json11

json11 is a tiny JSON library for C++11, providing JSON parsing and serialization.

The core object provided by the library is json11::Json. A Json object represents any JSON value: null, bool, number (int or double), string (std::string), array (std::vector), or object (std::map).

Json objects act like values. They can be assigned, copied, moved, compared for equality or order, and so on. There are also helper methods Json::dump, to serialize a Json to a string, and Json::parse (static) to parse a std::string as a Json object.

It's easy to make a JSON object with C++11's new initializer syntax:

Json my_json = Json::object {
    { "key1", "value1" },
    { "key2", false },
    { "key3", Json::array { 1, 2, 3 } },
};
std::string json_str = my_json.dump();

There are also implicit constructors that allow standard and user-defined types to be automatically converted to JSON. For example:

class Point {
public:
    int x;
    int y;
    Point (int x, int y) : x(x), y(y) {}
    Json to_json() const { return Json::array { x, y }; }
};

std::vector<Point> points = { { 1, 2 }, { 10, 20 }, { 100, 200 } };
std::string points_json = Json(points).dump();

JSON values can have their values queried and inspected:

Json json = Json::array { Json::object { { "k", "v" } } };
std::string str = json[0]["k"].string_value();

Parsing

To parse a string, you can simply call

Json json = Json::parse("{ \"key\": \"value1\" }");

If you need to parse json data in multiple step, because you are using non-blocking io for example, you can create a parser object. It will hold the parsing state and you can give it the data as it comes along:

JsonParser parser;
std::string data = read_data();
while (!data.empty()) {
    parse.consume(data);
}

if (!parser.last_error().empty()) {
    /* an error occured */
    ...
}

Json json = parser.json();

More documentation is still to come. For now, see json11.hpp.