libstdc++
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00001 // Safe sequence/iterator base implementation -*- C++ -*- 00002 00003 // Copyright (C) 2003-2019 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file debug/safe_base.h 00026 * This file is a GNU debug extension to the Standard C++ Library. 00027 */ 00028 00029 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H 00030 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1 00031 00032 #include <ext/concurrence.h> 00033 00034 namespace __gnu_debug 00035 { 00036 class _Safe_sequence_base; 00037 00038 /** \brief Basic functionality for a @a safe iterator. 00039 * 00040 * The %_Safe_iterator_base base class implements the functionality 00041 * of a safe iterator that is not specific to a particular iterator 00042 * type. It contains a pointer back to the sequence it references 00043 * along with iterator version information and pointers to form a 00044 * doubly-linked list of iterators referenced by the container. 00045 * 00046 * This class must not perform any operations that can throw an 00047 * exception, or the exception guarantees of derived iterators will 00048 * be broken. 00049 */ 00050 class _Safe_iterator_base 00051 { 00052 friend class _Safe_sequence_base; 00053 00054 public: 00055 /** The sequence this iterator references; may be NULL to indicate 00056 a singular iterator. */ 00057 _Safe_sequence_base* _M_sequence; 00058 00059 /** The version number of this iterator. The sentinel value 0 is 00060 * used to indicate an invalidated iterator (i.e., one that is 00061 * singular because of an operation on the container). This 00062 * version number must equal the version number in the sequence 00063 * referenced by _M_sequence for the iterator to be 00064 * non-singular. 00065 */ 00066 unsigned int _M_version; 00067 00068 /** Pointer to the previous iterator in the sequence's list of 00069 iterators. Only valid when _M_sequence != NULL. */ 00070 _Safe_iterator_base* _M_prior; 00071 00072 /** Pointer to the next iterator in the sequence's list of 00073 iterators. Only valid when _M_sequence != NULL. */ 00074 _Safe_iterator_base* _M_next; 00075 00076 protected: 00077 /** Initializes the iterator and makes it singular. */ 00078 _Safe_iterator_base() 00079 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00080 { } 00081 00082 /** Initialize the iterator to reference the sequence pointed to 00083 * by @p __seq. @p __constant is true when we are initializing a 00084 * constant iterator, and false if it is a mutable iterator. Note 00085 * that @p __seq may be NULL, in which case the iterator will be 00086 * singular. Otherwise, the iterator will reference @p __seq and 00087 * be nonsingular. 00088 */ 00089 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 00090 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00091 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 00092 00093 /** Initializes the iterator to reference the same sequence that 00094 @p __x does. @p __constant is true if this is a constant 00095 iterator, and false if it is mutable. */ 00096 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 00097 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00098 { this->_M_attach(__x._M_sequence, __constant); } 00099 00100 ~_Safe_iterator_base() { this->_M_detach(); } 00101 00102 /** For use in _Safe_iterator. */ 00103 __gnu_cxx::__mutex& 00104 _M_get_mutex() throw (); 00105 00106 /** Attaches this iterator to the given sequence, detaching it 00107 * from whatever sequence it was attached to originally. If the 00108 * new sequence is the NULL pointer, the iterator is left 00109 * unattached. 00110 */ 00111 void 00112 _M_attach(_Safe_sequence_base* __seq, bool __constant); 00113 00114 /** Likewise, but not thread-safe. */ 00115 void 00116 _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw (); 00117 00118 /** Detach the iterator for whatever sequence it is attached to, 00119 * if any. 00120 */ 00121 void 00122 _M_detach(); 00123 00124 public: 00125 /** Likewise, but not thread-safe. */ 00126 void 00127 _M_detach_single() throw (); 00128 00129 /** Determines if we are attached to the given sequence. */ 00130 bool 00131 _M_attached_to(const _Safe_sequence_base* __seq) const 00132 { return _M_sequence == __seq; } 00133 00134 /** Is this iterator singular? */ 00135 _GLIBCXX_PURE bool 00136 _M_singular() const throw (); 00137 00138 /** Can we compare this iterator to the given iterator @p __x? 00139 Returns true if both iterators are nonsingular and reference 00140 the same sequence. */ 00141 _GLIBCXX_PURE bool 00142 _M_can_compare(const _Safe_iterator_base& __x) const throw (); 00143 00144 /** Invalidate the iterator, making it singular. */ 00145 void 00146 _M_invalidate() 00147 { _M_version = 0; } 00148 00149 /** Reset all member variables */ 00150 void 00151 _M_reset() throw (); 00152 00153 /** Unlink itself */ 00154 void 00155 _M_unlink() throw () 00156 { 00157 if (_M_prior) 00158 _M_prior->_M_next = _M_next; 00159 if (_M_next) 00160 _M_next->_M_prior = _M_prior; 00161 } 00162 }; 00163 00164 /** Iterators that derive from _Safe_iterator_base can be determined singular 00165 * or non-singular. 