shared_ptr.h

Go to the documentation of this file.
00001 // shared_ptr and weak_ptr implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 // GCC Note: Based on files from version 1.32.0 of the Boost library.
00026 
00027 //  shared_count.hpp
00028 //  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
00029 
00030 //  shared_ptr.hpp
00031 //  Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
00032 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
00033 
00034 //  weak_ptr.hpp
00035 //  Copyright (C) 2001, 2002, 2003 Peter Dimov
00036 
00037 //  enable_shared_from_this.hpp
00038 //  Copyright (C) 2002 Peter Dimov
00039 
00040 // Distributed under the Boost Software License, Version 1.0. (See
00041 // accompanying file LICENSE_1_0.txt or copy at
00042 // http://www.boost.org/LICENSE_1_0.txt)
00043 
00044 /** @file bits/shared_ptr.h
00045  *  This is an internal header file, included by other library headers.
00046  *  You should not attempt to use it directly.
00047  */
00048 
00049 #ifndef _SHARED_PTR_H
00050 #define _SHARED_PTR_H 1
00051 
00052 #include <bits/shared_ptr_base.h>
00053 
00054 _GLIBCXX_BEGIN_NAMESPACE(std)
00055 
00056   /**
00057    * @addtogroup pointer_abstractions
00058    * @{
00059    */
00060 
00061   /// 2.2.3.7 shared_ptr I/O
00062   template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
00063     inline std::basic_ostream<_Ch, _Tr>&
00064     operator<<(std::basic_ostream<_Ch, _Tr>& __os,
00065            const __shared_ptr<_Tp, _Lp>& __p)
00066     {
00067       __os << __p.get();
00068       return __os;
00069     }
00070 
00071   /// 2.2.3.10 shared_ptr get_deleter (experimental)
00072   template<typename _Del, typename _Tp, _Lock_policy _Lp>
00073     inline _Del*
00074     get_deleter(const __shared_ptr<_Tp, _Lp>& __p)
00075     {
00076 #ifdef __GXX_RTTI
00077       return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
00078 #else
00079       return 0;
00080 #endif
00081     }
00082 
00083 
00084   /**
00085    *  @brief  A smart pointer with reference-counted copy semantics.
00086    *
00087    *  The object pointed to is deleted when the last shared_ptr pointing to
00088    *  it is destroyed or reset.
00089   */
00090   template<typename _Tp>
00091     class shared_ptr : public __shared_ptr<_Tp>
00092     {
00093     public:
00094       /**
00095        *  @brief  Construct an empty %shared_ptr.
00096        *  @post   use_count()==0 && get()==0
00097        */
00098       shared_ptr() : __shared_ptr<_Tp>() { }
00099 
00100       /**
00101        *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
00102        *  @param  __p  A pointer that is convertible to element_type*.
00103        *  @post   use_count() == 1 && get() == __p
00104        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
00105        */
00106       template<typename _Tp1>
00107     explicit shared_ptr(_Tp1* __p) : __shared_ptr<_Tp>(__p) { }
00108 
00109       /**
00110        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
00111        *          and the deleter @a __d.
00112        *  @param  __p  A pointer.
00113        *  @param  __d  A deleter.
00114        *  @post   use_count() == 1 && get() == __p
00115        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00116        *
00117        *  Requirements: _Deleter's copy constructor and destructor must
00118        *  not throw
00119        *
00120        *  __shared_ptr will release __p by calling __d(__p)
00121        */
00122       template<typename _Tp1, typename _Deleter>
00123     shared_ptr(_Tp1* __p, _Deleter __d) : __shared_ptr<_Tp>(__p, __d) { }
00124 
00125       /**
00126        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
00127        *          and the deleter @a __d.
00128        *  @param  __p  A pointer.
00129        *  @param  __d  A deleter.
00130        *  @param  __a  An allocator.
00131        *  @post   use_count() == 1 && get() == __p
00132        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00133        *
00134        *  Requirements: _Deleter's copy constructor and destructor must
00135        *  not throw _Alloc's copy constructor and destructor must not
00136        *  throw.
