libstdc++-v3/include/bits/shared_ptr.h

   1 // shared_ptr and weak_ptr implementation -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 // GCC Note: Based on files from version 1.32.0 of the Boost library.
  26
  27 //  shared_count.hpp
  28 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
  29
  30 //  shared_ptr.hpp
  31 //  Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
  32 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
  33
  34 //  weak_ptr.hpp
  35 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
  36
  37 //  enable_shared_from_this.hpp
  38 //  Copyright (C) 2002 Peter Dimov
  39
  40 // Distributed under the Boost Software License, Version 1.0. (See
  41 // accompanying file LICENSE_1_0.txt or copy at
  42 // http://www.boost.org/LICENSE_1_0.txt)
  43
  44 /** @file bits/shared_ptr.h
  45  *  This is an internal header file, included by other library headers.
  46  *  You should not attempt to use it directly.
  47  */
  48
  49 #ifndef _SHARED_PTR_H
  50 #define _SHARED_PTR_H 1
  51
  52 #include <bits/shared_ptr_base.h>
  53
  54 _GLIBCXX_BEGIN_NAMESPACE(std)
  55
  56   /**
  57    * @addtogroup pointer_abstractions
  58    * @{
  59    */
  60
  61   /// 2.2.3.7 shared_ptr I/O
  62   template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
  63     inline std::basic_ostream<_Ch, _Tr>&
  64     operator<<(std::basic_ostream<_Ch, _Tr>& __os,
  65                const __shared_ptr<_Tp, _Lp>& __p)
  66     {
  67       __os << __p.get();
  68       return __os;
  69     }
  70
  71   /// 2.2.3.10 shared_ptr get_deleter (experimental)
  72   template<typename _Del, typename _Tp, _Lock_policy _Lp>
  73     inline _Del*
  74     get_deleter(const __shared_ptr<_Tp, _Lp>& __p)
  75     {
  76 #ifdef __GXX_RTTI
  77       return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
  78 #else
  79       return 0;
  80 #endif
  81     }
  82
  83
  84   /**
  85    *  @brief  A smart pointer with reference-counted copy semantics.
  86    *
  87    *  The object pointed to is deleted when the last shared_ptr pointing to
  88    *  it is destroyed or reset.
  89   */
  90   template<typename _Tp>
  91     class shared_ptr : public __shared_ptr<_Tp>
  92     {
  93     public:
  94       /**
  95        *  @brief  Construct an empty %shared_ptr.
  96        *  @post   use_count()==0 && get()==0
  97        */
  98       constexpr shared_ptr()
  99       : __shared_ptr<_Tp>() { }
 100
 101       /**
 102        *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
 103        *  @param  __p  A pointer that is convertible to element_type*.
 104        *  @post   use_count() == 1 && get() == __p
 105        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
 106        */
 107       template<typename _Tp1>
 108         explicit shared_ptr(_Tp1* __p)
 109         : __shared_ptr<_Tp>(__p) { }
 110
 111       /**
 112        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
 113        *          and the deleter @a __d.
 114        *  @param  __p  A pointer.
 115        *  @param  __d  A deleter.
 116        *  @post   use_count() == 1 && get() == __p
 117        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 118        *
 119        *  Requirements: _Deleter's copy constructor and destructor must
 120        *  not throw
 121        *
 122        *  __shared_ptr will release __p by calling __d(__p)
 123        */
 124       template<typename _Tp1, typename _Deleter>
 125         shared_ptr(_Tp1* __p, _Deleter __d) : __shared_ptr<_Tp>(__p, __d) { }
 126
 127       /**
 128        *  @brief  Construct a %shared_ptr that owns a null pointer
 129        *          and the deleter @a __d.
 130        *  @param  __p  A null pointer constant.
 131        *  @param  __d  A deleter.
 132        *  @post   use_count() == 1 && get() == __p
 133        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 134        *
 135        *  Requirements: _Deleter's copy constructor and destructor must
 136        *  not throw
 137        *
 138        *  The last owner will call __d(__p)
 139        */
 140       template<typename _Deleter>
 141         shared_ptr(nullptr_t __p, _Deleter __d)
 142         : __shared_ptr<_Tp>(__p, __d) { }
 143
 144       /**
 145        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
 146        *          and the deleter @a __d.
 147        *  @param  __p  A pointer.
 148        *  @param  __d  A deleter.
 149        *  @param  __a  An allocator.
 150        *  @post   use_count() == 1 && get() == __p
 151        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 152        *
 153        *  Requirements: _Deleter's copy constructor and destructor must
 154        *  not throw _Alloc's copy constructor and destructor must not
 155        *  throw.
