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// Custom pointer adapter and sample storage policies

// Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 3, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

/**

 *  @file ext/pointer.h

 *  This file is a GNU extension to the Standard C++ Library.

 *

 *  @author Bob Walters

 *

 * Provides reusable _Pointer_adapter for assisting in the development of

 * custom pointer types that can be used with the standard containers via

 * the allocator::pointer and allocator::const_pointer typedefs.

 */

#ifndef _POINTER_H

#define _POINTER_H 1

#pragma GCC system_header

#include <iosfwd>

#include <bits/stl_iterator_base_types.h>

#include <ext/cast.h>

#include <ext/type_traits.h>

#if __cplusplus >= 201103L

# include <bits/ptr_traits.h>

#endif

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)

{

_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**

   * @brief A storage policy for use with _Pointer_adapter<> which yields a

   *        standard pointer.

   *

   *  A _Storage_policy is required to provide 4 things:

   *    1) A get() API for returning the stored pointer value.

   *    2) An set() API for storing a pointer value.

   *    3) An element_type typedef to define the type this points to.

   *    4) An operator<() to support pointer comparison.

   *    5) An operator==() to support pointer comparison.

   */

  template<typename _Tp>

    class _Std_pointer_impl

    {

    public:

      // the type this pointer points to.

      typedef _Tp element_type;

      // A method to fetch the pointer value as a standard T* value;

      inline _Tp*

      get() const

      { return _M_value; }

      // A method to set the pointer value, from a standard T* value;

      inline void

      set(element_type* __arg)

      { _M_value = __arg; }

      // Comparison of pointers

      inline bool

      operator<(const _Std_pointer_impl& __rarg) const

      { return (_M_value < __rarg._M_value); }

      inline bool

      operator==(const _Std_pointer_impl& __rarg) const

      { return (_M_value == __rarg._M_value); }

    private:

      element_type* _M_value;

    };

  /**

   * @brief A storage policy for use with _Pointer_adapter<> which stores

   *        the pointer's address as an offset value which is relative to

   *        its own address.

   *

   * This is intended for pointers within shared memory regions which

   * might be mapped at different addresses by different processes.

   * For null pointers, a value of 1 is used.  (0 is legitimate

   * sometimes for nodes in circularly linked lists) This value was

   * chosen as the least likely to generate an incorrect null, As

   * there is no reason why any normal pointer would point 1 byte into

   * its own pointer address.

   */

  template<typename _Tp>

    class _Relative_pointer_impl

    {

    public:

      typedef _Tp element_type;

      _Tp*

      get() const

      {

        if (_M_diff == 1)

          return 0;

        else

          return reinterpret_cast<_Tp*>(reinterpret_cast<_UIntPtrType>(this)

                                        + _M_diff);

      }

      void

      set(_Tp* __arg)

      {

        if (!__arg)

          _M_diff = 1;

        else

          _M_diff = reinterpret_cast<_UIntPtrType>(__arg)

                    - reinterpret_cast<_UIntPtrType>(this);

      }

      // Comparison of pointers

      inline bool

      operator<(const _Relative_pointer_impl& __rarg) const

      { return (reinterpret_cast<_UIntPtrType>(this->get())

                < reinterpret_cast<_UIntPtrType>(__rarg.get())); }

      inline bool

      operator==(const _Relative_pointer_impl& __rarg) const

      { return (reinterpret_cast<_UIntPtrType>(this->get())

                == reinterpret_cast<_UIntPtrType>(__rarg.get())); }

    private:

#ifdef _GLIBCXX_USE_LONG_LONG

      typedef __gnu_cxx::__conditional_type<

         (sizeof(unsigned long) >= sizeof(void*)),

         unsigned long, unsigned long long>::__type _UIntPtrType;

#else

      typedef unsigned long _UIntPtrType;

#endif

      _UIntPtrType _M_diff;

    };

  /**

   * Relative_pointer_impl needs a specialization for const T because of

   * the casting done during pointer arithmetic.

   */

  template<typename _Tp>

    class _Relative_pointer_impl<const _Tp>

    {

    public:

      typedef const _Tp element_type;

      const _Tp*

      get() const

      {

        if (_M_diff == 1)

          return 0;

        else

          return reinterpret_cast<const _Tp*>

              (reinterpret_cast<_UIntPtrType>(this) + _M_diff);

      }

      void

      set(const _Tp* __arg)

      {

        if (!__arg)

          _M_diff = 1;

        else

          _M_diff = reinterpret_cast<_UIntPtrType>(__arg)

                    - reinterpret_cast<_UIntPtrType>(this);

      }

      // Comparison of pointers

      inline bool

      operator<(const _Relative_pointer_impl& __rarg) const

      { return (reinterpret_cast<_UIntPtrType>(this->get())