00137        *
00138        *  __shared_ptr will release __p by calling __d(__p)
00139        */
00140       template<typename _Tp1, typename _Deleter, typename _Alloc>
00141     shared_ptr(_Tp1* __p, _Deleter __d, const _Alloc& __a)
00142     : __shared_ptr<_Tp>(__p, __d, __a) { }
00143 
00144       // Aliasing constructor
00145 
00146       /**
00147        *  @brief  Constructs a %shared_ptr instance that stores @a __p
00148        *          and shares ownership with @a __r.
00149        *  @param  __r  A %shared_ptr.
00150        *  @param  __p  A pointer that will remain valid while @a *__r is valid.
00151        *  @post   get() == __p && use_count() == __r.use_count()
00152        *
00153        *  This can be used to construct a @c shared_ptr to a sub-object
00154        *  of an object managed by an existing @c shared_ptr.
00155        *
00156        * @code
00157        * shared_ptr< pair<int,int> > pii(new pair<int,int>());
00158        * shared_ptr<int> pi(pii, &pii->first);
00159        * assert(pii.use_count() == 2);
00160        * @endcode
00161        */
00162       template<typename _Tp1>
00163     shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p)
00164     : __shared_ptr<_Tp>(__r, __p) { }
00165 
00166       /**
00167        *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
00168        *          otherwise construct a %shared_ptr that shares ownership
00169        *          with @a __r.
00170        *  @param  __r  A %shared_ptr.
00171        *  @post   get() == __r.get() && use_count() == __r.use_count()
00172        */
00173       template<typename _Tp1>
00174     shared_ptr(const shared_ptr<_Tp1>& __r) : __shared_ptr<_Tp>(__r) { }
00175 
00176       /**
00177        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
00178        *  @param  __r  A %shared_ptr rvalue.
00179        *  @post   *this contains the old value of @a __r, @a __r is empty.
00180        */
00181       shared_ptr(shared_ptr&& __r)
00182       : __shared_ptr<_Tp>(std::move(__r)) { }
00183 
00184       /**
00185        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
00186        *  @param  __r  A %shared_ptr rvalue.
00187        *  @post   *this contains the old value of @a __r, @a __r is empty.
00188        */
00189       template<typename _Tp1>
00190     shared_ptr(shared_ptr<_Tp1>&& __r)
00191     : __shared_ptr<_Tp>(std::move(__r)) { }
00192 
00193       /**
00194        *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
00195        *          and stores a copy of the pointer stored in @a __r.
00196        *  @param  __r  A weak_ptr.
00197        *  @post   use_count() == __r.use_count()
00198        *  @throw  bad_weak_ptr when __r.expired(),
00199        *          in which case the constructor has no effect.
00200        */
00201       template<typename _Tp1>
00202     explicit shared_ptr(const weak_ptr<_Tp1>& __r)
00203     : __shared_ptr<_Tp>(__r) { }
00204 
00205 #if _GLIBCXX_DEPRECATED
00206       template<typename _Tp1>
00207     shared_ptr(std::auto_ptr<_Tp1>&& __r)
00208     : __shared_ptr<_Tp>(std::move(__r)) { }
00209 #endif
00210 
00211       template<typename _Tp1, typename _Del>
00212     shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
00213     : __shared_ptr<_Tp>(std::move(__r)) { }
00214 
00215       template<typename _Tp1>
00216     shared_ptr&
00217     operator=(const shared_ptr<_Tp1>& __r) // never throws
00218     {
00219       this->__shared_ptr<_Tp>::operator=(__r);
00220       return *this;
00221     }
00222 
00223 #if _GLIBCXX_DEPRECATED
00224       template<typename _Tp1>
00225     shared_ptr&
00226     operator=(std::auto_ptr<_Tp1>&& __r)
00227     {
00228       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00229       return *this;
00230     }
00231 #endif
00232 
00233       shared_ptr&
00234       operator=(shared_ptr&& __r)
00235       {
00236     this->__shared_ptr<_Tp>::operator=(std::move(__r));
00237     return *this;
00238       }
00239 
00240       template<class _Tp1>
00241     shared_ptr&
00242     operator=(shared_ptr<_Tp1>&& __r)
00243     {
00244       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00245       return *this;
00246     }
00247 
00248       template<typename _Tp1, typename _Del>
00249     shared_ptr&
00250     operator=(std::unique_ptr<_Tp1, _Del>&& __r)
00251     {
00252       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00253       return *this;
00254     }
00255 
00256     private:
00257       // This constructor is non-standard, it is used by allocate_shared.
