Re: usage of snd_seq_queue_status_get_real_time()

[Steve deRosier <derosier@pianodisc.com>]

Ah, good point, color me dumb.  ;)  I've fixed that.  Thanks.

Note however it doesn't seem to fix the issue.  What did make it work for me was using
snd_seq_queue_status_malloc() and snd_seq_queue_status_free() instead of using the snd_seq_queue_status_alloca() macro.  Not sure why the macro didn't work for me, but the full fledged functions seem to make everything work.

My final working function (in case anyone cares):
snd_seq_real_time_t CMIDIPort::GetRealQueueTime( void )
{
  snd_seq_queue_status_t * qs;
  snd_seq_real_time_t rt;
  rt.tv_sec = 0;
  rt.tv_nsec = 0;

  if( snd_seq_queue_status_malloc( &qs ) )
    return rt;
  if( snd_seq_get_queue_status( hSeq, mQueue, qs ) == 0 )
    rt = *snd_seq_queue_status_get_real_time( qs );
  snd_seq_queue_status_free( qs );

  return rt;
}
 
An interesting note... On repeated calls, it will return the same time value for a few calls in a row.  Does the status information only get updated every so often?  Like maybe the driver only transfers a chunk at a time and so the time info in the status only gets updated each time the buffer is full or empty?

Thanks for you help,
- Steve


Clemens Ladisch wrote:
> Steve deRosier wrote:
> 
>>I figured that it returns a pointer to a local var considering the
>>const in the return type, but that still doesn't explain why the
>>data never changes.
> 
> 
> Local variables cease to exist when the function returns.  The data on
> the stack will be overwritten by the calling function (which explains
> why you see a constant, meaningless value).
> 
> You should return the snd_seq_real_time_t by value.
> 
> 
> HTH
> Clemens
> 


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