 156        *
 157        *  __shared_ptr will release __p by calling __d(__p)
 158        */
 159       template<typename _Tp1, typename _Deleter, typename _Alloc>
 160         shared_ptr(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 161         : __shared_ptr<_Tp>(__p, __d, __a) { }
 162
 163       /**
 164        *  @brief  Construct a %shared_ptr that owns a null pointer
 165        *          and the deleter @a __d.
 166        *  @param  __p  A null pointer constant.
 167        *  @param  __d  A deleter.
 168        *  @param  __a  An allocator.
 169        *  @post   use_count() == 1 && get() == __p
 170        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 171        *
 172        *  Requirements: _Deleter's copy constructor and destructor must
 173        *  not throw _Alloc's copy constructor and destructor must not
 174        *  throw.
 175        *
 176        *  The last owner will call __d(__p)
 177        */
 178       template<typename _Deleter, typename _Alloc>
 179         shared_ptr(nullptr_t __p, _Deleter __d, const _Alloc& __a)
 180         : __shared_ptr<_Tp>(__p, __d, __a) { }
 181
 182       // Aliasing constructor
 183
 184       /**
 185        *  @brief  Constructs a %shared_ptr instance that stores @a __p
 186        *          and shares ownership with @a __r.
 187        *  @param  __r  A %shared_ptr.
 188        *  @param  __p  A pointer that will remain valid while @a *__r is valid.
 189        *  @post   get() == __p && use_count() == __r.use_count()
 190        *
 191        *  This can be used to construct a @c shared_ptr to a sub-object
 192        *  of an object managed by an existing @c shared_ptr.
 193        *
 194        * @code
 195        * shared_ptr< pair<int,int> > pii(new pair<int,int>());
 196        * shared_ptr<int> pi(pii, &pii->first);
 197        * assert(pii.use_count() == 2);
 198        * @endcode
 199        */
 200       template<typename _Tp1>
 201         shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p)
 202         : __shared_ptr<_Tp>(__r, __p) { }
 203
 204       /**
 205        *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
 206        *          otherwise construct a %shared_ptr that shares ownership
 207        *          with @a __r.
 208        *  @param  __r  A %shared_ptr.
 209        *  @post   get() == __r.get() && use_count() == __r.use_count()
 210        */
 211       template<typename _Tp1, typename = typename
 212                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 213         shared_ptr(const shared_ptr<_Tp1>& __r)
 214         : __shared_ptr<_Tp>(__r) { }
 215
 216       /**
 217        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
 218        *  @param  __r  A %shared_ptr rvalue.
 219        *  @post   *this contains the old value of @a __r, @a __r is empty.
 220        */
 221       shared_ptr(shared_ptr&& __r)
 222       : __shared_ptr<_Tp>(std::move(__r)) { }
 223
 224       /**
 225        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
 226        *  @param  __r  A %shared_ptr rvalue.
 227        *  @post   *this contains the old value of @a __r, @a __r is empty.
 228        */
 229       template<typename _Tp1, typename = typename
 230                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 231         shared_ptr(shared_ptr<_Tp1>&& __r)
 232         : __shared_ptr<_Tp>(std::move(__r)) { }
 233
 234       /**
 235        *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
 236        *          and stores a copy of the pointer stored in @a __r.
 237        *  @param  __r  A weak_ptr.
 238        *  @post   use_count() == __r.use_count()
 239        *  @throw  bad_weak_ptr when __r.expired(),
 240        *          in which case the constructor has no effect.
 241        */
 242       template<typename _Tp1>
 243         explicit shared_ptr(const weak_ptr<_Tp1>& __r)
 244         : __shared_ptr<_Tp>(__r) { }
 245
 246 #if _GLIBCXX_DEPRECATED
 247       template<typename _Tp1>
 248         shared_ptr(std::auto_ptr<_Tp1>&& __r)
 249         : __shared_ptr<_Tp>(std::move(__r)) { }
 250 #endif
 251
 252       template<typename _Tp1, typename _Del>
 253         shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
 254         : __shared_ptr<_Tp>(std::move(__r)) { }
 255
 256       /**
 257        *  @brief  Construct an empty %shared_ptr.
 258        *  @param  __p  A null pointer constant.
