libstdc++

pointer.h
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1 // Custom pointer adapter and sample storage policies
2
3 // Copyright (C) 2008-2013 Free Software Foundation, Inc.
4 //
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)
9 // any later version.
10
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.
15
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.
19
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/>.
24
25 /**
26 * @file ext/pointer.h
27 * This file is a GNU extension to the Standard C++ Library.
28 *
29 * @author Bob Walters
30 *
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.
34 */
35
36 #ifndef _POINTER_H
37 #define _POINTER_H 1
38
39 #pragma GCC system_header
40
41 #include <iosfwd>
42 #include <bits/stl_iterator_base_types.h>
43 #include <ext/cast.h>
44 #include <ext/type_traits.h>
45 #if __cplusplus >= 201103L
46 # include <bits/move.h>
47 # include <bits/ptr_traits.h>
48 #endif
49
50 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
51 {
52 _GLIBCXX_BEGIN_NAMESPACE_VERSION
53
54 /**
55 * @brief A storage policy for use with _Pointer_adapter<> which yields a
56 * standard pointer.
57 *
58 * A _Storage_policy is required to provide 4 things:
59 * 1) A get() API for returning the stored pointer value.
60 * 2) An set() API for storing a pointer value.
61 * 3) An element_type typedef to define the type this points to.
62 * 4) An operator<() to support pointer comparison.
63 * 5) An operator==() to support pointer comparison.
64 */
65 template<typename _Tp>
66 class _Std_pointer_impl
67 {
68 public:
69 // the type this pointer points to.
70 typedef _Tp element_type;
71
72 // A method to fetch the pointer value as a standard T* value;
73 inline _Tp*
74 get() const
75 { return _M_value; }
76
77 // A method to set the pointer value, from a standard T* value;
78 inline void
79 set(element_type* __arg)
80 { _M_value = __arg; }
81
82 // Comparison of pointers
83 inline bool
84 operator<(const _Std_pointer_impl& __rarg) const
85 { return (_M_value < __rarg._M_value); }
86
87 inline bool
88 operator==(const _Std_pointer_impl& __rarg) const
89 { return (_M_value == __rarg._M_value); }
90
91 private:
92 element_type* _M_value;
93 };
94
95 /**
96 * @brief A storage policy for use with _Pointer_adapter<> which stores
97 * the pointer's address as an offset value which is relative to
98 * its own address.
99 *
100 * This is intended for pointers within shared memory regions which
101 * might be mapped at different addresses by different processes.
102 * For null pointers, a value of 1 is used. (0 is legitimate
103 * sometimes for nodes in circularly linked lists) This value was
104 * chosen as the least likely to generate an incorrect null, As
105 * there is no reason why any normal pointer would point 1 byte into
106 * its own pointer address.
107 */
108 template<typename _Tp>
109 class _Relative_pointer_impl
110 {
111 public:
112 typedef _Tp element_type;
113
114 _Tp*
115 get() const
116 {
117 if (_M_diff == 1)
118 return 0;
119 else
120 return reinterpret_cast<_Tp*>(reinterpret_cast<_UIntPtrType>(this)
121 + _M_diff);
122 }
123
124 void
125 set(_Tp* __arg)
126 {
127 if (!__arg)
128 _M_diff = 1;
129 else
130 _M_diff = reinterpret_cast<_UIntPtrType>(__arg)
131 - reinterpret_cast<_UIntPtrType>(this);
132 }
133
134 // Comparison of pointers
135 inline bool
136 operator<(const _Relative_pointer_impl& __rarg) const
137 { return (reinterpret_cast<_UIntPtrType>(this->get())
138 < reinterpret_cast<_UIntPtrType>(__rarg.get())); }
139
140 inline bool
141 operator==(const _Relative_pointer_impl& __rarg) const
142 { return (reinterpret_cast<_UIntPtrType>(this->get())
143 == reinterpret_cast<_UIntPtrType>(__rarg.get())); }
144
145 private:
146 #ifdef _GLIBCXX_USE_LONG_LONG
147 typedef __gnu_cxx::__conditional_type<
148 (sizeof(unsigned long) >= sizeof(void*)),
149 unsigned long, unsigned long long>::__type _UIntPtrType;
150 #else
151 typedef unsigned long _UIntPtrType;
152 #endif
153 _UIntPtrType _M_diff;
154 };
155
156 /**
157 * Relative_pointer_impl needs a specialization for const T because of
158 * the casting done during pointer arithmetic.
