00001 // Safe sequence/iterator base implementation -*- C++ -*- 00002 00003 // Copyright (C) 2003, 2004, 2005, 2006, 2009 00004 // Free Software Foundation, Inc. 00005 // 00006 // This file is part of the GNU ISO C++ Library. This library is free 00007 // software; you can redistribute it and/or modify it under the 00008 // terms of the GNU General Public License as published by the 00009 // Free Software Foundation; either version 3, or (at your option) 00010 // any later version. 00011 00012 // This library is distributed in the hope that it will be useful, 00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00015 // GNU General Public License for more details. 00016 00017 // Under Section 7 of GPL version 3, you are granted additional 00018 // permissions described in the GCC Runtime Library Exception, version 00019 // 3.1, as published by the Free Software Foundation. 00020 00021 // You should have received a copy of the GNU General Public License and 00022 // a copy of the GCC Runtime Library Exception along with this program; 00023 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00024 // <http://www.gnu.org/licenses/>. 00025 00026 /** @file debug/safe_base.h 00027 * This file is a GNU debug extension to the Standard C++ Library. 00028 */ 00029 00030 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H 00031 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1 00032 00033 #include <ext/concurrence.h> 00034 00035 namespace __gnu_debug 00036 { 00037 class _Safe_sequence_base; 00038 00039 /** \brief Basic functionality for a "safe" iterator. 00040 * 00041 * The %_Safe_iterator_base base class implements the functionality 00042 * of a safe iterator that is not specific to a particular iterator 00043 * type. It contains a pointer back to the sequence it references 00044 * along with iterator version information and pointers to form a 00045 * doubly-linked list of iterators referenced by the container. 00046 * 00047 * This class must not perform any operations that can throw an 00048 * exception, or the exception guarantees of derived iterators will 00049 * be broken. 00050 */ 00051 class _Safe_iterator_base 00052 { 00053 public: 00054 /** The sequence this iterator references; may be NULL to indicate 00055 a singular iterator. */ 00056 _Safe_sequence_base* _M_sequence; 00057 00058 /** The version number of this iterator. The sentinel value 0 is 00059 * used to indicate an invalidated iterator (i.e., one that is 00060 * singular because of an operation on the container). This 00061 * version number must equal the version number in the sequence 00062 * referenced by _M_sequence for the iterator to be 00063 * non-singular. 00064 */ 00065 unsigned int _M_version; 00066 00067 /** Pointer to the previous iterator in the sequence's list of 00068 iterators. Only valid when _M_sequence != NULL. */ 00069 _Safe_iterator_base* _M_prior; 00070 00071 /** Pointer to the next iterator in the sequence's list of 00072 iterators. Only valid when _M_sequence != NULL. */ 00073 _Safe_iterator_base* _M_next; 00074 00075 protected: 00076 /** Initializes the iterator and makes it singular. */ 00077 _Safe_iterator_base() 00078 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00079 { } 00080 00081 /** Initialize the iterator to reference the sequence pointed to 00082 * by @p__seq. @p __constant is true when we are initializing a 00083 * constant iterator, and false if it is a mutable iterator. Note 00084 * that @p __seq may be NULL, in which case the iterator will be 00085 * singular. Otherwise, the iterator will reference @p __seq and 00086 * be nonsingular. 00087 */ 00088 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) 00089 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00090 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } 00091 00092 /** Initializes the iterator to reference the same sequence that 00093 @p __x does. @p __constant is true if this is a constant 00094 iterator, and false if it is mutable. */ 00095 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) 00096 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) 00097 { this->_M_attach(__x._M_sequence, __constant); } 00098 00099 _Safe_iterator_base& 00100 operator=(const _Safe_iterator_base&); 00101 00102 explicit 00103 _Safe_iterator_base(const _Safe_iterator_base&); 00104 00105 ~_Safe_iterator_base() { this->_M_detach(); } 00106 00107 /** For use in _Safe_iterator. */ 00108 __gnu_cxx::__mutex& _M_get_mutex(); 00109 00110 public: 00111 /** Attaches this iterator to the given sequence, detaching it 00112 * from whatever sequence it was attached to originally. If the 00113 * new sequence is the NULL pointer, the iterator is left 00114 * unattached. 