smart_ptr/detail/sp_counted_base_vacpp_ppc.hpp

0001 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED
0002 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED
0003
0004 //
0005 //  detail/sp_counted_base_vacpp_ppc.hpp - xlC(vacpp) on POWER
0006 //   based on: detail/sp_counted_base_w32.hpp
0007 //
0008 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
0009 //  Copyright 2004-2005 Peter Dimov
0010 //  Copyright 2006 Michael van der Westhuizen
0011 //  Copyright 2012 IBM Corp.
0012 //
0013 //  Distributed under the Boost Software License, Version 1.0. (See
0014 //  accompanying file LICENSE_1_0.txt or copy at
0015 //  http://www.boost.org/LICENSE_1_0.txt)
0016 //
0017 //
0018 //  Lock-free algorithm by Alexander Terekhov
0019 //
0020 //  Thanks to Ben Hitchings for the #weak + (#shared != 0)
0021 //  formulation
0022 //
0023
0024 #include <boost/smart_ptr/detail/sp_typeinfo_.hpp>
0025 #include <boost/smart_ptr/detail/sp_obsolete.hpp>
0026 #include <boost/config.hpp>
0027
0028 #if defined(BOOST_SP_REPORT_IMPLEMENTATION)
0029
0030 #include <boost/config/pragma_message.hpp>
0031 BOOST_PRAGMA_MESSAGE("Using xlC/PowerPC sp_counted_base")
0032
0033 #endif
0034
0035 BOOST_SP_OBSOLETE()
0036
0037 extern "builtin" void __lwsync(void);
0038 extern "builtin" void __isync(void);
0039 extern "builtin" int __fetch_and_add(volatile int* addr, int val);
0040 extern "builtin" int __compare_and_swap(volatile int*, int*, int);
0041
0042 namespace boost
0043 {
0044
0045 namespace detail
0046 {
0047
0048 inline void atomic_increment( int *pw )
0049 {
0050    // ++*pw;
0051    __lwsync();
0052    __fetch_and_add(pw, 1);
0053    __isync();
0054 }
0055
0056 inline int atomic_decrement( int *pw )
0057 {
0058    // return --*pw;
0059    __lwsync();
0060    int originalValue = __fetch_and_add(pw, -1);
0061    __isync();
0062
0063    return (originalValue - 1);
0064 }
0065
0066 inline int atomic_conditional_increment( int *pw )
0067 {
0068    // if( *pw != 0 ) ++*pw;
0069    // return *pw;
0070
0071    __lwsync();
0072    int v = *const_cast<volatile int*>(pw);
0073    for (;;)
0074    // loop until state is known
0075    {
0076       if (v == 0) return 0;
0077       if (__compare_and_swap(pw, &v, v + 1))
0078       {
0079          __isync(); return (v + 1);
0080       }
0081    }
0082 }
0083
0084 class BOOST_SYMBOL_VISIBLE sp_counted_base
0085 {
0086 private:
0087
0088     sp_counted_base( sp_counted_base const & );
0089     sp_counted_base & operator= ( sp_counted_base const & );
0090
0091     int use_count_;        // #shared
0092     int weak_count_;       // #weak + (#shared != 0)
0093     char pad[64] __attribute__((__aligned__(64)));
0094             // pad to prevent false sharing
0095 public:
0096
0097     sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
0098     {
0099     }
0100
0101     virtual ~sp_counted_base() // nothrow
0102     {
0103     }
0104
0105     // dispose() is called when use_count_ drops to zero, to release
0106     // the resources managed by *this.
0107
0108     virtual void dispose() = 0; // nothrow
0109
0110     // destroy() is called when weak_count_ drops to zero.
0111
0112     virtual void destroy() // nothrow
0113     {
0114         delete this;
0115     }
0116
0117     virtual void * get_deleter( sp_typeinfo_ const & ti ) = 0;
0118     virtual void * get_local_deleter( sp_typeinfo_ const & ti ) = 0;
0119     virtual void * get_untyped_deleter() = 0;
0120
0121     void add_ref_copy()
0122     {
0123         atomic_increment( &use_count_ );
0124     }
0125
0126     bool add_ref_lock() // true on success
0127     {
0128         return atomic_conditional_increment( &use_count_ ) != 0;
0129     }
0130
0131     void release() // nothrow
0132     {
0133         if( atomic_decrement( &use_count_ ) == 0 )
0134         {
0135             dispose();
0136             weak_release();
0137         }
0138     }
0139
0140     void weak_add_ref() // nothrow
0141     {
0142         atomic_increment( &weak_count_ );
0143     }
0144
0145     void weak_release() // nothrow
0146     {
0147         if( atomic_decrement( &weak_count_ ) == 0 )
0148         {
0149             destroy();
0150         }
0151     }
0152
0153     long use_count() const // nothrow
0154     {
0155         return *const_cast<volatile int*>(&use_count_);
0156     }
0157 };
0158
0159 } // namespace detail
0160
0161 } // namespace boost
0162
0163 #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_VACPP_PPC_HPP_INCLUDED