159 */
160 template<typename _Tp>
161 class _Relative_pointer_impl<const _Tp>
162 {
163 public:
164 typedef const _Tp element_type;
165
166 const _Tp*
167 get() const
168 {
169 if (_M_diff == 1)
170 return 0;
171 else
172 return reinterpret_cast<const _Tp*>
173 (reinterpret_cast<_UIntPtrType>(this) + _M_diff);
174 }
175
176 void
177 set(const _Tp* __arg)
178 {
179 if (!__arg)
180 _M_diff = 1;
181 else
182 _M_diff = reinterpret_cast<_UIntPtrType>(__arg)
183 - reinterpret_cast<_UIntPtrType>(this);
184 }
185
186 // Comparison of pointers
187 inline bool
188 operator<(const _Relative_pointer_impl& __rarg) const
189 { return (reinterpret_cast<_UIntPtrType>(this->get())
190 < reinterpret_cast<_UIntPtrType>(__rarg.get())); }
191
192 inline bool
193 operator==(const _Relative_pointer_impl& __rarg) const
194 { return (reinterpret_cast<_UIntPtrType>(this->get())
195 == reinterpret_cast<_UIntPtrType>(__rarg.get())); }
196
197 private:
198 #ifdef _GLIBCXX_USE_LONG_LONG
199 typedef __gnu_cxx::__conditional_type<
200 (sizeof(unsigned long) >= sizeof(void*)),
201 unsigned long, unsigned long long>::__type _UIntPtrType;
202 #else
203 typedef unsigned long _UIntPtrType;
204 #endif
205 _UIntPtrType _M_diff;
206 };
207
208 /**
209 * The specialization on this type helps resolve the problem of
210 * reference to void, and eliminates the need to specialize
211 * _Pointer_adapter for cases of void*, const void*, and so on.
212 */
213 struct _Invalid_type { };
214
215 template<typename _Tp>
216 struct _Reference_type
217 { typedef _Tp& reference; };
218
219 template<>
220 struct _Reference_type<void>
221 { typedef _Invalid_type& reference; };
222
223 template<>
224 struct _Reference_type<const void>
225 { typedef const _Invalid_type& reference; };
226
227 template<>
228 struct _Reference_type<volatile void>
229 { typedef volatile _Invalid_type& reference; };
230
231 template<>
232 struct _Reference_type<volatile const void>
233 { typedef const volatile _Invalid_type& reference; };
234
235 /**
236 * This structure accommodates the way in which
237 * std::iterator_traits<> is normally specialized for const T*, so
238 * that value_type is still T.
239 */
240 template<typename _Tp>
241 struct _Unqualified_type
242 { typedef _Tp type; };
243
244 template<typename _Tp>
245 struct _Unqualified_type<const _Tp>
246 { typedef _Tp type; };
247
248 /**
249 * The following provides an 'alternative pointer' that works with
250 * the containers when specified as the pointer typedef of the
251 * allocator.
252 *
253 * The pointer type used with the containers doesn't have to be this
254 * class, but it must support the implicit conversions, pointer
255 * arithmetic, comparison operators, etc. that are supported by this
256 * class, and avoid raising compile-time ambiguities. Because
257 * creating a working pointer can be challenging, this pointer
258 * template was designed to wrapper an easier storage policy type,
259 * so that it becomes reusable for creating other pointer types.
260 *
261 * A key point of this class is also that it allows container
262 * writers to 'assume' Allocator::pointer is a typedef for a normal
263 * pointer. This class supports most of the conventions of a true
264 * pointer, and can, for instance handle implicit conversion to
265 * const and base class pointer types. The only impositions on
266 * container writers to support extended pointers are: 1) use the
267 * Allocator::pointer typedef appropriately for pointer types. 2)
268 * if you need pointer casting, use the __pointer_cast<> functions
269 * from ext/cast.h. This allows pointer cast operations to be
270 * overloaded as necessary by custom pointers.
