libstdc++
shared_ptr.h
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00001 // shared_ptr and weak_ptr implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2007, 2008, 2009, 2010, 2011 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  *  Do not attempt to use it directly. @headername{memory}
00047  */
00048 
00049 #ifndef _SHARED_PTR_H
00050 #define _SHARED_PTR_H 1
00051 
00052 #include <bits/shared_ptr_base.h>
00053 
00054 namespace std _GLIBCXX_VISIBILITY(default)
00055 {
00056 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00057 
00058   /**
00059    * @addtogroup pointer_abstractions
00060    * @{
00061    */
00062 
00063   /// 2.2.3.7 shared_ptr I/O
00064   template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
00065     inline std::basic_ostream<_Ch, _Tr>&
00066     operator<<(std::basic_ostream<_Ch, _Tr>& __os,
00067            const __shared_ptr<_Tp, _Lp>& __p)
00068     {
00069       __os << __p.get();
00070       return __os;
00071     }
00072 
00073   /// 2.2.3.10 shared_ptr get_deleter (experimental)
00074   template<typename _Del, typename _Tp, _Lock_policy _Lp>
00075     inline _Del*
00076     get_deleter(const __shared_ptr<_Tp, _Lp>& __p)
00077     {
00078 #ifdef __GXX_RTTI
00079       return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
00080 #else
00081       return 0;
00082 #endif
00083     }
00084 
00085 
00086   /**
00087    *  @brief  A smart pointer with reference-counted copy semantics.
00088    *
00089    *  The object pointed to is deleted when the last shared_ptr pointing to
00090    *  it is destroyed or reset.
00091   */
00092   template<typename _Tp>
00093     class shared_ptr : public __shared_ptr<_Tp>
00094     {
00095     public:
00096       /**
00097        *  @brief  Construct an empty %shared_ptr.
00098        *  @post   use_count()==0 && get()==0
00099        */
00100       constexpr shared_ptr()
00101       : __shared_ptr<_Tp>() { }
00102 
00103       shared_ptr(const shared_ptr&) = default; // never throws
00104 
00105       /**
00106        *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
00107        *  @param  __p  A pointer that is convertible to element_type*.
00108        *  @post   use_count() == 1 && get() == __p
00109        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
00110        */
00111       template<typename _Tp1>
00112     explicit shared_ptr(_Tp1* __p)
00113         : __shared_ptr<_Tp>(__p) { }
00114 
00115       /**
00116        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
00117        *          and the deleter @a __d.
00118        *  @param  __p  A pointer.
00119        *  @param  __d  A deleter.
00120        *  @post   use_count() == 1 && get() == __p
00121        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00122        *
00123        *  Requirements: _Deleter's copy constructor and destructor must
00124        *  not throw
00125        *
00126        *  __shared_ptr will release __p by calling __d(__p)
00127        */
00128       template<typename _Tp1, typename _Deleter>
00129     shared_ptr(_Tp1* __p, _Deleter __d)
00130         : __shared_ptr<_Tp>(__p, __d) { }
00131 
00132       /**
00133        *  @brief  Construct a %shared_ptr that owns a null pointer
00134        *          and the deleter @a __d.
00135        *  @param  __p  A null pointer constant.
00136        *  @param  __d  A deleter.
00137        *  @post   use_count() == 1 && get() == __p
00138        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00139        *
00140        *  Requirements: _Deleter's copy constructor and destructor must
00141        *  not throw
00142        *
00143        *  The last owner will call __d(__p)
00144        */
00145       template<typename _Deleter>
00146     shared_ptr(nullptr_t __p, _Deleter __d)
00147         : __shared_ptr<_Tp>(__p, __d) { }
00148 
00149       /**
00150        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
00151        *          and the deleter @a __d.
00152        *  @param  __p  A pointer.
00153        *  @param  __d  A deleter.
00154        *  @param  __a  An allocator.
00155        *  @post   use_count() == 1 && get() == __p
00156        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00157        *
00158        *  Requirements: _Deleter's copy constructor and destructor must
00159        *  not throw _Alloc's copy constructor and destructor must not
00160        *  throw.
00161        *
00162        *  __shared_ptr will release __p by calling __d(__p)
00163        */
00164       template<typename _Tp1, typename _Deleter, typename _Alloc>
00165     shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
00166     : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
00167 
00168       /**
00169        *  @brief  Construct a %shared_ptr that owns a null pointer
00170        *          and the deleter @a __d.
00171        *  @param  __p  A null pointer constant.
00172        *  @param  __d  A deleter.
00173        *  @param  __a  An allocator.
