[pulseaudio-discuss] pa_stream_readable_size() returns 4294967295
lennart at poettering.net
Wed Dec 16 04:44:02 PST 2009
On Fri, 11.12.09 03:27, Tanu Kaskinen (tanuk at iki.fi) wrote:
> to, 2009-12-10 kello 21:20 +0100, Mads Kiilerich kirjoitti:
> > With reference to
> > http://0pointer.de/lennart/projects/pulseaudio/doxygen/stream_8h.html#aa2e5ff19aa36b90471c34badbdfdf345
> > and using pulseaudio-0.9.15-17.fc11.i586:
> > My experiments shows that pa_stream_readable_size() sometimes returns
> > 4294967295 = 0xffffffff. That possibility is not described in the
> > documentation, AFAICS.
> > However, I have only seen that happen when not PA_STREAM_READY. Is the
> > ready state a precondition for calling this function? How should race
> > conditions be avoided?
> Yes, the READY state is a precondition.
> What kind of race conditions do you mean? Do you mean that how are you
> supposed to know prior to calling pa_stream_readable_size() whether the
> stream is still in READY state? Are you not able to reliably track the
> state with a state change callback (pa_set_state_callback)?
Also, you can just call _readable_size(), and then check if that
failed. Duplicating the state check externally is not necessary.
> I'm not terribly familiar with the client library details, so I'm not
> saying that there are no races. But since the library is
> single-threaded, I believe you can use the state callback to always have
> the same knowledge of the state as the library itself.
That is true. The PA libraries are not generally thread-safe, however
they are threads-aware.
> > It would have matched my expectations better if the type was ssize_t and
> > the value thus -1.
> Pulseaudio uses ((size_t) -1) in error cases in many places. I guess
> it's at least partially a matter of taste...
Yes, that is true.
> > Are there any other special values?
> I didn't write the code, but I'm quite sure that the answer is no.
Yes, that is correct. The answer is "no".
Lennart Poettering Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/ GnuPG 0x1A015CC4
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