libstdc++
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00001 // Custom pointer adapter and sample storage policies 00002 00003 // Copyright (C) 2008-2019 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 /** 00026 * @file ext/pointer.h 00027 * This file is a GNU extension to the Standard C++ Library. 00028 * 00029 * @author Bob Walters 00030 * 00031 * Provides reusable _Pointer_adapter for assisting in the development of 00032 * custom pointer types that can be used with the standard containers via 00033 * the allocator::pointer and allocator::const_pointer typedefs. 00034 */ 00035 00036 #ifndef _POINTER_H 00037 #define _POINTER_H 1 00038 00039 #pragma GCC system_header 00040 00041 #include <iosfwd> 00042 #include <bits/stl_iterator_base_types.h> 00043 #include <ext/cast.h> 00044 #include <ext/type_traits.h> 00045 #if __cplusplus >= 201103L 00046 # include <bits/move.h> 00047 # include <bits/ptr_traits.h> 00048 #endif 00049 00050 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 00051 { 00052 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00053 00054 /** 00055 * @brief A storage policy for use with _Pointer_adapter<> which yields a 00056 * standard pointer. 00057 * 00058 * A _Storage_policy is required to provide 4 things: 00059 * 1) A get() API for returning the stored pointer value. 00060 * 2) An set() API for storing a pointer value. 00061 * 3) An element_type typedef to define the type this points to. 00062 * 4) An operator<() to support pointer comparison. 00063 * 5) An operator==() to support pointer comparison. 00064 */ 00065 template<typename _Tp> 00066 class _Std_pointer_impl 00067 { 00068 public: 00069 // the type this pointer points to. 00070 typedef _Tp element_type; 00071 00072 // A method to fetch the pointer value as a standard T* value; 00073 inline _Tp* 00074 get() const 00075 { return _M_value; } 00076 00077 // A method to set the pointer value, from a standard T* value; 00078 inline void 00079 set(element_type* __arg) 00080 { _M_value = __arg; } 00081 00082 // Comparison of pointers 00083 inline bool 00084 operator<(const _Std_pointer_impl& __rarg) const 00085 { return (_M_value < __rarg._M_value); } 00086 00087 inline bool 00088 operator==(const _Std_pointer_impl& __rarg) const 00089 { return (_M_value == __rarg._M_value); } 00090 00091 private: 00092 element_type* _M_value; 00093 }; 00094 00095 /** 00096 * @brief A storage policy for use with _Pointer_adapter<> which stores 00097 * the pointer's address as an offset value which is relative to 00098 * its own address. 00099 * 00100 * This is intended for pointers within shared memory regions which 00101 * might be mapped at different addresses by different processes. 00102 * For null pointers, a value of 1 is used. (0 is legitimate 00103 * sometimes for nodes in circularly linked lists) This value was 00104 * chosen as the least likely to generate an incorrect null, As 00105 * there is no reason why any normal pointer would point 1 byte into 00106 * its own pointer address. 00107 */ 00108 template<typename _Tp> 00109 class _Relative_pointer_impl 00110 { 00111 public: 00112 typedef _Tp element_type; 00113 00114 _Tp* 00115 get() const 00116 { 00117 if (_M_diff == 1) 00118 return 0; 00119 else 00120 return reinterpret_cast<_Tp*>(reinterpret_cast<_UIntPtrType>(this) 00121 + _M_diff); 00122 } 00123 00124 void 00125 set(_Tp* __arg) 00126 { 00127 if (!__arg) 00128 _M_diff = 1; 00129 else 00130 _M_diff = reinterpret_cast<_UIntPtrType>(__arg) 00131 - reinterpret_cast<_UIntPtrType>(this); 00132 } 00133 00134 // Comparison of pointers 00135 inline bool 00136 operator<(const _Relative_pointer_impl& __rarg) const 00137 { return (reinterpret_cast<_UIntPtrType>(this->get()) 00138 < reinterpret_cast<_UIntPtrType>(__rarg.get())); } 00139 00140 inline bool 00141 operator==(const _Relative_pointer_impl& __rarg) const 00142 { return (reinterpret_cast<_UIntPtrType>(this->get()) 00143 == reinterpret_cast<_UIntPtrType>(__rarg.get())); } 00144 00145 private: 00146 #ifdef _GLIBCXX_USE_LONG_LONG 00147 typedef __gnu_cxx::__conditional_type< 00148 (sizeof(unsigned long) >= sizeof(void*)), 00149 unsigned long, unsigned long long>::__type _UIntPtrType; 00150 #else 00151 typedef unsigned long _UIntPtrType; 00152 #endif 00153 _UIntPtrType _M_diff; 00154 }; 00155 00156 /** 00157 * Relative_pointer_impl needs a specialization for const T because of 00158 * the casting done during pointer arithmetic. 