00174        *  @post   use_count() == 1 && get() == __p
00175        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
00176        *
00177        *  Requirements: _Deleter's copy constructor and destructor must
00178        *  not throw _Alloc's copy constructor and destructor must not
00179        *  throw.
00180        *
00181        *  The last owner will call __d(__p)
00182        */
00183       template<typename _Deleter, typename _Alloc>
00184     shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
00185     : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
00186 
00187       // Aliasing constructor
00188 
00189       /**
00190        *  @brief  Constructs a %shared_ptr instance that stores @a __p
00191        *          and shares ownership with @a __r.
00192        *  @param  __r  A %shared_ptr.
00193        *  @param  __p  A pointer that will remain valid while @a *__r is valid.
00194        *  @post   get() == __p && use_count() == __r.use_count()
00195        *
00196        *  This can be used to construct a @c shared_ptr to a sub-object
00197        *  of an object managed by an existing @c shared_ptr.
00198        *
00199        * @code
00200        * shared_ptr< pair<int,int> > pii(new pair<int,int>());
00201        * shared_ptr<int> pi(pii, &pii->first);
00202        * assert(pii.use_count() == 2);
00203        * @endcode
00204        */
00205       template<typename _Tp1>
00206     shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p)
00207     : __shared_ptr<_Tp>(__r, __p) { }
00208 
00209       /**
00210        *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
00211        *          otherwise construct a %shared_ptr that shares ownership
00212        *          with @a __r.
00213        *  @param  __r  A %shared_ptr.
00214        *  @post   get() == __r.get() && use_count() == __r.use_count()
00215        */
00216       template<typename _Tp1, typename = typename
00217            std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
00218     shared_ptr(const shared_ptr<_Tp1>& __r)
00219         : __shared_ptr<_Tp>(__r) { }
00220 
00221       /**
00222        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
00223        *  @param  __r  A %shared_ptr rvalue.
00224        *  @post   *this contains the old value of @a __r, @a __r is empty.
00225        */
00226       shared_ptr(shared_ptr&& __r)
00227       : __shared_ptr<_Tp>(std::move(__r)) { }
00228 
00229       /**
00230        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
00231        *  @param  __r  A %shared_ptr rvalue.
00232        *  @post   *this contains the old value of @a __r, @a __r is empty.
00233        */
00234       template<typename _Tp1, typename = typename
00235            std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
00236     shared_ptr(shared_ptr<_Tp1>&& __r)
00237     : __shared_ptr<_Tp>(std::move(__r)) { }
00238 
00239       /**
00240        *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
00241        *          and stores a copy of the pointer stored in @a __r.
00242        *  @param  __r  A weak_ptr.
00243        *  @post   use_count() == __r.use_count()
00244        *  @throw  bad_weak_ptr when __r.expired(),
00245        *          in which case the constructor has no effect.
00246        */
00247       template<typename _Tp1>
00248     explicit shared_ptr(const weak_ptr<_Tp1>& __r)
00249     : __shared_ptr<_Tp>(__r) { }
00250 
00251 #if _GLIBCXX_USE_DEPRECATED
00252       template<typename _Tp1>
00253     shared_ptr(std::auto_ptr<_Tp1>&& __r)
00254     : __shared_ptr<_Tp>(std::move(__r)) { }
00255 #endif
00256 
00257       template<typename _Tp1, typename _Del>
00258     shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
00259     : __shared_ptr<_Tp>(std::move(__r)) { }
00260 
00261       /**
00262        *  @brief  Construct an empty %shared_ptr.
00263        *  @param  __p  A null pointer constant.
00264        *  @post   use_count() == 0 && get() == nullptr
00265        */
00266       constexpr shared_ptr(nullptr_t __p)
00267       : __shared_ptr<_Tp>(__p) { }
00268 
00269       shared_ptr& operator=(const shared_ptr&) = default;
00270 
00271       template<typename _Tp1>
00272     shared_ptr&
00273     operator=(const shared_ptr<_Tp1>& __r) // never throws
00274     {
00275       this->__shared_ptr<_Tp>::operator=(__r);
00276       return *this;
00277     }
00278 
00279 #if _GLIBCXX_USE_DEPRECATED
00280       template<typename _Tp1>
00281     shared_ptr&
00282     operator=(std::auto_ptr<_Tp1>&& __r)
00283     {
00284       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00285       return *this;
00286     }
00287 #endif
00288 
00289       shared_ptr&
00290       operator=(shared_ptr&& __r)
00291       {
00292     this->__shared_ptr<_Tp>::operator=(std::move(__r));
00293     return *this;
00294       }
00295 
00296       template<class _Tp1>
00297     shared_ptr&
00298     operator=(shared_ptr<_Tp1>&& __r)
00299     {
00300       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00301       return *this;
00302     }
00303 
00304       template<typename _Tp1, typename _Del>
00305     shared_ptr&
00306     operator=(std::unique_ptr<_Tp1, _Del>&& __r)
00307     {
00308       this->__shared_ptr<_Tp>::operator=(std::move(__r));
00309       return *this;
00310     }
00311 
00312     private:
00313       // This constructor is non-standard, it is used by allocate_shared.
