subranges: detach cache logic from computation logic Having both the logic around cache checking and setting makes is a bit harder to follow. In addition, this allow to gather the computation logic next to the other related function.

findmissingrange: properly queue new subrange for slicing The previous code was buggy and used the wrong variable leading to no extra slicing being performed to file the sample at the requested size.

findmissingrange: fix reversed value in debug output "oops"