ceph/src/jaegertracing/opentelemetry-cpp/third_party/nlohmann-json/doc/examples/sax_parse.cpp

   1 #include <iostream>
   2 #include <iomanip>
   3 #include <sstream>
   4 #include <nlohmann/json.hpp>
   5
   6 using json = nlohmann::json;
   7
   8 // a simple event consumer that collects string representations of the passed
   9 // values; not inheriting from json::json_sax_t is not required, but can
  10 // help not to forget a required function
  11 class sax_event_consumer : public json::json_sax_t
  12 {
  13   public:
  14     std::vector<std::string> events;
  15
  16     bool null() override
  17     {
  18         events.push_back("value: null");
  19         return true;
  20     }
  21
  22     bool boolean(bool val) override
  23     {
  24         events.push_back("value: " + std::string(val ? "true" : "false"));
  25         return true;
  26     }
  27
  28     bool number_integer(number_integer_t val) override
  29     {
  30         events.push_back("value: " + std::to_string(val));
  31         return true;
  32     }
  33
  34     bool number_unsigned(number_unsigned_t val) override
  35     {
  36         events.push_back("value: " + std::to_string(val));
  37         return true;
  38     }
  39
  40     bool number_float(number_float_t val, const string_t& s) override
  41     {
  42         events.push_back("value: " + s);
  43         return true;
  44     }
  45
  46     bool string(string_t& val) override
  47     {
  48         events.push_back("value: " + val);
  49         return true;
  50     }
  51
  52     bool start_object(std::size_t elements) override
  53     {
  54         events.push_back("start: object");
  55         return true;
  56     }
  57
  58     bool end_object() override
  59     {
  60         events.push_back("end: object");
  61         return true;
  62     }
  63
  64     bool start_array(std::size_t elements) override
  65     {
  66         events.push_back("start: array");
  67         return true;
  68     }
  69
  70     bool end_array() override
  71     {
  72         events.push_back("end: array");
  73         return true;
  74     }
  75
  76     bool key(string_t& val) override
  77     {
  78         events.push_back("key: " + val);
  79         return true;
  80     }
  81
  82     bool binary(json::binary_t& val) override
  83     {
  84         events.push_back("binary");
  85         return true;
  86     }
  87
  88     bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
  89     {
  90         events.push_back("error: " + std::string(ex.what()));
  91         return false;
  92     }
  93 };
  94
  95 int main()
  96 {
  97     // a JSON text
  98     auto text = R"(
  99     {
 100         "Image": {
 101             "Width":  800,
 102             "Height": 600,
 103             "Title":  "View from 15th Floor",
 104             "Thumbnail": {
 105                 "Url":    "http://www.example.com/image/481989943",
 106                 "Height": 125,
 107                 "Width":  100
 108             },
 109             "Animated" : false,
 110             "IDs": [116, 943, 234, 38793],
 111             "Distance": 12.723374634
 112         }
 113     }
 114     )";
 115
 116     // create a SAX event consumer object
 117     sax_event_consumer sec;
 118
 119     // parse and serialize JSON
 120     bool result = json::sax_parse(text, &sec);
 121
 122     // output the recorded events
 123     for (auto& event : sec.events)
 124     {
 125         std::cout << "(" << event << ") ";
 126     }
 127
 128     // output the result of sax_parse
 129     std::cout << "\nresult: " << std::boolalpha << result << std::endl;
 130 }