ceph/src/boost/libs/json/example/pretty.cpp

   1 //
   2 // Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // Official repository: https://github.com/boostorg/json
   8 //
   9
  10 //[example_pretty
  11
  12 /*
  13     This example parses a JSON file and pretty-prints
  14     it to standard output.
  15 */
  16
  17 #include <boost/json.hpp>
  18 #include <iomanip>
  19 #include <iostream>
  20
  21 #include "file.hpp"
  22
  23 namespace json = boost::json;
  24
  25 json::value
  26 parse_file( char const* filename )
  27 {
  28     file f( filename, "r" );
  29     json::stream_parser p;
  30     json::error_code ec;
  31     do
  32     {
  33         char buf[4096];
  34         auto const nread = f.read( buf, sizeof(buf) );
  35         p.write( buf, nread, ec );
  36     }
  37     while( ! f.eof() );
  38     if( ec )
  39         return nullptr;
  40     p.finish( ec );
  41     if( ec )
  42         return nullptr;
  43     return p.release();
  44 }
  45
  46 void
  47 pretty_print( std::ostream& os, json::value const& jv, std::string* indent = nullptr )
  48 {
  49     std::string indent_;
  50     if(! indent)
  51         indent = &indent_;
  52     switch(jv.kind())
  53     {
  54     case json::kind::object:
  55     {
  56         os << "{\n";
  57         indent->append(4, ' ');
  58         auto const& obj = jv.get_object();
  59         if(! obj.empty())
  60         {
  61             auto it = obj.begin();
  62             for(;;)
  63             {
  64                 os << *indent << json::serialize(it->key()) << " : ";
  65                 pretty_print(os, it->value(), indent);
  66                 if(++it == obj.end())
  67                     break;
  68                 os << ",\n";
  69             }
  70         }
  71         os << "\n";
  72         indent->resize(indent->size() - 4);
  73         os << *indent << "}";
  74         break;
  75     }
  76
  77     case json::kind::array:
  78     {
  79         os << "[\n";
  80         indent->append(4, ' ');
  81         auto const& arr = jv.get_array();
  82         if(! arr.empty())
  83         {
  84             auto it = arr.begin();
  85             for(;;)
  86             {
  87                 os << *indent;
  88                 pretty_print( os, *it, indent);
  89                 if(++it == arr.end())
  90                     break;
  91                 os << ",\n";
  92             }
  93         }
  94         os << "\n";
  95         indent->resize(indent->size() - 4);
  96         os << *indent << "]";
  97         break;
  98     }
  99
 100     case json::kind::string:
 101     {
 102         os << json::serialize(jv.get_string());
 103         break;
 104     }
 105
 106     case json::kind::uint64:
 107         os << jv.get_uint64();
 108         break;
 109
 110     case json::kind::int64:
 111         os << jv.get_int64();
 112         break;
 113
 114     case json::kind::double_:
 115         os << jv.get_double();
 116         break;
 117
 118     case json::kind::bool_:
 119         if(jv.get_bool())
 120             os << "true";
 121         else
 122             os << "false";
 123         break;
 124
 125     case json::kind::null:
 126         os << "null";
 127         break;
 128     }
 129
 130     if(indent->empty())
 131         os << "\n";
 132 }
 133
 134 int
 135 main(int argc, char** argv)
 136 {
 137     if(argc != 2)
 138     {
 139         std::cerr <<
 140             "Usage: pretty <filename>"
 141             << std::endl;
 142         return EXIT_FAILURE;
 143     }
 144
 145     try
 146     {
 147         // Parse the file as JSON
 148         auto const jv = parse_file( argv[1] );
 149
 150         // Now pretty-print the value
 151         pretty_print(std::cout, jv);
 152     }
 153     catch(std::exception const& e)
 154     {
 155         std::cerr <<
 156             "Caught exception: "
 157             << e.what() << std::endl;
 158         return EXIT_FAILURE;
 159     }
 160
 161     return EXIT_SUCCESS;
 162 }
 163
 164 //]