1// Safe sequence/iterator base implementation -*- C++ -*- 2 3// Copyright (C) 2003-2020 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/** @file debug/safe_base.h 26 * This file is a GNU debug extension to the Standard C++ Library. 27 */ 28 29#ifndef _GLIBCXX_DEBUG_SAFE_BASE_H 30#define _GLIBCXX_DEBUG_SAFE_BASE_H 1 31 32#include <ext/concurrence.h> 33 34namespace __gnu_debug 35{ 36 class _Safe_sequence_base; 37 38 /** \brief Basic functionality for a @a safe iterator. 39 * 40 * The %_Safe_iterator_base base class implements the functionality 41 * of a safe iterator that is not specific to a particular iterator 42 * type. It contains a pointer back to the sequence it references 43 * along with iterator version information and pointers to form a 44 * doubly-linked list of iterators referenced by the container. 45 * 46 * This class must not perform any operations that can throw an 47 * exception, or the exception guarantees of derived iterators will 48 * be broken. 49 */ 50 class _Safe_iterator_base 51 { 52 friend class _Safe_sequence_base; 53 54 public: 55 /** The sequence this iterator references; may be NULL to indicate 56 a singular iterator. */ 57 _Safe_sequence_base* _M_sequence; 58 59 /** The version number of this iterator. The sentinel value 0 is 60 * used to indicate an invalidated iterator (i.e., one that is 61 * singular because of an operation on the container). This 62 * version number must equal the version number in the sequence 63 * referenced by _M_sequence for the iterator to be 64 * non-singular. 65 */ 66 unsigned int _M_version; 67 68 /** Pointer to the previous iterator in the sequence's list of 69 iterators. Only valid when _M_sequence != NULL. */ 70 _Safe_iterator_base* _M_prior; 71 72 /** Pointer to the next iterator in the sequence's list of 73 iterators. Only valid when _M_sequence != NULL. */ 74 _Safe_iterator_base* _M_next; 75 76 protected: 77 /** Initializes the iterator and makes it singular. */ 78 _Safe_iterator_base() 79 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 80 { } 81 82 /** Initialize the iterator to reference the sequence pointed to 83 * by @p __seq. @p __constant is true when we are initializing a 84 * constant iterator, and false if it is a mutable iterator. Note 85 * that @p __seq may be NULL, in which case the iterator will be 86 * singular. Otherwise, the iterator will reference @p __seq and 87 * be nonsingular. 88 */ 89 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 90 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 91 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 92 93 /** Initializes the iterator to reference the same sequence that 94 @p __x does. @p __constant is true if this is a constant 95 iterator, and false if it is mutable. */ 96 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 97 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 98 { this->_M_attach(__x._M_sequence, __constant); } 99 100 ~_Safe_iterator_base() { this->_M_detach(); } 101 102 /** For use in _Safe_iterator. */ 103 __gnu_cxx::__mutex& 104 _M_get_mutex() throw (); 105 106 /** Attaches this iterator to the given sequence, detaching it 107 * from whatever sequence it was attached to originally. If the 108 * new sequence is the NULL pointer, the iterator is left 109 * unattached. 110 */ 111 void 112 _M_attach(_Safe_sequence_base* __seq, bool __constant); 113 114 /** Likewise, but not thread-safe. */ 115 void 116 _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw (); 117 118 /** Detach the iterator for whatever sequence it is attached to, 119 * if any. 120 */ 121 void 122 _M_detach(); 123 124 public: 125 /** Likewise, but not thread-safe. */ 126 void 127 _M_detach_single() throw (); 128 129 /** Determines if we are attached to the given sequence. */ 130 bool 131 _M_attached_to(const _Safe_sequence_base* __seq) const 132 { return _M_sequence == __seq; } 133 134 /** Is this iterator singular? */ 135 _GLIBCXX_PURE bool 136 _M_singular() const throw (); 137 138 /** Can we compare this iterator to the given iterator @p __x? 139 Returns true if both iterators are nonsingular and reference 140 the same sequence. */ 141 _GLIBCXX_PURE bool 142 _M_can_compare(const _Safe_iterator_base& __x) const throw (); 143 144 /** Invalidate the iterator, making it singular. */ 145 void 146 _M_invalidate() 147 { _M_version = 0; } 148 149 /** Reset all member variables */ 150 void 151 _M_reset() throw (); 152 153 /** Unlink itself */ 154 void 155 _M_unlink() throw () 156 { 157 if (_M_prior) 158 _M_prior->_M_next = _M_next; 159 if (_M_next) 160 _M_next->_M_prior = _M_prior; 161 } 162 }; 163 164 /** Iterators that derive from _Safe_iterator_base can be determined singular 165 * or non-singular. 