Symmetric cipher padding?

[Brad Hards]

I'm having a little trouble with padding (at least I think that is the 
problem, I'm a very newbie at this). I want to support both PKCS#7 
padding and also avoiding padding for when the input is a block size. 
Is there any description of how gcrypt does padding?

If I'm doing CBC, and the data is finished, how do I say "pad as 
required and give me the result"?

Brad