00258       template<typename _Alloc, typename... _Args>
00259     shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
00260     : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
00261     { }
00262 
00263       template<typename _Tp1, typename _Alloc, typename... _Args>
00264     friend shared_ptr<_Tp1>
00265     allocate_shared(_Alloc __a, _Args&&... __args);
00266     };
00267 
00268   // 20.8.13.2.7 shared_ptr comparisons
00269   template<typename _Tp1, typename _Tp2>
00270     inline bool
00271     operator==(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00272     { return __a.get() == __b.get(); }
00273 
00274   template<typename _Tp1, typename _Tp2>
00275     inline bool
00276     operator!=(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00277     { return __a.get() != __b.get(); }
00278 
00279   template<typename _Tp1, typename _Tp2>
00280     inline bool
00281     operator<(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00282     { return __a.get() < __b.get(); }
00283 
00284   template<typename _Tp>
00285     struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
00286     { };
00287 
00288   // 20.8.13.2.9 shared_ptr specialized algorithms.
00289   template<typename _Tp>
00290     inline void
00291     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b)
00292     { __a.swap(__b); }
00293 
00294   // 20.8.13.2.10 shared_ptr casts.
00295   template<typename _Tp, typename _Tp1>
00296     inline shared_ptr<_Tp>
00297     static_pointer_cast(const shared_ptr<_Tp1>& __r)
00298     { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
00299 
00300   template<typename _Tp, typename _Tp1>
00301     inline shared_ptr<_Tp>
00302     const_pointer_cast(const shared_ptr<_Tp1>& __r)
00303     { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
00304 
00305   template<typename _Tp, typename _Tp1>
00306     inline shared_ptr<_Tp>
00307     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
00308     {
00309       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
00310     return shared_ptr<_Tp>(__r, __p);
00311       return shared_ptr<_Tp>();
00312     }
00313 
00314 
00315   /**
00316    *  @brief  A smart pointer with weak semantics.
00317    *
00318    *  With forwarding constructors and assignment operators.
00319    */
00320   template<typename _Tp>
00321     class weak_ptr : public __weak_ptr<_Tp>
00322     {
00323     public:
00324       weak_ptr() : __weak_ptr<_Tp>() { }
00325 
00326       template<typename _Tp1>
00327     weak_ptr(const weak_ptr<_Tp1>& __r)
00328     : __weak_ptr<_Tp>(__r) { }
00329 
00330       template<typename _Tp1>
00331     weak_ptr(const shared_ptr<_Tp1>& __r)
00332     : __weak_ptr<_Tp>(__r) { }
00333 
00334       template<typename _Tp1>
00335     weak_ptr&
00336     operator=(const weak_ptr<_Tp1>& __r) // never throws
00337     {
00338       this->__weak_ptr<_Tp>::operator=(__r);
00339       return *this;
00340     }
00341 
00342       template<typename _Tp1>
00343     weak_ptr&
00344     operator=(const shared_ptr<_Tp1>& __r) // never throws
00345     {
00346       this->__weak_ptr<_Tp>::operator=(__r);
00347       return *this;
00348     }
00349 
00350       shared_ptr<_Tp>
00351       lock() const // never throws
00352       {
00353 #ifdef __GTHREADS
00354     if (this->expired())
00355       return shared_ptr<_Tp>();
00356 
00357     __try
00358       {
00359         return shared_ptr<_Tp>(*this);
00360       }
00361     __catch(const bad_weak_ptr&)
00362       {
00363         return shared_ptr<_Tp>();
00364       }
00365 #else
00366     return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
00367 #endif
00368       }
00369     };
00370 
00371   // 20.8.13.3.7 weak_ptr specialized algorithms.
