[Need advice] When to decode '+' to ' '?

Hello!


Say I have a percent-encoded URI and decode
all the percent blocks. The result will
still carry '+'s representing spaces sometimes.
What do I do with that? How do I fully decode
the URI without hurting '+'s that do not represent
spaces. Also for the other way around: Should
I always percent-encode '+'s to save them?
I didn't find anything about it in RFC 3986.

Any help appreciated. Thanks in advance!



Sebastian