shared_ptr.h

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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     explicit
00208     shared_ptr(std::auto_ptr<_Tp1>&& __r)
00209     : __shared_ptr<_Tp>(std::move(__r)) { }
00210 #endif
00211 
00212       template<typename _Tp1, typename _Del>
00213     explicit shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
00214     : __shared_ptr<_Tp>(std::move(__r)) { }
00215 
00216       template<typename _Tp1>
00217     shared_ptr&
00218     operator=(const shared_ptr<_Tp1>& __r) // never throws
00219     {
00220       this->__shared_ptr<_Tp>::operator=(__r);
00221       return *this;
00222     }
00223 
00224 #if _GLIBCXX_DEPRECATED
00225       template<typename _Tp1>
00226     shared_ptr&
00227     operator=(std::auto_ptr<_Tp1>&& __r)
00228     {
00229       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00230       return *this;
00231     }
00232 #endif
00233 
00234       shared_ptr&
00235       operator=(shared_ptr&& __r)
00236       {
00237     this->__shared_ptr<_Tp>::operator=(std::move(__r));
00238     return *this;
00239       }
00240 
00241       template<class _Tp1>
00242     shared_ptr&
00243     operator=(shared_ptr<_Tp1>&& __r)
00244     {
00245       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00246       return *this;
00247     }
00248 
00249       template<typename _Tp1, typename _Del>
00250     shared_ptr&
00251     operator=(std::unique_ptr<_Tp1, _Del>&& __r)
00252     {
00253       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00254       return *this;
00255     }
00256 
00257     private:
00258       // This constructor is non-standard, it is used by allocate_shared.
00259       template<typename _Alloc, typename... _Args>
00260     shared_ptr(_Sp_make_shared_tag __tag, _Alloc __a, _Args&&... __args)
00261     : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
00262     { }
00263 
00264       template<typename _Tp1, typename _Alloc, typename... _Args>
00265     friend shared_ptr<_Tp1>
00266     allocate_shared(_Alloc __a, _Args&&... __args);
00267     };
00268 
00269   // 20.8.13.2.7 shared_ptr comparisons
00270   template<typename _Tp1, typename _Tp2>
00271     inline bool
00272     operator==(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00273     { return __a.get() == __b.get(); }
00274 
00275   template<typename _Tp1, typename _Tp2>
00276     inline bool
00277     operator!=(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00278     { return __a.get() != __b.get(); }
00279 
00280   template<typename _Tp1, typename _Tp2>
00281     inline bool
00282     operator<(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00283     { return __a.get() < __b.get(); }
00284 
00285   template<typename _Tp>
00286     struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
00287     { };
00288 
00289   // 20.8.13.2.9 shared_ptr specialized algorithms.
00290   template<typename _Tp>
00291     inline void
00292     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b)
00293     { __a.swap(__b); }
00294 
00295   // 20.8.13.2.10 shared_ptr casts.
00296   template<typename _Tp, typename _Tp1>
00297     inline shared_ptr<_Tp>
00298     static_pointer_cast(const shared_ptr<_Tp1>& __r)
00299     { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
00300 
00301   template<typename _Tp, typename _Tp1>
00302     inline shared_ptr<_Tp>
00303     const_pointer_cast(const shared_ptr<_Tp1>& __r)
00304     { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
00305 
00306   template<typename _Tp, typename _Tp1>
00307     inline shared_ptr<_Tp>
00308     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
00309     {
00310       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
00311     return shared_ptr<_Tp>(__r, __p);
00312       return shared_ptr<_Tp>();
00313     }
00314 
00315 
00316   /**
00317    *  @brief  A smart pointer with weak semantics.
00318    *
00319    *  With forwarding constructors and assignment operators.
00320    */
00321   template<typename _Tp>
00322     class weak_ptr : public __weak_ptr<_Tp>
00323     {
00324     public:
00325       weak_ptr() : __weak_ptr<_Tp>() { }
00326 
00327       template<typename _Tp1>
00328     weak_ptr(const weak_ptr<_Tp1>& __r)
00329     : __weak_ptr<_Tp>(__r) { }
00330 
00331       template<typename _Tp1>
00332     weak_ptr(const shared_ptr<_Tp1>& __r)
00333     : __weak_ptr<_Tp>(__r) { }
00334 
00335       template<typename _Tp1>
00336     weak_ptr&
00337     operator=(const weak_ptr<_Tp1>& __r) // never throws
00338     {
00339       this->__weak_ptr<_Tp>::operator=(__r);
00340       return *this;
00341     }
00342 
00343       template<typename _Tp1>
00344     weak_ptr&
00345     operator=(const shared_ptr<_Tp1>& __r) // never throws
00346     {
00347       this->__weak_ptr<_Tp>::operator=(__r);
00348       return *this;
00349     }
00350 
00351       shared_ptr<_Tp>
00352       lock() const // never throws
00353       {
00354 #ifdef __GTHREADS
00355     if (this->expired())
00356       return shared_ptr<_Tp>();
00357 
00358     __try
00359       {
00360         return shared_ptr<_Tp>(*this);
00361       }
00362     __catch(const bad_weak_ptr&)
00363       {
00364         return shared_ptr<_Tp>();
00365       }
00366 #else
00367     return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
00368 #endif
00369       }
00370     };
00371 
00372   // 20.8.13.3.7 weak_ptr specialized algorithms.