00159 */ 00160 template<typename _Tp> 00161 class _Relative_pointer_impl<const _Tp> 00162 { 00163 public: 00164 typedef const _Tp element_type; 00165 00166 const _Tp* 00167 get() const 00168 { 00169 if (_M_diff == 1) 00170 return 0; 00171 else 00172 return reinterpret_cast<const _Tp*> 00173 (reinterpret_cast<_UIntPtrType>(this) + _M_diff); 00174 } 00175 00176 void 00177 set(const _Tp* __arg) 00178 { 00179 if (!__arg) 00180 _M_diff = 1; 00181 else 00182 _M_diff = reinterpret_cast<_UIntPtrType>(__arg) 00183 - reinterpret_cast<_UIntPtrType>(this); 00184 } 00185 00186 // Comparison of pointers 00187 inline bool 00188 operator<(const _Relative_pointer_impl& __rarg) const 00189 { return (reinterpret_cast<_UIntPtrType>(this->get()) 00190 < reinterpret_cast<_UIntPtrType>(__rarg.get())); } 00191 00192 inline bool 00193 operator==(const _Relative_pointer_impl& __rarg) const 00194 { return (reinterpret_cast<_UIntPtrType>(this->get()) 00195 == reinterpret_cast<_UIntPtrType>(__rarg.get())); } 00196 00197 private: 00198 #ifdef _GLIBCXX_USE_LONG_LONG 00199 typedef __gnu_cxx::__conditional_type< 00200 (sizeof(unsigned long) >= sizeof(void*)), 00201 unsigned long, unsigned long long>::__type _UIntPtrType; 00202 #else 00203 typedef unsigned long _UIntPtrType; 00204 #endif 00205 _UIntPtrType _M_diff; 00206 }; 00207 00208 /** 00209 * The specialization on this type helps resolve the problem of 00210 * reference to void, and eliminates the need to specialize 00211 * _Pointer_adapter for cases of void*, const void*, and so on. 00212 */ 00213 struct _Invalid_type { }; 00214 00215 template<typename _Tp> 00216 struct _Reference_type 00217 { typedef _Tp& reference; }; 00218 00219 template<> 00220 struct _Reference_type<void> 00221 { typedef _Invalid_type& reference; }; 00222 00223 template<> 00224 struct _Reference_type<const void> 00225 { typedef const _Invalid_type& reference; }; 00226 00227 template<> 00228 struct _Reference_type<volatile void> 00229 { typedef volatile _Invalid_type& reference; }; 00230 00231 template<> 00232 struct _Reference_type<volatile const void> 00233 { typedef const volatile _Invalid_type& reference; }; 00234 00235 /** 00236 * This structure accommodates the way in which 00237 * std::iterator_traits<> is normally specialized for const T*, so 00238 * that value_type is still T. 00239 */ 00240 template<typename _Tp> 00241 struct _Unqualified_type 00242 { typedef _Tp type; }; 00243 00244 template<typename _Tp> 00245 struct _Unqualified_type<const _Tp> 00246 { typedef _Tp type; }; 00247 00248 /** 00249 * The following provides an 'alternative pointer' that works with 00250 * the containers when specified as the pointer typedef of the 00251 * allocator. 00252 * 00253 * The pointer type used with the containers doesn't have to be this 00254 * class, but it must support the implicit conversions, pointer 00255 * arithmetic, comparison operators, etc. that are supported by this 00256 * class, and avoid raising compile-time ambiguities. Because 00257 * creating a working pointer can be challenging, this pointer 00258 * template was designed to wrapper an easier storage policy type, 00259 * so that it becomes reusable for creating other pointer types. 00260 * 00261 * A key point of this class is also that it allows container 00262 * writers to 'assume' Allocator::pointer is a typedef for a normal 00263 * pointer. This class supports most of the conventions of a true 00264 * pointer, and can, for instance handle implicit conversion to 00265 * const and base class pointer types. The only impositions on 00266 * container writers to support extended pointers are: 1) use the 00267 * Allocator::pointer typedef appropriately for pointer types. 