1 // Custom pointer adapter and sample storage policies
3 // Copyright (C) 2008-2022 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
27 * This file is a GNU extension to the Standard C++ Library.
31 * Provides reusable _Pointer_adapter for assisting in the development of
32 * custom pointer types that can be used with the standard containers via
33 * the allocator::pointer and allocator::const_pointer typedefs.
39 #pragma GCC system_header
45 #include <bits/stl_iterator_base_types.h>
47 #include <ext/type_traits.h>
48 #if __cplusplus >= 201103L
49 # include <bits/move.h>
50 # include <bits/ptr_traits.h>
52 #if __cplusplus > 201703L
53 # include <iterator> // for indirectly_readable_traits
56 namespace __gnu_cxx
_GLIBCXX_VISIBILITY(default)
58 _GLIBCXX_BEGIN_NAMESPACE_VERSION
61 * @brief A storage policy for use with _Pointer_adapter<> which yields a
64 * A _Storage_policy is required to provide 4 things:
65 * 1) A get() API for returning the stored pointer value.
66 * 2) An set() API for storing a pointer value.
67 * 3) An element_type typedef to define the type this points to.
68 * 4) An operator<() to support pointer comparison.
69 * 5) An operator==() to support pointer comparison.
71 template<typename _Tp
>
72 class _Std_pointer_impl
75 // the type this pointer points to.
76 typedef _Tp element_type
;
78 // A method to fetch the pointer value as a standard T* value;
83 // A method to set the pointer value, from a standard T* value;
85 set(element_type
* __arg
)
88 // Comparison of pointers
90 operator<(const _Std_pointer_impl
& __rarg
) const
91 { return (_M_value
< __rarg
._M_value
); }
94 operator==(const _Std_pointer_impl
& __rarg
) const
95 { return (_M_value
== __rarg
._M_value
); }
98 element_type
* _M_value
;
102 * @brief A storage policy for use with _Pointer_adapter<> which stores
103 * the pointer's address as an offset value which is relative to
106 * This is intended for pointers within shared memory regions which
107 * might be mapped at different addresses by different processes.
108 * For null pointers, a value of 1 is used. (0 is legitimate
109 * sometimes for nodes in circularly linked lists) This value was
110 * chosen as the least likely to generate an incorrect null, As
111 * there is no reason why any normal pointer would point 1 byte into
112 * its own pointer address.
114 template<typename _Tp
>
115 class _Relative_pointer_impl
118 typedef _Tp element_type
;
126 return reinterpret_cast<_Tp
*>(reinterpret_cast<uintptr_t>(this)
136 _M_diff
= reinterpret_cast<uintptr_t>(__arg
)
137 - reinterpret_cast<uintptr_t>(this);
140 // Comparison of pointers
142 operator<(const _Relative_pointer_impl
& __rarg
) const
143 { return (reinterpret_cast<uintptr_t>(this->get())
144 < reinterpret_cast<uintptr_t>(__rarg
.get())); }
147 operator==(const _Relative_pointer_impl
& __rarg
) const
148 { return (reinterpret_cast<uintptr_t>(this->get())
149 == reinterpret_cast<uintptr_t>(__rarg
.get())); }
152 typedef __UINTPTR_TYPE__
uintptr_t;
157 * Relative_pointer_impl needs a specialization for const T because of
158 * the casting done during pointer arithmetic.
160 template<typename _Tp
>
161 class _Relative_pointer_impl
<const _Tp
>
164 typedef const _Tp element_type
;
172 return reinterpret_cast<const _Tp
*>
173 (reinterpret_cast<uintptr_t>(this) + _M_diff
);
177 set(const _Tp
* __arg
)
182 _M_diff
= reinterpret_cast<uintptr_t>(__arg
)
183 - reinterpret_cast<uintptr_t>(this);
186 // Comparison of pointers
188 operator<(const _Relative_pointer_impl
& __rarg
) const
189 { return (reinterpret_cast<uintptr_t>(this->get())
190 < reinterpret_cast<uintptr_t>(__rarg
.get())); }
193 operator==(const _Relative_pointer_impl
& __rarg
) const
194 { return (reinterpret_cast<uintptr_t>(this->get())
195 == reinterpret_cast<uintptr_t>(__rarg
.get())); }
198 typedef __UINTPTR_TYPE__
uintptr_t;
203 * The specialization on this type helps resolve the problem of
204 * reference to void, and eliminates the need to specialize
205 * _Pointer_adapter for cases of void*, const void*, and so on.
