ceph/src/boost/libs/property_tree/examples/empty_ptree_trick.cpp

   1 // ----------------------------------------------------------------------------
   2 // Copyright (C) 2002-2006 Marcin Kalicinski
   3 //
   4 // Distributed under the Boost Software License, Version 1.0.
   5 // (See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // For more information, see www.boost.org
   9 // ----------------------------------------------------------------------------
  10
  11 #include <boost/property_tree/ptree.hpp>
  12 #include <boost/property_tree/info_parser.hpp>
  13 #include <iostream>
  14 #include <iomanip>
  15 #include <string>
  16
  17 using namespace boost::property_tree;
  18
  19 // Process settings using empty ptree trick. Note that it is considerably simpler
  20 // than version which does not use the "trick"
  21 void process_settings(const std::string &filename)
  22 {
  23     ptree pt;
  24     read_info(filename, pt);
  25     const ptree &settings = pt.get_child("settings", empty_ptree<ptree>());
  26     std::cout << "\n    Processing " << filename << std::endl;
  27     std::cout << "        Setting 1 is " << settings.get("setting1", 0) << std::endl;
  28     std::cout << "        Setting 2 is " << settings.get("setting2", 0.0) << std::endl;
  29     std::cout << "        Setting 3 is " << settings.get("setting3", "default") << std::endl;
  30 }
  31
  32 // Process settings not using empty ptree trick. This one must duplicate much of the code.
  33 void process_settings_without_trick(const std::string &filename)
  34 {
  35     ptree pt;
  36     read_info(filename, pt);
  37     if (boost::optional<ptree &> settings = pt.get_child_optional("settings"))
  38     {
  39         std::cout << "\n    Processing " << filename << std::endl;
  40         std::cout << "        Setting 1 is " << settings.get().get("setting1", 0) << std::endl;
  41         std::cout << "        Setting 2 is " << settings.get().get("setting2", 0.0) << std::endl;
  42         std::cout << "        Setting 3 is " << settings.get().get("setting3", "default") << std::endl;
  43     }
  44     else
  45     {
  46         std::cout << "\n    Processing " << filename << std::endl;
  47         std::cout << "        Setting 1 is " << 0 << std::endl;
  48         std::cout << "        Setting 2 is " << 0.0 << std::endl;
  49         std::cout << "        Setting 3 is " << "default" << std::endl;
  50     }
  51 }
  52
  53 int main()
  54 {
  55     try
  56     {
  57         std::cout << "Processing settings with empty-ptree-trick:\n";
  58         process_settings("settings_fully-existent.info");
  59         process_settings("settings_partially-existent.info");
  60         process_settings("settings_non-existent.info");
  61         std::cout << "\nProcessing settings without empty-ptree-trick:\n";
  62         process_settings_without_trick("settings_fully-existent.info");
  63         process_settings_without_trick("settings_partially-existent.info");
  64         process_settings_without_trick("settings_non-existent.info");
  65     }
  66     catch (std::exception &e)
  67     {
  68         std::cout << "Error: " << e.what() << "\n";
  69     }
  70     return 0;
  71 }