1// Safe sequence/iterator base implementation -*- C++ -*- 2 3// Copyright (C) 2003, 2004, 2005, 2006, 2009, 2010 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 35namespace __gnu_debug 36{ 37 class _Safe_sequence_base; 38 39 /** \brief Basic functionality for a @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() throw (); 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) throw (); 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() throw (); 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 _GLIBCXX_PURE bool _M_singular() const throw (); 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 _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw (); 140 141 /** Invalidate the iterator, making it singular. */ 142 void 143 _M_invalidate() 144 { _M_version = 0; } 145 146 /** Reset all member variables */ 147 void 148 _M_reset() throw (); 149 150 /** Unlink itself */ 151 void 152 _M_unlink() throw () 153 { 154 if (_M_prior) 155 _M_prior->_M_next = _M_next; 156 if (_M_next) 157 _M_next->_M_prior = _M_prior; 158 } 159 }; 160 161 /** 162 * @brief Base class that supports tracking of iterators that 163 * reference a sequence. 164 * 165 * The %_Safe_sequence_base class provides basic support for 166 * tracking iterators into a sequence. Sequences that track 167 * iterators must derived from %_Safe_sequence_base publicly, so 168 * that safe iterators (which inherit _Safe_iterator_base) can 169 * attach to them. This class contains two linked lists of 170 * iterators, one for constant iterators and one for mutable 171 * iterators, and a version number that allows very fast 172 * invalidation of all iterators that reference the container. 173 * 174 * This class must ensure that no operation on it may throw an 175 * exception, otherwise @a safe sequences may fail to provide the 176 * exception-safety guarantees required by the C++ standard. 177 */ 178 class _Safe_sequence_base 179 { 180 public: 181 /// The list of mutable iterators that reference this container 182 _Safe_iterator_base* _M_iterators; 183 184 /// The list of constant iterators that reference this container 185 _Safe_iterator_base* _M_const_iterators; 186 187 /// The container version number. This number may never be 0. 188 mutable unsigned int _M_version; 189 190 protected: 191 // Initialize with a version number of 1 and no iterators 192 _Safe_sequence_base() 193 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 194 { } 195 196 /** Notify all iterators that reference this sequence that the 197 sequence is being destroyed. */ 198 ~_Safe_sequence_base() 199 { this->_M_detach_all(); } 200 201 /** Detach all iterators, leaving them singular. */ 202 void 203 _M_detach_all(); 204 205 /** Detach all singular iterators. 206 * @post for all iterators i attached to this sequence, 207 * i->_M_version == _M_version. 208 */ 209 void 210 _M_detach_singular(); 211 212 /** Revalidates all attached singular iterators. This method may 213 * be used to validate iterators that were invalidated before 214 * (but for some reason, such as an exception, need to become 215 * valid again). 216 */ 217 void 218 _M_revalidate_singular(); 219 220 /** Swap this sequence with the given sequence. This operation 221 * also swaps ownership of the iterators, so that when the 222 * operation is complete all iterators that originally referenced 223 * one container now reference the other container. 224 */ 225 void 226 _M_swap(_Safe_sequence_base& __x); 227 228 /** For use in _Safe_sequence. */ 229 __gnu_cxx::__mutex& _M_get_mutex() throw (); 230 231 public: 232 /** Invalidates all iterators. */ 233 void 234 _M_invalidate_all() const 235 { if (++_M_version == 0) _M_version = 1; } 236 237 /** Attach an iterator to this sequence. */ 238 void 239 _M_attach(_Safe_iterator_base* __it, bool __constant); 240 241 /** Likewise but not thread safe. */ 242 void 243 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw (); 244 245 /** Detach an iterator from this sequence */ 246 void 247 _M_detach(_Safe_iterator_base* __it); 248 249 /** Likewise but not thread safe. */ 250 void 251 _M_detach_single(_Safe_iterator_base* __it) throw (); 252 }; 253} // namespace __gnu_debug 254 255#endif 256