IlmThreadSemaphore.h

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2005, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
//
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///////////////////////////////////////////////////////////////////////////

#ifndef INCLUDED_ILM_THREAD_SEMAPHORE_H
#define INCLUDED_ILM_THREAD_SEMAPHORE_H

//-----------------------------------------------------------------------------
//
//	class Semaphore -- a wrapper class for
//	system-dependent counting semaphores
//
//-----------------------------------------------------------------------------

#include "IlmBaseConfig.h"

#if defined _WIN32 || defined _WIN64
    #ifdef NOMINMAX
        #undef NOMINMAX
    #endif
    #define NOMINMAX
    #include <windows.h>
#elif HAVE_PTHREAD && !HAVE_POSIX_SEMAPHORES
    #include <pthread.h>
#elif HAVE_PTHREAD && HAVE_POSIX_SEMAPHORES
    #include <semaphore.h>
#endif

namespace IlmThread {


class Semaphore
{
  public:

    Semaphore (unsigned int value = 0);
    virtual ~Semaphore();

    void	wait();
    bool	tryWait();
    void	post();
    int		value() const;

  private:

    #if defined _WIN32 || defined _WIN64

    mutable HANDLE _semaphore;

    #elif HAVE_PTHREAD && !HAVE_POSIX_SEMAPHORES

    //
    // If the platform has Posix threads but no semapohores,
    // then we implement them ourselves using condition variables
    //

    struct sema_t
    {
        unsigned int count;
        unsigned long numWaiting;
        pthread_mutex_t mutex;
        pthread_cond_t nonZero;
    };

    mutable sema_t _semaphore;

    #elif HAVE_PTHREAD && HAVE_POSIX_SEMAPHORES

    mutable sem_t _semaphore;

    #endif

    void operator = (const Semaphore& s);	// not implemented
    Semaphore (const Semaphore& s);		// not implemented
};


} // namespace IlmThread

#endif