A Guide to Using Msgpack::type::make_array_ref for Efficient Data Processing

MessagePack is a binary serialization format designed for efficient data exchange between various programming languages. It’s similar to JSON, but with a smaller footprint and faster encoding/decoding speeds. The MessagePack C++ library offers an extensive range of tools and functions for working with this format, and one of them is msgpack::type::make_array_ref.

In this blog post, we will delve into the inner workings of msgpack::type::make_array_ref, examining its role and the benefits it offers. We will also go through some practical examples to help you understand how to use this function effectively in your projects.

What is msgpack::type::make_array_ref?

The msgpack::type::make_array_ref function is a utility provided by the MessagePack C++ library to create an array reference object. This object wraps an existing C++ array or a collection of elements, allowing them to be treated as a single entity in the MessagePack serialization and deserialization processes.

The main advantage of using msgpack::type::make_array_ref is its performance. Instead of creating a new std::vector or std::list object and copying the data, it creates a lightweight reference to the existing data, minimizing memory usage and improving serialization speed.

Let’s look at the typical signature of this function:

template 
msgpack::type::array_ref make_array_ref(const T& t);

As you can see, the function is templated and takes a single argument, which is a reference to the array or collection of elements you want to wrap.

How to Use msgpack::type::make_array_ref

A Practical Example with Tuples

Now that we have a basic understanding of msgpack::type::make_array_ref let’s see how to use it in a practical example.

Imagine you have an application that needs to send and receive data structures containing multiple elements of different types. One way to achieve this is by using a std::tuple and serializing it using MessagePack.

#include 
#include 
#include 

int main() {
    // Create a tuple containing different types of data
    std::tuple<int, float, std::string> data{42, 3.14f, "Hello, MessagePack"};

    // Serialize the tuple
    msgpack::sbuffer sbuf;
    msgpack::pack(sbuf, data);

    // Deserialize the tuple
    msgpack::object_handle oh = msgpack::unpack(sbuf.data(), sbuf.size());
    msgpack::object obj = oh.get();

    // Convert the deserialized object back to the tuple
    std::tuple<int, float, std::string> deserialized_data;
    obj.convert(deserialized_data);

    // Print the deserialized data
    std::cout << "Deserialized data: (" << std::get<0>(deserialized_data) << ", "
              << std::get<1>(deserialized_data) << ", "
              << std::get<2>(deserialized_data) << ")" << std::endl;

    return 0;
}

While this approach works, it’s not very efficient, especially when dealing with large arrays or collections. To improve performance, we can use msgpack::type::make_array_ref to wrap the tuple and create an array reference object. Here’s the modified version of the code:

#include 
#include 
#include 

int main() {
    // Create a tuple containing different types of data
    std::tuple<int, float, std::string> data{42, 3.14f, "Hello, MessagePack"};

    // Wrap the tuple using make_array_ref
    auto array_ref = msgpack::type::make_array_ref(data);

    // Serialize the array reference
    msgpack::sbuffer sbuf;
    msgpack::pack(sbuf, array_ref);

    // Deserialize the array reference
    msgpack::object_handle oh = msgpack::unpack(sbuf.data(), sbuf.size());
    msgpack::object obj = oh.get();

    // Convert the deserialized object back to the tuple
    std::tuple<int, float, std::string> deserialized_data;
    obj.convert(deserialized_data);

    // Print the deserialized data
    std::cout << "Deserialized data: (" << std::get<0>(deserialized_data) << ", "
              << std::get<1>(deserialized_data) << ", "
              << std::get<2>(deserialized_data) << ")" << std::endl;

    return 0;
}

By using msgpack::type::make_array_ref, we’ve improved the efficiency of our serialization process. It’s important to note that this function is not limited to tuples; it can also be used with other container types, such as arrays or even custom classes.

Working with Arrays

Let’s take a look at another example, where we’ll use msgpack::type::make_array_ref to serialize and deserialize a plain C++ array.

