IlmThreadMutex.h

Go to the documentation of this file.

///////////////////////////////////////////////////////////////////////////
//
// 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.
//
///////////////////////////////////////////////////////////////////////////

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

#ifdef ILMBASE_FORCE_CXX03
#   if defined _WIN32 || defined _WIN64
#      ifdef NOMINMAX
#         undef NOMINMAX
#      endif
#      define NOMINMAX
#      include <windows.h>
#   elif HAVE_PTHREAD
#      include <pthread.h>
#   endif
#else
#   include <mutex>
#endif

ILMTHREAD_INTERNAL_NAMESPACE_HEADER_ENTER


// in c++11, this can just be
//
// using Mutex = std::mutex;
// unfortunately we can't use std::unique_lock as a replacement for Lock since
// they have different API.
//
// if we decide to break the API, we can just
//
// using Lock = std::lock_guard<std::mutex>;
// or
// using Lock = std::unique_lock<std::mutex>;
//
// (or eliminate the type completely and have people use the std library) 
#ifdef ILMBASE_FORCE_CXX03

class Lock;

class ILMTHREAD_EXPORT 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;
};
#else
using Mutex = std::mutex;
#endif

class ILMTHREAD_EXPORT Lock
{
  public:

    Lock (const Mutex& m, bool autoLock = true):
        _mutex (const_cast<Mutex &>(m)), _locked (false)
    {
        if (autoLock)
        {
            _mutex.lock();
            _locked = true;
        }
    }
    
    ~Lock ()
    {
        if (_locked)
            _mutex.unlock();
    }
    Lock (const Lock&) = delete;
    Lock &operator= (const Lock&) = delete;
    Lock (Lock&&) = delete;
    Lock& operator= (Lock&&) = delete;

    void acquire ()
    {
        _mutex.lock();
        _locked = true;
    }
    
    void release ()
    {
        _mutex.unlock();
        _locked = false;
    }
    
    bool locked ()
    {
        return _locked;
    }

  private:

    Mutex & _mutex;
    bool    _locked;
};


ILMTHREAD_INTERNAL_NAMESPACE_HEADER_EXIT

#endif // INCLUDED_ILM_THREAD_MUTEX_H