1 // <memory> -*- C++ -*- 2 3 // Copyright (C) 2001, 2002 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 2, 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 // You should have received a copy of the GNU General Public License along 17 // with this library; see the file COPYING. If not, write to the Free 18 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 19 // USA. 20 21 // As a special exception, you may use this file as part of a free software 22 // library without restriction. Specifically, if other files instantiate 23 // templates or use macros or inline functions from this file, or you compile 24 // this file and link it with other files to produce an executable, this 25 // file does not by itself cause the resulting executable to be covered by 26 // the GNU General Public License. This exception does not however 27 // invalidate any other reasons why the executable file might be covered by 28 // the GNU General Public License. 29 30 /* 31 * Copyright (c) 1997-1999 32 * Silicon Graphics Computer Systems, Inc. 33 * 34 * Permission to use, copy, modify, distribute and sell this software 35 * and its documentation for any purpose is hereby granted without fee, 36 * provided that the above copyright notice appear in all copies and 37 * that both that copyright notice and this permission notice appear 38 * in supporting documentation. Silicon Graphics makes no 39 * representations about the suitability of this software for any 40 * purpose. It is provided "as is" without express or implied warranty. 41 * 42 */ 43 44 /** @file memory 45 * This is a Standard C++ Library header. You should @c #include this header 46 * in your programs, rather than any of the "st[dl]_*.h" implementation files. 47 */ 48 49 #ifndef _CPP_MEMORY 50 #define _CPP_MEMORY 1 51 52 #pragma GCC system_header 53 54 #include <bits/stl_algobase.h> 55 #include <bits/stl_alloc.h> 56 #include <bits/stl_construct.h> 57 #include <bits/stl_iterator_base_types.h> //for iterator_traits 58 #include <bits/stl_uninitialized.h> 59 #include <bits/stl_raw_storage_iter.h> 60 61 // Since this entire file is within namespace std, there's no reason to 62 // waste two spaces along the left column. Thus the leading indentation is 63 // slightly violated from here on. 64 namespace std 65 { 66 /** 67 * @if maint 68 * This is a helper function. The unused second parameter exists to 69 * permit the real get_temporary_buffer to use template parameter deduction. 70 * 71 * XXX This should perhaps use the pool. 72 * @endif 73 */ 74 template <typename _Tp> 75 pair<_Tp*, ptrdiff_t> 76 __get_temporary_buffer(ptrdiff_t __len, _Tp*) 77 { 78 if (__len > ptrdiff_t(INT_MAX / sizeof(_Tp))) 79 __len = INT_MAX / sizeof(_Tp); 80 81 while (__len > 0) { 82 _Tp* __tmp = (_Tp*) std::malloc((std::size_t)__len * sizeof(_Tp)); 83 if (__tmp != 0) 84 return pair<_Tp*, ptrdiff_t>(__tmp, __len); 85 __len /= 2; 86 } 87 88 return pair<_Tp*, ptrdiff_t>((_Tp*)0, 0); 89 } 90 91 /** 92 * @brief This is a mostly-useless wrapper around malloc(). 93 * @param len The number of objects of type Tp. 94 * @return See full description. 95 * 96 * Reinventing the wheel, but this time with prettier spokes! 97 * 98 * This function tries to obtain storage for @c len adjacent Tp objects. 99 * The objects themselves are not constructed, of course. A pair<> is 100 * returned containing "the buffer s address and capacity (in the units of 101 * sizeof(Tp)), or a pair of 0 values if no storage can be obtained." 102 * Note that the capacity obtained may be less than that requested if the 103 * memory is unavailable; you should compare len with the .second return 104 * value. 105 */ 106 template<typename _Tp> 107 inline pair<_Tp*,ptrdiff_t> 108 get_temporary_buffer(ptrdiff_t __len) 109 { 110 return __get_temporary_buffer(__len, (_Tp*) 0); 111 } 112 113 /** 114 * @brief The companion to get_temporary_buffer(). 