166 **/ 167 inline bool 168 __check_singular_aux(const _Safe_iterator_base* __x) 169 { return __x->_M_singular(); } 170 171 /** 172 * @brief Base class that supports tracking of iterators that 173 * reference a sequence. 174 * 175 * The %_Safe_sequence_base class provides basic support for 176 * tracking iterators into a sequence. Sequences that track 177 * iterators must derived from %_Safe_sequence_base publicly, so 178 * that safe iterators (which inherit _Safe_iterator_base) can 179 * attach to them. This class contains two linked lists of 180 * iterators, one for constant iterators and one for mutable 181 * iterators, and a version number that allows very fast 182 * invalidation of all iterators that reference the container. 183 * 184 * This class must ensure that no operation on it may throw an 185 * exception, otherwise @a safe sequences may fail to provide the 186 * exception-safety guarantees required by the C++ standard. 187 */ 188 class _Safe_sequence_base 189 { 190 friend class _Safe_iterator_base; 191 192 public: 193 /// The list of mutable iterators that reference this container 194 _Safe_iterator_base* _M_iterators; 195 196 /// The list of constant iterators that reference this container 197 _Safe_iterator_base* _M_const_iterators; 198 199 /// The container version number. This number may never be 0. 200 mutable unsigned int _M_version; 201 202 protected: 203 // Initialize with a version number of 1 and no iterators 204 _Safe_sequence_base() _GLIBCXX_NOEXCEPT 205 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 206 { } 207 208#if __cplusplus >= 201103L 209 _Safe_sequence_base(const _Safe_sequence_base&) noexcept 210 : _Safe_sequence_base() { } 211 212 // Move constructor swap iterators. 213 _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept 214 : _Safe_sequence_base() 215 { _M_swap(__seq); } 216#endif 217 218 /** Notify all iterators that reference this sequence that the 219 sequence is being destroyed. */ 220 ~_Safe_sequence_base() 221 { this->_M_detach_all(); } 222 223 /** Detach all iterators, leaving them singular. */ 224 void 225 _M_detach_all(); 226 227 /** Detach all singular iterators. 228 * @post for all iterators i attached to this sequence, 229 * i->_M_version == _M_version. 230 */ 231 void 232 _M_detach_singular(); 233 234 /** Revalidates all attached singular iterators. This method may 235 * be used to validate iterators that were invalidated before 236 * (but for some reason, such as an exception, need to become 237 * valid again). 238 */ 239 void 240 _M_revalidate_singular(); 241 242 /** Swap this sequence with the given sequence. This operation 243 * also swaps ownership of the iterators, so that when the 244 * operation is complete all iterators that originally referenced 245 * one container now reference the other container. 246 */ 247 void 248 _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT; 249 250 /** For use in _Safe_sequence. */ 251 __gnu_cxx::__mutex& 252 _M_get_mutex() throw (); 253 254 /** Invalidates all iterators. */ 255 void 256 _M_invalidate_all() const 257 { if (++_M_version == 0) _M_version = 1; } 258 259 private: 260 /** Attach an iterator to this sequence. */ 261 void 262 _M_attach(_Safe_iterator_base* __it, bool __constant); 263 264 /** Likewise but not thread safe. */ 265 void 266 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw (); 267 268 /** Detach an iterator from this sequence */ 269 void 270 _M_detach(_Safe_iterator_base* __it); 271 272 /** Likewise but not thread safe. */ 273 void 274 _M_detach_single(_Safe_iterator_base* __it) throw (); 275 }; 276} // namespace __gnu_debug 277 278#endif 279