///////////////////////////////////////////////////////////////////////////

//

// Copyright (c) 2005-2012, Industrial Light & Magic, a division of Lucas

// Digital Ltd. LLC

// 

// All rights reserved.

// 

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// *       Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// *       Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// *       Neither the name of Industrial Light & Magic nor the names of

// its contributors may be used to endorse or promote products derived

// from this software without specific prior written permission. 

// 

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

///////////////////////////////////////////////////////////////////////////

//-----------------------------------------------------------------------------

//

//	class Semaphore -- implementation for for platforms that do

//	support Posix threads but do not support Posix semaphores,

//	for example, OS X

//

//-----------------------------------------------------------------------------

#include "IlmBaseConfig.h"

#if HAVE_PTHREAD && !HAVE_POSIX_SEMAPHORES

#include "IlmThreadSemaphore.h"

#include "Iex.h"

#include <assert.h>

ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_ENTER

Semaphore::Semaphore (unsigned int value)

{

    if (int error = ::pthread_mutex_init (&_semaphore.mutex, 0))

        IEX_NAMESPACE::throwErrnoExc ("Cannot initialize mutex (%T).", error);

    if (int error = ::pthread_cond_init (&_semaphore.nonZero, 0))

        IEX_NAMESPACE::throwErrnoExc ("Cannot initialize condition variable (%T).",

                            error);

    _semaphore.count = value;

    _semaphore.numWaiting = 0;

}

Semaphore::~Semaphore ()

{

    int error = ::pthread_cond_destroy (&_semaphore.nonZero);

    assert (error == 0);

    error = ::pthread_mutex_destroy (&_semaphore.mutex);

    assert (error == 0);

}

void

Semaphore::wait ()

{

    ::pthread_mutex_lock (&_semaphore.mutex);

    _semaphore.numWaiting++;

    while (_semaphore.count == 0)

    {

        if (int error = ::pthread_cond_wait (&_semaphore.nonZero,

                                             &_semaphore.mutex))

        {

            ::pthread_mutex_unlock (&_semaphore.mutex);

            IEX_NAMESPACE::throwErrnoExc ("Cannot wait on condition variable (%T).",

                                          error);

        }

    }

    _semaphore.numWaiting--;

    _semaphore.count--;

    ::pthread_mutex_unlock (&_semaphore.mutex);

}

bool

Semaphore::tryWait ()

{

    ::pthread_mutex_lock (&_semaphore.mutex);

    if (_semaphore.count == 0)

    {

        ::pthread_mutex_unlock (&_semaphore.mutex);

        return false;

    }

    else

    {

        _semaphore.count--;

        ::pthread_mutex_unlock (&_semaphore.mutex);

        return true;

    }

}

void

Semaphore::post ()

{

    ::pthread_mutex_lock (&_semaphore.mutex);

    if (_semaphore.numWaiting > 0)

    {

        if (int error = ::pthread_cond_signal (&_semaphore.nonZero))

        {

            ::pthread_mutex_unlock (&_semaphore.mutex);

            IEX_NAMESPACE::throwErrnoExc ("Cannot signal condition variable (%T).",

                                error);

        }

    }

    _semaphore.count++;

    ::pthread_mutex_unlock (&_semaphore.mutex);

}

int

Semaphore::value () const

{

    ::pthread_mutex_lock (&_semaphore.mutex);

    int value = _semaphore.count;

    ::pthread_mutex_unlock (&_semaphore.mutex);

    return value;

}

ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_EXIT

#endif