271 *
272 * Note: The const qualifier works with this pointer adapter as
273 * follows:
274 *
275 * _Tp* == _Pointer_adapter<_Std_pointer_impl<_Tp> >;
276 * const _Tp* == _Pointer_adapter<_Std_pointer_impl<const _Tp> >;
277 * _Tp* const == const _Pointer_adapter<_Std_pointer_impl<_Tp> >;
278 * const _Tp* const == const _Pointer_adapter<_Std_pointer_impl<const _Tp> >;
279 */
280 template<typename _Storage_policy>
281 class _Pointer_adapter : public _Storage_policy
282 {
283 public:
284 typedef typename _Storage_policy::element_type element_type;
285
286 // These are needed for iterator_traits
287 typedef std::random_access_iterator_tag iterator_category;
288 typedef typename _Unqualified_type<element_type>::type value_type;
289 typedef std::ptrdiff_t difference_type;
290 typedef _Pointer_adapter pointer;
291 typedef typename _Reference_type<element_type>::reference reference;
292
293 // Reminder: 'const' methods mean that the method is valid when the
294 // pointer is immutable, and has nothing to do with whether the
295 // 'pointee' is const.
296
297 // Default Constructor (Convert from element_type*)
298 _Pointer_adapter(element_type* __arg = 0)
299 { _Storage_policy::set(__arg); }
300
301 // Copy constructor from _Pointer_adapter of same type.
302 _Pointer_adapter(const _Pointer_adapter& __arg)
303 { _Storage_policy::set(__arg.get()); }
304
305 // Convert from _Up* if conversion to element_type* is valid.
306 template<typename _Up>
307 _Pointer_adapter(_Up* __arg)
308 { _Storage_policy::set(__arg); }
309
310 // Conversion from another _Pointer_adapter if _Up if static cast is
311 // valid.
312 template<typename _Up>
313 _Pointer_adapter(const _Pointer_adapter<_Up>& __arg)
314 { _Storage_policy::set(__arg.get()); }
315
316 // Destructor
317 ~_Pointer_adapter() { }
318
319 // Assignment operator
320 _Pointer_adapter&
321 operator=(const _Pointer_adapter& __arg)
322 {
323 _Storage_policy::set(__arg.get());
324 return *this;
325 }
326
327 template<typename _Up>
328 _Pointer_adapter&
329 operator=(const _Pointer_adapter<_Up>& __arg)
330 {
331 _Storage_policy::set(__arg.get());
332 return *this;
333 }
334
335 template<typename _Up>
336 _Pointer_adapter&
337 operator=(_Up* __arg)
338 {
339 _Storage_policy::set(__arg);
340 return *this;
341 }
342
343 // Operator*, returns element_type&
344 inline reference
345 operator*() const
346 { return *(_Storage_policy::get()); }
347
348 // Operator->, returns element_type*
349 inline element_type*
350 operator->() const
351 { return _Storage_policy::get(); }
352
353 // Operator[], returns a element_type& to the item at that loc.
354 inline reference
355 operator[](std::ptrdiff_t __index) const
356 { return _Storage_policy::get()[__index]; }
357
358 // To allow implicit conversion to "bool", for "if (ptr)..."
359 private:
360 typedef element_type*(_Pointer_adapter::*__unspecified_bool_type)() const;
361
362 public:
363 operator __unspecified_bool_type() const
364 {
365 return _Storage_policy::get() == 0 ? 0 :
366 &_Pointer_adapter::operator->;
367 }
368
369 // ! operator (for: if (!ptr)...)
