memory.cpp revision 242945 
1//===------------------------ memory.cpp ----------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is dual licensed under the MIT and the University of Illinois Open
6// Source Licenses. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#define _LIBCPP_BUILDING_MEMORY
11#include "memory"
12#include "mutex"
13#include "thread"
14
15_LIBCPP_BEGIN_NAMESPACE_STD
16
17namespace
18{
19
20template <class T>
21inline T
22increment(T& t) _NOEXCEPT
23{
24    return __sync_add_and_fetch(&t, 1);
25}
26
27template <class T>
28inline T
29decrement(T& t) _NOEXCEPT
30{
31    return __sync_add_and_fetch(&t, -1);
32}
33
34}  // namespace
35
36const allocator_arg_t allocator_arg = allocator_arg_t();
37
38bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {}
39
40const char*
41bad_weak_ptr::what() const _NOEXCEPT
42{
43    return "bad_weak_ptr";
44}
45
46__shared_count::~__shared_count()
47{
48}
49
50void
51__shared_count::__add_shared() _NOEXCEPT
52{
53    increment(__shared_owners_);
54}
55
56bool
57__shared_count::__release_shared() _NOEXCEPT
58{
59    if (decrement(__shared_owners_) == -1)
60    {
61        __on_zero_shared();
62        return true;
63    }
64    return false;
65}
66
67__shared_weak_count::~__shared_weak_count()
68{
69}
70
71void
72__shared_weak_count::__add_shared() _NOEXCEPT
73{
74    __shared_count::__add_shared();
75}
76
77void
78__shared_weak_count::__add_weak() _NOEXCEPT
79{
80    increment(__shared_weak_owners_);
81}
82
83void
84__shared_weak_count::__release_shared() _NOEXCEPT
85{
86    if (__shared_count::__release_shared())
87        __release_weak();
88}
89
90void
91__shared_weak_count::__release_weak() _NOEXCEPT
92{
93    if (decrement(__shared_weak_owners_) == -1)
94        __on_zero_shared_weak();
95}
96
97__shared_weak_count*
98__shared_weak_count::lock() _NOEXCEPT
99{
100    long object_owners = __shared_owners_;
101    while (object_owners != -1)
102    {
103        if (__sync_bool_compare_and_swap(&__shared_owners_,
104                                         object_owners,
105                                         object_owners+1))
106            return this;
107        object_owners = __shared_owners_;
108    }
109    return 0;
110}
111
112#ifndef _LIBCPP_NO_RTTI
113
114const void*
115__shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
116{
117    return 0;
118}
119
120#endif  // _LIBCPP_NO_RTTI
121
122#if __has_feature(cxx_atomic)
123
124static const std::size_t __sp_mut_count = 16;
125static mutex mut_back[__sp_mut_count];
126
127_LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
128   : __lx(p)
129{
130}
131
132void
133__sp_mut::lock() _NOEXCEPT
134{
135    mutex& m = *static_cast<mutex*>(__lx);
136    unsigned count = 0;
137    while (!m.try_lock())
138    {
139        if (++count > 16)
140        {
141            m.lock();
142            break;
143        }
144        this_thread::yield();
145    }
146}
147
148void
149__sp_mut::unlock() _NOEXCEPT
150{
151    static_cast<mutex*>(__lx)->unlock();
152}
153
154__sp_mut&
155__get_sp_mut(const void* p)
156{
157    static __sp_mut muts[__sp_mut_count]
158    {
159        &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
160        &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
161        &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11],
162        &mut_back[12], &mut_back[13], &mut_back[14], &mut_back[15]
163    };
164    return muts[hash<const void*>()(p) & (__sp_mut_count-1)];
165}
166
167#endif // __has_feature(cxx_atomic)
168
169void
170declare_reachable(void*)
171{
172}
173
174void
175declare_no_pointers(char*, size_t)
176{
177}
178
179void
180undeclare_no_pointers(char*, size_t)
181{
182}
183
184pointer_safety
185get_pointer_safety() _NOEXCEPT
186{
187    return pointer_safety::relaxed;
188}
189
190void*
191__undeclare_reachable(void* p)
192{
193    return p;
194}
195
196void*
197align(size_t alignment, size_t size, void*& ptr, size_t& space)
198{
199    void* r = nullptr;
200    if (size <= space)
201    {
202        char* p1 = static_cast<char*>(ptr);
203        char* p2 = (char*)((size_t)(p1 + (alignment - 1)) & -alignment);
204        size_t d = static_cast<size_t>(p2 - p1);
205        if (d <= space - size)
206        {
207            r = p2;
208            ptr = r;
209            space -= d;
210        }
211    }
212    return r;
213}
214
215_LIBCPP_END_NAMESPACE_STD
216