00314       template<typename _Alloc, typename... _Args>
00315     shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
00316            _Args&&... __args)
00317     : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
00318     { }
00319 
00320       template<typename _Tp1, typename _Alloc, typename... _Args>
00321     friend shared_ptr<_Tp1>
00322     allocate_shared(const _Alloc& __a, _Args&&... __args);
00323     };
00324 
00325   // 20.8.13.2.7 shared_ptr comparisons
00326   template<typename _Tp1, typename _Tp2>
00327     inline bool
00328     operator==(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00329     { return __a.get() == __b.get(); }
00330 
00331   template<typename _Tp>
00332     inline bool
00333     operator==(const shared_ptr<_Tp>& __a, nullptr_t)
00334     { return __a.get() == nullptr; }
00335 
00336   template<typename _Tp>
00337     inline bool
00338     operator==(nullptr_t, const shared_ptr<_Tp>& __b)
00339     { return nullptr == __b.get(); }
00340 
00341   template<typename _Tp1, typename _Tp2>
00342     inline bool
00343     operator!=(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00344     { return __a.get() != __b.get(); }
00345 
00346   template<typename _Tp>
00347     inline bool
00348     operator!=(const shared_ptr<_Tp>& __a, nullptr_t)
00349     { return __a.get() != nullptr; }
00350 
00351   template<typename _Tp>
00352     inline bool
00353     operator!=(nullptr_t, const shared_ptr<_Tp>& __b)
00354     { return nullptr != __b.get(); }
00355 
00356   template<typename _Tp1, typename _Tp2>
00357     inline bool
00358     operator<(const shared_ptr<_Tp1>& __a, const shared_ptr<_Tp2>& __b)
00359     { return __a.get() < __b.get(); }
00360 
00361   template<typename _Tp>
00362     struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
00363     { };
00364 
00365   // 20.8.13.2.9 shared_ptr specialized algorithms.
00366   template<typename _Tp>
00367     inline void
00368     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b)
00369     { __a.swap(__b); }
00370 
00371   // 20.8.13.2.10 shared_ptr casts.
00372   template<typename _Tp, typename _Tp1>
00373     inline shared_ptr<_Tp>
00374     static_pointer_cast(const shared_ptr<_Tp1>& __r)
00375     { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
00376 
00377   template<typename _Tp, typename _Tp1>
00378     inline shared_ptr<_Tp>
00379     const_pointer_cast(const shared_ptr<_Tp1>& __r)
00380     { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
00381 
00382   template<typename _Tp, typename _Tp1>
00383     inline shared_ptr<_Tp>
00384     dynamic_pointer_cast(const shared_ptr<_Tp1>& __r)
00385     {
00386       if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
00387     return shared_ptr<_Tp>(__r, __p);
00388       return shared_ptr<_Tp>();
00389     }
00390 
00391 
00392   /**
00393    *  @brief  A smart pointer with weak semantics.
00394    *
00395    *  With forwarding constructors and assignment operators.
00396    */
00397   template<typename _Tp>
00398     class weak_ptr : public __weak_ptr<_Tp>
00399     {
00400     public:
00401       constexpr weak_ptr()
00402       : __weak_ptr<_Tp>() { }
00403 
00404       template<typename _Tp1, typename = typename
00405            std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
00406     weak_ptr(const weak_ptr<_Tp1>& __r)
00407     : __weak_ptr<_Tp>(__r) { }
00408 
00409       template<typename _Tp1, typename = typename
00410            std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
00411     weak_ptr(const shared_ptr<_Tp1>& __r)
00412     : __weak_ptr<_Tp>(__r) { }
00413 
00414       template<typename _Tp1>
00415     weak_ptr&
00416     operator=(const weak_ptr<_Tp1>& __r) // never throws
00417     {
00418       this->__weak_ptr<_Tp>::operator=(__r);
00419       return *this;
00420     }
00421 
00422       template<typename _Tp1>
00423     weak_ptr&
00424     operator=(const shared_ptr<_Tp1>& __r) // never throws
00425     {
00426       this->__weak_ptr<_Tp>::operator=(__r);
00427       return *this;
00428     }
00429 
00430       shared_ptr<_Tp>
00431       lock() const // never throws
00432       {
00433 #ifdef __GTHREADS
00434     if (this->expired())
00435       return shared_ptr<_Tp>();
00436 
00437     __try
00438       {
00439         return shared_ptr<_Tp>(*this);
00440       }
00441     __catch(const bad_weak_ptr&)
00442       {
00443         return shared_ptr<_Tp>();
00444       }
00445 #else
00446     return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
00447 #endif
00448       }
00449     };
00450 
00451   // 20.8.13.3.7 weak_ptr specialized algorithms.
