[LAU] NEWBIE needs help: Multi-buffering

I want to write a small audio signal processing application. What I want to do is to successive blocks of N samples, process them and display the results in real time. The processing takes a lot more time than sampling interval, however it can be comfortably done in the time it takes to collect N samples. That is why I like to have an arrangement where I can queue two or three buffers for audio input and process the first full buffer in plenty of time while the audio software is filling in the next buffer. As soon as I finish processing the buffer, I could queue it to be filled again. I would also like use callbacks as much as possible. I have tried PORTAUDIO and it does not seem to do multi-buffering I have tried JACK briefly but it suffers from lack of documentation and as far as I could gather it had no facilities for this kind of thing. I know I could write a higher level interface for PORTAUDIO to simulate multi-buffering but it means I have to copy input buffer into intermediate buffers to simulate multi-buffering and apart from synchronisation problems that I may encounter, it is a solution that appears very inelegant to me. Is there anything out there which can do multi-buffer audio I/O ? Any pointers to web pages, advice or admonition is very welcome!