                < reinterpret_cast<_UIntPtrType>(__rarg.get())); }

      inline bool

      operator==(const _Relative_pointer_impl& __rarg) const

      { return (reinterpret_cast<_UIntPtrType>(this->get())

                == reinterpret_cast<_UIntPtrType>(__rarg.get())); }

    private:

#ifdef _GLIBCXX_USE_LONG_LONG

      typedef __gnu_cxx::__conditional_type<

         (sizeof(unsigned long) >= sizeof(void*)),

         unsigned long, unsigned long long>::__type _UIntPtrType;

#else

      typedef unsigned long _UIntPtrType;

#endif

       _UIntPtrType _M_diff;

    };

  /**

   * The specialization on this type helps resolve the problem of

   * reference to void, and eliminates the need to specialize

   * _Pointer_adapter for cases of void*, const void*, and so on.

   */

  struct _Invalid_type { };

  template<typename _Tp>

    struct _Reference_type

    { typedef _Tp& reference; };

  template<>

    struct _Reference_type<void>

    { typedef _Invalid_type& reference; };

  template<>

    struct _Reference_type<const void>

    { typedef const _Invalid_type& reference; };

  template<>

    struct _Reference_type<volatile void>

    { typedef volatile _Invalid_type&  reference; };

  template<>

    struct _Reference_type<volatile const void>

    { typedef const volatile _Invalid_type&  reference; };

  /**

   * This structure accommodates the way in which

   * std::iterator_traits<> is normally specialized for const T*, so

   * that value_type is still T.

   */

  template<typename _Tp>

    struct _Unqualified_type

    { typedef _Tp type; };

  template<typename _Tp>

    struct _Unqualified_type<const _Tp>

    { typedef _Tp type; };

  /**

   * The following provides an 'alternative pointer' that works with

   * the containers when specified as the pointer typedef of the

   * allocator.

   *

   * The pointer type used with the containers doesn't have to be this

   * class, but it must support the implicit conversions, pointer

   * arithmetic, comparison operators, etc. that are supported by this

   * class, and avoid raising compile-time ambiguities.  Because

   * creating a working pointer can be challenging, this pointer

   * template was designed to wrapper an easier storage policy type,

   * so that it becomes reusable for creating other pointer types.

   *

   * A key point of this class is also that it allows container

   * writers to 'assume' Allocator::pointer is a typedef for a normal

   * pointer.  This class supports most of the conventions of a true

   * pointer, and can, for instance handle implicit conversion to

   * const and base class pointer types.  The only impositions on

   * container writers to support extended pointers are: 1) use the

   * Allocator::pointer typedef appropriately for pointer types.  2)

   * if you need pointer casting, use the __pointer_cast<> functions

   * from ext/cast.h.  This allows pointer cast operations to be

   * overloaded as necessary by custom pointers.

   *

   * Note: The const qualifier works with this pointer adapter as

   * follows:

   *

   * _Tp*             == _Pointer_adapter<_Std_pointer_impl<_Tp> >;

   * const _Tp*       == _Pointer_adapter<_Std_pointer_impl<const _Tp> >;

   * _Tp* const       == const _Pointer_adapter<_Std_pointer_impl<_Tp> >;

   * const _Tp* const == const _Pointer_adapter<_Std_pointer_impl<const _Tp> >;

   */

  template<typename _Storage_policy>

    class _Pointer_adapter : public _Storage_policy

    {

    public:

      typedef typename _Storage_policy::element_type element_type;

      // These are needed for iterator_traits

      typedef std::random_access_iterator_tag                iterator_category;

      typedef typename _Unqualified_type<element_type>::type value_type;

      typedef std::ptrdiff_t                                 difference_type;

      typedef _Pointer_adapter                               pointer;

      typedef typename _Reference_type<element_type>::reference  reference;

      // Reminder: 'const' methods mean that the method is valid when the 

      // pointer is immutable, and has nothing to do with whether the 

      // 'pointee' is const.

      // Default Constructor (Convert from element_type*)

      _Pointer_adapter(element_type* __arg = 0)

      { _Storage_policy::set(__arg); }

      // Copy constructor from _Pointer_adapter of same type.

