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