370 inline bool
371 operator!() const
372 { return (_Storage_policy::get() == 0); }
373
374 // Pointer differences
375 inline friend std::ptrdiff_t
376 operator-(const _Pointer_adapter& __lhs, element_type* __rhs)
377 { return (__lhs.get() - __rhs); }
378
379 inline friend std::ptrdiff_t
380 operator-(element_type* __lhs, const _Pointer_adapter& __rhs)
381 { return (__lhs - __rhs.get()); }
382
383 template<typename _Up>
384 inline friend std::ptrdiff_t
385 operator-(const _Pointer_adapter& __lhs, _Up* __rhs)
386 { return (__lhs.get() - __rhs); }
387
388 template<typename _Up>
389 inline friend std::ptrdiff_t
390 operator-(_Up* __lhs, const _Pointer_adapter& __rhs)
391 { return (__lhs - __rhs.get()); }
392
393 template<typename _Up>
394 inline std::ptrdiff_t
395 operator-(const _Pointer_adapter<_Up>& __rhs) const
396 { return (_Storage_policy::get() - __rhs.get()); }
397
398 // Pointer math
399 // Note: There is a reason for all this overloading based on different
400 // integer types. In some libstdc++-v3 test cases, a templated
401 // operator+ is declared which can match any types. This operator
402 // tends to "steal" the recognition of _Pointer_adapter's own operator+
403 // unless the integer type matches perfectly.
404
405 #define _CXX_POINTER_ARITH_OPERATOR_SET(INT_TYPE) \
406 inline friend _Pointer_adapter \
407 operator+(const _Pointer_adapter& __lhs, INT_TYPE __offset) \
408 { return _Pointer_adapter(__lhs.get() + __offset); } \
409 \
410 inline friend _Pointer_adapter \
411 operator+(INT_TYPE __offset, const _Pointer_adapter& __rhs) \
412 { return _Pointer_adapter(__rhs.get() + __offset); } \
413 \
414 inline friend _Pointer_adapter \
415 operator-(const _Pointer_adapter& __lhs, INT_TYPE __offset) \
416 { return _Pointer_adapter(__lhs.get() - __offset); } \
417 \
418 inline _Pointer_adapter& \
419 operator+=(INT_TYPE __offset) \
420 { \
421 _Storage_policy::set(_Storage_policy::get() + __offset); \
422 return *this; \
423 } \
424 \
425 inline _Pointer_adapter& \
426 operator-=(INT_TYPE __offset) \
427 { \
428 _Storage_policy::set(_Storage_policy::get() - __offset); \
429 return *this; \
430 } \
431 // END of _CXX_POINTER_ARITH_OPERATOR_SET macro
432
433 // Expand into the various pointer arithmetic operators needed.
434 _CXX_POINTER_ARITH_OPERATOR_SET(short);
435 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned short);
436 _CXX_POINTER_ARITH_OPERATOR_SET(int);
437 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned int);
438 _CXX_POINTER_ARITH_OPERATOR_SET(long);
439 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long);
440
441 // Mathematical Manipulators
442 inline _Pointer_adapter&
443 operator++()
444 {
445 _Storage_policy::set(_Storage_policy::get() + 1);
446 return *this;
447 }
448
449 inline _Pointer_adapter
450 operator++(int)
451 {
452 _Pointer_adapter tmp(*this);
453 _Storage_policy::set(_Storage_policy::get() + 1);
454 return tmp;
455 }
456
457 inline _Pointer_adapter&
458 operator--()
459 {
460 _Storage_policy::set(_Storage_policy::get() - 1);
461 return *this;
462 }
463
464 inline _Pointer_adapter
465 operator--(int)
466 {
467 _Pointer_adapter tmp(*this);
468 _Storage_policy::set(_Storage_policy::get() - 1);
469 return tmp;
470 }
471
472 }; // class _Pointer_adapter
473
474
475 #define _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(OPERATOR) \
476 template<typename _Tp1, typename _Tp2> \
477 inline bool \
478 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, _Tp2 __rhs) \
479 { return __lhs.get() OPERATOR __rhs; } \
480 \
481 template<typename _Tp1, typename _Tp2> \
482 inline bool \
483 operator OPERATOR(_Tp1 __lhs, const _Pointer_adapter<_Tp2>& __rhs) \
484 { return __lhs OPERATOR __rhs.get(); } \
485 \
486 template<typename _Tp1, typename _Tp2> \
487 inline bool \
488 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, \
489 const _Pointer_adapter<_Tp2>& __rhs) \
490 { return __lhs.get() OPERATOR __rhs.get(); } \
491 \
492 // End GCC_CXX_POINTER_COMPARISON_OPERATION_SET Macro
493
494 // Expand into the various comparison operators needed.
