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msgpack extension

The msgpack extension implements encode to and decode from the MessagePack data format. You can either parse into or serialize from a variant-like data structure, basic_json, or your own data structures, using json_type_traits.

decode_msgpack

basic_msgpack_cursor

encode_msgpack

basic_msgpack_encoder

msgpack_options

Mappings between MessagePack and jsoncons data items

MessagePack data item ext type jsoncons data item jsoncons tag
nil null
true, false bool
negative fixnum, int 8, int 16, int 32, int 64 int64
positive fixnum, uint 8, uint 16, uint 32, uint 64 uint64
float32, float64 double
fixstr, str 8, str 16, str 32 string
bin 8, bin 16, bin 32 byte_string
fixext1, fixext2, fixext4, fixext8, fixext16, ext8, ext16, ext32 0-127 byte_string
4 byte length -1 (timestamp 32) uint64 epoch_second
8 byte length -1 (timestamp 64) string epoch_nanosecond
12 byte length -1 (timestamp 96) string epoch_nanosecond
array array
map object

Examples

ext format code example

#include <jsoncons/json.hpp>
#include <jsoncons_ext/msgpack/msgpack.hpp>
#include <cassert>

using namespace jsoncons;

int main()
{
    std::vector<uint8_t> input = {

        0x82, // map, length 2
          0xa5, // string, length 5
            'H','e','l','l','o',
          0xa5, // string, length 5
            'W','o','r','l','d',
          0xa4, // string, length 4
             'D','a','t','a',
          0xc7, // ext8 format code
            0x06, // length 6
            0x07, // type
              'f','o','o','b','a','r'
    };

    ojson j = msgpack::decode_msgpack<ojson>(input);

    std::cout << "(1)\n" << pretty_print(j) << "\n\n";
    std::cout << "(2) " << j["Data"].tag() << "("  << j["Data"].ext_tag() << ")\n\n";
    
    // Get ext value as a std::vector<uint8_t>
    auto v = j["Data"].as<std::vector<uint8_t>>(); 

    std::cout << "(3)\n";
    std::cout << byte_string_view(v) << "\n\n";

    std::vector<uint8_t> output;
    msgpack::encode_msgpack(j,output);
    assert(output == input);
}

Output:

(1)
{
    "Hello": "World",
    "Data": "Zm9vYmFy"
}

(2) ext(7)

(3)
66,6f,6f,62,61,72

JSON to message pack

Input JSON file book.json

[
    {
        "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
    },
    {
        "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
    }
]
#include <jsoncons/json.hpp>
#include <jsoncons_ext/msgpack/msgpack.hpp>

using namespace jsoncons;

int main()
{
    std::ifstream is("input/book.json");
    ojson j1;
    is >> j1;

    // Encode ojson to MessagePack
    std::vector<uint8_t> v;
    msgpack::encode_msgpack(j1, v);

    // Decode MessagePack to ojson 
    ojson j2 = msgpack::decode_msgpack<ojson>(v);

    std::cout << pretty_print(j2) << std::endl;

    // or to json (now alphabetically sorted)
    json j3 = msgpack::decode_msgpack<json>(v);

    // or to wjson (converts from utf8 to wide characters)
    wjson j4 = msgpack::decode_msgpack<wjson>(v);
}

Output:

[
    {
        "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
    },
    {
        "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
    }
]