Ooof. replace "measureHashrefLength" with "measureFieldLength" in my explanation.

How 'bout you replace it yourself? Because you posted as a registered user (most desirable, IMHO), you can go back and edit your post. However, please be sure the edits are readily apparent via  <strike> ... </strike> or  <del> ... </del><ins> ... </ins> tags, or an "Update: ..." paragraph or paragraphs added at the end of the post — or both! Uncited changes to a post just make the replies of other monks seem incoherent. Please see Markup in the Monastery, Writeup Formatting Tips, etc.