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       shared_ptr() : __shared_ptr<_Tp>() { }
  99
 100       /**
 101        *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
 102        *  @param  __p  A pointer that is convertible to element_type*.
 103        *  @post   use_count() == 1 && get() == __p
 104        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
 105        */
 106       template<typename _Tp1>
 107         explicit shared_ptr(_Tp1* __p) : __shared_ptr<_Tp>(__p) { }
 108
 109       /**
 110        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
 111        *          and the deleter @a __d.
 112        *  @param  __p  A pointer.
 113        *  @param  __d  A deleter.
 114        *  @post   use_count() == 1 && get() == __p
 115        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 116        *
 117        *  Requirements: _Deleter's copy constructor and destructor must
 118        *  not throw
 119        *
 120        *  __shared_ptr will release __p by calling __d(__p)
 121        */
 122       template<typename _Tp1, typename _Deleter>
 123         shared_ptr(_Tp1* __p, _Deleter __d) : __shared_ptr<_Tp>(__p, __d) { }
 124
 125       /**
 126        *  @brief  Construct a %shared_ptr that owns a null pointer
 127        *          and the deleter @a __d.
 128        *  @param  __p  A null pointer constant.
 129        *  @param  __d  A deleter.
 130        *  @post   use_count() == 1 && get() == __p
 131        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 132        *
 133        *  Requirements: _Deleter's copy constructor and destructor must
 134        *  not throw
 135        *
 136        *  The last owner will call __d(__p)
 137        */
 138       template<typename _Deleter>
 139         shared_ptr(nullptr_t __p, _Deleter __d)
 140         : __shared_ptr<_Tp>(__p, __d) { }
 141
 142       /**
 143        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
 144        *          and the deleter @a __d.
 145        *  @param  __p  A pointer.
 146        *  @param  __d  A deleter.
 147        *  @param  __a  An allocator.
 148        *  @post   use_count() == 1 && get() == __p
 149        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 150        *
 151        *  Requirements: _Deleter's copy constructor and destructor must
 152        *  not throw _Alloc's copy constructor and destructor must not
 153        *  throw.
 154        *
 155        *  __shared_ptr will release __p by calling __d(__p)
 156        */
 157       template<typename _Tp1, typename _Deleter, typename _Alloc>
 158         shared_ptr(_Tp1* __p, _Deleter __d, const _Alloc& __a)
 159         : __shared_ptr<_Tp>(__p, __d, __a) { }
 160
 161       /**
 162        *  @brief  Construct a %shared_ptr that owns a null pointer
 163        *          and the deleter @a __d.
 164        *  @param  __p  A null pointer constant.
 165        *  @param  __d  A deleter.
 166        *  @param  __a  An allocator.
 167        *  @post   use_count() == 1 && get() == __p
 168        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
 169        *
 170        *  Requirements: _Deleter's copy constructor and destructor must
 171        *  not throw _Alloc's copy constructor and destructor must not
 172        *  throw.
 173        *
 174        *  The last owner will call __d(__p)
 175        */
 176       template<typename _Deleter, typename _Alloc>
 177         shared_ptr(nullptr_t __p, _Deleter __d, const _Alloc& __a)
 178         : __shared_ptr<_Tp>(__p, __d, __a) { }
 179
 180       // Aliasing constructor
 181
 182       /**
 183        *  @brief  Constructs a %shared_ptr instance that stores @a __p
 184        *          and shares ownership with @a __r.
 185        *  @param  __r  A %shared_ptr.
 186        *  @param  __p  A pointer that will remain valid while @a *__r is valid.
 187        *  @post   get() == __p && use_count() == __r.use_count()
 188        *
 189        *  This can be used to construct a @c shared_ptr to a sub-object
 190        *  of an object managed by an existing @c shared_ptr.
 191        *
 192        * @code
 193        * shared_ptr< pair<int,int> > pii(new pair<int,int>());
 194        * shared_ptr<int> pi(pii, &pii->first);
 195        * assert(pii.use_count() == 2);
 196        * @endcode
 197        */
 198       template<typename _Tp1>
 199         shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p)
 200         : __shared_ptr<_Tp>(__r, __p) { }
 201
 202       /**
 203        *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
 204        *          otherwise construct a %shared_ptr that shares ownership
 205        *          with @a __r.
