Unicode dictionary coding? UTF8, UTF32, etc

[Theodore H. Smith]

Can someone give me some advice? If I was to write a dictionary class 
for Unicode, would I be better off writing it using a b-tree, or 
hash-bin system? Or maybe an array of pointers to arrays system?

I suppose, that if I wanted an array of pointers to arrays, that I 
couldn't use UTF32, I could only use UTF8, right? Are there any 
advantages I could make of UTF8 having "dissallowed" character ranges, 
when writing some dictionary code?

Is there some kind of place on the internet I should look up about 
Unicode dictionaries? I'm assuming that this matter has been dealt with 
in ICU already...

Thanks a lot!