1 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
2 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_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 //
11 // detail/sp_counted_base_gcc_x86.hpp - g++ on 486+ or AMD64
12 //
13 // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
14 // Copyright 2004-2005 Peter Dimov
15 //
16 // Distributed under the Boost Software License, Version 1.0. (See
17 // accompanying file LICENSE_1_0.txt or copy at
18 // http://www.boost.org/LICENSE_1_0.txt)
19 //
20 //
21 // Lock-free algorithm by Alexander Terekhov
22 //
23 // Thanks to Ben Hitchings for the #weak + (#shared != 0)
24 // formulation
25 //
26
27 #include <boost/detail/sp_typeinfo.hpp>
28
29 namespace boost
30 {
31
32 namespace detail
33 {
34
atomic_exchange_and_add(int * pw,int dv)35 inline int atomic_exchange_and_add( int * pw, int dv )
36 {
37 // int r = *pw;
38 // *pw += dv;
39 // return r;
40
41 int r;
42
43 __asm__ __volatile__
44 (
45 "lock\n\t"
46 "xadd %1, %0":
47 "=m"( *pw ), "=r"( r ): // outputs (%0, %1)
48 "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1)
49 "memory", "cc" // clobbers
50 );
51
52 return r;
53 }
54
atomic_increment(int * pw)55 inline void atomic_increment( int * pw )
56 {
57 //atomic_exchange_and_add( pw, 1 );
58
59 __asm__
60 (
61 "lock\n\t"
62 "incl %0":
63 "=m"( *pw ): // output (%0)
64 "m"( *pw ): // input (%1)
65 "cc" // clobbers
66 );
67 }
68
atomic_conditional_increment(int * pw)69 inline int atomic_conditional_increment( int * pw )
70 {
71 // int rv = *pw;
72 // if( rv != 0 ) ++*pw;
73 // return rv;
74
75 int rv, tmp;
76
77 __asm__
78 (
79 "movl %0, %%eax\n\t"
80 "0:\n\t"
81 "test %%eax, %%eax\n\t"
82 "je 1f\n\t"
83 "movl %%eax, %2\n\t"
84 "incl %2\n\t"
85 "lock\n\t"
86 "cmpxchgl %2, %0\n\t"
87 "jne 0b\n\t"
88 "1:":
89 "=m"( *pw ), "=&a"( rv ), "=&r"( tmp ): // outputs (%0, %1, %2)
90 "m"( *pw ): // input (%3)
91 "cc" // clobbers
92 );
93
94 return rv;
95 }
96
97 class sp_counted_base
98 {
99 private:
100
101 sp_counted_base( sp_counted_base const & );
102 sp_counted_base & operator= ( sp_counted_base const & );
103
104 int use_count_; // #shared
105 int weak_count_; // #weak + (#shared != 0)
106
107 public:
108
sp_counted_base()109 sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
110 {
111 }
112
~sp_counted_base()113 virtual ~sp_counted_base() // nothrow
114 {
115 }
116
117 // dispose() is called when use_count_ drops to zero, to release
118 // the resources managed by *this.
119
120 virtual void dispose() = 0; // nothrow
121
122 // destroy() is called when weak_count_ drops to zero.
123
destroy()124 virtual void destroy() // nothrow
125 {
126 delete this;
127 }
128
129 virtual void * get_deleter( sp_typeinfo const & ti ) = 0;
130 virtual void * get_local_deleter( sp_typeinfo const & ti ) = 0;
131 virtual void * get_untyped_deleter() = 0;
132
add_ref_copy()133 void add_ref_copy()
134 {
135 atomic_increment( &use_count_ );
136 }
137
add_ref_lock()138 bool add_ref_lock() // true on success
139 {
140 return atomic_conditional_increment( &use_count_ ) != 0;
141 }
142
release()143 void release() // nothrow
144 {
145 if( atomic_exchange_and_add( &use_count_, -1 ) == 1 )
146 {
147 dispose();
148 weak_release();
149 }
150 }
151
weak_add_ref()152 void weak_add_ref() // nothrow
153 {
154 atomic_increment( &weak_count_ );
155 }
156
weak_release()157 void weak_release() // nothrow
158 {
159 if( atomic_exchange_and_add( &weak_count_, -1 ) == 1 )
160 {
161 destroy();
162 }
163 }
164
use_count() const165 long use_count() const // nothrow
166 {
167 return static_cast<int const volatile &>( use_count_ );
168 }
169 };
170
171 } // namespace detail
172
173 } // namespace boost
174
175 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
176