00373   template<typename _Tp>
00374     inline void
00375     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b)
00376     { __a.swap(__b); }
00377 
00378 
00379   /// Primary template owner_less
00380   template<typename _Tp>
00381     struct owner_less;
00382 
00383   /// Partial specialization of owner_less for shared_ptr.
00384   template<typename _Tp>
00385     struct owner_less<shared_ptr<_Tp>>
00386     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
00387     { };
00388 
00389   /// Partial specialization of owner_less for weak_ptr.
00390   template<typename _Tp>
00391     struct owner_less<weak_ptr<_Tp>>
00392     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
00393     { };
00394 
00395   /**
00396    *  @brief Base class allowing use of member function shared_from_this.
00397    */
00398   template<typename _Tp>
00399     class enable_shared_from_this
00400     {
00401     protected:
00402       enable_shared_from_this() { }
00403 
00404       enable_shared_from_this(const enable_shared_from_this&) { }
00405 
00406       enable_shared_from_this&
00407       operator=(const enable_shared_from_this&)
00408       { return *this; }
00409 
00410       ~enable_shared_from_this() { }
00411 
00412     public:
00413       shared_ptr<_Tp>
00414       shared_from_this()
00415       { return shared_ptr<_Tp>(this->_M_weak_this); }
00416 
00417       shared_ptr<const _Tp>
00418       shared_from_this() const
00419       { return shared_ptr<const _Tp>(this->_M_weak_this); }
00420 
00421     private:
00422       template<typename _Tp1>
00423     void
00424     _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
00425     { _M_weak_this._M_assign(__p, __n); }
00426 
00427       template<typename _Tp1>
00428     friend void
00429     __enable_shared_from_this_helper(const __shared_count<>& __pn,
00430                      const enable_shared_from_this* __pe,
00431                      const _Tp1* __px)
00432     {
00433       if (__pe != 0)
00434         __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
00435     }
00436 
00437       mutable weak_ptr<_Tp>  _M_weak_this;
00438     };
00439 
00440   /**
00441    *  @brief  Create an object that is owned by a shared_ptr.
00442    *  @param  __a     An allocator.
00443    *  @param  __args  Arguments for the @a _Tp object's constructor.
00444    *  @return A shared_ptr that owns the newly created object.
00445    *  @throw  An exception thrown from @a _Alloc::allocate or from the
00446    *          constructor of @a _Tp.
00447    *
00448    *  A copy of @a __a will be used to allocate memory for the shared_ptr
00449    *  and the new object.
00450    */
00451   template<typename _Tp, typename _Alloc, typename... _Args>
00452     inline shared_ptr<_Tp>
00453     allocate_shared(_Alloc __a, _Args&&... __args)
00454     {
00455       return shared_ptr<_Tp>(_Sp_make_shared_tag(), std::forward<_Alloc>(__a),
00456                  std::forward<_Args>(__args)...);
00457     }
00458 
00459   /**
00460    *  @brief  Create an object that is owned by a shared_ptr.
00461    *  @param  __args  Arguments for the @a _Tp object's constructor.
00462    *  @return A shared_ptr that owns the newly created object.
00463    *  @throw  std::bad_alloc, or an exception thrown from the
00464    *          constructor of @a _Tp.
00465    */
00466   template<typename _Tp, typename... _Args>
00467     inline shared_ptr<_Tp>
00468     make_shared(_Args&&... __args)
00469     {
00470       typedef typename std::remove_const<_Tp>::type _Tp_nc;
00471       return allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
00472                   std::forward<_Args>(__args)...);
00473     }
00474 
00475   // @} group pointer_abstractions
00476 
00477 _GLIBCXX_END_NAMESPACE
00478 
00479 #endif // _SHARED_PTR_H

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