115 * @param p A buffer previously allocated by get_temporary_buffer. 116 * @return None. 117 * 118 * Frees the memory pointed to by p. 119 */ 120 template<typename _Tp> 121 void 122 return_temporary_buffer(_Tp* __p) 123 { 124 std::free(__p); 125 } 126 127 128 /** 129 * A wrapper class to provide auto_ptr with reference semantics. For 130 * example, an auto_ptr can be assigned (or constructed from) the result of 131 * a function which returns an auto_ptr by value. 132 * 133 * All the auto_ptr_ref stuff should happen behind the scenes. 134 */ 135 template<typename _Tp1> 136 struct auto_ptr_ref 137 { 138 _Tp1* _M_ptr; 139 140 explicit 141 auto_ptr_ref(_Tp1* __p) 142 : _M_ptr(__p) {} 143 }; 144 145 146 /** 147 * @brief A simple smart pointer providing strict ownership semantics. 148 * 149 * The Standard says: 150 * <pre> 151 * An @c auto_ptr owns the object it holds a pointer to. Copying an 152 * @c auto_ptr copies the pointer and transfers ownership to the destination. 153 * If more than one @c auto_ptr owns the same object at the same time the 154 * behavior of the program is undefined. 155 * 156 * The uses of @c auto_ptr include providing temporary exception-safety for 157 * dynamically allocated memory, passing ownership of dynamically allocated 158 * memory to a function, and returning dynamically allocated memory from a 159 * function. @c auto_ptr does not meet the CopyConstructible and Assignable 160 * requirements for Standard Library <a href="tables.html#65">container</a> 161 * elements and thus instantiating a Standard Library container with an 162 * @c auto_ptr results in undefined behavior. 163 * </pre> 164 * Quoted from [20.4.5]/3. 165 * 166 * Good examples of what can and cannot be done with auto_ptr can be found 167 * in the libstdc++ testsuite. 168 * 169 * @if maint 170 * _GLIBCPP_RESOLVE_LIB_DEFECTS 171 * 127. auto_ptr<> conversion issues 172 * These resolutions have all been incorporated. 173 * @endif 174 */ 175 template<typename _Tp> 176 class auto_ptr 177 { 178 private: 179 _Tp* _M_ptr; 180 181 public: 182 /// The pointed-to type. 183 typedef _Tp element_type; 184 185 /** 186 * @brief An %auto_ptr is usually constructed from a raw pointer. 187 * @param p A pointer (defaults to NULL). 188 * 189 * This object now @e owns the object pointed to by @a p. 190 */ 191 explicit 192 auto_ptr(element_type* __p = 0) throw() 193 : _M_ptr(__p) { } 194 195 /** 196 * @brief An %auto_ptr can be constructed from another %auto_ptr. 197 * @param a Another %auto_ptr of the same type. 198 * 199 * This object now @e owns the object previously owned by @a a, which has 200 * given up ownsership. 201 */ 202 auto_ptr(auto_ptr& __a) throw() 203 : _M_ptr(__a.release()) { } 204 205 /** 206 * @brief An %auto_ptr can be constructed from another %auto_ptr. 207 * @param a Another %auto_ptr of a different but related type. 208 * 209 * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. 210 * 211 * This object now @e owns the object previously owned by @a a, which has 212 * given up ownsership. 213 */ 214 template<typename _Tp1> 215 auto_ptr(auto_ptr<_Tp1>& __a) throw() 216 : _M_ptr(__a.release()) { } 217 218 /** 219 * @brief %auto_ptr assignment operator. 220 * @param a Another %auto_ptr of the same type. 221 * 222 * This object now @e owns the object previously owned by @a a, which has 223 * given up ownsership. The object that this one @e used to own and 224 * track has been deleted. 225 */ 226 auto_ptr& 227 operator=(auto_ptr& __a) throw() 228 { 229 reset(__a.release()); 230 return *this; 231 } 232 233 /** 234 * @brief %auto_ptr assignment operator. 