IlmThread.h

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///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2005-2012, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
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// modification, are permitted provided that the following conditions are
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// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
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// in the documentation and/or other materials provided with the
// distribution.
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// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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///////////////////////////////////////////////////////////////////////////

#ifndef INCLUDED_ILM_THREAD_H
#define INCLUDED_ILM_THREAD_H

//-----------------------------------------------------------------------------
//
//      class Thread
//
//      Class Thread is a portable interface to a system-dependent thread
//      primitive.  In order to make a thread actually do something useful,
//      you must derive a subclass from class Thread and implement the
//      run() function.  If the operating system supports threading then
//      the run() function will be executed int a new thread.
//
//      The actual creation of the thread is done by the start() routine
//      which then calls the run() function.  In general the start()
//      routine should be called from the constructor of the derived class.
//
//      The base-class thread destructor will join/destroy the thread.
//
//      IMPORTANT: Due to the mechanisms that encapsulate the low-level
//      threading primitives in a C++ class there is a race condition
//      with code resembling the following:
//
//          {
//              WorkerThread myThread;
//          } // myThread goes out of scope, is destroyed
//            // and the thread is joined
//
//      The race is between the parent thread joining the child thread
//      in the destructor of myThread, and the run() function in the
//      child thread.  If the destructor gets executed first then run()
//      will be called with an invalid "this" pointer.
//
//      This issue can be fixed by using a Semaphore to keep track of
//      whether the run() function has already been called.  You can
//      include a Semaphore member variable within your derived class
//      which you post() on in the run() function, and wait() on in the
//      destructor before the thread is joined.  Alternatively you could
//      do something like this:
//
//          Semaphore runStarted;
//
//          void WorkerThread::run ()
//          {
//              runStarted.post()
//              // do some work
//              ...
//          }
//
//          {
//              WorkerThread myThread;
//              runStarted.wait ();    // ensure that we have started
//                                     // the run function
//          } // myThread goes out of scope, is destroyed
//            // and the thread is joined
//
//-----------------------------------------------------------------------------

#include "IlmBaseConfig.h"
#include "IlmThreadExport.h"
#include "IlmThreadNamespace.h"

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

ILMTHREAD_INTERNAL_NAMESPACE_HEADER_ENTER

//
// Query function to determine if the current platform supports
// threads AND this library was compiled with threading enabled.
//

ILMTHREAD_EXPORT bool supportsThreads ();


class ILMTHREAD_EXPORT Thread
{
  public:

    Thread ();
    virtual ~Thread ();

    void                start ();
    virtual void        run () = 0;
    
  private:

    #if defined _WIN32 || defined _WIN64
        HANDLE _thread;
    #elif HAVE_PTHREAD
        pthread_t _thread;
    #endif

    void operator = (const Thread& t);  // not implemented
    Thread (const Thread& t);           // not implemented
};


ILMTHREAD_INTERNAL_NAMESPACE_HEADER_EXIT

#endif // INCLUDED_ILM_THREAD_H