207 struct _Invalid_type
{ };
209 template<typename _Tp
>
210 struct _Reference_type
211 { typedef _Tp
& reference
; };
214 struct _Reference_type
<void>
215 { typedef _Invalid_type
& reference
; };
218 struct _Reference_type
<const void>
219 { typedef const _Invalid_type
& reference
; };
222 struct _Reference_type
<volatile void>
223 { typedef volatile _Invalid_type
& reference
; };
226 struct _Reference_type
<volatile const void>
227 { typedef const volatile _Invalid_type
& reference
; };
230 * This structure accommodates the way in which
231 * std::iterator_traits<> is normally specialized for const T*, so
232 * that value_type is still T.
234 template<typename _Tp
>
235 struct _Unqualified_type
236 { typedef _Tp type
; };
238 template<typename _Tp
>
239 struct _Unqualified_type
<const _Tp
>
240 { typedef _Tp type
; };
243 * The following provides an 'alternative pointer' that works with
244 * the containers when specified as the pointer typedef of the
247 * The pointer type used with the containers doesn't have to be this
248 * class, but it must support the implicit conversions, pointer
249 * arithmetic, comparison operators, etc. that are supported by this
250 * class, and avoid raising compile-time ambiguities. Because
251 * creating a working pointer can be challenging, this pointer
252 * template was designed to wrapper an easier storage policy type,
253 * so that it becomes reusable for creating other pointer types.
255 * A key point of this class is also that it allows container
256 * writers to 'assume' Allocator::pointer is a typedef for a normal
257 * pointer. This class supports most of the conventions of a true
258 * pointer, and can, for instance handle implicit conversion to
259 * const and base class pointer types. The only impositions on
260 * container writers to support extended pointers are: 1) use the
261 * Allocator::pointer typedef appropriately for pointer types. 2)
262 * if you need pointer casting, use the __pointer_cast<> functions
263 * from ext/cast.h. This allows pointer cast operations to be
264 * overloaded as necessary by custom pointers.
266 * Note: The const qualifier works with this pointer adapter as
269 * _Tp* == _Pointer_adapter<_Std_pointer_impl<_Tp> >;
270 * const _Tp* == _Pointer_adapter<_Std_pointer_impl<const _Tp> >;
271 * _Tp* const == const _Pointer_adapter<_Std_pointer_impl<_Tp> >;
272 * const _Tp* const == const _Pointer_adapter<_Std_pointer_impl<const _Tp> >;
274 template<typename _Storage_policy
>
275 class _Pointer_adapter
: public _Storage_policy
278 typedef typename
_Storage_policy::element_type element_type
;
280 // These are needed for iterator_traits
281 typedef std::random_access_iterator_tag iterator_category
;
282 typedef typename _Unqualified_type
<element_type
>::type value_type
;
283 typedef std::ptrdiff_t difference_type
;
284 typedef _Pointer_adapter pointer
;
285 typedef typename _Reference_type
<element_type
>::reference reference
;
287 // Reminder: 'const' methods mean that the method is valid when the
288 // pointer is immutable, and has nothing to do with whether the
289 // 'pointee' is const.
291 // Default Constructor (Convert from element_type*)
292 _Pointer_adapter(element_type
* __arg
= 0)
293 { _Storage_policy::set(__arg
); }
295 // Copy constructor from _Pointer_adapter of same type.
296 _Pointer_adapter(const _Pointer_adapter
& __arg
)
297 { _Storage_policy::set(__arg
.get()); }
299 // Convert from _Up* if conversion to element_type* is valid.
300 template<typename _Up
>
301 _Pointer_adapter(_Up
* __arg
)
302 { _Storage_policy::set(__arg
); }
304 // Conversion from another _Pointer_adapter if _Up if static cast is
306 template<typename _Up
>
307 _Pointer_adapter(const _Pointer_adapter
<_Up
>& __arg
)
308 { _Storage_policy::set(__arg
.get()); }
311 ~_Pointer_adapter() { }
313 // Assignment operator
315 operator=(const _Pointer_adapter
& __arg
)
317 _Storage_policy::set(__arg
.get());
321 template<typename _Up
>
323 operator=(const _Pointer_adapter
<_Up
>& __arg
)
325 _Storage_policy::set(__arg
.get());
329 template<typename _Up
>
331 operator=(_Up
* __arg
)
333 _Storage_policy::set(__arg
);
337 // Operator*, returns element_type&
340 { return *(_Storage_policy::get()); }
342 // Operator->, returns element_type*
345 { return _Storage_policy::get(); }
347 // Operator[], returns a element_type& to the item at that loc.
349 operator[](std::ptrdiff_t __index
) const
350 { return _Storage_policy::get()[__index
]; }
352 // To allow implicit conversion to "bool", for "if (ptr)..."