00166 **/ 00167 inline bool 00168 __check_singular_aux(const _Safe_iterator_base* __x) 00169 { return __x->_M_singular(); } 00170 00171 /** 00172 * @brief Base class that supports tracking of iterators that 00173 * reference a sequence. 00174 * 00175 * The %_Safe_sequence_base class provides basic support for 00176 * tracking iterators into a sequence. Sequences that track 00177 * iterators must derived from %_Safe_sequence_base publicly, so 00178 * that safe iterators (which inherit _Safe_iterator_base) can 00179 * attach to them. This class contains two linked lists of 00180 * iterators, one for constant iterators and one for mutable 00181 * iterators, and a version number that allows very fast 00182 * invalidation of all iterators that reference the container. 00183 * 00184 * This class must ensure that no operation on it may throw an 00185 * exception, otherwise @a safe sequences may fail to provide the 00186 * exception-safety guarantees required by the C++ standard. 00187 */ 00188 class _Safe_sequence_base 00189 { 00190 friend class _Safe_iterator_base; 00191 00192 public: 00193 /// The list of mutable iterators that reference this container 00194 _Safe_iterator_base* _M_iterators; 00195 00196 /// The list of constant iterators that reference this container 00197 _Safe_iterator_base* _M_const_iterators; 00198 00199 /// The container version number. This number may never be 0. 00200 mutable unsigned int _M_version; 00201 00202 protected: 00203 // Initialize with a version number of 1 and no iterators 00204 _Safe_sequence_base() _GLIBCXX_NOEXCEPT 00205 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 00206 { } 00207 00208 #if __cplusplus >= 201103L 00209 _Safe_sequence_base(const _Safe_sequence_base&) noexcept 00210 : _Safe_sequence_base() { } 00211 00212 // Move constructor swap iterators. 00213 _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept 00214 : _Safe_sequence_base() 00215 { _M_swap(__seq); } 00216 #endif 00217 00218 /** Notify all iterators that reference this sequence that the 00219 sequence is being destroyed. */ 00220 ~_Safe_sequence_base() 00221 { this->_M_detach_all(); } 00222 00223 /** Detach all iterators, leaving them singular. */ 00224 void 00225 _M_detach_all(); 00226 00227 /** Detach all singular iterators. 00228 * @post for all iterators i attached to this sequence, 00229 * i->_M_version == _M_version. 00230 */ 00231 void 00232 _M_detach_singular(); 00233 00234 /** Revalidates all attached singular iterators. This method may 00235 * be used to validate iterators that were invalidated before 00236 * (but for some reason, such as an exception, need to become 00237 * valid again). 00238 */ 00239 void 00240 _M_revalidate_singular(); 00241 00242 /** Swap this sequence with the given sequence. This operation 00243 * also swaps ownership of the iterators, so that when the 00244 * operation is complete all iterators that originally referenced 00245 * one container now reference the other container. 00246 */ 00247 void 00248 _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT; 00249 00250 /** For use in _Safe_sequence. */ 00251 __gnu_cxx::__mutex& 00252 _M_get_mutex() throw (); 00253 00254 /** Invalidates all iterators. */ 00255 void 00256 _M_invalidate_all() const 00257 { if (++_M_version == 0) _M_version = 1; } 00258 00259 private: 00260 /** Attach an iterator to this sequence. */ 00261 void 00262 _M_attach(_Safe_iterator_base* __it, bool __constant); 00263 00264 /** Likewise but not thread safe. */ 00265 void 00266 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw (); 00267 00268 /** Detach an iterator from this sequence */ 00269 void 00270 _M_detach(_Safe_iterator_base* __it); 00271 00272 /** Likewise but not thread safe. */ 00273 void 00274 _M_detach_single(_Safe_iterator_base* __it) throw (); 00275 }; 00276 } // namespace __gnu_debug 00277 00278 #endif