00452   template<typename _Tp>
00453     inline void
00454     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b)
00455     { __a.swap(__b); }
00456 
00457 
00458   /// Primary template owner_less
00459   template<typename _Tp>
00460     struct owner_less;
00461 
00462   /// Partial specialization of owner_less for shared_ptr.
00463   template<typename _Tp>
00464     struct owner_less<shared_ptr<_Tp>>
00465     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
00466     { };
00467 
00468   /// Partial specialization of owner_less for weak_ptr.
00469   template<typename _Tp>
00470     struct owner_less<weak_ptr<_Tp>>
00471     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
00472     { };
00473 
00474   /**
00475    *  @brief Base class allowing use of member function shared_from_this.
00476    */
00477   template<typename _Tp>
00478     class enable_shared_from_this
00479     {
00480     protected:
00481       constexpr enable_shared_from_this() { }
00482 
00483       enable_shared_from_this(const enable_shared_from_this&) { }
00484 
00485       enable_shared_from_this&
00486       operator=(const enable_shared_from_this&)
00487       { return *this; }
00488 
00489       ~enable_shared_from_this() { }
00490 
00491     public:
00492       shared_ptr<_Tp>
00493       shared_from_this()
00494       { return shared_ptr<_Tp>(this->_M_weak_this); }
00495 
00496       shared_ptr<const _Tp>
00497       shared_from_this() const
00498       { return shared_ptr<const _Tp>(this->_M_weak_this); }
00499 
00500     private:
00501       template<typename _Tp1>
00502     void
00503     _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const
00504     { _M_weak_this._M_assign(__p, __n); }
00505 
00506       template<typename _Tp1>
00507     friend void
00508     __enable_shared_from_this_helper(const __shared_count<>& __pn,
00509                      const enable_shared_from_this* __pe,
00510                      const _Tp1* __px)
00511     {
00512       if (__pe != 0)
00513         __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
00514     }
00515 
00516       mutable weak_ptr<_Tp>  _M_weak_this;
00517     };
00518 
00519   /**
00520    *  @brief  Create an object that is owned by a shared_ptr.
00521    *  @param  __a     An allocator.
00522    *  @param  __args  Arguments for the @a _Tp object's constructor.
00523    *  @return A shared_ptr that owns the newly created object.
00524    *  @throw  An exception thrown from @a _Alloc::allocate or from the
00525    *          constructor of @a _Tp.
00526    *
00527    *  A copy of @a __a will be used to allocate memory for the shared_ptr
00528    *  and the new object.
00529    */
00530   template<typename _Tp, typename _Alloc, typename... _Args>
00531     inline shared_ptr<_Tp>
00532     allocate_shared(const _Alloc& __a, _Args&&... __args)
00533     {
00534       return shared_ptr<_Tp>(_Sp_make_shared_tag(), __a,
00535                  std::forward<_Args>(__args)...);
00536     }
00537 
00538   /**
00539    *  @brief  Create an object that is owned by a shared_ptr.
00540    *  @param  __args  Arguments for the @a _Tp object's constructor.
00541    *  @return A shared_ptr that owns the newly created object.
00542    *  @throw  std::bad_alloc, or an exception thrown from the
00543    *          constructor of @a _Tp.
00544    */
00545   template<typename _Tp, typename... _Args>
00546     inline shared_ptr<_Tp>
00547     make_shared(_Args&&... __args)
00548     {
00549       typedef typename std::remove_const<_Tp>::type _Tp_nc;
00550       return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
00551                        std::forward<_Args>(__args)...);
00552     }
00553 
00554   /// std::hash specialization for shared_ptr.
00555   template<typename _Tp>
00556     struct hash<shared_ptr<_Tp>>
00557     : public std::unary_function<shared_ptr<_Tp>, size_t>
00558     {
00559       size_t
00560       operator()(const shared_ptr<_Tp>& __s) const
00561       { return std::hash<_Tp*>()(__s.get()); }
00562     };
00563 
00564   // @} group pointer_abstractions
00565 
00566 _GLIBCXX_END_NAMESPACE_VERSION
00567 } // namespace
00568 
00569 #endif // _SHARED_PTR_H