[IIIIIIIIIIIIIII]

This StackOverflow replay happens to answer this question exactly, the actual definition of "CFWS" is near the bottom of the text:

https://stackoverflow.com/a/42193413/544779

It's just an excerpt of the spec, but I link to it instead of to the spec because I think it's easier to read (formatting/colors) and it has links to the spec anyway.

[StavrosK]

Ahh, thank you, I missed that part of the spec. The "folding" part was what confused me, thanks again.