Some problems about BSplineElements

[KMushaL]

Hi, professor!
I have some problems about class BSplineElements.
I can't understand what these following variables and functions do, and I don't know the relationship between them and the comments "This class represents a function on the interval, partitioned into "res" blocks."

Also, the difination of constructor worried me too, what the meaning of the input argument 'offset' and the code of the last if part?

I am a green hand, these questions worried me too long, I hope to get your reply, thanks a lot.

[KMushaL]

Also, I can't understand the class BSplineSupportSizes, especially what the meaning of the word 'interval' and these BOUNDS's difination.