353 #if __cplusplus >= 201103L
354 explicit operator bool() const { return _Storage_policy::get() != 0; }
357 typedef element_type
*(_Pointer_adapter::*__unspecified_bool_type
)() const;
360 operator __unspecified_bool_type() const
362 return _Storage_policy::get() == 0 ? 0 :
363 &_Pointer_adapter::operator->;
366 // ! operator (for: if (!ptr)...)
369 { return (_Storage_policy::get() == 0); }
372 // Pointer differences
373 inline friend std::ptrdiff_t
374 operator-(const _Pointer_adapter
& __lhs
, element_type
* __rhs
)
375 { return (__lhs
.get() - __rhs
); }
377 inline friend std::ptrdiff_t
378 operator-(element_type
* __lhs
, const _Pointer_adapter
& __rhs
)
379 { return (__lhs
- __rhs
.get()); }
381 template<typename _Up
>
382 inline friend std::ptrdiff_t
383 operator-(const _Pointer_adapter
& __lhs
, _Up
* __rhs
)
384 { return (__lhs
.get() - __rhs
); }
386 template<typename _Up
>
387 inline friend std::ptrdiff_t
388 operator-(_Up
* __lhs
, const _Pointer_adapter
& __rhs
)
389 { return (__lhs
- __rhs
.get()); }
391 template<typename _Up
>
392 inline std::ptrdiff_t
393 operator-(const _Pointer_adapter
<_Up
>& __rhs
) const
394 { return (_Storage_policy::get() - __rhs
.get()); }
397 // Note: There is a reason for all this overloading based on different
398 // integer types. In some libstdc++-v3 test cases, a templated
399 // operator+ is declared which can match any types. This operator
400 // tends to "steal" the recognition of _Pointer_adapter's own operator+
401 // unless the integer type matches perfectly.
403 #define _CXX_POINTER_ARITH_OPERATOR_SET(INT_TYPE) \
404 inline friend _Pointer_adapter \
405 operator+(const _Pointer_adapter& __lhs, INT_TYPE __offset) \
406 { return _Pointer_adapter(__lhs.get() + __offset); } \
408 inline friend _Pointer_adapter \
409 operator+(INT_TYPE __offset, const _Pointer_adapter& __rhs) \
410 { return _Pointer_adapter(__rhs.get() + __offset); } \
412 inline friend _Pointer_adapter \
413 operator-(const _Pointer_adapter& __lhs, INT_TYPE __offset) \
414 { return _Pointer_adapter(__lhs.get() - __offset); } \
416 inline _Pointer_adapter& \
417 operator+=(INT_TYPE __offset) \
419 _Storage_policy::set(_Storage_policy::get() + __offset); \
423 inline _Pointer_adapter& \
424 operator-=(INT_TYPE __offset) \
426 _Storage_policy::set(_Storage_policy::get() - __offset); \
429 // END of _CXX_POINTER_ARITH_OPERATOR_SET macro
431 // Expand into the various pointer arithmetic operators needed.
432 _CXX_POINTER_ARITH_OPERATOR_SET(short);
433 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned short);
434 _CXX_POINTER_ARITH_OPERATOR_SET(int);
435 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned int);
436 _CXX_POINTER_ARITH_OPERATOR_SET(long);
437 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long);
438 #ifdef _GLIBCXX_USE_LONG_LONG
439 _CXX_POINTER_ARITH_OPERATOR_SET(long long);
440 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long long);
443 // Mathematical Manipulators
444 inline _Pointer_adapter
&
447 _Storage_policy::set(_Storage_policy::get() + 1);
451 inline _Pointer_adapter
454 _Pointer_adapter
__tmp(*this);
455 _Storage_policy::set(_Storage_policy::get() + 1);
459 inline _Pointer_adapter
&
462 _Storage_policy::set(_Storage_policy::get() - 1);
466 inline _Pointer_adapter
469 _Pointer_adapter
__tmp(*this);
470 _Storage_policy::set(_Storage_policy::get() - 1);
474 #if __cpp_lib_three_way_comparison
475 friend std::strong_ordering
476 operator<=>(const _Pointer_adapter
& __lhs
, const _Pointer_adapter
& __rhs
)
478 { return __lhs
.get() <=> __rhs
.get(); }
480 }; // class _Pointer_adapter
483 #define _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(OPERATOR) \
484 template<typename _Tp1, typename _Tp2> \
486 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, _Tp2 __rhs) \
487 { return __lhs.get() OPERATOR __rhs; } \
489 template<typename _Tp1, typename _Tp2> \
491 operator OPERATOR(_Tp1 __lhs, const _Pointer_adapter<_Tp2>& __rhs) \
492 { return __lhs OPERATOR __rhs.get(); } \
494 template<typename _Tp1, typename _Tp2> \
496 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, \
497 const _Pointer_adapter<_Tp2>& __rhs) \
498 { return __lhs.get() OPERATOR __rhs.get(); } \
500 // End GCC_CXX_POINTER_COMPARISON_OPERATION_SET Macro
502 // Expand into the various comparison operators needed.
