Question

I use unsigned ints representing a bunch of airplanes in a game. Each plane has two states, flying and grounded. I would like to store this state together with the planes number. What is the “best” way to achieve that? I could use std::maps with the planes and their state in it but that seems overkill and slow. Could it be done using bit flags ?
The assigning and testing of the test should be quick.

Pseudo code:

unsigned int Boing = 777;

if( Boing is flying)
 set some bit;

is Boing flying? (how to check for the current state)

Any hint on a simple and fast technique is appreciated!

Answer 1

The fastest and cleanest way is probably to avoid bitfields, and simply define a struct:

struct Plane
{
    bool isFlying;
    unsigned int number;
}

...


std::vector<Plane> planes;
Plane p;
p.isFlying = true;
p.number = 777;
planes.push_back(p);

This method will use more memory than trying to cram the flag into the same word, but will take less work to get/set the fields. Unless you’re memory-constrained, I would strongly recommend avoiding trying to pack everything tightly.

You could even consider using an enum rather than a bool for the state.