contrib/libc++/src/memory.cpp

   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 #ifndef _LIBCPP_HAS_NO_THREADS
  13 #include "mutex"
  14 #include "thread"
  15 #endif
  16
  17 _LIBCPP_BEGIN_NAMESPACE_STD
  18
  19 namespace
  20 {
  21
  22 template <class T>
  23 inline T
  24 increment(T& t) _NOEXCEPT
  25 {
  26     return __sync_add_and_fetch(&t, 1);
  27 }
  28
  29 template <class T>
  30 inline T
  31 decrement(T& t) _NOEXCEPT
  32 {
  33     return __sync_add_and_fetch(&t, -1);
  34 }
  35
  36 }  // namespace
  37
  38 const allocator_arg_t allocator_arg = allocator_arg_t();
  39
  40 bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {}
  41
  42 const char*
  43 bad_weak_ptr::what() const _NOEXCEPT
  44 {
  45     return "bad_weak_ptr";
  46 }
  47
  48 __shared_count::~__shared_count()
  49 {
  50 }
  51
  52 void
  53 __shared_count::__add_shared() _NOEXCEPT
  54 {
  55     increment(__shared_owners_);
  56 }
  57
  58 bool
  59 __shared_count::__release_shared() _NOEXCEPT
  60 {
  61     if (decrement(__shared_owners_) == -1)
  62     {
  63         __on_zero_shared();
  64         return true;
  65     }
  66     return false;
  67 }
  68
  69 __shared_weak_count::~__shared_weak_count()
  70 {
  71 }
  72
  73 void
  74 __shared_weak_count::__add_shared() _NOEXCEPT
  75 {
  76     __shared_count::__add_shared();
  77 }
  78
  79 void
  80 __shared_weak_count::__add_weak() _NOEXCEPT
  81 {
  82     increment(__shared_weak_owners_);
  83 }
  84
  85 void
  86 __shared_weak_count::__release_shared() _NOEXCEPT
  87 {
  88     if (__shared_count::__release_shared())
  89         __release_weak();
  90 }
  91
  92 void
  93 __shared_weak_count::__release_weak() _NOEXCEPT
  94 {
  95     if (decrement(__shared_weak_owners_) == -1)
  96         __on_zero_shared_weak();
  97 }
  98
  99 __shared_weak_count*
 100 __shared_weak_count::lock() _NOEXCEPT
 101 {
 102     long object_owners = __shared_owners_;
 103     while (object_owners != -1)
 104     {
 105         if (__sync_bool_compare_and_swap(&__shared_owners_,
 106                                          object_owners,
 107                                          object_owners+1))
 108             return this;
 109         object_owners = __shared_owners_;
 110     }
 111     return 0;
 112 }
 113
 114 #if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
 115
 116 const void*
 117 __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
 118 {
 119     return 0;
 120 }
 121
 122 #endif  // _LIBCPP_NO_RTTI
 123
 124 #if __has_feature(cxx_atomic) && !defined(_LIBCPP_HAS_NO_THREADS)
 125
 126 static const std::size_t __sp_mut_count = 16;
 127 static pthread_mutex_t mut_back_imp[__sp_mut_count] =
 128 {
 129     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 130     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 131     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 132     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER
 133 };
 134
 135 static mutex* mut_back = reinterpret_cast<std::mutex*>(mut_back_imp);
 136
 137 _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
 138    : __lx(p)
 139 {
 140 }
 141
 142 void
 143 __sp_mut::lock() _NOEXCEPT
 144 {
 145     mutex& m = *static_cast<mutex*>(__lx);
 146     unsigned count = 0;
 147     while (!m.try_lock())
 148     {
 149         if (++count > 16)
 150         {
 151             m.lock();
 152             break;
 153         }
 154         this_thread::yield();
 155     }
 156 }
 157
 158 void
 159 __sp_mut::unlock() _NOEXCEPT
 160 {
 161     static_cast<mutex*>(__lx)->unlock();
 162 }
 163
 164 __sp_mut&
 165 __get_sp_mut(const void* p)
 166 {
 167     static __sp_mut muts[__sp_mut_count]
 168     {
 169         &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
 170         &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
 171         &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11],
 172         &mut_back[12], &mut_back[13], &mut_back[14], &mut_back[15]
 173     };
 174     return muts[hash<const void*>()(p) & (__sp_mut_count-1)];
 175 }
 176
 177 #endif // __has_feature(cxx_atomic) && !_LIBCPP_HAS_NO_THREADS
 178
 179 void
 180 declare_reachable(void*)
 181 {
 182 }
 183
 184 void
 185 declare_no_pointers(char*, size_t)
 186 {
 187 }
 188
 189 void
 190 undeclare_no_pointers(char*, size_t)
 191 {
 192 }
 193
 194 pointer_safety
 195 get_pointer_safety() _NOEXCEPT
 196 {
 197     return pointer_safety::relaxed;
 198 }
 199
 200 void*
 201 __undeclare_reachable(void* p)
 202 {
 203     return p;
 204 }
 205
 206 void*
 207 align(size_t alignment, size_t size, void*& ptr, size_t& space)
 208 {
 209     void* r = nullptr;
 210     if (size <= space)
 211     {
 212         char* p1 = static_cast<char*>(ptr);
 213         char* p2 = reinterpret_cast<char*>(reinterpret_cast<size_t>(p1 + (alignment - 1)) & -alignment);
 214         size_t d = static_cast<size_t>(p2 - p1);
 215         if (d <= space - size)
 216         {
 217             r = p2;
 218             ptr = r;
 219             space -= d;
 220         }
 221     }
 222     return r;
 223 }
 224
 225 _LIBCPP_END_NAMESPACE_STD