msgpack_cpp

C++ header-only msgpack library that supports (de)serializing types directly, including custom types, as well as a dicitionary type msgpackcpp::value à la nlohmann::json or boost::json::value.

Examples

Basic types

#include "msgpack.h"
#include "msgpack_sinks.h"

int main()
{
    using msgpackcpp::serialize;
    using msgpackcpp::deserialize;
    using msgpackcpp::sink;
    using msgpackcpp::source;

    // Some data
    int                         a = 1, aa;
    double                      b = 3.15, bb;
    std::string                 c = "hello there", cc;
    std::vector<char>           d = {0,1,2,3,4,5,6,7,8,9}, dd;
    std::map<std::string, int>  e = {{"a", 1}, {"b", 2}}, ee;


    // Serialize
    std::vector<char> buf;
    auto out = sink(buf);
    serialize(out, a);
    serialize(out, b);
    serialize(out, c);
    serialize(out, d);
    serialize(out, e);

    // Deserialize
    auto in = source(buf);
    deserialize(in, aa);
    deserialize(in, bb);
    deserialize(in, cc);
    deserialize(in, dd);
    deserialize(in, ee);
}

Custom types

Option 1 : define serialize() and deserialize() functions in the same namespace as your custom struct. Note the use of std::tie. std::tuple is serialized like a msgpack array. This ensures your custom type is serialized into a single msgpack object.

#include "msgpack.h"
#include "msgpack_sinks.h"

namespace mynamespace
{
    struct my_struct1
    {
        int                 my_int{};
        float               my_float{};
        std::string         my_string;
        std::vector<short>  my_audio;
    };

    template<SINK_TYPE Sink>
    void serialize(Sink& out, const my_struct& obj)
    {
        auto packed = std::tie(obj.my_int, obj.my_float, obj.my_string, obj.my_audio);
        serialize(out, packed);
    }

    template<SOURCE_TYPE Source>
    void deserialize(Source& in, my_struct& obj)
    {
        auto packed = std::tie(obj.my_int, obj.my_float, obj.my_string, obj.my_audio);
        deserialize(in, packed);
    }  
}

int main()
{
    using msgpackcpp::serialize;
    using msgpackcpp::deserialize;
    using msgpackcpp::sink;
    using msgpackcpp::source;

    mynamespace::my_struct a = {1, 3.14, "hello there", {0, 1, 2, 3, 4}};
    mynamespace::my_struct b;

    // Serialize
    std::stringstream buf;
    auto out = sink(buf);
    serialize(out, a);

    // Deserialize
    auto in = source(buf);
    deserialize(in, b);
}

Option 2 : use Boost.Describe to describe your struct. This automatically makes the following functions available:

• serialize(Sink& out, const CustomType& obj, bool as_map = false)
• deserialize(Source& in, CustomType& obj, bool as_map = false)

When as_map == false then you get exactly the same behaviour as above. When as_map == true your type is serialized like a msgpack map where the keys are the member variable names of your struct.

#include <boost/describe/class.hpp>
#include "msgpack.h"
#include "msgpack_sinks.h"
#include "msgpack_describe.h"

namespace mynamespace
{
    struct my_struct1
    {
        int                 my_int{};
        float               my_float{};
        std::string         my_string;
        std::vector<short>  my_audio;
    };

    BOOST_DESCRIBE_STRUCT(my_struct, (), (my_int, my_float, my_string, my_audio))
}

int main()
{
    using msgpackcpp::serialize;
    using msgpackcpp::deserialize;
    using msgpackcpp::sink;
    using msgpackcpp::source;

    mynamespace::my_struct a = {1, 3.14, "hello there", {0, 1, 2, 3, 4}};
    mynamespace::my_struct b;

    // Serialize
    std::stringstream buf;
    auto out = sink(buf);
    serialize(out, a, /*as_map=*/false); // serialize to a msgpack array
    serialize(out, a, /*as_map=*/true);  // serialize to a msgpack map

    // Deserialize
    auto in = source(buf);
    deserialize(in, b, /*as_map=*/false);
    deserialize(in, b, /*as_map=*/true);
}

Dictionary value

#include "msgpack.h"
#include "msgpack_sinks.h"

const auto REQUIRE = [](auto res) {if (!res)throw std::runtime_error("bad");};

int main()
{
    using msgpackcpp::serialize;
    using msgpackcpp::deserialize;
    using msgpackcpp::sink;
    using msgpackcpp::source;

    // Data
    msgpackcpp::value jv0 = {
        {"pi", 3.141},
        {"happy", true},
        {"name", "Niels"},
        {"nothing", nullptr},
        {"answer", {
            {"everything", -42}
        }},
        {"list", {1, 0, 2}},
        {"object", {
            {"currency", "USD"},
            {"value", 42.99}
        }}
    };

    // Serialize (pack)
    std::vector<char> buf;
    auto out = sink(buf);
    jv0.pack(out);

    // Deserialize (unpack)
    msgpackcpp::value jv1;
    auto in = source(buf);
    jv1.unpack(in);

    // Check
    REQUIRE(jv1.is_object());
    REQUIRE(jv1.size() == 7);
    REQUIRE(jv1.at("pi").as_real() == 3.141);
    REQUIRE(jv1.at("happy").as_bool() == true);
    REQUIRE(jv1.at("name").as_str() == "Niels");
    REQUIRE(jv1.at("nothing").is_null());
    REQUIRE(jv1.at("answer").at("everything").as_int64() == -42);
    REQUIRE(jv1.at("list").as_array().size() == 3);
    REQUIRE(jv1.at("object").at("currency").as_str() == "USD");
    REQUIRE(jv1.at("object").at("value").as_real() == 42.99);
}

Installation

Just copy the contents of the include folder in your project with msgpack_describe.h as an optional header.

Dependencies

You just need a C++17 compiler. If you want to avail yourself of the convenient Boost.Describe integration in msgpack_describe.h, then you'll require that Boost library.

API

The library provides the following functions for basic and STL types:

namespace msgpackcpp
{
    template<SINK_TYPE Sink, class Type>
    void serialize(Sink& out, const Type& obj);

    template<SOURCE_TYPE Source, class Type>
    void deserialize(Source& in, Type& obj);
}

where:

• out is a templated function object with signature void(const char* data, size_t len) which writes serialized data.
• in is a templated function object with signature void(char* data, size_t len) which reads serialized data.

When c++20 is enabled SINK_TYPE and SOURCE_TYPE are concepts which check those signatures.

The library also provides functions sink() and source() which take a type and return function objects (c++ lambda) which satisfy the SINK_TYPE and SOURCE_TYPE concepts. Currently overloads for std::vector<char> and std::iostream are provided though users can write their own sink/source types.

This library also provides a dictionary type msgpackcpp::value very similar to nlohmann::json or boost::json::value which can be (de)serialized using member functions .pack() and .unpack(). Conversions from msgpackcpp::value to and from custom types is not supported and discouraged. This library allows you to serialize and deserialized types directly without having to go through msgpackcpp::value.

Documentation

There is none. Hopefully the code is readable.