IlmThreadMutex.h

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2005, 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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// *       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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///////////////////////////////////////////////////////////////////////////

#ifndef INCLUDED_ILM_THREAD_MUTEX_H
#define INCLUDED_ILM_THREAD_MUTEX_H

//-----------------------------------------------------------------------------
//
//	class Mutex, class Lock
//
//	Class Mutex is a wrapper for a system-dependent mutual exclusion
//	mechanism.  Actual locking and unlocking of a Mutex object must
//	be performed using an instance of a Lock (defined below).
//
//	Class lock provides safe locking and unlocking of mutexes even in
//	the presence of C++ exceptions.  Constructing a Lock object locks
//	the mutex; destroying the Lock unlocks the mutex.
//
//	Lock objects are not themselves thread-safe.  You should never
//	share a Lock object among multiple threads.
//
//	Typical usage:
//
//	    Mutex mtx;	// Create a Mutex object that is visible
//	    		//to multiple threads
//
//	    ...		// create some threads
//
//	    // Then, within each thread, construct a critical section like so:
//
//	    {
//		Lock lock (mtx);	// Lock constructor locks the mutex
//		...			// do some computation on shared data
//	    }				// leaving the block unlocks the mutex
//
//-----------------------------------------------------------------------------

#include "IlmBaseConfig.h"

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

namespace IlmThread {

class Lock;


class Mutex
{
  public:

    Mutex ();
    virtual ~Mutex ();

  private:

    void	lock () const;
    void	unlock () const;

    #if defined _WIN32 || defined _WIN64
    mutable CRITICAL_SECTION _mutex;
    #elif HAVE_PTHREAD
    mutable pthread_mutex_t _mutex;
    #endif

    void operator = (const Mutex& M);	// not implemented
    Mutex (const Mutex& M);		// not implemented

    friend class Lock;
};


class Lock
{
  public:

    Lock (const Mutex& m, bool autoLock = true):
    _mutex (m),
    _locked (false)
    {
        if (autoLock)
        {
            _mutex.lock();
            _locked = true;
        }
    }

    ~Lock ()
    {
        if (_locked)
            _mutex.unlock();
    }

    void acquire ()
    {
        _mutex.lock();
        _locked = true;
    }

    void release ()
    {
        _mutex.unlock();
        _locked = false;
    }

    bool locked ()
    {
        return _locked;
    }

  private:

    const Mutex &	_mutex;
    bool		_locked;
};


} // namespace IlmThread

#endif