 206        *  @param  __r  A %shared_ptr.
 207        *  @post   get() == __r.get() && use_count() == __r.use_count()
 208        */
 209       template<typename _Tp1, typename = typename
 210                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 211         shared_ptr(const shared_ptr<_Tp1>& __r)
 212         : __shared_ptr<_Tp>(__r) { }
 213
 214       /**
 215        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
 216        *  @param  __r  A %shared_ptr rvalue.
 217        *  @post   *this contains the old value of @a __r, @a __r is empty.
 218        */
 219       shared_ptr(shared_ptr&& __r)
 220       : __shared_ptr<_Tp>(std::move(__r)) { }
 221
 222       /**
 223        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
 224        *  @param  __r  A %shared_ptr rvalue.
 225        *  @post   *this contains the old value of @a __r, @a __r is empty.
 226        */
 227       template<typename _Tp1, typename = typename
 228                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 229         shared_ptr(shared_ptr<_Tp1>&& __r)
 230         : __shared_ptr<_Tp>(std::move(__r)) { }
 231
 232       /**
 233        *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
 234        *          and stores a copy of the pointer stored in @a __r.
 235        *  @param  __r  A weak_ptr.
 236        *  @post   use_count() == __r.use_count()
 237        *  @throw  bad_weak_ptr when __r.expired(),
 238        *          in which case the constructor has no effect.
 239        */
 240       template<typename _Tp1>
 241         explicit shared_ptr(const weak_ptr<_Tp1>& __r)
 242         : __shared_ptr<_Tp>(__r) { }
 243
 244 #if _GLIBCXX_DEPRECATED
 245       template<typename _Tp1>
 246         shared_ptr(std::auto_ptr<_Tp1>&& __r)
 247         : __shared_ptr<_Tp>(std::move(__r)) { }
 248 #endif
 249
 250       template<typename _Tp1, typename _Del>
 251         shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
 252         : __shared_ptr<_Tp>(std::move(__r)) { }
 253
 254       /**
 255        *  @brief  Construct an empty %shared_ptr.
 256        *  @param  __p  A null pointer constant.
 257        *  @post   use_count() == 0 && get() == nullptr
 258        */
 259       shared_ptr(nullptr_t __p) : __shared_ptr<_Tp>(__p) { }
 260
 261       template<typename _Tp1>
 262         shared_ptr&
 263         operator=(const shared_ptr<_Tp1>& __r) // never throws
 264         {
 265           this->__shared_ptr<_Tp>::operator=(__r);
 266           return *this;
 267         }
 268
 269 #if _GLIBCXX_DEPRECATED
 270       template<typename _Tp1>
 271         shared_ptr&
 272         operator=(std::auto_ptr<_Tp1>&& __r)
 273         {
 274           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 275           return *this;
 276         }
 277 #endif
 278
 279       shared_ptr&
 280       operator=(shared_ptr&& __r)
 281       {
 282         this->__shared_ptr<_Tp>::operator=(std::move(__r));
 283         return *this;
 284       }
 285
 286       template<class _Tp1>
 287         shared_ptr&
 288         operator=(shared_ptr<_Tp1>&& __r)
 289         {
 290           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 291           return *this;
 292         }
 293
 294       template<typename _Tp1, typename _Del>
 295         shared_ptr&
 296         operator=(std::unique_ptr<_Tp1, _Del>&& __r)
 297         {
 298           this->__shared_ptr<_Tp>::operator=(std::move(__r));
 299           return *this;
 300         }
 301
 302     private:
 303       // This constructor is non-standard, it is used by allocate_shared.