#include 
#include 
#include 

int main() {
    // Create an array of integers
    std::array<int, 5> data{1, 2, 3, 4, 5};

    // Wrap the array using make_array_ref
    auto array_ref = msgpack::type::make_array_ref(data);

    // Serialize the array reference
    msgpack::sbuffer sbuf;
    msgpack::pack(sbuf, array_ref);

    // Deserialize the array reference
    msgpack::object_handle oh = msgpack::unpack(sbuf.data(), sbuf.size());
    msgpack::object obj = oh.get();

    // Convert the deserialized object back to the array
    std::array<int, 5> deserialized_data;
    obj.convert(deserialized_data);

    // Print the deserialized data
    std::cout << "Deserialized data: ";
    for (const auto& element : deserialized_data) {
        std::cout << element << " ";
    }
    std::cout << std::endl;

    return 0;
}

Integrating with Custom Classes

Finally, let’s see how msgpack::type::make_array_ref can be used to serialize and deserialize instances of a custom class.

#include 
#include 
#include 

class Person {
public:
    Person() = default;
    Person(const std::string& name, int age) : name_(name), age_(age) {}

    // Getter and setter functions
    const std::string& name() const { return name_; }
    void setName(const std::string& name) { name_ = name; }

    int age() const { return age_; }
    void setAge(int age) { age_ = age; }

private:
    std::string name_;
    int age_;
};

// Define serialization and deserialization for the Person class
namespace msgpack {
MSGPACK_API_VERSION_NAMESPACE(MSGPACK_DEFAULT_API_NS) {
namespace adaptor {

template <>
struct convert {
    msgpack::object const& operator()(msgpack::object const& o, Person& p) const {
        if (o.type != msgpack::type::ARRAY || o.via.array.size != 2) {
            throw msgpack::type_error();
        }

        p.setName(o.via.array.ptr[0].as());
        p.setAge(o.via.array.ptr[1].as());

        return o;
    }
};

template <>
struct pack {
    template 
    msgpack::packer& operator()(msgpack::packer& o, Person const& p) const {
        o.pack_array(2);
        o.pack(p.name());
        o.pack(p.age());

        return o;
    }
};

template <>
struct object_with_zone {
    void operator()(msgpack::object::with_zone& o, Person const& p) const {
        o.type = msgpack::type::ARRAY;
        msgpack::object* v = o.zone.allocate_align(sizeof(msgpack::object) * 2);
        o.via.array.ptr = v;
        o.via.array.size = 2;

        v[0] = msgpack::object(p.name(), o.zone);
        v[1] = msgpack::object(p.age(), o.zone);
    }
};

}  // namespace adaptor
}  // MSGPACK_API_VERSION_NAMESPACE(MSGPACK_DEFAULT_API_NS)
}  // namespace msgpack

int main() {
    // Create a Person object
    Person person("Alice", 30);

    // Wrap the Person object using make_array_ref
    auto array_ref = msgpack::type::make_array_ref(person);

    // Serialize the array reference
    msgpack::sbuffer sbuf;
    msgpack::pack(sbuf, array_ref);

    // Deserialize the array reference
    msgpack::object_handle oh = msgpack::unpack(sbuf.data(), sbuf.size());
    msgpack::object obj = oh.get();

    // Convert the deserialized object back to a Person object
    Person deserialized_person;
    obj.convert(deserialized_person);

    // Print the deserialized data
    std::cout << "Deserialized data: " << deserialized_person.name() << ", " << deserialized_person.age() << std::endl;

    return 0;
}

In this example, we’ve defined a custom Person class and specified how it should be serialized and deserialized using MessagePack. After creating a Person object, we wrap it using msgpack::type::make_array_ref and proceed with the serialization and deserialization processes as before.

Conclusion

The msgpack::type::make_array_ref function is a powerful and efficient utility provided by the MessagePack C++ library. It allows developers to create lightweight array reference objects that wrap existing data structures, minimizing memory usage and improving serialization speed.

Through practical examples, we’ve demonstrated how to use msgpack::type::make_array_ref with different container types, including tuples, arrays, and custom classes. By understanding and utilizing this function, you can optimize your applications and achieve better performance when dealing with MessagePack serialization and deserialization in C++.

Whether you’re working on large-scale data exchange systems or simply looking for a more efficient way to serialize your custom data structures, msgpack::type::make_array_ref offers an effective solution. It’s a valuable tool for any developer working with the MessagePack C++ library, and integrating it into your projects can lead to significant performance improvements.