0;

      while(it != arg.end() && *it == charset::backslash) {
        ++it;
        ++n_backslashes;
      }

      if(it == arg.end()) {
        // Escape all backslashes, but let the terminating double quotation mark
        // we add below be interpreted  as a metacharacter.
        ret.append(n_backslashes * 2, charset::backslash);
        break;
      }
      else if(*it == charset::doublequote) {
        // Escape all backslashes and the following double quotation mark.
        ret.append(n_backslashes * 2 + 1, charset::backslash);
        ret.push_back(*it);
      }
      else {
        // Backslashes aren't special here.
        ret.append(n_backslashes, charset::backslash);
        ret.push_back(*it);
      }
    }

    ret.push_back(charset::doublequote);
  }

  return ret;
}

// Based on the discussion thread: https://www.reddit.com/r/cpp/comments/3vpjqg/a_new_platform_independent_process_library_for_c11/cxq1wsj
std::mutex create_process_mutex;