Daily Unreal Column #68 - TCircularBuffer

Sometimes you want to store fixed amount of elements in a container. On top of that, once you reach the limit, you want the newest element to replace the old one. That's what TCircularBuffer is for.

TCircularBuffer doesn’t have a default constructor and requires you to declare its size the moment its being created.

TCircularBuffer<float> Foo(1024);

It also only has three functions available:

• Capacity — returns the number of elements this buffer can store

• GetNextIndex — calculates the next index that follows the given index as parameter to this function

• GetPreviousIndex — calculates the previous index to the given index as parameter to this function

Let’s take a look at an example usage.

TCircularBuffer<float> Foo(1024);
for (int32 Index = 0; Index < 10000; Index++)
{
    Foo[Index] = FMath::FRand();
}

Notice that Index variable far exceeds the range of 0-1023 but this is fine. This is exactly what circular buffer is great at. Internally it uses a mask that allows us to pass any Index and it will apply the mask to it, effectively clamping it to the expected range of 0-1023.