1 // Safe sequence/iterator base implementation -*- C++ -*- 2 3 // Copyright (C) 2003, 2004, 2005, 2006, 2009 4 // Free Software Foundation, Inc. 5 // 6 // This file is part of the GNU ISO C++ Library. This library is free 7 // software; you can redistribute it and/or modify it under the 8 // terms of the GNU General Public License as published by the 9 // Free Software Foundation; either version 3, or (at your option) 10 // any later version. 11 12 // This library is distributed in the hope that it will be useful, 13 // but WITHOUT ANY WARRANTY; without even the implied warranty of 14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 // GNU General Public License for more details. 16 17 // Under Section 7 of GPL version 3, you are granted additional 18 // permissions described in the GCC Runtime Library Exception, version 19 // 3.1, as published by the Free Software Foundation. 20 21 // You should have received a copy of the GNU General Public License and 22 // a copy of the GCC Runtime Library Exception along with this program; 23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24 // <http://www.gnu.org/licenses/>. 25 26 /** @file debug/safe_base.h 27 * This file is a GNU debug extension to the Standard C++ Library. 28 */ 29 30 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H 31 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1 32 33 #include <ext/concurrence.h> 34 35 namespace __gnu_debug 36 { 37 class _Safe_sequence_base; 38 39 /** \brief Basic functionality for a "safe" iterator. 40 * 41 * The %_Safe_iterator_base base class implements the functionality 42 * of a safe iterator that is not specific to a particular iterator 43 * type. It contains a pointer back to the sequence it references 44 * along with iterator version information and pointers to form a 45 * doubly-linked list of iterators referenced by the container. 46 * 47 * This class must not perform any operations that can throw an 48 * exception, or the exception guarantees of derived iterators will 49 * be broken. 50 */ 51 class _Safe_iterator_base 52 { 53 public: 54 /** The sequence this iterator references; may be NULL to indicate 55 a singular iterator. */ 56 _Safe_sequence_base* _M_sequence; 57 58 /** The version number of this iterator. The sentinel value 0 is 59 * used to indicate an invalidated iterator (i.e., one that is 60 * singular because of an operation on the container). This 61 * version number must equal the version number in the sequence 62 * referenced by _M_sequence for the iterator to be 63 * non-singular. 64 */ 65 unsigned int _M_version; 66 67 /** Pointer to the previous iterator in the sequence's list of 68 iterators. Only valid when _M_sequence != NULL. */ 69 _Safe_iterator_base* _M_prior; 70 71 /** Pointer to the next iterator in the sequence's list of 72 iterators. Only valid when _M_sequence != NULL. */ 73 _Safe_iterator_base* _M_next; 74 75 protected: 76 /** Initializes the iterator and makes it singular. */ 77 _Safe_iterator_base() 78 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 79 { } 80 81 /** Initialize the iterator to reference the sequence pointed to 82 * by @p__seq. @p __constant is true when we are initializing a 83 * constant iterator, and false if it is a mutable iterator. Note 84 * that @p __seq may be NULL, in which case the iterator will be 85 * singular. Otherwise, the iterator will reference @p __seq and 86 * be nonsingular. 87 */ 88 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 89 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 90 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 91 92 /** Initializes the iterator to reference the same sequence that 93 @p __x does. @p __constant is true if this is a constant 94 iterator, and false if it is mutable. */ 95 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 96 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 97 { this->_M_attach(__x._M_sequence, __constant); } 98 99 _Safe_iterator_base& 100 operator=(const _Safe_iterator_base&); 101 102 explicit 103 _Safe_iterator_base(const _Safe_iterator_base&); 104 105 ~_Safe_iterator_base() { this->_M_detach(); } 106 107 /** For use in _Safe_iterator. */ 108 __gnu_cxx::__mutex& _M_get_mutex(); 109 110 public: 111 /** Attaches this iterator to the given sequence, detaching it 112 * from whatever sequence it was attached to originally. If the 113 * new sequence is the NULL pointer, the iterator is left 114 * unattached. 115 */ 116 void _M_attach(_Safe_sequence_base* __seq, bool __constant); 117 118 /** Likewise, but not thread-safe. */ 119 void _M_attach_single(_Safe_sequence_base* __seq, bool __constant); 120 121 /** Detach the iterator for whatever sequence it is attached to, 122 * if any. 123 */ 124 void _M_detach(); 125 126 /** Likewise, but not thread-safe. */ 127 void _M_detach_single(); 128 129 /** Determines if we are attached to the given sequence. */ 130 bool _M_attached_to(const _Safe_sequence_base* __seq) const 131 { return _M_sequence == __seq; } 132 133 /** Is this iterator singular? */ 134 bool _M_singular() const; 135 136 /** Can we compare this iterator to the given iterator @p __x? 137 Returns true if both iterators are nonsingular and reference 138 the same sequence. */ 139 bool _M_can_compare(const _Safe_iterator_base& __x) const; 140 }; 141 142 /** 143 * @brief Base class that supports tracking of iterators that 144 * reference a sequence. 145 * 146 * The %_Safe_sequence_base class provides basic support for 147 * tracking iterators into a sequence. Sequences that track 148 * iterators must derived from %_Safe_sequence_base publicly, so 149 * that safe iterators (which inherit _Safe_iterator_base) can 150 * attach to them. This class contains two linked lists of 151 * iterators, one for constant iterators and one for mutable 152 * iterators, and a version number that allows very fast 153 * invalidation of all iterators that reference the container. 154 * 155 * This class must ensure that no operation on it may throw an 156 * exception, otherwise "safe" sequences may fail to provide the 157 * exception-safety guarantees required by the C++ standard. 158 */ 159 class _Safe_sequence_base 160 { 161 public: 162 /// The list of mutable iterators that reference this container 163 _Safe_iterator_base* _M_iterators; 164 165 /// The list of constant iterators that reference this container 166 _Safe_iterator_base* _M_const_iterators; 167 168 /// The container version number. This number may never be 0. 169 mutable unsigned int _M_version; 170 171 protected: 172 // Initialize with a version number of 1 and no iterators 173 _Safe_sequence_base() 174 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 175 { } 176 177 /** Notify all iterators that reference this sequence that the 178 sequence is being destroyed. */ 179 ~_Safe_sequence_base() 180 { this->_M_detach_all(); } 181 182 /** Detach all iterators, leaving them singular. */ 183 void 184 _M_detach_all(); 185 186 /** Detach all singular iterators. 187 * @post for all iterators i attached to this sequence, 188 * i->_M_version == _M_version. 189 */ 190 void 191 _M_detach_singular(); 192 193 /** Revalidates all attached singular iterators. This method may 194 * be used to validate iterators that were invalidated before 195 * (but for some reason, such as an exception, need to become 196 * valid again). 197 */ 198 void 199 _M_revalidate_singular(); 200 201 /** Swap this sequence with the given sequence. This operation 202 * also swaps ownership of the iterators, so that when the 203 * operation is complete all iterators that originally referenced 204 * one container now reference the other container. 205 */ 206 void 207 _M_swap(_Safe_sequence_base& __x); 208 209 /** For use in _Safe_sequence. */ 210 __gnu_cxx::__mutex& _M_get_mutex(); 211 212 public: 213 /** Invalidates all iterators. */ 214 void 215 _M_invalidate_all() const 216 { if (++_M_version == 0) _M_version = 1; } 217 }; 218 } // namespace __gnu_debug 219 220 #endif 221