235 * @param a Another %auto_ptr of a different but related type. 236 * 237 * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. 238 * 239 * This object now @e owns the object previously owned by @a a, which has 240 * given up ownsership. The object that this one @e used to own and 241 * track has been deleted. 242 */ 243 template <typename _Tp1> 244 auto_ptr& 245 operator=(auto_ptr<_Tp1>& __a) throw() 246 { 247 reset(__a.release()); 248 return *this; 249 } 250 251 /** 252 * When the %auto_ptr goes out of scope, the object it owns is deleted. 253 * If it no longer owns anything (i.e., @c get() is @c NULL), then this 254 * has no effect. 255 * 256 * @if maint 257 * The C++ standard says there is supposed to be an empty throw 258 * specification here, but omitting it is standard conforming. Its 259 * presence can be detected only if _Tp::~_Tp() throws, but this is 260 * prohibited. [17.4.3.6]/2 261 * @end maint 262 */ 263 ~auto_ptr() { delete _M_ptr; } 264 265 /** 266 * @brief Smart pointer dereferencing. 267 * 268 * If this %auto_ptr no longer owns anything, then this operation will 269 * crash. (For a smart pointer, "no longer owns anything" is the same as 270 * being a null pointer, and you know what happens when you dereference 271 * one of those...) 272 */ 273 element_type& 274 operator*() const throw() { return *_M_ptr; } 275 276 /** 277 * @brief Smart pointer dereferencing. 278 * 279 * This returns the pointer itself, which the language then will 280 * automatically cause to be dereferenced. 281 */ 282 element_type* 283 operator->() const throw() { return _M_ptr; } 284 285 /** 286 * @brief Bypassing the smart pointer. 287 * @return The raw pointer being managed. 288 * 289 * You can get a copy of the pointer that this object owns, for 290 * situations such as passing to a function which only accepts a raw 291 * pointer. 292 * 293 * @note This %auto_ptr still owns the memory. 294 */ 295 element_type* 296 get() const throw() { return _M_ptr; } 297 298 /** 299 * @brief Bypassing the smart pointer. 300 * @return The raw pointer being managed. 301 * 302 * You can get a copy of the pointer that this object owns, for 303 * situations such as passing to a function which only accepts a raw 304 * pointer. 305 * 306 * @note This %auto_ptr no longer owns the memory. When this object 307 * goes out of scope, nothing will happen. 308 */ 309 element_type* 310 release() throw() 311 { 312 element_type* __tmp = _M_ptr; 313 _M_ptr = 0; 314 return __tmp; 315 } 316 317 /** 318 * @brief Forcibly deletes the managed object. 319 * @param p A pointer (defaults to NULL). 320 * 321 * This object now @e owns the object pointed to by @a p. The previous 322 * object has been deleted. 323 */ 324 void 325 reset(element_type* __p = 0) throw() 326 { 327 if (__p != _M_ptr) 328 { 329 delete _M_ptr; 330 _M_ptr = __p; 331 } 332 } 333 334 /** @{ 335 * @brief Automatic conversions 336 * 337 * These operations convert an %auto_ptr into and from an auto_ptr_ref 338 * automatically as needed. This allows constructs such as 339 * @code 340 * auto_ptr<Derived> func_returning_auto_ptr(.....); 341 * ... 342 * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); 343 * @endcode 344 */ 345 auto_ptr(auto_ptr_ref<element_type> __ref) throw() 346 : _M_ptr(__ref._M_ptr) {} 347 348 auto_ptr& 349 operator=(auto_ptr_ref<element_type> __ref) throw() 350 { 351 if (__ref._M_ptr != this->get()) 352 { 353 delete _M_ptr; 354 _M_ptr = __ref._M_ptr; 355 } 356 return *this; 357 } 358 359 template<typename _Tp1> 360 operator auto_ptr_ref<_Tp1>() throw() 361 { return auto_ptr_ref<_Tp1>(this->release()); } 362 363 template<typename _Tp1> 364 operator auto_ptr<_Tp1>() throw() 365 { return auto_ptr<_Tp1>(this->release()); } 366 /** @} */ 367 }; 368 369 } // namespace std 370 371 #endif /* _CPP_MEMORY */ 372