#ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED
#define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED

//
//  detail/sp_counted_base_vacpp_ppc.hpp - xlC(vacpp) on POWER
//   based on: detail/sp_counted_base_w32.hpp
//
//  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
//  Copyright 2004-2005 Peter Dimov
//  Copyright 2006 Michael van der Westhuizen
//  Copyright 2012 IBM Corp.
//
//  Distributed under the Boost Software License, Version 1.0. (See
//  accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
//
//  Lock-free algorithm by Alexander Terekhov
//
//  Thanks to Ben Hitchings for the #weak + (#shared != 0)
//  formulation
//

#include <boost/smart_ptr/detail/sp_typeinfo_.hpp>
#include <boost/smart_ptr/detail/sp_obsolete.hpp>
#include <boost/config.hpp>

#if defined(BOOST_SP_REPORT_IMPLEMENTATION)

#include <boost/config/pragma_message.hpp>
BOOST_PRAGMA_MESSAGE("Using xlC/PowerPC sp_counted_base")

#endif

BOOST_SP_OBSOLETE()

extern "builtin" void __lwsync(void);
extern "builtin" void
__isync(void);
extern "builtin" int
__fetch_and_add(volatile int* addr, int val);
extern "builtin" int
__compare_and_swap(volatile int*, int*, int);

namespace boost {

namespace detail {

inline void
atomic_increment( int *pw )
{
    // ++*pw;
    __lwsync();
    __fetch_and_add(pw, 1);
    __isync();
}

inline int
atomic_decrement( int *pw )
{
    // return --*pw;
    __lwsync();
    int originalValue = __fetch_and_add(pw, -1);
    __isync();

    return (originalValue - 1);
}

inline int
atomic_conditional_increment( int *pw )
{
    // if( *pw != 0 ) ++*pw;
    // return *pw;

    __lwsync();
    int v = *const_cast<volatile int*>(pw);

    for (;;)
        // loop until state is known
    {
        if (v == 0)
        {
            return 0;
        }

        if (__compare_and_swap(pw, &v, v + 1))
        {
            __isync();
            return (v + 1);
        }
    }
}

class BOOST_SYMBOL_VISIBLE sp_counted_base
{
  private:

    sp_counted_base( sp_counted_base const & );
    sp_counted_base &
    operator= ( sp_counted_base const & );

    int use_count_;        // #shared
    int weak_count_;       // #weak + (#shared != 0)
    char pad[64]
    __attribute__((__aligned__(64)));
    // pad to prevent false sharing
  public:

    sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
    {
    }

    virtual
    ~sp_counted_base() // nothrow
    {
    }

    // dispose() is called when use_count_ drops to zero, to release
    // the resources managed by *this.

    virtual void
    dispose() = 0; // nothrow

    // destroy() is called when weak_count_ drops to zero.

    virtual void
    destroy() // nothrow
    {
        delete this;
    }

    virtual void *
    get_deleter( sp_typeinfo_ const & ti ) = 0;
    virtual void *
    get_local_deleter( sp_typeinfo_ const & ti ) = 0;
    virtual void *
    get_untyped_deleter() = 0;

    void
    add_ref_copy()
    {
        atomic_increment( &use_count_ );
    }

    bool
    add_ref_lock() // true on success
    {
        return atomic_conditional_increment( &use_count_ ) != 0;
    }

    void
    release() // nothrow
    {
        if ( atomic_decrement( &use_count_ ) == 0 )
        {
            dispose();
            weak_release();
        }
    }

    void
    weak_add_ref() // nothrow
    {
        atomic_increment( &weak_count_ );
    }

    void
    weak_release() // nothrow
    {
        if ( atomic_decrement( &weak_count_ ) == 0 )
        {
            destroy();
        }
    }

    long
    use_count() const // nothrow
    {
        return *const_cast<volatile int*>(&use_count_);
    }
};

} // namespace detail

} // namespace boost

#endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED
