auto_ptr.h

Go to the documentation of this file.
00001 // auto_ptr implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2007, 2008, 2009 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 /** @file backward/auto_ptr.h
00026  *  This is an internal header file, included by other library headers.
00027  *  You should not attempt to use it directly.
00028  */
00029 
00030 #ifndef _STL_AUTO_PTR_H
00031 #define _STL_AUTO_PTR_H 1
00032 
00033 #include <bits/c++config.h>
00034 #include <debug/debug.h>
00035 
00036 _GLIBCXX_BEGIN_NAMESPACE(std)
00037 
00038   /**
00039    *  A wrapper class to provide auto_ptr with reference semantics.
00040    *  For example, an auto_ptr can be assigned (or constructed from)
00041    *  the result of a function which returns an auto_ptr by value.
00042    *
00043    *  All the auto_ptr_ref stuff should happen behind the scenes.
00044    */
00045   template<typename _Tp1>
00046     struct auto_ptr_ref
00047     {
00048       _Tp1* _M_ptr;
00049       
00050       explicit
00051       auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
00052     } _GLIBCXX_DEPRECATED_ATTR;
00053 
00054 
00055   /**
00056    *  @brief  A simple smart pointer providing strict ownership semantics.
00057    *
00058    *  The Standard says:
00059    *  <pre>
00060    *  An @c auto_ptr owns the object it holds a pointer to.  Copying
00061    *  an @c auto_ptr copies the pointer and transfers ownership to the
00062    *  destination.  If more than one @c auto_ptr owns the same object
00063    *  at the same time the behavior of the program is undefined.
00064    *
00065    *  The uses of @c auto_ptr include providing temporary
00066    *  exception-safety for dynamically allocated memory, passing
00067    *  ownership of dynamically allocated memory to a function, and
00068    *  returning dynamically allocated memory from a function.  @c
00069    *  auto_ptr does not meet the CopyConstructible and Assignable
00070    *  requirements for Standard Library <a
00071    *  href="tables.html#65">container</a> elements and thus
00072    *  instantiating a Standard Library container with an @c auto_ptr
00073    *  results in undefined behavior.
00074    *  </pre>
00075    *  Quoted from [20.4.5]/3.
00076    *
00077    *  Good examples of what can and cannot be done with auto_ptr can
00078    *  be found in the libstdc++ testsuite.
00079    *
00080    *  _GLIBCXX_RESOLVE_LIB_DEFECTS
00081    *  127.  auto_ptr<> conversion issues
00082    *  These resolutions have all been incorporated.
00083    */
00084   template<typename _Tp>
00085     class auto_ptr
00086     {
00087     private:
00088       _Tp* _M_ptr;
00089       
00090     public:
00091       /// The pointed-to type.
00092       typedef _Tp element_type;
00093       
00094       /**
00095        *  @brief  An %auto_ptr is usually constructed from a raw pointer.
00096        *  @param  p  A pointer (defaults to NULL).
00097        *
00098        *  This object now @e owns the object pointed to by @a p.
00099        */
00100       explicit
00101       auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
00102 
00103       /**
00104        *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
00105        *  @param  a  Another %auto_ptr of the same type.
00106        *
00107        *  This object now @e owns the object previously owned by @a a,
00108        *  which has given up ownership.
00109        */
00110       auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
00111 
00112       /**
00113        *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
00114        *  @param  a  Another %auto_ptr of a different but related type.
00115        *
00116        *  A pointer-to-Tp1 must be convertible to a
00117        *  pointer-to-Tp/element_type.
00118        *
00119        *  This object now @e owns the object previously owned by @a a,
00120        *  which has given up ownership.
00121        */
00122       template<typename _Tp1>
00123         auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
00124 
00125       /**
00126        *  @brief  %auto_ptr assignment operator.
00127        *  @param  a  Another %auto_ptr of the same type.
00128        *
00129        *  This object now @e owns the object previously owned by @a a,
00130        *  which has given up ownership.  The object that this one @e
00131        *  used to own and track has been deleted.
00132        */
00133       auto_ptr&
00134       operator=(auto_ptr& __a) throw()
00135       {
00136     reset(__a.release());
00137     return *this;
00138       }
00139 
00140       /**
00141        *  @brief  %auto_ptr assignment operator.
00142        *  @param  a  Another %auto_ptr of a different but related type.
00143        *
00144        *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
00145        *
00146        *  This object now @e owns the object previously owned by @a a,
00147        *  which has given up ownership.  The object that this one @e
00148        *  used to own and track has been deleted.
