/* -*-c++-*- OpenThreads library, Copyright (C) 2008  The Open Thread Group
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef _OPENTHREADS_ATOMIC_
#define _OPENTHREADS_ATOMIC_

#include <OpenThreads/Config>

#if defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
# include <windows.h>
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
# include <atomic.h>
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
# include "Mutex"
# include "ScopedLock"
#endif

namespace OpenThreads {

/**
 *  @class Atomic
 *  @brief  This class provides an atomic increment and decrement operation.
 */
class Atomic {
 public:
    Atomic(unsigned value = 0) : _value(value)
    { }
    unsigned operator++()
    {
#if defined(_OPENTHREADS_ATOMIC_USE_GCC_BUILTINS)
        return __sync_add_and_fetch(&_value, 1);
#elif defined(_OPENTHREADS_ATOMIC_USE_MIPOSPRO_BUILTINS)
        return __add_and_fetch(&_value, 1);
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
        return atomic_inc_uint_nv(&_value);
#elif defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
        return InterlockedIncrement(&_value);
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
        ScopedLock<Mutex> lock(_mutex);
        return ++_value;
#else
        return ++_value;
#endif
    }
    unsigned operator--()
    {
#if defined(_OPENTHREADS_ATOMIC_USE_GCC_BUILTINS)
        return __sync_sub_and_fetch(&_value, 1);
#elif defined(_OPENTHREADS_ATOMIC_USE_MIPOSPRO_BUILTINS)
        return __sub_and_fetch(&_value, 1);
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
        return atomic_dec_uint_nv(&_value);
#elif defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
        return InterlockedDecrement(&_value);
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
        ScopedLock<Mutex> lock(_mutex);
        return --_value;
#else
        return --_value;
#endif
    }
    operator unsigned() const
    {
#if defined(_OPENTHREADS_ATOMIC_USE_GCC_BUILTINS)
        __sync_synchronize();
        return _value;
#elif defined(_OPENTHREADS_ATOMIC_USE_MIPOSPRO_BUILTINS)
        __synchronize(_value);
        return _value;
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
        membar_consumer(); // Hmm, do we need???
        return _value;
#elif defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
        return static_cast<unsigned const volatile &>(_value);
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
        ScopedLock<Mutex> lock(_mutex);
        return _value;
#else
        return _value;
#endif
    }
    
 private:

    Atomic(const Atomic&);
    Atomic& operator=(const Atomic&);
    
#if defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
    mutable Mutex _mutex;
#endif
#if defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
    __declspec(align(32)) volatile long _value;
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
    volatile uint_t _value;
#else
    volatile unsigned _value;
#endif
};

/**
 *  @class AtomicPtr
 *  @brief  This class provides an atomic pointer assignment using cas operations.
 */
template<typename T>
class AtomicPtr {
public:
    AtomicPtr(T* ptr = 0) : _ptr(ptr)
    { }
    ~AtomicPtr()
    { _ptr = 0; }

    // assigns a new pointer
    bool assign(T* ptrNew, const T* const ptrOld)
    {
#if defined(_OPENTHREADS_ATOMIC_USE_GCC_BUILTINS)
        return __sync_bool_compare_and_swap(&_ptr, ptrOld, ptrNew);
#elif defined(_OPENTHREADS_ATOMIC_USE_MIPOSPRO_BUILTINS)
        return __compare_and_swap(&_ptr, ptrOld, ptrNew);
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
        return ptrOld == atomic_cas_ptr(&_ptr, ptrOld, ptrNew);
#elif defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
        return ptrOld == InterlockedCompareExchangePointer(&_ptr, ptrNew, ptrOld);
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
        ScopedLock<Mutex> lock(_mutex);
        if (_ptr != ptrOld)
            return false;
        _ptr = ptrNew;
        return true;
#else
        if (_ptr != ptrOld)
            return false;
        _ptr = ptrNew;
        return true;
#endif
    }

    T* get() const
    {
#if defined(_OPENTHREADS_ATOMIC_USE_GCC_BUILTINS)
        __sync_synchronize();
        return _ptr;
#elif defined(_OPENTHREADS_ATOMIC_USE_MIPOSPRO_BUILTINS)
        __synchronize(_ptr);
        return _ptr;
#elif defined(_OPENTHREADS_ATOMIC_USE_SUN)
        membar_consumer(); // Hmm, do we need???
        return _ptr;
#elif defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
        return _ptr;
#elif defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
        ScopedLock<Mutex> lock(_mutex);
        return _ptr;
#else
        return _ptr;
#endif
    }

private:
    AtomicPtr(const AtomicPtr&);
    AtomicPtr& operator=(const AtomicPtr&);

#if defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
    mutable Mutex _mutex;
#endif
#if defined(_OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED)
    __declspec(align(32))
#endif
    T* volatile _ptr;
};

}

#endif // _OPENTHREADS_ATOMIC_