[Boost-users] How to write a block-wise filter...

From: Stephen Webb (swebb75ky_at_[hidden])
Date: 2006-05-17 18:54:40

I don't really have my head around the Boost IO filter architecture yet, but
I have managed to get a very basic filter working.  I'm having some trouble
with end-of-input issues.  I think what I'm trying to do comes up
frequently, so hopefully this will be a straightforward answer...

What I'm trying to do is write a filter that takes in input one character at
a time (for simplicity -- for now), and outputs encrypted characters.  The
block size is 4 bytes, so every 4 characters I can encrypt, and then spit
out the result.  If I hit the end of input, then I want to pad the
plaintext, encrypt and output the final block.  My trouble is knowing when
the end-of-input has arrived.  Is there a well defined way that my output
filter is notified of a close event or something similar?  I did see close
functions defined in the example filters, but mine isn't getting called.  I
tried to look at the base64 encode/decode headers (which would have to deal
with the same issue) but I couldn't really follow it.

Any help is appreciated.

Thanks

-Steve