1// Safe sequence/iterator base implementation -*- C++ -*- 2 3// Copyright (C) 2003, 2004, 2005, 2006 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 2, 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// You should have received a copy of the GNU General Public License along 18// with this library; see the file COPYING. If not, write to the Free 19// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 20// USA. 21 22// As a special exception, you may use this file as part of a free software 23// library without restriction. Specifically, if other files instantiate 24// templates or use macros or inline functions from this file, or you compile 25// this file and link it with other files to produce an executable, this 26// file does not by itself cause the resulting executable to be covered by 27// the GNU General Public License. This exception does not however 28// invalidate any other reasons why the executable file might be covered by 29// the GNU General Public License. 30 31/** @file debug/safe_base.h 32 * This file is a GNU debug extension to the Standard C++ Library. 33 */ 34 35#ifndef _GLIBCXX_DEBUG_SAFE_BASE_H 36#define _GLIBCXX_DEBUG_SAFE_BASE_H 1 37 38#include <ext/concurrence.h> 39 40namespace __gnu_debug 41{ 42 class _Safe_sequence_base; 43 44 /** \brief Basic functionality for a "safe" iterator. 45 * 46 * The %_Safe_iterator_base base class implements the functionality 47 * of a safe iterator that is not specific to a particular iterator 48 * type. It contains a pointer back to the sequence it references 49 * along with iterator version information and pointers to form a 50 * doubly-linked list of iterators referenced by the container. 51 * 52 * This class must not perform any operations that can throw an 53 * exception, or the exception guarantees of derived iterators will 54 * be broken. 55 */ 56 class _Safe_iterator_base 57 { 58 public: 59 /** The sequence this iterator references; may be NULL to indicate 60 a singular iterator. */ 61 _Safe_sequence_base* _M_sequence; 62 63 /** The version number of this iterator. The sentinel value 0 is 64 * used to indicate an invalidated iterator (i.e., one that is 65 * singular because of an operation on the container). This 66 * version number must equal the version number in the sequence 67 * referenced by _M_sequence for the iterator to be 68 * non-singular. 69 */ 70 unsigned int _M_version; 71 72 /** Pointer to the previous iterator in the sequence's list of 73 iterators. Only valid when _M_sequence != NULL. */ 74 _Safe_iterator_base* _M_prior; 75 76 /** Pointer to the next iterator in the sequence's list of 77 iterators. Only valid when _M_sequence != NULL. */ 78 _Safe_iterator_base* _M_next; 79 80 protected: 81 /** Initializes the iterator and makes it singular. */ 82 _Safe_iterator_base() 83 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 84 { } 85 86 /** Initialize the iterator to reference the sequence pointed to 87 * by @p__seq. @p __constant is true when we are initializing a 88 * constant iterator, and false if it is a mutable iterator. Note 89 * that @p __seq may be NULL, in which case the iterator will be 90 * singular. Otherwise, the iterator will reference @p __seq and 91 * be nonsingular. 92 */ 93 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 94 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 95 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 96 97 /** Initializes the iterator to reference the same sequence that 98 @p __x does. @p __constant is true if this is a constant 99 iterator, and false if it is mutable. */ 100 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 101 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 102 { this->_M_attach(__x._M_sequence, __constant); } 103 104 _Safe_iterator_base& 105 operator=(const _Safe_iterator_base&); 106 107 explicit 108 _Safe_iterator_base(const _Safe_iterator_base&); 109 110 ~_Safe_iterator_base() { this->_M_detach(); } 111 112 /** For use in _Safe_iterator. */ 113 __gnu_cxx::__mutex& _M_get_mutex(); 114 115 public: 116 /** Attaches this iterator to the given sequence, detaching it 117 * from whatever sequence it was attached to originally. If the 118 * new sequence is the NULL pointer, the iterator is left 119 * unattached. 120 */ 121 void _M_attach(_Safe_sequence_base* __seq, bool __constant); 122 123 /** Likewise, but not thread-safe. */ 124 void _M_attach_single(_Safe_sequence_base* __seq, bool __constant); 125 126 /** Detach the iterator for whatever sequence it is attached to, 127 * if any. 128 */ 129 void _M_detach(); 130 131 /** Likewise, but not thread-safe. */ 132 void _M_detach_single(); 133 134 /** Determines if we are attached to the given sequence. */ 135 bool _M_attached_to(const _Safe_sequence_base* __seq) const 136 { return _M_sequence == __seq; } 137 138 /** Is this iterator singular? */ 139 bool _M_singular() const; 140 141 /** Can we compare this iterator to the given iterator @p __x? 142 Returns true if both iterators are nonsingular and reference 143 the same sequence. */ 144 bool _M_can_compare(const _Safe_iterator_base& __x) const; 145 }; 146 147 /** 148 * @brief Base class that supports tracking of iterators that 149 * reference a sequence. 150 * 151 * The %_Safe_sequence_base class provides basic support for 152 * tracking iterators into a sequence. Sequences that track 153 * iterators must derived from %_Safe_sequence_base publicly, so 154 * that safe iterators (which inherit _Safe_iterator_base) can 155 * attach to them. This class contains two linked lists of 156 * iterators, one for constant iterators and one for mutable 157 * iterators, and a version number that allows very fast 158 * invalidation of all iterators that reference the container. 159 * 160 * This class must ensure that no operation on it may throw an 161 * exception, otherwise "safe" sequences may fail to provide the 162 * exception-safety guarantees required by the C++ standard. 163 */ 164 class _Safe_sequence_base 165 { 166 public: 167 /// The list of mutable iterators that reference this container 168 _Safe_iterator_base* _M_iterators; 169 170 /// The list of constant iterators that reference this container 171 _Safe_iterator_base* _M_const_iterators; 172 173 /// The container version number. This number may never be 0. 174 mutable unsigned int _M_version; 175 176 protected: 177 // Initialize with a version number of 1 and no iterators 178 _Safe_sequence_base() 179 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 180 { } 181 182 /** Notify all iterators that reference this sequence that the 183 sequence is being destroyed. */ 184 ~_Safe_sequence_base() 185 { this->_M_detach_all(); } 186 187 /** Detach all iterators, leaving them singular. */ 188 void 189 _M_detach_all(); 190 191 /** Detach all singular iterators. 192 * @post for all iterators i attached to this sequence, 193 * i->_M_version == _M_version. 194 */ 195 void 196 _M_detach_singular(); 197 198 /** Revalidates all attached singular iterators. This method may 199 * be used to validate iterators that were invalidated before 200 * (but for some reasion, such as an exception, need to become 201 * valid again). 202 */ 203 void 204 _M_revalidate_singular(); 205 206 /** Swap this sequence with the given sequence. This operation 207 * also swaps ownership of the iterators, so that when the 208 * operation is complete all iterators that originally referenced 209 * one container now reference the other container. 210 */ 211 void 212 _M_swap(_Safe_sequence_base& __x); 213 214 /** For use in _Safe_sequence. */ 215 __gnu_cxx::__mutex& _M_get_mutex(); 216 217 public: 218 /** Invalidates all iterators. */ 219 void 220 _M_invalidate_all() const 221 { if (++_M_version == 0) _M_version = 1; } 222 }; 223} // namespace __gnu_debug 224 225#endif 226