00372   template<typename _Tp>
00373     inline void
00374     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b)
00375     { __a.swap(__b); }
00376 
00377 
00378   /// Primary template owner_less
00379   template<typename _Tp>
00380     struct owner_less;
00381 
00382   /// Partial specialization of owner_less for shared_ptr.
00383   template<typename _Tp>
00384     struct owner_less<shared_ptr<_Tp>>
00385     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
00386     { };
00387 
00388   /// Partial specialization of owner_less for weak_ptr.
00389   template<typename _Tp>
00390     struct owner_less<weak_ptr<_Tp>>
00391     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
00392     { };
00393 
00394   /**
00395    *  @brief Base class allowing use of member function shared_from_this.
00396    */
00397   template<typename _Tp>
00398     class enable_shared_from_this
00399     {
00400     protected:
00401       enable_shared_from_this() { }
00402 
00403       enable_shared_from_this(const enable_shared_from_this&) { }
00404 
00405       enable_shared_from_this&
00406       operator=(const enable_shared_from_this&)
00407       { return *this; }
00408 
00409       ~enable_shared_from_this() { }
00410 
00411     public:
00412       shared_ptr<_Tp>
00413       shared_from_this()
00414       { return shared_ptr<_Tp>(this->_M_weak_this); }
00415 
00416       shared_ptr<const _Tp>
00417       shared_from_this() const
00418       { return shared_ptr<const _Tp>(this->_M_weak_this); }
00419 
00420     private:
00421       template<typename _Tp1>
00422     void
00423     _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
00424     { _M_weak_this._M_assign(__p, __n); }
00425 
00426       template<typename _Tp1>
00427     friend void
00428     __enable_shared_from_this_helper(const __shared_count<>& __pn,
00429                      const enable_shared_from_this* __pe,
00430                      const _Tp1* __px)
00431     {
00432       if (__pe != 0)
00433         __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
00434     }
00435 
00436       mutable weak_ptr<_Tp>  _M_weak_this;
00437     };
00438 
00439   /**
00440    *  @brief  Create an object that is owned by a shared_ptr.
00441    *  @param  __a     An allocator.
00442    *  @param  __args  Arguments for the @a _Tp object's constructor.
00443    *  @return A shared_ptr that owns the newly created object.
00444    *  @throw  An exception thrown from @a _Alloc::allocate or from the
00445    *          constructor of @a _Tp.
00446    *
00447    *  A copy of @a __a will be used to allocate memory for the shared_ptr
00448    *  and the new object.
00449    */
00450   template<typename _Tp, typename _Alloc, typename... _Args>
00451     inline shared_ptr<_Tp>
00452     allocate_shared(_Alloc __a, _Args&&... __args)
00453     {
00454       return shared_ptr<_Tp>(_Sp_make_shared_tag(), std::forward<_Alloc>(__a),
00455                  std::forward<_Args>(__args)...);
00456     }
00457 
00458   /**
00459    *  @brief  Create an object that is owned by a shared_ptr.
00460    *  @param  __args  Arguments for the @a _Tp object's constructor.
00461    *  @return A shared_ptr that owns the newly created object.
00462    *  @throw  std::bad_alloc, or an exception thrown from the
00463    *          constructor of @a _Tp.
00464    */
00465   template<typename _Tp, typename... _Args>
00466     inline shared_ptr<_Tp>
00467     make_shared(_Args&&... __args)
00468     {
00469       typedef typename std::remove_const<_Tp>::type _Tp_nc;
00470       return allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
00471                   std::forward<_Args>(__args)...);
00472     }
00473 
00474   // @} group pointer_abstractions
00475 
00476 _GLIBCXX_END_NAMESPACE
00477 
00478 #endif // _SHARED_PTR_H