getRealIndex function Null safety

int getRealIndex(
  1. int position,
  2. int base,
  3. int? length
)

Converts an index of a set size to the corresponding index of a collection of another size as if they were circular.

Takes a position from collection Foo, a base from where Foo's index originated and the length of a second collection Baa, for which the correlating index is sought.

For example; We have a Carousel of 10000(simulating infinity) but only 6 images. We need to repeat the images to give the illusion of a never ending stream. By calling _getRealIndex with position and base we get an offset. This offset modulo our length, 6, will return a number between 0 and 5, which represent the image to be placed in the given position.

Implementation

int getRealIndex(int position, int base, int? length) {
  final int offset = position - base;
  return remainder(offset, length);
}