PStore#open_and_lock_file

# File tmp/rubies/ruby-3.2.0/lib/pstore.rb, line 618
def open_and_lock_file(filename, read_only)
  if read_only
    begin
      file = File.new(filename, **RD_ACCESS)
      begin
        file.flock(File::LOCK_SH)
        return file
      rescue
        file.close
        raise
      end
    rescue Errno::ENOENT
      return nil
    end
  else
    file = File.new(filename, **RDWR_ACCESS)
    file.flock(File::LOCK_EX)
    return file
  end
end