2) 00268 * if you need pointer casting, use the __pointer_cast<> functions 00269 * from ext/cast.h. This allows pointer cast operations to be 00270 * overloaded as necessary by custom pointers. 00271 * 00272 * Note: The const qualifier works with this pointer adapter as 00273 * follows: 00274 * 00275 * _Tp* == _Pointer_adapter<_Std_pointer_impl<_Tp> >; 00276 * const _Tp* == _Pointer_adapter<_Std_pointer_impl<const _Tp> >; 00277 * _Tp* const == const _Pointer_adapter<_Std_pointer_impl<_Tp> >; 00278 * const _Tp* const == const _Pointer_adapter<_Std_pointer_impl<const _Tp> >; 00279 */ 00280 template<typename _Storage_policy> 00281 class _Pointer_adapter : public _Storage_policy 00282 { 00283 public: 00284 typedef typename _Storage_policy::element_type element_type; 00285 00286 // These are needed for iterator_traits 00287 typedef std::random_access_iterator_tag iterator_category; 00288 typedef typename _Unqualified_type<element_type>::type value_type; 00289 typedef std::ptrdiff_t difference_type; 00290 typedef _Pointer_adapter pointer; 00291 typedef typename _Reference_type<element_type>::reference reference; 00292 00293 // Reminder: 'const' methods mean that the method is valid when the 00294 // pointer is immutable, and has nothing to do with whether the 00295 // 'pointee' is const. 00296 00297 // Default Constructor (Convert from element_type*) 00298 _Pointer_adapter(element_type* __arg = 0) 00299 { _Storage_policy::set(__arg); } 00300 00301 // Copy constructor from _Pointer_adapter of same type. 00302 _Pointer_adapter(const _Pointer_adapter& __arg) 00303 { _Storage_policy::set(__arg.get()); } 00304 00305 // Convert from _Up* if conversion to element_type* is valid. 00306 template<typename _Up> 00307 _Pointer_adapter(_Up* __arg) 00308 { _Storage_policy::set(__arg); } 00309 00310 // Conversion from another _Pointer_adapter if _Up if static cast is 00311 // valid. 00312 template<typename _Up> 00313 _Pointer_adapter(const _Pointer_adapter<_Up>& __arg) 00314 { _Storage_policy::set(__arg.get()); } 00315 00316 // Destructor 00317 ~_Pointer_adapter() { } 00318 00319 // Assignment operator 00320 _Pointer_adapter& 00321 operator=(const _Pointer_adapter& __arg) 00322 { 00323 _Storage_policy::set(__arg.get()); 00324 return *this; 00325 } 00326 00327 template<typename _Up> 00328 _Pointer_adapter& 00329 operator=(const _Pointer_adapter<_Up>& __arg) 00330 { 00331 _Storage_policy::set(__arg.get()); 00332 return *this; 00333 } 00334 00335 template<typename _Up> 00336 _Pointer_adapter& 00337 operator=(_Up* __arg) 00338 { 00339 _Storage_policy::set(__arg); 00340 return *this; 00341 } 00342 00343 // Operator*, returns element_type& 00344 inline reference 00345 operator*() const 00346 { return *(_Storage_policy::get()); } 00347 00348 // Operator->, returns element_type* 00349 inline element_type* 00350 operator->() const 00351 { return _Storage_policy::get(); } 00352 00353 // Operator[], returns a element_type& to the item at that loc. 00354 inline reference 00355 operator[](std::ptrdiff_t __index) const 00356 { return _Storage_policy::get()[__index]; } 00357 00358 // To allow implicit conversion to "bool", for "if (ptr)..." 00359 #if __cplusplus >= 201103L 00360 explicit operator bool() const { return _Storage_policy::get() != 0; } 00361 #else 00362 private: 00363 typedef element_type*(_Pointer_adapter::*__unspecified_bool_type)() const; 00364 00365 public: 00366 operator __unspecified_bool_type() const 00367 { 00368 return _Storage_policy::get() == 0 ? 0 : 00369 &_Pointer_adapter::operator->; 00370 } 00371 00372 // ! operator (for: if (!ptr)...) 00373 inline bool 00374 operator!