Skip to main content

Overloading in Overdrive: A Generic Data-Centric Messaging Library for DDS

Slides of my Silicon Valley Code Camp (2013) talk are now available. If you attended this session in person please evaluate it. I take feedback/comments seriously!

Abstract: When it comes to sending data across a network, applications send either binary or self-describing data (XML). Both approaches have merits. Data Distribution Service (DDS) combines the best of both in what’s called “data-centric messaging”. DDS shares the type description once, upfront, and later on sends binary data that meets the type description. You typically use IDL or XSD to specify the types and run them through a code generator for type-safe wrapper APIs for your application in your programming language. Simple and fast! As it turns out, however, C++11 bends the rules once again. In this presentation you will learn about a template-based C++11 messaging library that gives the DDS code generator a run for its money. The types and objects in your C++11 application are mapped to standard DDS X-Types type descriptions and serialized format, respectively, using template meta-programming. If you have never heard about SFINAE you won’t stop talking about it after you see "overloading in overdrive" in this presentation. What’s more? I will share my newfound hatred for std::vector of bool/enums. This presentation will cover DDS-XTypes, DDS_TypeCode, DDS_DynamicData, STL, type_traits, Boost Fusion, and overloading with enable_if (lots and lots of it!).

Comments

Post a Comment

Popular Content

Unit Testing C++ Templates and Mock Injection Using Traits

Unit testing your template code comes up from time to time. (You test your templates, right?) Some templates are easy to test. No others. Sometimes it's not clear how to about injecting mock code into the template code that's under test. I've seen several reasons why code injection becomes challenging. Here I've outlined some examples below with roughly increasing code injection difficulty. Template accepts a type argument and an object of the same type by reference in constructor Template accepts a type argument. Makes a copy of the constructor argument or simply does not take one Template accepts a type argument and instantiates multiple interrelated templates without virtual functions Lets start with the easy ones. Template accepts a type argument and an object of the same type by reference in constructor This one appears straight-forward because the unit test simply instantiates the template under test with a mock type. Some assertion might be tested in
Post a Comment
Read more

Covariance and Contravariance in C++ Standard Library

Covariance and Contravariance are concepts that come up often as you go deeper into generic programming. While designing a language that supports parametric polymorphism (e.g., templates in C++, generics in Java, C#), the language designer has a choice between Invariance, Covariance, and Contravariance when dealing with generic types. C++'s choice is "invariance". Let's look at an example. struct Vehicle {}; struct Car : Vehicle {}; std::vector<Vehicle *> vehicles; std::vector<Car *> cars; vehicles = cars; // Does not compile The above program does not compile because C++ templates are invariant. Of course, each time a C++ template is instantiated, the compiler creates a brand new type that uniquely represents that instantiation. Any other type to the same template creates another unique type that has nothing to do with the earlier one. Any two unrelated user-defined types in C++ can't be assigned to each-other by default. You have to provide a
14 comments
Read more

Multi-dimensional arrays in C++11

What new can be said about multi-dimensional arrays in C++? As it turns out, quite a bit! With the advent of C++11, we get new standard library class std::array. We also get new language features, such as template aliases and variadic templates. So I'll talk about interesting ways in which they come together. It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array? int native[3][4]; std::array<std::array<int, 3>, 4> arr; No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is: std::array<std::array<int, 4>, 3> arr; That's quite annoying for
20 comments
Read more