      _Pointer_adapter(const _Pointer_adapter& __arg)

      { _Storage_policy::set(__arg.get()); }

      // Convert from _Up* if conversion to element_type* is valid.

      template<typename _Up>

        _Pointer_adapter(_Up* __arg)

        { _Storage_policy::set(__arg); }

      // Conversion from another _Pointer_adapter if _Up if static cast is

      // valid.

      template<typename _Up>

        _Pointer_adapter(const _Pointer_adapter<_Up>& __arg)

        { _Storage_policy::set(__arg.get()); }

      // Destructor

      ~_Pointer_adapter() { }

      // Assignment operator

      _Pointer_adapter&

      operator=(const _Pointer_adapter& __arg)

      {

        _Storage_policy::set(__arg.get());

        return *this;

      }

      template<typename _Up>

        _Pointer_adapter&

        operator=(const _Pointer_adapter<_Up>& __arg)

        {

          _Storage_policy::set(__arg.get());

          return *this;

        }

      template<typename _Up>

        _Pointer_adapter&

        operator=(_Up* __arg)

        {

          _Storage_policy::set(__arg);

          return *this;

        }

      // Operator*, returns element_type&

      inline reference

      operator*() const

      { return *(_Storage_policy::get()); }

      // Operator->, returns element_type*

      inline element_type*

      operator->() const

      { return _Storage_policy::get(); }

      // Operator[], returns a element_type& to the item at that loc.

      inline reference

      operator[](std::ptrdiff_t __index) const

      { return _Storage_policy::get()[__index]; }

      // To allow implicit conversion to "bool", for "if (ptr)..."

    private:

      typedef element_type*(_Pointer_adapter::*__unspecified_bool_type)() const;

    public:

      operator __unspecified_bool_type() const

      {

        return _Storage_policy::get() == 0 ? 0 :

                         &_Pointer_adapter::operator->;

      }

      // ! operator (for: if (!ptr)...)

      inline bool

      operator!() const

      { return (_Storage_policy::get() == 0); }

      // Pointer differences

      inline friend std::ptrdiff_t

      operator-(const _Pointer_adapter& __lhs, element_type* __rhs)

      { return (__lhs.get() - __rhs); }

      inline friend std::ptrdiff_t

      operator-(element_type* __lhs, const _Pointer_adapter& __rhs)

      { return (__lhs - __rhs.get()); }

      template<typename _Up>

        inline friend std::ptrdiff_t

        operator-(const _Pointer_adapter& __lhs, _Up* __rhs)

        { return (__lhs.get() - __rhs); }

      template<typename _Up>

        inline friend std::ptrdiff_t

        operator-(_Up* __lhs, const _Pointer_adapter& __rhs)

        { return (__lhs - __rhs.get()); }

      template<typename _Up>

        inline std::ptrdiff_t

        operator-(const _Pointer_adapter<_Up>& __rhs) const

        { return (_Storage_policy::get() - __rhs.get()); }

      // Pointer math

      // Note: There is a reason for all this overloading based on different

      // integer types.  In some libstdc++-v3 test cases, a templated

      // operator+ is declared which can match any types.  This operator

      // tends to "steal" the recognition of _Pointer_adapter's own operator+ 

      // unless the integer type matches perfectly.

#define _CXX_POINTER_ARITH_OPERATOR_SET(INT_TYPE) \

      inline friend _Pointer_adapter \

      operator+(const _Pointer_adapter& __lhs, INT_TYPE __offset) \

      { return _Pointer_adapter(__lhs.get() + __offset); } \

\

      inline friend _Pointer_adapter \

      operator+(INT_TYPE __offset, const _Pointer_adapter& __rhs) \

      { return _Pointer_adapter(__rhs.get() + __offset); } \

\

      inline friend _Pointer_adapter \

      operator-(const _Pointer_adapter& __lhs, INT_TYPE __offset) \

      { return _Pointer_adapter(__lhs.get() - __offset); } \

\

      inline _Pointer_adapter& \

      operator+=(INT_TYPE __offset) \

      { \

        _Storage_policy::set(_Storage_policy::get() + __offset); \

        return *this; \

      } \

\

      inline _Pointer_adapter& \

      operator-=(INT_TYPE __offset) \

      { \

        _Storage_policy::set(_Storage_policy::get() - __offset); \

        return *this; \

      } \

// END of _CXX_POINTER_ARITH_OPERATOR_SET macro

      // Expand into the various pointer arithmetic operators needed.

      _CXX_POINTER_ARITH_OPERATOR_SET(short);

      _CXX_POINTER_ARITH_OPERATOR_SET(unsigned short);

      _CXX_POINTER_ARITH_OPERATOR_SET(int);

      _CXX_POINTER_ARITH_OPERATOR_SET(unsigned int);

      _CXX_POINTER_ARITH_OPERATOR_SET(long);

      _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long);

      // Mathematical Manipulators

      inline _Pointer_adapter&

      operator++()

      {

        _Storage_policy::set(_Storage_policy::get() + 1);

        return *this;

      }

      inline _Pointer_adapter

      operator++(int)

      {

        _Pointer_adapter tmp(*this);

        _Storage_policy::set(_Storage_policy::get() + 1);

        return tmp;

      }

      inline _Pointer_adapter&

      operator--()

