Question

In a previous program that I have written in C I needed a single object with several “core” data in it that can be accessed by all the functions in my program, I end up picking a struct and i have used a pointer to this struct for reading or writing data; it was fast and good for the job, also it was cheap because accessing a pointer is probably one of the cheapest thing that you can do in C and I have never found something better so I’m happy with this solution.

Now in C++ I have the same problem, I need to share a state composed of some primitive types, I’m tempted to use one of the so called POD, which basically mean, struct, again, but this time with references for safety.

Supposing that I need this “Blob” of data to be carried around my program, a struct accessed by reference is the fastest thing in C++? How much a getter methods can cost?

Answer 1

If your getter code is inline (in the header file), then the compiler can eliminate the need to call a function in the machine code it outputs.

eg:

class Data
{
private:
  int number_;
public:
  int GetNumber() { return number_; }
};

The compiler will see GetNumber’s definition, will know what it does is simple and and where you’ve called GetNumber(), it will simply replace it with number_. So, using a getter versus accessing the member directly will result in the equivalent code, and both will perform the same.