 304       template<typename _Alloc, typename... _Args>
 305         shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
 306         : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
 307         { }
 308
 309       template<typename _Tp1, typename _Alloc, typename... _Args>
 310         friend shared_ptr<_Tp1>
 311         allocate_shared(_Alloc __a, _Args&&... __args);
 312     };
 313
 314   // 20.8.13.2.7 shared_ptr comparisons
 315   template<typename _Tp1, typename _Tp2>
 316     inline bool
 317     operator==(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 318     { return __a.get() == __b.get(); }
 319
 320   template<typename _Tp>
 321     inline bool
 322     operator==(const shared_ptr<_Tp>& __a, nullptr_t)
 323     { return __a.get() == nullptr; }
 324
 325   template<typename _Tp>
 326     inline bool
 327     operator==(nullptr_t, const shared_ptr<_Tp>& __b)
 328     { return nullptr == __b.get(); }
 329
 330   template<typename _Tp1, typename _Tp2>
 331     inline bool
 332     operator!=(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 333     { return __a.get() != __b.get(); }
 334
 335   template<typename _Tp>
 336     inline bool
 337     operator!=(const shared_ptr<_Tp>& __a, nullptr_t)
 338     { return __a.get() != nullptr; }
 339
 340   template<typename _Tp>
 341     inline bool
 342     operator!=(nullptr_t, const shared_ptr<_Tp>& __b)
 343     { return nullptr != __b.get(); }
 344
 345   template<typename _Tp1, typename _Tp2>
 346     inline bool
 347     operator<(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
 348     { return __a.get() < __b.get(); }
 349
 350   template<typename _Tp>
 351     struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
 352     { };
 353
 354   // 20.8.13.2.9 shared_ptr specialized algorithms.
 355   template<typename _Tp>
 356     inline void
 357     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b)
 358     { __a.swap(__b); }
 359
 360   // 20.8.13.2.10 shared_ptr casts.
 361   template<typename _Tp, typename _Tp1>
 362     inline shared_ptr<_Tp>
 363     static_pointer_cast(const shared_ptr<_Tp1>& __r)
 364     { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
 365
 366   template<typename _Tp, typename _Tp1>
 367     inline shared_ptr<_Tp>
 368     const_pointer_cast(const shared_ptr<_Tp1>& __r)
 369     { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
 370
 371   template<typename _Tp, typename _Tp1>
 372     inline shared_ptr<_Tp>
 373     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
 374     {
 375       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
 376         return shared_ptr<_Tp>(__r, __p);
 377       return shared_ptr<_Tp>();
 378     }
 379
 380
 381   /**
 382    *  @brief  A smart pointer with weak semantics.
 383    *
 384    *  With forwarding constructors and assignment operators.
 385    */
 386   template<typename _Tp>
 387     class weak_ptr : public __weak_ptr<_Tp>
 388     {
 389     public:
 390       weak_ptr() : __weak_ptr<_Tp>() { }
 391
 392       template<typename _Tp1, typename = typename
 393                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 394         weak_ptr(const weak_ptr<_Tp1>& __r)
 395         : __weak_ptr<_Tp>(__r) { }
 396
 397       template<typename _Tp1, typename = typename
 398                std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
 399         weak_ptr(const shared_ptr<_Tp1>& __r)
 400         : __weak_ptr<_Tp>(__r) { }
 401
 402       template<typename _Tp1>
 403         weak_ptr&
 404         operator=(const weak_ptr<_Tp1>& __r) // never throws
 405         {
 406           this->__weak_ptr<_Tp>::operator=(__r);
 407           return *this;
 408         }
 409
 410       template<typename _Tp1>
 411         weak_ptr&
 412         operator=(const shared_ptr<_Tp1>& __r) // never throws
 413         {
 414           this->__weak_ptr<_Tp>::operator=(__r);
 415           return *this;
 416         }
 417
 418       shared_ptr<_Tp>
 419       lock() const // never throws
 420       {
 421 #ifdef __GTHREADS
 422         if (this->expired())
 423           return shared_ptr<_Tp>();
 424
 425         __try
 426           {
 427             return shared_ptr<_Tp>(*this);
 428           }
 429         __catch(const bad_weak_ptr&)
 430           {
 431             return shared_ptr<_Tp>();
 432           }
 433 #else
 434         return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
 435 #endif
 436       }
 437     };
 438
 439   // 20.8.13.3.7 weak_ptr specialized algorithms.