      {

        _Storage_policy::set(_Storage_policy::get() - 1);

        return *this;

      }

      inline _Pointer_adapter

      operator--(int)

      {

        _Pointer_adapter tmp(*this);

        _Storage_policy::set(_Storage_policy::get() - 1);

        return tmp;

      }

    }; // class _Pointer_adapter

#define _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(OPERATOR) \

  template<typename _Tp1, typename _Tp2> \

    inline bool \

    operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, _Tp2 __rhs) \

    { return __lhs.get() OPERATOR __rhs; } \

\

  template<typename _Tp1, typename _Tp2> \

    inline bool \

    operator OPERATOR(_Tp1 __lhs, const _Pointer_adapter<_Tp2>& __rhs) \

    { return __lhs OPERATOR __rhs.get(); } \

\

  template<typename _Tp1, typename _Tp2> \

    inline bool \

    operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, \

                              const _Pointer_adapter<_Tp2>& __rhs) \

    { return __lhs.get() OPERATOR __rhs.get(); } \

\

// End GCC_CXX_POINTER_COMPARISON_OPERATION_SET Macro

  // Expand into the various comparison operators needed.

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(==)

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(!=)

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<)

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<=)

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>)

  _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>=)

  // These are here for expressions like "ptr == 0", "ptr != 0"

  template<typename _Tp>

    inline bool

    operator==(const _Pointer_adapter<_Tp>& __lhs, int __rhs)

    { return __lhs.get() == reinterpret_cast<void*>(__rhs); }

  template<typename _Tp>

    inline bool

    operator==(int __lhs, const _Pointer_adapter<_Tp>& __rhs)

    { return __rhs.get() == reinterpret_cast<void*>(__lhs); }

  template<typename _Tp>

    inline bool

    operator!=(const _Pointer_adapter<_Tp>& __lhs, int __rhs)

    { return __lhs.get() != reinterpret_cast<void*>(__rhs); }

  template<typename _Tp>

    inline bool

    operator!=(int __lhs, const _Pointer_adapter<_Tp>& __rhs)

    { return __rhs.get() != reinterpret_cast<void*>(__lhs); }

  /**

   * Comparison operators for _Pointer_adapter defer to the base class'

   * comparison operators, when possible.

   */

  template<typename _Tp>

    inline bool

    operator==(const _Pointer_adapter<_Tp>& __lhs,

               const _Pointer_adapter<_Tp>& __rhs)

    { return __lhs._Tp::operator==(__rhs); }

  template<typename _Tp>

    inline bool

    operator<=(const _Pointer_adapter<_Tp>& __lhs,

               const _Pointer_adapter<_Tp>& __rhs)

    { return __lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs); }

  template<typename _Tp>

    inline bool

    operator!=(const _Pointer_adapter<_Tp>& __lhs,

               const _Pointer_adapter<_Tp>& __rhs)

    { return !(__lhs._Tp::operator==(__rhs)); }

  template<typename _Tp>

    inline bool

    operator>(const _Pointer_adapter<_Tp>& __lhs,

              const _Pointer_adapter<_Tp>& __rhs)

    { return !(__lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs)); }

  template<typename _Tp>

    inline bool

    operator>=(const _Pointer_adapter<_Tp>& __lhs,

               const _Pointer_adapter<_Tp>& __rhs)

    { return !(__lhs._Tp::operator<(__rhs)); }

  template<typename _CharT, typename _Traits, typename _StoreT>

    inline std::basic_ostream<_CharT, _Traits>&

    operator<<(std::basic_ostream<_CharT, _Traits>& __os,

               const _Pointer_adapter<_StoreT>& __p)

    { return (__os << __p.get()); }

_GLIBCXX_END_NAMESPACE_VERSION

} // namespace

#if __cplusplus >= 201103L

namespace std _GLIBCXX_VISIBILITY(default)

{

_GLIBCXX_BEGIN_NAMESPACE_VERSION

  template<typename _Storage_policy>

    struct pointer_traits<__gnu_cxx::_Pointer_adapter<_Storage_policy>>

    {

      /// The pointer type

      typedef __gnu_cxx::_Pointer_adapter<_Storage_policy>         pointer;

      /// The type pointed to

      typedef typename pointer::element_type            element_type;

      /// Type used to represent the difference between two pointers

      typedef typename pointer::difference_type         difference_type;

      template<typename _Up>

        using rebind = typename __gnu_cxx::_Pointer_adapter<

        typename pointer_traits<_Storage_policy>::rebind<_Up>>;

      static pointer pointer_to(typename pointer::reference __r) noexcept

      { return pointer(std::addressof(__r)); }

    };

_GLIBCXX_END_NAMESPACE_VERSION

} // namespace

#endif

#endif // _POINTER_H