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