 440   template<typename _Tp>
 441     inline void
 442     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b)
 443     { __a.swap(__b); }
 444
 445
 446   /// Primary template owner_less
 447   template<typename _Tp>
 448     struct owner_less;
 449
 450   /// Partial specialization of owner_less for shared_ptr.
 451   template<typename _Tp>
 452     struct owner_less<shared_ptr<_Tp>>
 453     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
 454     { };
 455
 456   /// Partial specialization of owner_less for weak_ptr.
 457   template<typename _Tp>
 458     struct owner_less<weak_ptr<_Tp>>
 459     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
 460     { };
 461
 462   /**
 463    *  @brief Base class allowing use of member function shared_from_this.
 464    */
 465   template<typename _Tp>
 466     class enable_shared_from_this
 467     {
 468     protected:
 469       enable_shared_from_this() { }
 470
 471       enable_shared_from_this(const enable_shared_from_this&) { }
 472
 473       enable_shared_from_this&
 474       operator=(const enable_shared_from_this&)
 475       { return *this; }
 476
 477       ~enable_shared_from_this() { }
 478
 479     public:
 480       shared_ptr<_Tp>
 481       shared_from_this()
 482       { return shared_ptr<_Tp>(this->_M_weak_this); }
 483
 484       shared_ptr<const _Tp>
 485       shared_from_this() const
 486       { return shared_ptr<const _Tp>(this->_M_weak_this); }
 487
 488     private:
 489       template<typename _Tp1>
 490         void
 491         _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
 492         { _M_weak_this._M_assign(__p, __n); }
 493
 494       template<typename _Tp1>
 495         friend void
 496         __enable_shared_from_this_helper(const __shared_count<>& __pn,
 497                                          const enable_shared_from_this* __pe,
 498                                          const _Tp1* __px)
 499         {
 500           if (__pe != 0)
 501             __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
 502         }
 503
 504       mutable weak_ptr<_Tp>  _M_weak_this;
 505     };
 506
 507   /**
 508    *  @brief  Create an object that is owned by a shared_ptr.
 509    *  @param  __a     An allocator.
 510    *  @param  __args  Arguments for the @a _Tp object's constructor.
 511    *  @return A shared_ptr that owns the newly created object.
 512    *  @throw  An exception thrown from @a _Alloc::allocate or from the
 513    *          constructor of @a _Tp.
 514    *
 515    *  A copy of @a __a will be used to allocate memory for the shared_ptr
 516    *  and the new object.
 517    */
 518   template<typename _Tp, typename _Alloc, typename... _Args>
 519     inline shared_ptr<_Tp>
 520     allocate_shared(_Alloc __a, _Args&&... __args)
 521     {
 522       return shared_ptr<_Tp>(_Sp_make_shared_tag(), std::forward<_Alloc>(__a),
 523                              std::forward<_Args>(__args)...);
 524     }
 525
 526   /**
 527    *  @brief  Create an object that is owned by a shared_ptr.
 528    *  @param  __args  Arguments for the @a _Tp object's constructor.
 529    *  @return A shared_ptr that owns the newly created object.
 530    *  @throw  std::bad_alloc, or an exception thrown from the
 531    *          constructor of @a _Tp.
 532    */
 533   template<typename _Tp, typename... _Args>
 534     inline shared_ptr<_Tp>
 535     make_shared(_Args&&... __args)
 536     {
 537       typedef typename std::remove_const<_Tp>::type _Tp_nc;
 538       return allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
 539                                   std::forward<_Args>(__args)...);
 540     }
 541
 542   /// std::hash specialization for shared_ptr.
 543   template<typename _Tp>
 544     struct hash<shared_ptr<_Tp>>
 545     : public std::unary_function<shared_ptr<_Tp>, size_t>
 546     {
 547       size_t
 548       operator()(const shared_ptr<_Tp>& __s) const
 549       { return std::hash<_Tp*>()(__s.get()); }
 550     };
 551
 552   // @} group pointer_abstractions
 553
 554 _GLIBCXX_END_NAMESPACE
 555
 556 #endif // _SHARED_PTR_H