jsoncpp

A C++ library for interacting with JSON & JSON5.

JSON is a lightweight data-interchange format. It can represent numbers, strings, list, key-value pairs and so on.

jsoncpp is a c++ library that allows manipulating JSON values, including serialization and deserialization to and from strings.

C Language

C Language press this to obtain: Zua https://github.com/liqiongfan/Zua

Requirements

• make
• re2c
• bison
• g++ or clang++ with compile arg: -std=c++11

Build & Test

A simple example for running the jsoncpp is to clone the repository and then open the terminal running the commands: make

$ cd jsoncpp
$ make

output:
{"backwardsCompatible":"with JSON","andIn":["arrays"],"positiveSign":1,"andTrailing":8675309.000000,"leadingDecimalPoint":0.867531,"trailingComma":"in objects","hexadecimal":0xdecaf,"lineBreaks":"Look, Mom! No \\n's!","singleQuotes":"I can use \"double quotes\" here","unquoted":"and you can quote me on that"}

mac

When using in mac, you should use make macBuild & make run if your g++ compiler not support -fsanitize=leak option, if your mac's g++ compiler support, you can omit this notice.

$ cd jsoncpp
$ make macBuild & make run

output:
{"backwardsCompatible":"with JSON","andIn":["arrays"],"positiveSign":1,"andTrailing":8675309.000000,"leadingDecimalPoint":0.867531,"trailingComma":"in objects","hexadecimal":0xdecaf,"lineBreaks":"Look, Mom! No \\n's!","singleQuotes":"I can use \"double quotes\" here","unquoted":"and you can quote me on that"}

APIs

• json fromJson(const std::string &str)

  decoding json string into json structure, if error occured, jsoncpp will throw std::string exception, so you should try catch the exception forever.

• std::string toString(bool hex=false)

  encoding json structure into string, if you set the parameter hex to true, the output string will contain hex value for it's original style. if not it will change into integer for result.

Data value

• C++: long store json integer value.
• C++: double store json floating value.
• C++: struct boolean or C++ true or false store the json bool value
• C++: struct null store json null value
• C++: struct infinity store the +Inf or -Inf
• C++: struct hex store the hex value
• C++: std::vector<json> store the array value
• C++: std::unordered_map<std::string, json> store the object value

Encoding example

#include <iostream>
#include "json_language.hh"

int main()
{
  json::object obj;
  obj.insert({"program", "jsoncpp"});  
  obj.insert({"version", "v1.0.0"});
  obj.insert({"is_ok", json::boolean(true)});

  json::array vec;
  vec.push_back("c++");
  vec.push_back("linux");
  vec.push_back("make");
  vec.push_back(1);
  vec.push_back(json::boolean(false));
  vec.push_back(json::null());

  obj.insert({"items", vec});

  json p = obj;
  std::cout << p.toString() << std::endl;
  
  return 0;
}

output:
{"items":["c++","linux","make",1,true,null],"is_ok":false,"version":"v1.0.0","program":"jsoncpp"}

Decoding Example

#include <iostream>
#include "json_language.hh"

int main()
{
    
    std::string str(R"(
{
  // comments
  unquoted: 'and you can quote me on that',
  singleQuotes: 'I can use "double quotes" here',
  lineBreaks: "Look, Mom! \
No \\n's!",
  hexadecimal: 0xdecaf,
  leadingDecimalPoint: .8675309, andTrailing: 8675309.,
  positiveSign: +1,
  trailingComma: 'in objects', andIn: ['arrays',],
  "backwardsCompatible": "with JSON",
}
    )");

    try {
        json v = fromJson(str);
        std::cout << v.toString(true) << std::endl;
    } catch (const std::string &msg) {
        std::cout << msg << std::endl;
    }

    return 0;
}

output:
{"backwardsCompatible":"with JSON","andIn":["arrays"],"positiveSign":1,"andTrailing":8675309.000000,"leadingDecimalPoint":0.867531,"trailingComma":"in objects","hexadecimal":0xdecaf,"lineBreaks":"Look, Mom! No \\n's!","singleQuotes":"I can use \"double quotes\" here","unquoted":"and you can quote me on that"}

Quick way access data

#include <iostream>
#include "json_language.hh"


  json::array vec;
  vec.push_back("c++");
  vec.push_back("linux");
  vec.push_back("make");
  vec.push_back(1);
  vec.push_back(json::boolean(true));
  vec.push_back(json::null());


  json x = vec;
  if (x[0].has()) {
    std::cout << x[0].get_string() << std::endl;
  }


  json::object obj;
  obj.insert({"program", "jsoncpp"});  
  obj.insert({"version", "v1.0.0"});
  obj.insert({"is_ok", false});

  json p = obj;
  if (p["is_ok"].has()) {
    std::cout << p["is_ok"].get_bool().yes << std::endl;
  }

End

Have fun.