() const 00375 { return (_Storage_policy::get() == 0); } 00376 #endif 00377 00378 // Pointer differences 00379 inline friend std::ptrdiff_t 00380 operator-(const _Pointer_adapter& __lhs, element_type* __rhs) 00381 { return (__lhs.get() - __rhs); } 00382 00383 inline friend std::ptrdiff_t 00384 operator-(element_type* __lhs, const _Pointer_adapter& __rhs) 00385 { return (__lhs - __rhs.get()); } 00386 00387 template<typename _Up> 00388 inline friend std::ptrdiff_t 00389 operator-(const _Pointer_adapter& __lhs, _Up* __rhs) 00390 { return (__lhs.get() - __rhs); } 00391 00392 template<typename _Up> 00393 inline friend std::ptrdiff_t 00394 operator-(_Up* __lhs, const _Pointer_adapter& __rhs) 00395 { return (__lhs - __rhs.get()); } 00396 00397 template<typename _Up> 00398 inline std::ptrdiff_t 00399 operator-(const _Pointer_adapter<_Up>& __rhs) const 00400 { return (_Storage_policy::get() - __rhs.get()); } 00401 00402 // Pointer math 00403 // Note: There is a reason for all this overloading based on different 00404 // integer types. In some libstdc++-v3 test cases, a templated 00405 // operator+ is declared which can match any types. This operator 00406 // tends to "steal" the recognition of _Pointer_adapter's own operator+ 00407 // unless the integer type matches perfectly. 00408 00409 #define _CXX_POINTER_ARITH_OPERATOR_SET(INT_TYPE) \ 00410 inline friend _Pointer_adapter \ 00411 operator+(const _Pointer_adapter& __lhs, INT_TYPE __offset) \ 00412 { return _Pointer_adapter(__lhs.get() + __offset); } \ 00413 \ 00414 inline friend _Pointer_adapter \ 00415 operator+(INT_TYPE __offset, const _Pointer_adapter& __rhs) \ 00416 { return _Pointer_adapter(__rhs.get() + __offset); } \ 00417 \ 00418 inline friend _Pointer_adapter \ 00419 operator-(const _Pointer_adapter& __lhs, INT_TYPE __offset) \ 00420 { return _Pointer_adapter(__lhs.get() - __offset); } \ 00421 \ 00422 inline _Pointer_adapter& \ 00423 operator+=(INT_TYPE __offset) \ 00424 { \ 00425 _Storage_policy::set(_Storage_policy::get() + __offset); \ 00426 return *this; \ 00427 } \ 00428 \ 00429 inline _Pointer_adapter& \ 00430 operator-=(INT_TYPE __offset) \ 00431 { \ 00432 _Storage_policy::set(_Storage_policy::get() - __offset); \ 00433 return *this; \ 00434 } \ 00435 // END of _CXX_POINTER_ARITH_OPERATOR_SET macro 00436 00437 // Expand into the various pointer arithmetic operators needed. 00438 _CXX_POINTER_ARITH_OPERATOR_SET(short); 00439 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned short); 00440 _CXX_POINTER_ARITH_OPERATOR_SET(int); 00441 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned int); 00442 _CXX_POINTER_ARITH_OPERATOR_SET(long); 00443 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long); 00444 #ifdef _GLIBCXX_USE_LONG_LONG 00445 _CXX_POINTER_ARITH_OPERATOR_SET(long long); 00446 _CXX_POINTER_ARITH_OPERATOR_SET(unsigned long long); 00447 #endif 00448 00449 // Mathematical Manipulators 00450 inline _Pointer_adapter& 00451 operator++() 00452 { 00453 _Storage_policy::set(_Storage_policy::get() + 1); 00454 return *this; 00455 } 00456 00457 inline _Pointer_adapter 00458 operator++(int) 00459 { 00460 _Pointer_adapter __tmp(*this); 00461 _Storage_policy::set(_Storage_policy::get() + 1); 00462 return __tmp; 00463 } 00464 00465 inline _Pointer_adapter& 00466 operator--() 00467 { 00468 _Storage_policy::set(_Storage_policy::get() - 1); 00469 return *this; 00470 } 00471 00472 inline _Pointer_adapter 00473 operator--(int) 00474 { 00475 _Pointer_adapter __tmp(*this); 00476 _Storage_policy::set(_Storage_policy::get() - 1); 00477 return __tmp; 00478 } 00479 00480 }; // class _Pointer_adapter 00481 00482 00483 #define _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(OPERATOR) \ 00484 template<typename _Tp1, typename _Tp2> \ 00485 inline bool \ 00486 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, _Tp2 __rhs) \ 00487 { return __lhs.get() OPERATOR __rhs; } \ 00488 \ 00489 template<typename _Tp1, typename _Tp2> \ 00490 inline bool \ 00491 operator OPERATOR(_Tp1 __lhs, const _Pointer_adapter<_Tp2>& __rhs) \ 00492 { return __lhs OPERATOR __rhs.get(); } \ 00493 \ 00494 template<typename _Tp1, typename _Tp2> \ 00495 inline bool \ 00496 operator OPERATOR(const _Pointer_adapter<_Tp1>& __lhs, \ 00497 const _Pointer_adapter<_Tp2>& __rhs) \ 00498 { return __lhs.get() OPERATOR __rhs.get(); } \ 00499 \ 00500 // End GCC_CXX_POINTER_COMPARISON_OPERATION_SET Macro 00501 00502 // Expand into the various comparison operators needed. 