00149        */
00150       template<typename _Tp1>
00151         auto_ptr&
00152         operator=(auto_ptr<_Tp1>& __a) throw()
00153         {
00154       reset(__a.release());
00155       return *this;
00156     }
00157 
00158       /**
00159        *  When the %auto_ptr goes out of scope, the object it owns is
00160        *  deleted.  If it no longer owns anything (i.e., @c get() is
00161        *  @c NULL), then this has no effect.
00162        *
00163        *  The C++ standard says there is supposed to be an empty throw
00164        *  specification here, but omitting it is standard conforming.  Its
00165        *  presence can be detected only if _Tp::~_Tp() throws, but this is
00166        *  prohibited.  [17.4.3.6]/2
00167        */
00168       ~auto_ptr() { delete _M_ptr; }
00169       
00170       /**
00171        *  @brief  Smart pointer dereferencing.
00172        *
00173        *  If this %auto_ptr no longer owns anything, then this
00174        *  operation will crash.  (For a smart pointer, "no longer owns
00175        *  anything" is the same as being a null pointer, and you know
00176        *  what happens when you dereference one of those...)
00177        */
00178       element_type&
00179       operator*() const throw() 
00180       {
00181     _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
00182     return *_M_ptr; 
00183       }
00184       
00185       /**
00186        *  @brief  Smart pointer dereferencing.
00187        *
00188        *  This returns the pointer itself, which the language then will
00189        *  automatically cause to be dereferenced.
00190        */
00191       element_type*
00192       operator->() const throw() 
00193       {
00194     _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
00195     return _M_ptr; 
00196       }
00197       
00198       /**
00199        *  @brief  Bypassing the smart pointer.
00200        *  @return  The raw pointer being managed.
00201        *
00202        *  You can get a copy of the pointer that this object owns, for
00203        *  situations such as passing to a function which only accepts
00204        *  a raw pointer.
00205        *
00206        *  @note  This %auto_ptr still owns the memory.
00207        */
00208       element_type*
00209       get() const throw() { return _M_ptr; }
00210       
00211       /**
00212        *  @brief  Bypassing the smart pointer.
00213        *  @return  The raw pointer being managed.
00214        *
00215        *  You can get a copy of the pointer that this object owns, for
00216        *  situations such as passing to a function which only accepts
00217        *  a raw pointer.
00218        *
00219        *  @note  This %auto_ptr no longer owns the memory.  When this object
00220        *  goes out of scope, nothing will happen.
00221        */
00222       element_type*
00223       release() throw()
00224       {
00225     element_type* __tmp = _M_ptr;
00226     _M_ptr = 0;
00227     return __tmp;
00228       }
00229       
00230       /**
00231        *  @brief  Forcibly deletes the managed object.
00232        *  @param  p  A pointer (defaults to NULL).
00233        *
00234        *  This object now @e owns the object pointed to by @a p.  The
00235        *  previous object has been deleted.
00236        */
00237       void
00238       reset(element_type* __p = 0) throw()
00239       {
00240     if (__p != _M_ptr)
00241       {
00242         delete _M_ptr;
00243         _M_ptr = __p;
00244       }
00245       }
00246       
00247       /** 
00248        *  @brief  Automatic conversions
00249        *
00250        *  These operations convert an %auto_ptr into and from an auto_ptr_ref
00251        *  automatically as needed.  This allows constructs such as
00252        *  @code
00253        *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
00254        *    ...
00255        *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
00256        *  @endcode
00257        */
00258       auto_ptr(auto_ptr_ref<element_type> __ref) throw()
00259       : _M_ptr(__ref._M_ptr) { }
00260       
00261       auto_ptr&
00262       operator=(auto_ptr_ref<element_type> __ref) throw()
00263       {
00264     if (__ref._M_ptr != this->get())
00265       {
00266         delete _M_ptr;
00267         _M_ptr = __ref._M_ptr;
00268       }
00269     return *this;
00270       }
00271       
00272       template<typename _Tp1>
00273         operator auto_ptr_ref<_Tp1>() throw()
00274         { return auto_ptr_ref<_Tp1>(this->release()); }
00275 
00276       template<typename _Tp1>
00277         operator auto_ptr<_Tp1>() throw()
00278         { return auto_ptr<_Tp1>(this->release()); }
00279     } _GLIBCXX_DEPRECATED_ATTR;
00280 
00281   // _GLIBCXX_RESOLVE_LIB_DEFECTS
00282   // 541. shared_ptr template assignment and void
00283   template<>
00284     class auto_ptr<void>
00285     {
00286     public:
00287       typedef void element_type;
00288     } _GLIBCXX_DEPRECATED_ATTR;
00289 
00290 _GLIBCXX_END_NAMESPACE
00291 
00292 #endif /* _STL_AUTO_PTR_H */

Generated on Thu Jul 23 21:15:57 2009 for libstdc++ by  doxygen 1.5.8