linuxaudio.org

Olivier Guilyardi:

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>

> Ken Restivo wrote:

>> It has been over 7 years since I last messed around with writing Pthreads applications.

>>

>> I recall it as a painful, ugly, brain-numbing task. I located an exercise I did back then to address the consumer/producer problem in Pthreads, and just the sight of it is giving me a headache.

>>

>> I'm being lazy, so instead of researching everything that's out there, I'll ask here: can anyone recommend a relatively simple and painless abstraction library (GPL or LGPL of course) that will give me functions to create a thread in which I can stuff things into a ring buffer, and another thread in which I can pull stuff out of it?

>>

>> By the way, I know that JACK has a very nice event buffer which is insanely easy to use (and I have), and makes multithreading almost transparent, but this isn't a JACK app.

>

> I don't know of any abstraction library, but creating/terminating a normal

> thread with pthread is really an easy task IMO. It's about 10 lines in C.

>

> For inter-thread communication there's Portaudio's ring buffer:

> http://portaudio.com/trac/browser/portaudio/trunk/src/common/pa_ringbuff...

>

> It can easily be used out of Portaudio (I'm currently doing that), and it

> features memory barriers [1] which AFAIK Jack's ringbuffer doesn't.

>

> One problem with everything Portaudio is this heavy naming scheme. For a simpler

> API, you might like my little wrapper:

> http://jackbeat.samalyse.org/browser/jackbeat/trunk/src/core/ringbuffer....

>

Nice. It's probably quicker to copy the jack_ringbuffer.c file out of jack

though.
> Portaudio actually also offers a callback mechanism (with hidden thread

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> creation), so if you're coding an non-JACK audio app, you might want to check it

> out.

>

> For thread synchronization, semaphores (man semaphore.h) are really easy to use.

> However, if you need a lock-free equivalent (for realtime, ...) phtread mutex

> and especially pthread_mutex_trylock are your friends.

>

Those friends can be really cranky sometimes though.

By using atomic operations instead, it's possible to avoid

a lot of headache by not having to synchronize at all.

Performance might be better too. Midishare has lockfree

atomic functions for lifo and fifi queues:

http://midishare.cvs.sourceforge.net/viewvc/midishare/midishare/src/comm...

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