libstdc++-v3/include/ext/pointer.h

   1 // Custom pointer adapter and sample storage policies
   2
   3 // Copyright (C) 2008, 2009 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  * @author Bob Walters
  28  *
  29  * Provides reusable _Pointer_adapter for assisting in the development of
  30  * custom pointer types that can be used with the standard containers via
  31  * the allocator::pointer and allocator::const_pointer typedefs.
  32  */
  33
  34 #ifndef _POINTER_H
  35 #define _POINTER_H 1
  36
  37 #pragma GCC system_header
  38
  39 #include <iosfwd>
  40 #include <bits/stl_iterator_base_types.h>
  41 #include <ext/cast.h>
  42 #include <ext/type_traits.h>
  43
  44 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  45
  46   /**
  47    * @brief A storage policy for use with _Pointer_adapter<> which yields a
  48    *        standard pointer.
  49    *
  50    *  A _Storage_policy is required to provide 4 things:
  51    *    1) A get() API for returning the stored pointer value.
  52    *    2) An set() API for storing a pointer value.
  53    *    3) An element_type typedef to define the type this points to.
  54    *    4) An operator<() to support pointer comparison.
  55    *    5) An operator==() to support pointer comparison.
  56    */
  57   template<typename _Tp>
  58     class _Std_pointer_impl
  59     {
  60     public:
  61       // the type this pointer points to.
  62       typedef _Tp element_type;
  63
  64       // A method to fetch the pointer value as a standard T* value;
  65       inline _Tp*
  66       get() const
  67       { return _M_value; }
  68
  69       // A method to set the pointer value, from a standard T* value;
  70       inline void
  71       set(element_type* __arg)
  72       { _M_value = __arg; }
  73
  74       // Comparison of pointers
  75       inline bool
  76       operator<(const _Std_pointer_impl& __rarg) const
  77       { return (_M_value < __rarg._M_value); }
  78
  79       inline bool
  80       operator==(const _Std_pointer_impl& __rarg) const
  81       { return (_M_value == __rarg._M_value); }
  82
  83     private:
  84       element_type* _M_value;
  85     };
  86
  87   /**
  88    * @brief A storage policy for use with _Pointer_adapter<> which stores
  89    *        the pointer's address as an offset value which is relative to
  90    *        its own address.
  91    *
  92    * This is intended for pointers within shared memory regions which
  93    * might be mapped at different addresses by different processes.
  94    * For null pointers, a value of 1 is used.  (0 is legitimate
  95    * sometimes for nodes in circularly linked lists) This value was
  96    * chosen as the least likely to generate an incorrect null, As
  97    * there is no reason why any normal pointer would point 1 byte into
  98    * its own pointer address.
  99    */
 100   template<typename _Tp>
 101     class _Relative_pointer_impl
 102     {
 103     public:
 104       typedef _Tp element_type;
 105
 106       _Tp*
 107       get() const
 108       {
 109         if (_M_diff == 1)
 110           return 0;
 111         else
 112           return reinterpret_cast<_Tp*>(reinterpret_cast<_UIntPtrType>(this)
 113                                         + _M_diff);
 114       }
 115
 116       void
 117       set(_Tp* __arg)
 118       {
 119         if (!__arg)
 120           _M_diff = 1;
 121         else
 122           _M_diff = reinterpret_cast<_UIntPtrType>(__arg)
 123                     - reinterpret_cast<_UIntPtrType>(this);
 124       }
 125
 126       // Comparison of pointers
 127       inline bool
 128       operator<(const _Relative_pointer_impl& __rarg) const
 129       { return (reinterpret_cast<_UIntPtrType>(this->get())
 130                 < reinterpret_cast<_UIntPtrType>(__rarg.get())); }
 131
 132       inline bool
 133       operator==(const _Relative_pointer_impl& __rarg) const
 134       { return (reinterpret_cast<_UIntPtrType>(this->get())
 135                 == reinterpret_cast<_UIntPtrType>(__rarg.get())); }
 136
 137     private:
 138 #ifdef _GLIBCXX_USE_LONG_LONG
 139       typedef __gnu_cxx::__conditional_type<
 140          (sizeof(unsigned long) >= sizeof(void*)),
 141          unsigned long, unsigned long long>::__type _UIntPtrType;
 142 #else
 143       typedef unsigned long _UIntPtrType;
 144 #endif
 145       _UIntPtrType _M_diff;
 146     };
 147
 148   /**
 149    * Relative_pointer_impl needs a specialization for const T because of
 150    * the casting done during pointer arithmetic.