503 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(==)
504 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(!=)
505 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<)
506 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<=)
507 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>)
508 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>=)
510 // These are here for expressions like "ptr == 0", "ptr != 0"
511 template<typename _Tp
>
513 operator==(const _Pointer_adapter
<_Tp
>& __lhs
, int __rhs
)
514 { return __lhs
.get() == reinterpret_cast<void*>(__rhs
); }
516 template<typename _Tp
>
518 operator==(int __lhs
, const _Pointer_adapter
<_Tp
>& __rhs
)
519 { return __rhs
.get() == reinterpret_cast<void*>(__lhs
); }
521 template<typename _Tp
>
523 operator!=(const _Pointer_adapter
<_Tp
>& __lhs
, int __rhs
)
524 { return __lhs
.get() != reinterpret_cast<void*>(__rhs
); }
526 template<typename _Tp
>
528 operator!=(int __lhs
, const _Pointer_adapter
<_Tp
>& __rhs
)
529 { return __rhs
.get() != reinterpret_cast<void*>(__lhs
); }
532 * Comparison operators for _Pointer_adapter defer to the base class'
533 * comparison operators, when possible.
535 template<typename _Tp
>
537 operator==(const _Pointer_adapter
<_Tp
>& __lhs
,
538 const _Pointer_adapter
<_Tp
>& __rhs
)
539 { return __lhs
._Tp::operator==(__rhs
); }
541 template<typename _Tp
>
543 operator<=(const _Pointer_adapter
<_Tp
>& __lhs
,
544 const _Pointer_adapter
<_Tp
>& __rhs
)
545 { return __lhs
._Tp::operator<(__rhs
) || __lhs
._Tp::operator==(__rhs
); }
547 template<typename _Tp
>
549 operator!=(const _Pointer_adapter
<_Tp
>& __lhs
,
550 const _Pointer_adapter
<_Tp
>& __rhs
)
551 { return !(__lhs
._Tp::operator==(__rhs
)); }
553 template<typename _Tp
>
555 operator>(const _Pointer_adapter
<_Tp
>& __lhs
,
556 const _Pointer_adapter
<_Tp
>& __rhs
)
557 { return !(__lhs
._Tp::operator<(__rhs
) || __lhs
._Tp::operator==(__rhs
)); }
559 template<typename _Tp
>
561 operator>=(const _Pointer_adapter
<_Tp
>& __lhs
,
562 const _Pointer_adapter
<_Tp
>& __rhs
)
563 { return !(__lhs
._Tp::operator<(__rhs
)); }
566 template<typename _CharT
, typename _Traits
, typename _StoreT
>
567 inline std::basic_ostream
<_CharT
, _Traits
>&
568 operator<<(std::basic_ostream
<_CharT
, _Traits
>& __os
,
569 const _Pointer_adapter
<_StoreT
>& __p
)
570 { return (__os
<< __p
.get()); }
573 _GLIBCXX_END_NAMESPACE_VERSION
576 #if __cplusplus >= 201103L
577 namespace std
_GLIBCXX_VISIBILITY(default)
579 _GLIBCXX_BEGIN_NAMESPACE_VERSION
581 template<typename _Storage_policy
>
582 struct pointer_traits
<__gnu_cxx::_Pointer_adapter
<_Storage_policy
>>
585 typedef __gnu_cxx::_Pointer_adapter
<_Storage_policy
> pointer
;
586 /// The type pointed to
587 typedef typename
pointer::element_type element_type
;
588 /// Type used to represent the difference between two pointers
589 typedef typename
pointer::difference_type difference_type
;
591 template<typename _Up
>
592 using rebind
= typename
__gnu_cxx::_Pointer_adapter
<
593 typename pointer_traits
<_Storage_policy
>::template rebind
<_Up
>>;
595 static pointer
pointer_to(typename
pointer::reference __r
) noexcept
596 { return pointer(std::addressof(__r
)); }
599 #if __cpp_lib_concepts
600 template<typename _Policy
>
601 struct indirectly_readable_traits
<__gnu_cxx::_Pointer_adapter
<_Policy
>>
604 = typename
__gnu_cxx::_Pointer_adapter
<_Policy
>::value_type
;
607 _GLIBCXX_END_NAMESPACE_VERSION