495 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(==)
496 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(!=)
497 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<)
498 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<=)
499 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>)
500 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>=)
501
502 // These are here for expressions like "ptr == 0", "ptr != 0"
503 template<typename _Tp>
504 inline bool
505 operator==(const _Pointer_adapter<_Tp>& __lhs, int __rhs)
506 { return __lhs.get() == reinterpret_cast<void*>(__rhs); }
507
508 template<typename _Tp>
509 inline bool
510 operator==(int __lhs, const _Pointer_adapter<_Tp>& __rhs)
511 { return __rhs.get() == reinterpret_cast<void*>(__lhs); }
512
513 template<typename _Tp>
514 inline bool
515 operator!=(const _Pointer_adapter<_Tp>& __lhs, int __rhs)
516 { return __lhs.get() != reinterpret_cast<void*>(__rhs); }
517
518 template<typename _Tp>
519 inline bool
520 operator!=(int __lhs, const _Pointer_adapter<_Tp>& __rhs)
521 { return __rhs.get() != reinterpret_cast<void*>(__lhs); }
522
523 /**
524 * Comparison operators for _Pointer_adapter defer to the base class'
525 * comparison operators, when possible.
526 */
527 template<typename _Tp>
528 inline bool
529 operator==(const _Pointer_adapter<_Tp>& __lhs,
530 const _Pointer_adapter<_Tp>& __rhs)
531 { return __lhs._Tp::operator==(__rhs); }
532
533 template<typename _Tp>
534 inline bool
535 operator<=(const _Pointer_adapter<_Tp>& __lhs,
536 const _Pointer_adapter<_Tp>& __rhs)
537 { return __lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs); }
538
539 template<typename _Tp>
540 inline bool
541 operator!=(const _Pointer_adapter<_Tp>& __lhs,
542 const _Pointer_adapter<_Tp>& __rhs)
543 { return !(__lhs._Tp::operator==(__rhs)); }
544
545 template<typename _Tp>
546 inline bool
547 operator>(const _Pointer_adapter<_Tp>& __lhs,
548 const _Pointer_adapter<_Tp>& __rhs)
549 { return !(__lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs)); }
550
551 template<typename _Tp>
552 inline bool
553 operator>=(const _Pointer_adapter<_Tp>& __lhs,
554 const _Pointer_adapter<_Tp>& __rhs)
555 { return !(__lhs._Tp::operator<(__rhs)); }
556
557 template<typename _CharT, typename _Traits, typename _StoreT>
558 inline std::basic_ostream<_CharT, _Traits>&
559 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
560 const _Pointer_adapter<_StoreT>& __p)
561 { return (__os << __p.get()); }
562
563 _GLIBCXX_END_NAMESPACE_VERSION
564 } // namespace
565
566 #if __cplusplus >= 201103L
567 namespace std _GLIBCXX_VISIBILITY(default)
568 {
569 _GLIBCXX_BEGIN_NAMESPACE_VERSION
570
571 template<typename _Storage_policy>
572 struct pointer_traits<__gnu_cxx::_Pointer_adapter<_Storage_policy>>
573 {
574 /// The pointer type
575 typedef __gnu_cxx::_Pointer_adapter<_Storage_policy> pointer;
576 /// The type pointed to
577 typedef typename pointer::element_type element_type;
578 /// Type used to represent the difference between two pointers
579 typedef typename pointer::difference_type difference_type;
580
581 template<typename _Up>
582 using rebind = typename __gnu_cxx::_Pointer_adapter<
583 typename pointer_traits<_Storage_policy>::rebind<_Up>>;
584
585 static pointer pointer_to(typename pointer::reference __r) noexcept
586 { return pointer(std::addressof(__r)); }
587 };
588
589 _GLIBCXX_END_NAMESPACE_VERSION
590 } // namespace
591 #endif
592
593 #endif // _POINTER_H