 259        *  @post   use_count() == 0 && get() == nullptr
 260        */
 261       constexpr shared_ptr(nullptr_t __p)
 262       : __shared_ptr<_Tp>(__p) { }
 263
 264       template<typename _Tp1>
 265         shared_ptr&
 266         operator=(const shared_ptr<_Tp1>& __r) // never throws
 267         {
 268           this->__shared_ptr<_Tp>::operator=(__r);
 269           return *this;
 270         }
 271
 272 #if _GLIBCXX_DEPRECATED
 273       template<typename _Tp1>
 274         shared_ptr&
 275         operator=(std::auto_ptr<_Tp1>&& __r)
 276         {
 277           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 278           return *this;
 279         }
 280 #endif
 281
 282       shared_ptr&
 283       operator=(shared_ptr&& __r)
 284       {
 285         this->__shared_ptr<_Tp>::operator=(std::move(__r));
 286         return *this;
 287       }
 288
 289       template<class _Tp1>
 290         shared_ptr&
 291         operator=(shared_ptr<_Tp1>&& __r)
 292         {
 293           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 294           return *this;
 295         }
 296
 297       template<typename _Tp1, typename _Del>
 298         shared_ptr&
 299         operator=(std::unique_ptr<_Tp1, _Del>&& __r)
 300         {
 301           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 302           return *this;
 303         }
 304
 305     private:
 306       // This constructor is non-standard, it is used by allocate_shared.
 307       template<typename _Alloc, typename... _Args>
 308         shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 309         : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
 310         { }
 311
 312       template<typename _Tp1, typename _Alloc, typename... _Args>
 313         friend shared_ptr<_Tp1>
 314         allocate_shared(_Alloc __a, _Args&&... __args);
 315     };
 316
 317   // 20.8.13.2.7 shared_ptr comparisons
 318   template<typename _Tp1, typename _Tp2>
 319     inline bool
 320     operator==(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 321     { return __a.get() == __b.get(); }
 322
 323   template<typename _Tp>
 324     inline bool
 325     operator==(const shared_ptr<_Tp>& __a, nullptr_t)
 326     { return __a.get() == nullptr; }
 327
 328   template<typename _Tp>
 329     inline bool
 330     operator==(nullptr_t, const shared_ptr<_Tp>& __b)
 331     { return nullptr == __b.get(); }
 332
 333   template<typename _Tp1, typename _Tp2>
 334     inline bool
 335     operator!=(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 336     { return __a.get() != __b.get(); }
 337
 338   template<typename _Tp>
 339     inline bool
 340     operator!=(const shared_ptr<_Tp>& __a, nullptr_t)
 341     { return __a.get() != nullptr; }
 342
 343   template<typename _Tp>
 344     inline bool
 345     operator!=(nullptr_t, const shared_ptr<_Tp>& __b)
 346     { return nullptr != __b.get(); }
 347
 348   template<typename _Tp1, typename _Tp2>
 349     inline bool
 350     operator<(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 351     { return __a.get() < __b.get(); }
 352
 353   template<typename _Tp>
 354     struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
 355     { };
 356
 357   // 20.8.13.2.9 shared_ptr specialized algorithms.
 358   template<typename _Tp>
 359     inline void
 360     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b)
 361     { __a.swap(__b); }
 362
 363   // 20.8.13.2.10 shared_ptr casts.
 364   template<typename _Tp, typename _Tp1>
 365     inline shared_ptr<_Tp>
 366     static_pointer_cast(const shared_ptr<_Tp1>& __r)
 367     { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
 368
 369   template<typename _Tp, typename _Tp1>
 370     inline shared_ptr<_Tp>
 371     const_pointer_cast(const shared_ptr<_Tp1>& __r)
 372     { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
 373
 374   template<typename _Tp, typename _Tp1>
 375     inline shared_ptr<_Tp>
 376     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
 377     {
 378       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
 379         return shared_ptr<_Tp>(__r, __p);
 380       return shared_ptr<_Tp>();
 381     }
 382
 383
 384   /**
 385    *  @brief  A smart pointer with weak semantics.
 386    *
 387    *  With forwarding constructors and assignment operators.
 388    */
 389   template<typename _Tp>
 390     class weak_ptr : public __weak_ptr<_Tp>
 391     {
 392     public:
 393       constexpr weak_ptr()
 394       : __weak_ptr<_Tp>() { }
 395
 396       template<typename _Tp1, typename = typename
 397                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 398         weak_ptr(const weak_ptr<_Tp1>& __r)
 399         : __weak_ptr<_Tp>(__r) { }
 400
 401       template<typename _Tp1, typename = typename
 402                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 403         weak_ptr(const shared_ptr<_Tp1>& __r)
 404         : __weak_ptr<_Tp>(__r) { }
 405
 406       template<typename _Tp1>
 407         weak_ptr&
 408         operator=(const weak_ptr<_Tp1>& __r) // never throws
 409         {
 410           this->__weak_ptr<_Tp>::operator=(__r);
 411           return *this;
 412         }
 413
 414       template<typename _Tp1>
 415         weak_ptr&
 416         operator=(const shared_ptr<_Tp1>& __r) // never throws
 417         {
 418           this->__weak_ptr<_Tp>::operator=(__r);
 419           return *this;
 420         }
 421
 422       shared_ptr<_Tp>
 423       lock() const // never throws
 424       {
 425 #ifdef __GTHREADS
 426         if (this->expired())
 427           return shared_ptr<_Tp>();
 428
 429         __try
 430           {
 431             return shared_ptr<_Tp>(*this);
 432           }
 433         __catch(const bad_weak_ptr&)
 434           {
 435             return shared_ptr<_Tp>();
 436           }
 437 #else
 438         return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
 439 #endif
 440       }
 441     };
 442
 443   // 20.8.13.3.7 weak_ptr specialized algorithms.
