Boost C++ Libraries

boost/detail/sp_counted_base_acc_ia64.hpp

#ifndef BOOST_DETAIL_SP_COUNTED_BASE_ACC_IA64_HPP_INCLUDED
#define BOOST_DETAIL_SP_COUNTED_BASE_ACC_IA64_HPP_INCLUDED

//
//  detail/sp_counted_base_acc_ia64.hpp - aC++ on HP-UX IA64
//
//  Copyright 2007 Baruch Zilber
//  Copyright 2007 Boris Gubenko
//
//  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
//

#include <boost/detail/sp_typeinfo.hpp>
#include <machine/sys/inline.h>

namespace boost
{

namespace detail
{

inline void atomic_increment( int * pw )
{
    // ++*pw;

    _Asm_fetchadd(_FASZ_W, _SEM_REL, pw, +1, _LDHINT_NONE);
} 

inline int atomic_decrement( int * pw )
{
    // return --*pw;

    int r = static_cast<int>(_Asm_fetchadd(_FASZ_W, _SEM_REL, pw, -1, _LDHINT_NONE));
    if (1 == r)
    {
        _Asm_mf();
    }
    
    return r - 1;
}

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

    int v = *pw;
    
    for (;;)
    {
        if (0 == v)
        {
            return 0;
        }
        
        _Asm_mov_to_ar(_AREG_CCV,
                       v,
                       (_UP_CALL_FENCE | _UP_SYS_FENCE | _DOWN_CALL_FENCE | _DOWN_SYS_FENCE));
        int r = static_cast<int>(_Asm_cmpxchg(_SZ_W, _SEM_ACQ, pw, v + 1, _LDHINT_NONE));
        if (r == v)
        {
            return r + 1;
        }
        
        v = r;
    }
}

class 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)

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;

    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 static_cast<int const volatile &>( use_count_ ); // TODO use ld.acq here
    }
};

} // namespace detail

} // namespace boost

#endif  // #ifndef BOOST_DETAIL_SP_COUNTED_BASE_ACC_IA64_HPP_INCLUDED