 151    */
 152   template<typename _Tp>
 153     class _Relative_pointer_impl<const _Tp>
 154     {
 155     public:
 156       typedef const _Tp element_type;
 157
 158       const _Tp*
 159       get() const
 160       {
 161         if (_M_diff == 1)
 162           return 0;
 163         else
 164           return reinterpret_cast<const _Tp*>
 165               (reinterpret_cast<_UIntPtrType>(this) + _M_diff);
 166       }
 167
 168       void
 169       set(const _Tp* __arg)
 170       {
 171         if (!__arg)
 172           _M_diff = 1;
 173         else
 174           _M_diff = reinterpret_cast<_UIntPtrType>(__arg)
 175                     - reinterpret_cast<_UIntPtrType>(this);
 176       }
 177
 178       // Comparison of pointers
 179       inline bool
 180       operator<(const _Relative_pointer_impl& __rarg) const
 181       { return (reinterpret_cast<_UIntPtrType>(this->get())
 182                 < reinterpret_cast<_UIntPtrType>(__rarg.get())); }
 183
 184       inline bool
 185       operator==(const _Relative_pointer_impl& __rarg) const
 186       { return (reinterpret_cast<_UIntPtrType>(this->get())
 187                 == reinterpret_cast<_UIntPtrType>(__rarg.get())); }
 188
 189     private:
 190 #ifdef _GLIBCXX_USE_LONG_LONG
 191       typedef __gnu_cxx::__conditional_type<
 192          (sizeof(unsigned long) >= sizeof(void*)),
 193          unsigned long, unsigned long long>::__type _UIntPtrType;
 194 #else
 195       typedef unsigned long _UIntPtrType;
 196 #endif
 197        _UIntPtrType _M_diff;
 198     };
 199
 200   /**
 201    * The specialization on this type helps resolve the problem of
 202    * reference to void, and eliminates the need to specialize
 203    * _Pointer_adapter for cases of void*, const void*, and so on.
 204    */
 205   struct _Invalid_type { };
 206
 207   template<typename _Tp>
 208     struct _Reference_type
 209     { typedef _Tp& reference; };
 210
 211   template<>
 212     struct _Reference_type<void>
 213     { typedef _Invalid_type& reference; };
 214
 215   template<>
 216     struct _Reference_type<const void>
 217     { typedef const _Invalid_type& reference; };
 218
 219   template<>
 220     struct _Reference_type<volatile void>
 221     { typedef volatile _Invalid_type&  reference; };
 222
 223   template<>
 224     struct _Reference_type<volatile const void>
 225     { typedef const volatile _Invalid_type&  reference; };
 226
 227   /**
 228    * This structure accomodates the way in which
 229    * std::iterator_traits<> is normally specialized for const T*, so
 230    * that value_type is still T.
 231    */
 232   template<typename _Tp>
 233     struct _Unqualified_type
 234     { typedef _Tp type; };
 235
 236   template<typename _Tp>
 237     struct _Unqualified_type<const _Tp>
 238     { typedef _Tp type; };
 239
 240   template<typename _Tp>
 241     struct _Unqualified_type<volatile _Tp>
 242     { typedef volatile _Tp type; };
 243
 244   template<typename _Tp>
 245     struct _Unqualified_type<volatile const _Tp>
 246     { typedef volatile _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' Alocator::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 is 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 arithmatic 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 __unused)
 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'es
 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
 564
 565 #endif // _POINTER_H