JSON parser. Implementation in C++11.
- It is a data structure class that conforms to the JSON specification, with parse and output (stringify) functions added.
- Works with one header file. It does not depend on external libraries such as boost.
- It implements some specifications of JSON5. (Can be disabled as an option)
- You can parse JSON with comments.
- Allows Trailing commas (sometimes called "final commas").
- Implements JSON Pointer.
- It can be built with an initializer list.
- It is designed so that exceptions do not occur when referencing or editing. (Excluding the at() function)
- For out-of-range reads, the default value is taken, and for writes, an element is created.
- Unlike javascript, numbers are divided into floating point numbers (double) and integers (std::intmax_t).
- Input/output is supported only for std::string (UTF-8).
- It does not support the parsing process of stream input.
Works in the C++11 environment. Nothing is required for operation.
We have confirmed the operation in the following environment.
- linux g++
- windows VisualStudio 2015,2017,2019
It can be used by including Json.h.
#include "Json.h"
try {
using Json = rlib::Json;
const Json j = Json::parse( // Build with a JSON string
u8R"({ // allows comments (JSON5)
"n" : -123.456e+2,
"list":[
32,
"ABC", // allows Trailing comma (JSON5)
],
"b": true,
"c": null
})");
double d0 = j["n"].get<double>(); // get -123.456e+2
double da = j.at("n").get<double>(); // This is the description referenced by at(). (An exception will be thrown if it is out of range)
double d1 = j["e"].get<double>(); // get 0.0 (Since a position that does not exist is specified, the default value can be taken.)
std::intmax_t n1 = j["n"].get<std::intmax_t>(); // get -12346 (You can take rounded integer values)
std::string s0 = j["list"][1].get<std::string>(); // get "ABC"
std::string sa = j.at(Json::Pointer("/list/1")).get<std::string>(); // It is a description specified by JSON Pointer.
std::string s1 = j["ary"][9].get<std::string>(); // get empty string (Since a position that does not exist is specified, the default value can be taken.)
Json list = j["list"]; // duplicate (deep copy) from "list"
list[10]["add"] = 123; // Added {"add": 123} to position [10] (positions of array [2-9] are padded with null)
bool compare = list == j["list"]; // It is a comparison. get false.
std::string json = list.stringify(); // get JSON string
list[10].erase("add"); // Removed associative array element ({"add": 123}) at position [10]
list.erase(9); // Removed element (null) at position [9]
const Json j1 = Json::Map{ // Build with initializer list
{"a", 123}, // { "a": 123,
{"b", Json::Array{456, "ABC", 0.5}}, // "b": [456, "ABC", 0.5],
{"c", Json::Map{ // "c": {
{"d", true}, // "d": true,
{"e", nullptr}, // "e": null
}}, // }
}; // }
std::map<Json, int> map{ {j,0},{j1,1} }; // Can be keys such as std::map, set
const Json& c = j1.at("f"); // Referenced with at() raises an exception if out of range
} catch (rlib::Json::ParseException& e) { // perse failure
std::cerr << e.what() << std::endl;
} catch (std::out_of_range& e) { // Out-of-range
std::cerr << e.what() << std::endl;
}- It also contains test code using BOOST.TEST. Json_test.cpp
- Code indentation is tabs, not spaces. On github, add "?ts=4" to the end of the URL and refer to it on tab 4. I'm sorry.