auto_ptr源码剖析

 /*
  * Copyright (c) 1997-1999
  * Silicon Graphics Computer Systems, Inc.
  *
  * Permission to use, copy, modify, distribute and sell this software
  * and its documentation for any purpose is hereby granted without fee,
  * provided that the above copyright notice appear in all copies and
  * that both that copyright notice and this permission notice appear
  * in supporting documentation.  Silicon Graphics makes no
  * representations about the suitability of this software for any
  * purpose.  It is provided "as is" without express or implied warranty.
  *
  */

 #ifndef __SGI_STL_MEMORY
 #define __SGI_STL_MEMORY

 #include <stl_algobase.h>
 #include <stl_alloc.h>
 #include <stl_construct.h>
 #include <stl_tempbuf.h>
 #include <stl_uninitialized.h>
 #include <stl_raw_storage_iter.h>

 __STL_BEGIN_NAMESPACE

 #if defined(__SGI_STL_USE_AUTO_PTR_CONVERSIONS) && \
     defined(__STL_MEMBER_TEMPLATES)

 template<class _Tp1> struct auto_ptr_ref {
   _Tp1* _M_ptr;
   auto_ptr_ref(_Tp1* __p) : _M_ptr(__p) {}
 };

 #endif

 template <class _Tp> class auto_ptr {
 private:
   _Tp* _M_ptr;  // 维护一个类型指针

 public:
   typedef _Tp element_type;

    // 构造函数，初始化所维护的指针
   explicit auto_ptr(_Tp* __p = ) __STL_NOTHROW : _M_ptr(__p) {}

   // 拷贝构造函数，转移控制权，将__a维护的指针转交给当前对象来维护；
   auto_ptr(auto_ptr& __a) __STL_NOTHROW : _M_ptr(__a.release()) {}

 #ifdef __STL_MEMBER_TEMPLATES
   template <class _Tp1> auto_ptr(auto_ptr<_Tp1>& __a) __STL_NOTHROW
     : _M_ptr(__a.release()) {}
 #endif /* __STL_MEMBER_TEMPLATES */

   // 赋值构造函数，重新设定控制权
   auto_ptr& operator=(auto_ptr& __a) __STL_NOTHROW {
     if (&__a != this) {
       delete _M_ptr; // 解除当前控制权，将所维护的指针所指向的对象析构掉。
       _M_ptr = __a.release(); // 重新设定控制权，将__a维护的指针转交给当前对象来维护。
     }
     return *this;
   }

 #ifdef __STL_MEMBER_TEMPLATES
   template <class _Tp1>
   auto_ptr& operator=(auto_ptr<_Tp1>& __a) __STL_NOTHROW {
     if (__a.get() != this->get()) {
       delete _M_ptr;
       _M_ptr = __a.release();
     }
     return *this;
   }
 #endif /* __STL_MEMBER_TEMPLATES */

   // Note: The C++ standard says there is supposed to be an empty throw
   // specification here, but omitting it is standard conforming.  Its
   // presence can be detected only if _Tp::~_Tp() throws, but (17.4.3.6/2)
   // this is prohibited.
   ~auto_ptr() { delete _M_ptr; } // 析构函数，释放所维护指针指向的资源

   _Tp& operator*() const __STL_NOTHROW {
     return *_M_ptr; // 重载*操作符，返回对象引用
   }
   _Tp* operator->() const __STL_NOTHROW {
     return _M_ptr; // 重载->操作符，返回对象地址
   }
   _Tp* get() const __STL_NOTHROW {
     return _M_ptr; // 获取所维护指针
   }
   _Tp* release() __STL_NOTHROW {
     _Tp* __tmp = _M_ptr;
     _M_ptr = ; // 转移控制权，当前对象不再维护任何指针
     return __tmp; // 让出控制权
   }
   // 重新设定控制权，如果以默认值调用，则释放对象，结束控制权
   void reset(_Tp* __p = ) __STL_NOTHROW {
     if (__p != _M_ptr) {
       delete _M_ptr;
       _M_ptr = __p;
     }
   }

   // According to the C++ standard, these conversions are required.  Most
   // present-day compilers, however, do not enforce that requirement---and,
   // in fact, most present-day compilers do not support the language
   // features that these conversions rely on.

 #if defined(__SGI_STL_USE_AUTO_PTR_CONVERSIONS) && \
     defined(__STL_MEMBER_TEMPLATES)

 public:
   auto_ptr(auto_ptr_ref<_Tp> __ref) __STL_NOTHROW
     : _M_ptr(__ref._M_ptr) {}

   auto_ptr& operator=(auto_ptr_ref<_Tp> __ref) __STL_NOTHROW {
     if (__ref._M_ptr != this->get()) {
       delete _M_ptr;
       _M_ptr = __ref._M_ptr;
     }
     return *this;
   }

   template <class _Tp1> operator auto_ptr_ref<_Tp1>() __STL_NOTHROW
     { return auto_ptr_ref<_Tp1>(this->release()); }
   template <class _Tp1> operator auto_ptr<_Tp1>() __STL_NOTHROW
     { return auto_ptr<_Tp1>(this->release()); }

 #endif /* auto ptr conversions && member templates */
 };

 __STL_END_NAMESPACE

 #endif /* __SGI_STL_MEMORY */

 // Local Variables:
 // mode:C++
 // End: