How to display a message packed structure

Question

I am trying to convert a struct into msgpack in C or C++. Please find the code below:

struct your_type {
    int a;
    float b;
    MSGPACK_DEFINE(a, b);
};

int main() {
    // packing
    std::stringstream ss;
    std::vector<std::map<std::string, your_type>> v 
    { 
        { 
            { "t", {1,2.7} }

        },
        {
            {"value", {2, 6.8} } 
        }
    };
    msgpack::pack(ss, v);
}

I understand how to transform this output to object using msgpack::object_handle. But I want to print the packed output in C, so to verify if it does look like the format we obtain after converting a dataframe into msgpack in Python. How can I display the msgpack::pack output?

Edited: hex_dump() as mentioned answer provided in the comments actually helps in obtaining the answer.

struct your_type {
    int a;
    int b;
    MSGPACK_DEFINE(a, b);
};

int main() {
    std::stringstream ss;

    std::vector<std::map<std::string, your_type>> v
    {
        {
            { "t",{ 1, 2 } }

        },
        {
            { "value",{ 3, 6 } }
        }
    };
    msgpack::pack(ss, v);
    hex_dump(std::cout, ss.str()) << std::endl;
}

I am able to convert this struct into hexvalues. But I am trying to make a float value for b in struct, so that "value" can take float values. I am not able to do so though. Could anyone please guide me in this?

Answer 1

msgpack::pack writes the packed content into its first parameter of a type std::stringstream, so it should be easy to print it:

msgpack::pack(ss, v)
std::string string_buffer = ss.str()
std::cout << s << '\n';

Answer 2

After some conversation, I understand your question contains two different part. One is how to print packed data as human readable hex format similar to python. The other is how to treat well float value in msgpack.

Here is the code to answer both two parts.

#include <sstream>
#include <iostream>
#include <msgpack.hpp>

inline std::ostream& hex_dump(std::ostream& o, std::string const& v) {
    std::ios::fmtflags f(o.flags());
    o << std::hex;
    for (auto c : v) {
        o << "\\x" << std::setw(2) << std::setfill('0') << (static_cast<int>(c) & 0xff);
    }
    o.flags(f);
    return o;
}

struct your_type {
    int a;
    float b;
    MSGPACK_DEFINE(a, b);
};

int main() {
    // packing
    std::stringstream ss;
    std::vector<std::map<std::string, your_type>> v 
    { 
        { 
            { "t", {1,2.7} }

        },
        {
            {"value", {2, 6.8} } 
        }
    };
    msgpack::pack(ss, v);

    // hex dump output
    hex_dump(std::cout, ss.str()) << std::endl;

    auto oh = msgpack::unpack(ss.str().data(), ss.str().size());
    // JSON output
    std::cout << oh.get() << std::endl;
}

Runnning Demo: https://wandbox.org/permlink/DanDq9QTW6JZ6MO0

The funtion hex_dump() outputs std::string to ostream as hex dump format.

You can use float value similar to int. There is no big difference.