# auto_ptr.h

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    00001 // auto_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 /** @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 _BACKWARD_AUTO_PTR_H
    00031 #define _BACKWARD_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, <em>no longer owns
    00175        *  anything</em> 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 /* _BACKWARD_AUTO_PTR_H */