00503 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(==) 00504 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(!=) 00505 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<) 00506 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(<=) 00507 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>) 00508 _GCC_CXX_POINTER_COMPARISON_OPERATION_SET(>=) 00509 00510 // These are here for expressions like "ptr == 0", "ptr != 0" 00511 template<typename _Tp> 00512 inline bool 00513 operator==(const _Pointer_adapter<_Tp>& __lhs, int __rhs) 00514 { return __lhs.get() == reinterpret_cast<void*>(__rhs); } 00515 00516 template<typename _Tp> 00517 inline bool 00518 operator==(int __lhs, const _Pointer_adapter<_Tp>& __rhs) 00519 { return __rhs.get() == reinterpret_cast<void*>(__lhs); } 00520 00521 template<typename _Tp> 00522 inline bool 00523 operator!=(const _Pointer_adapter<_Tp>& __lhs, int __rhs) 00524 { return __lhs.get() != reinterpret_cast<void*>(__rhs); } 00525 00526 template<typename _Tp> 00527 inline bool 00528 operator!=(int __lhs, const _Pointer_adapter<_Tp>& __rhs) 00529 { return __rhs.get() != reinterpret_cast<void*>(__lhs); } 00530 00531 /** 00532 * Comparison operators for _Pointer_adapter defer to the base class' 00533 * comparison operators, when possible. 00534 */ 00535 template<typename _Tp> 00536 inline bool 00537 operator==(const _Pointer_adapter<_Tp>& __lhs, 00538 const _Pointer_adapter<_Tp>& __rhs) 00539 { return __lhs._Tp::operator==(__rhs); } 00540 00541 template<typename _Tp> 00542 inline bool 00543 operator<=(const _Pointer_adapter<_Tp>& __lhs, 00544 const _Pointer_adapter<_Tp>& __rhs) 00545 { return __lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs); } 00546 00547 template<typename _Tp> 00548 inline bool 00549 operator!=(const _Pointer_adapter<_Tp>& __lhs, 00550 const _Pointer_adapter<_Tp>& __rhs) 00551 { return !(__lhs._Tp::operator==(__rhs)); } 00552 00553 template<typename _Tp> 00554 inline bool 00555 operator>(const _Pointer_adapter<_Tp>& __lhs, 00556 const _Pointer_adapter<_Tp>& __rhs) 00557 { return !(__lhs._Tp::operator<(__rhs) || __lhs._Tp::operator==(__rhs)); } 00558 00559 template<typename _Tp> 00560 inline bool 00561 operator>=(const _Pointer_adapter<_Tp>& __lhs, 00562 const _Pointer_adapter<_Tp>& __rhs) 00563 { return !(__lhs._Tp::operator<(__rhs)); } 00564 00565 template<typename _CharT, typename _Traits, typename _StoreT> 00566 inline std::basic_ostream<_CharT, _Traits>& 00567 operator<<(std::basic_ostream<_CharT, _Traits>& __os, 00568 const _Pointer_adapter<_StoreT>& __p) 00569 { return (__os << __p.get()); } 00570 00571 _GLIBCXX_END_NAMESPACE_VERSION 00572 } // namespace 00573 00574 #if __cplusplus >= 201103L 00575 namespace std _GLIBCXX_VISIBILITY(default) 00576 { 00577 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00578 00579 template<typename _Storage_policy> 00580 struct pointer_traits<__gnu_cxx::_Pointer_adapter<_Storage_policy>> 00581 { 00582 /// The pointer type 00583 typedef __gnu_cxx::_Pointer_adapter<_Storage_policy> pointer; 00584 /// The type pointed to 00585 typedef typename pointer::element_type element_type; 00586 /// Type used to represent the difference between two pointers 00587 typedef typename pointer::difference_type difference_type; 00588 00589 template<typename _Up> 00590 using rebind = typename __gnu_cxx::_Pointer_adapter< 00591 typename pointer_traits<_Storage_policy>::template rebind<_Up>>; 00592 00593 static pointer pointer_to(typename pointer::reference __r) noexcept 00594 { return pointer(std::addressof(__r)); } 00595 }; 00596 00597 _GLIBCXX_END_NAMESPACE_VERSION 00598 } // namespace 00599 #endif 00600 00601 #endif // _POINTER_H