 444   template<typename _Tp>
 445     inline void
 446     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b)
 447     { __a.swap(__b); }
 448
 449
 450   /// Primary template owner_less
 451   template<typename _Tp>
 452     struct owner_less;
 453
 454   /// Partial specialization of owner_less for shared_ptr.
 455   template<typename _Tp>
 456     struct owner_less<shared_ptr<_Tp>>
 457     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
 458     { };
 459
 460   /// Partial specialization of owner_less for weak_ptr.
 461   template<typename _Tp>
 462     struct owner_less<weak_ptr<_Tp>>
 463     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
 464     { };
 465
 466   /**
 467    *  @brief Base class allowing use of member function shared_from_this.
 468    */
 469   template<typename _Tp>
 470     class enable_shared_from_this
 471     {
 472     protected:
 473       constexpr enable_shared_from_this() { }
 474
 475       enable_shared_from_this(const enable_shared_from_this&) { }
 476
 477       enable_shared_from_this&
 478       operator=(const enable_shared_from_this&)
 479       { return *this; }
 480
 481       ~enable_shared_from_this() { }
 482
 483     public:
 484       shared_ptr<_Tp>
 485       shared_from_this()
 486       { return shared_ptr<_Tp>(this->_M_weak_this); }
 487
 488       shared_ptr<const _Tp>
 489       shared_from_this() const
 490       { return shared_ptr<const _Tp>(this->_M_weak_this); }
 491
 492     private:
 493       template<typename _Tp1>
 494         void
 495         _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
 496         { _M_weak_this._M_assign(__p, __n); }
 497
 498       template<typename _Tp1>
 499         friend void
 500         __enable_shared_from_this_helper(const __shared_count<>& __pn,
 501                                          const enable_shared_from_this* __pe,
 502                                          const _Tp1* __px)
 503         {
 504           if (__pe != 0)
 505             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
 506         }
 507
 508       mutable weak_ptr<_Tp>  _M_weak_this;
 509     };
 510
 511   /**
 512    *  @brief  Create an object that is owned by a shared_ptr.
 513    *  @param  __a     An allocator.
 514    *  @param  __args  Arguments for the @a _Tp object's constructor.
 515    *  @return A shared_ptr that owns the newly created object.
 516    *  @throw  An exception thrown from @a _Alloc::allocate or from the
 517    *          constructor of @a _Tp.
 518    *
 519    *  A copy of @a __a will be used to allocate memory for the shared_ptr
 520    *  and the new object.
 521    */
 522   template<typename _Tp, typename _Alloc, typename... _Args>
 523     inline shared_ptr<_Tp>
 524     allocate_shared(_Alloc __a, _Args&&... __args)
 525     {
 526       return shared_ptr<_Tp>(_Sp_make_shared_tag(), std::forward<_Alloc>(__a),
 527                              std::forward<_Args>(__args)...);
 528     }
 529
 530   /**
 531    *  @brief  Create an object that is owned by a shared_ptr.
 532    *  @param  __args  Arguments for the @a _Tp object's constructor.
 533    *  @return A shared_ptr that owns the newly created object.
 534    *  @throw  std::bad_alloc, or an exception thrown from the
 535    *          constructor of @a _Tp.
 536    */
 537   template<typename _Tp, typename... _Args>
 538     inline shared_ptr<_Tp>
 539     make_shared(_Args&&... __args)
 540     {
 541       typedef typename std::remove_const<_Tp>::type _Tp_nc;
 542       return allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
 543                                   std::forward<_Args>(__args)...);
 544     }
 545
 546   /// std::hash specialization for shared_ptr.
 547   template<typename _Tp>
 548     struct hash<shared_ptr<_Tp>>
 549     : public std::unary_function<shared_ptr<_Tp>, size_t>
 550     {
 551       size_t
 552       operator()(const shared_ptr<_Tp>& __s) const
 553       { return std::hash<_Tp*>()(__s.get()); }
 554     };
 555
 556   // @} group pointer_abstractions
 557
 558 _GLIBCXX_END_NAMESPACE
 559
 560 #endif // _SHARED_PTR_H