1 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
2 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
3 
4 // MS compatible compilers support #pragma once
5 
6 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
7 # pragma once
8 #endif
9 
10 //  detail/sp_counted_base_sync.hpp - g++ 4.1+ __sync intrinsics
11 //
12 //  Copyright (c) 2007 Peter Dimov
13 //
14 //  Distributed under the Boost Software License, Version 1.0.
15 //  See accompanying file LICENSE_1_0.txt or copy at
16 //  http://www.boost.org/LICENSE_1_0.txt
17 
18 #include <boost/detail/sp_typeinfo.hpp>
19 #include <limits.h>
20 
21 #if defined( __ia64__ ) && defined( __INTEL_COMPILER )
22 # include <ia64intrin.h>
23 #endif
24 
25 namespace boost
26 {
27 
28 namespace detail
29 {
30 
31 #if INT_MAX >= 2147483647
32 
33 typedef int sp_int32_t;
34 
35 #else
36 
37 typedef long sp_int32_t;
38 
39 #endif
40 
atomic_increment(sp_int32_t * pw)41 inline void atomic_increment( sp_int32_t * pw )
42 {
43     __sync_fetch_and_add( pw, 1 );
44 }
45 
atomic_decrement(sp_int32_t * pw)46 inline sp_int32_t atomic_decrement( sp_int32_t * pw )
47 {
48     return __sync_fetch_and_add( pw, -1 );
49 }
50 
atomic_conditional_increment(sp_int32_t * pw)51 inline sp_int32_t atomic_conditional_increment( sp_int32_t * pw )
52 {
53     // long r = *pw;
54     // if( r != 0 ) ++*pw;
55     // return r;
56 
57     sp_int32_t r = *pw;
58 
59     for( ;; )
60     {
61         if( r == 0 )
62         {
63             return r;
64         }
65 
66         sp_int32_t r2 = __sync_val_compare_and_swap( pw, r, r + 1 );
67 
68         if( r2 == r )
69         {
70             return r;
71         }
72         else
73         {
74             r = r2;
75         }
76     }
77 }
78 
79 class sp_counted_base
80 {
81 private:
82 
83     sp_counted_base( sp_counted_base const & );
84     sp_counted_base & operator= ( sp_counted_base const & );
85 
86     sp_int32_t use_count_;        // #shared
87     sp_int32_t weak_count_;       // #weak + (#shared != 0)
88 
89 public:
90 
sp_counted_base()91     sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
92     {
93     }
94 
~sp_counted_base()95     virtual ~sp_counted_base() // nothrow
96     {
97     }
98 
99     // dispose() is called when use_count_ drops to zero, to release
100     // the resources managed by *this.
101 
102     virtual void dispose() = 0; // nothrow
103 
104     // destroy() is called when weak_count_ drops to zero.
105 
destroy()106     virtual void destroy() // nothrow
107     {
108         delete this;
109     }
110 
111     virtual void * get_deleter( sp_typeinfo const & ti ) = 0;
112     virtual void * get_local_deleter( sp_typeinfo const & ti ) = 0;
113     virtual void * get_untyped_deleter() = 0;
114 
add_ref_copy()115     void add_ref_copy()
116     {
117         atomic_increment( &use_count_ );
118     }
119 
add_ref_lock()120     bool add_ref_lock() // true on success
121     {
122         return atomic_conditional_increment( &use_count_ ) != 0;
123     }
124 
release()125     void release() // nothrow
126     {
127         if( atomic_decrement( &use_count_ ) == 1 )
128         {
129             dispose();
130             weak_release();
131         }
132     }
133 
weak_add_ref()134     void weak_add_ref() // nothrow
135     {
136         atomic_increment( &weak_count_ );
137     }
138 
weak_release()139     void weak_release() // nothrow
140     {
141         if( atomic_decrement( &weak_count_ ) == 1 )
142         {
143             destroy();
144         }
145     }
146 
use_count() const147     long use_count() const // nothrow
148     {
149         return const_cast< sp_int32_t const volatile & >( use_count_ );
150     }
151 };
152 
153 } // namespace detail
154 
155 } // namespace boost
156 
157 #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
158