1 // Safe sequence/iterator base implementation -*- C++ -*- 2 3 // Copyright (C) 2003-2013 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 /** @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 34 namespace __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 public: 53 /** The sequence this iterator references; may be NULL to indicate 54 a singular iterator. */ 55 _Safe_sequence_base* _M_sequence; 56 57 /** The version number of this iterator. The sentinel value 0 is 58 * used to indicate an invalidated iterator (i.e., one that is 59 * singular because of an operation on the container). This 60 * version number must equal the version number in the sequence 61 * referenced by _M_sequence for the iterator to be 62 * non-singular. 63 */ 64 unsigned int _M_version; 65 66 /** Pointer to the previous iterator in the sequence's list of 67 iterators. Only valid when _M_sequence != NULL. */ 68 _Safe_iterator_base* _M_prior; 69 70 /** Pointer to the next iterator in the sequence's list of 71 iterators. Only valid when _M_sequence != NULL. */ 72 _Safe_iterator_base* _M_next; 73 74 protected: 75 /** Initializes the iterator and makes it singular. */ 76 _Safe_iterator_base() 77 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 78 { } 79 80 /** Initialize the iterator to reference the sequence pointed to 81 * by @p __seq. @p __constant is true when we are initializing a 82 * constant iterator, and false if it is a mutable iterator. Note 83 * that @p __seq may be NULL, in which case the iterator will be 84 * singular. Otherwise, the iterator will reference @p __seq and 85 * be nonsingular. 86 */ 87 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 88 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 89 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 90 91 /** Initializes the iterator to reference the same sequence that 92 @p __x does. @p __constant is true if this is a constant 93 iterator, and false if it is mutable. */ 94 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 95 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 96 { this->_M_attach(__x._M_sequence, __constant); } 97 98 _Safe_iterator_base& 99 operator=(const _Safe_iterator_base&); 100 101 explicit 102 _Safe_iterator_base(const _Safe_iterator_base&); 103 104 ~_Safe_iterator_base() { this->_M_detach(); } 105 106 /** For use in _Safe_iterator. */ 107 __gnu_cxx::__mutex& _M_get_mutex() throw (); 108 109 public: 110 /** Attaches this iterator to the given sequence, detaching it 111 * from whatever sequence it was attached to originally. If the 112 * new sequence is the NULL pointer, the iterator is left 113 * unattached. 114 */ 115 void _M_attach(_Safe_sequence_base* __seq, bool __constant); 116 117 /** Likewise, but not thread-safe. */ 118 void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw (); 119 120 /** Detach the iterator for whatever sequence it is attached to, 121 * if any. 122 */ 123 void _M_detach(); 124 125 /** Likewise, but not thread-safe. */ 126 void _M_detach_single() throw (); 127 128 /** Determines if we are attached to the given sequence. */ 129 bool _M_attached_to(const _Safe_sequence_base* __seq) const 130 { return _M_sequence == __seq; } 131 132 /** Is this iterator singular? */ 133 _GLIBCXX_PURE bool _M_singular() const throw (); 134 135 /** Can we compare this iterator to the given iterator @p __x? 136 Returns true if both iterators are nonsingular and reference 137 the same sequence. */ 138 _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw (); 139 140 /** Invalidate the iterator, making it singular. */ 141 void 142 _M_invalidate() 143 { _M_version = 0; } 144 145 /** Reset all member variables */ 146 void 147 _M_reset() throw (); 148 149 /** Unlink itself */ 150 void 151 _M_unlink() throw () 152 { 153 if (_M_prior) 154 _M_prior->_M_next = _M_next; 155 if (_M_next) 156 _M_next->_M_prior = _M_prior; 157 } 158 }; 159 160 /** 161 * @brief Base class that supports tracking of iterators that 162 * reference a sequence. 163 * 164 * The %_Safe_sequence_base class provides basic support for 165 * tracking iterators into a sequence. Sequences that track 166 * iterators must derived from %_Safe_sequence_base publicly, so 167 * that safe iterators (which inherit _Safe_iterator_base) can 168 * attach to them. This class contains two linked lists of 169 * iterators, one for constant iterators and one for mutable 170 * iterators, and a version number that allows very fast 171 * invalidation of all iterators that reference the container. 172 * 173 * This class must ensure that no operation on it may throw an 174 * exception, otherwise @a safe sequences may fail to provide the 175 * exception-safety guarantees required by the C++ standard. 176 */ 177 class _Safe_sequence_base 178 { 179 public: 180 /// The list of mutable iterators that reference this container 181 _Safe_iterator_base* _M_iterators; 182 183 /// The list of constant iterators that reference this container 184 _Safe_iterator_base* _M_const_iterators; 185 186 /// The container version number. This number may never be 0. 187 mutable unsigned int _M_version; 188 189 protected: 190 // Initialize with a version number of 1 and no iterators 191 _Safe_sequence_base() 192 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 193 { } 194 195 /** Notify all iterators that reference this sequence that the 196 sequence is being destroyed. */ 197 ~_Safe_sequence_base() 198 { this->_M_detach_all(); } 199 200 /** Detach all iterators, leaving them singular. */ 201 void 202 _M_detach_all(); 203 204 /** Detach all singular iterators. 205 * @post for all iterators i attached to this sequence, 206 * i->_M_version == _M_version. 207 */ 208 void 209 _M_detach_singular(); 210 211 /** Revalidates all attached singular iterators. This method may 212 * be used to validate iterators that were invalidated before 213 * (but for some reason, such as an exception, need to become 214 * valid again). 215 */ 216 void 217 _M_revalidate_singular(); 218 219 /** Swap this sequence with the given sequence. This operation 220 * also swaps ownership of the iterators, so that when the 221 * operation is complete all iterators that originally referenced 222 * one container now reference the other container. 223 */ 224 void 225 _M_swap(_Safe_sequence_base& __x); 226 227 /** For use in _Safe_sequence. */ 228 __gnu_cxx::__mutex& _M_get_mutex() throw (); 229 230 public: 231 /** Invalidates all iterators. */ 232 void 233 _M_invalidate_all() const 234 { if (++_M_version == 0) _M_version = 1; } 235 236 /** Attach an iterator to this sequence. */ 237 void 238 _M_attach(_Safe_iterator_base* __it, bool __constant); 239 240 /** Likewise but not thread safe. */ 241 void 242 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw (); 243 244 /** Detach an iterator from this sequence */ 245 void 246 _M_detach(_Safe_iterator_base* __it); 247 248 /** Likewise but not thread safe. */ 249 void 250 _M_detach_single(_Safe_iterator_base* __it) throw (); 251 }; 252 } // namespace __gnu_debug 253 254 #endif 255