00115 */ 00116 void _M_attach(_Safe_sequence_base* __seq, bool __constant); 00117 00118 /** Likewise, but not thread-safe. */ 00119 void _M_attach_single(_Safe_sequence_base* __seq, bool __constant); 00120 00121 /** Detach the iterator for whatever sequence it is attached to, 00122 * if any. 00123 */ 00124 void _M_detach(); 00125 00126 /** Likewise, but not thread-safe. */ 00127 void _M_detach_single(); 00128 00129 /** Determines if we are attached to the given sequence. */ 00130 bool _M_attached_to(const _Safe_sequence_base* __seq) const 00131 { return _M_sequence == __seq; } 00132 00133 /** Is this iterator singular? */ 00134 bool _M_singular() const; 00135 00136 /** Can we compare this iterator to the given iterator @p __x? 00137 Returns true if both iterators are nonsingular and reference 00138 the same sequence. */ 00139 bool _M_can_compare(const _Safe_iterator_base& __x) const; 00140 }; 00141 00142 /** 00143 * @brief Base class that supports tracking of iterators that 00144 * reference a sequence. 00145 * 00146 * The %_Safe_sequence_base class provides basic support for 00147 * tracking iterators into a sequence. Sequences that track 00148 * iterators must derived from %_Safe_sequence_base publicly, so 00149 * that safe iterators (which inherit _Safe_iterator_base) can 00150 * attach to them. This class contains two linked lists of 00151 * iterators, one for constant iterators and one for mutable 00152 * iterators, and a version number that allows very fast 00153 * invalidation of all iterators that reference the container. 00154 * 00155 * This class must ensure that no operation on it may throw an 00156 * exception, otherwise "safe" sequences may fail to provide the 00157 * exception-safety guarantees required by the C++ standard. 00158 */ 00159 class _Safe_sequence_base 00160 { 00161 public: 00162 /// The list of mutable iterators that reference this container 00163 _Safe_iterator_base* _M_iterators; 00164 00165 /// The list of constant iterators that reference this container 00166 _Safe_iterator_base* _M_const_iterators; 00167 00168 /// The container version number. This number may never be 0. 00169 mutable unsigned int _M_version; 00170 00171 protected: 00172 // Initialize with a version number of 1 and no iterators 00173 _Safe_sequence_base() 00174 : _M_iterators(0), _M_const_iterators(0), _M_version(1) 00175 { } 00176 00177 /** Notify all iterators that reference this sequence that the 00178 sequence is being destroyed. */ 00179 ~_Safe_sequence_base() 00180 { this->_M_detach_all(); } 00181 00182 /** Detach all iterators, leaving them singular. */ 00183 void 00184 _M_detach_all(); 00185 00186 /** Detach all singular iterators. 00187 * @post for all iterators i attached to this sequence, 00188 * i->_M_version == _M_version. 00189 */ 00190 void 00191 _M_detach_singular(); 00192 00193 /** Revalidates all attached singular iterators. This method may 00194 * be used to validate iterators that were invalidated before 00195 * (but for some reason, such as an exception, need to become 00196 * valid again). 00197 */ 00198 void 00199 _M_revalidate_singular(); 00200 00201 /** Swap this sequence with the given sequence. This operation 00202 * also swaps ownership of the iterators, so that when the 00203 * operation is complete all iterators that originally referenced 00204 * one container now reference the other container. 00205 */ 00206 void 00207 _M_swap(_Safe_sequence_base& __x); 00208 00209 /** For use in _Safe_sequence. */ 00210 __gnu_cxx::__mutex& _M_get_mutex(); 00211 00212 public: 00213 /** Invalidates all iterators. */ 00214 void 00215 _M_invalidate_all() const 00216 { if (++_M_version == 0) _M_version = 1; } 00217 }; 00218 } // namespace __gnu_debug 00219 00220 #endif