// Safe sequence/iterator base implementation -*- C++ -*- // Copyright (C) 2003-2020 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file debug/safe_base.h * This file is a GNU debug extension to the Standard C++ Library. */ #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H #define _GLIBCXX_DEBUG_SAFE_BASE_H 1 #include <ext/concurrence.h> namespace __gnu_debug { class _Safe_sequence_base; /** \brief Basic functionality for a @a safe iterator. * * The %_Safe_iterator_base base class implements the functionality * of a safe iterator that is not specific to a particular iterator * type. It contains a pointer back to the sequence it references * along with iterator version information and pointers to form a * doubly-linked list of iterators referenced by the container. * * This class must not perform any operations that can throw an * exception, or the exception guarantees of derived iterators will * be broken. */ class _Safe_iterator_base { friend class _Safe_sequence_base; public: /** The sequence this iterator references; may be NULL to indicate a singular iterator. */ _Safe_sequence_base* _M_sequence; /** The version number of this iterator. The sentinel value 0 is * used to indicate an invalidated iterator (i.e., one that is * singular because of an operation on the container). This * version number must equal the version number in the sequence * referenced by _M_sequence for the iterator to be * non-singular. */ unsigned int _M_version; /** Pointer to the previous iterator in the sequence's list of iterators. Only valid when _M_sequence != NULL. */ _Safe_iterator_base* _M_prior; /** Pointer to the next iterator in the sequence's list of iterators. Only valid when _M_sequence != NULL. */ _Safe_iterator_base* _M_next; protected: /** Initializes the iterator and makes it singular. */ _Safe_iterator_base() : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) { } /** Initialize the iterator to reference the sequence pointed to * by @p __seq. @p __constant is true when we are initializing a * constant iterator, and false if it is a mutable iterator. Note * that @p __seq may be NULL, in which case the iterator will be * singular. Otherwise, the iterator will reference @p __seq and * be nonsingular. */ _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant) : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); } /** Initializes the iterator to reference the same sequence that @p __x does. @p __constant is true if this is a constant iterator, and false if it is mutable. */ _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant) : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0) { this->_M_attach(__x._M_sequence, __constant); } ~_Safe_iterator_base() { this->_M_detach(); } /** For use in _Safe_iterator. */ __gnu_cxx::__mutex& _M_get_mutex() throw (); /** Attaches this iterator to the given sequence, detaching it * from whatever sequence it was attached to originally. If the * new sequence is the NULL pointer, the iterator is left * unattached. */ void _M_attach(_Safe_sequence_base* __seq, bool __constant); /** Likewise, but not thread-safe. */ void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw (); /** Detach the iterator for whatever sequence it is attached to, * if any. */ void _M_detach(); public: /** Likewise, but not thread-safe. */ void _M_detach_single() throw (); /** Determines if we are attached to the given sequence. */ bool _M_attached_to(const _Safe_sequence_base* __seq) const { return _M_sequence == __seq; } /** Is this iterator singular? */ _GLIBCXX_PURE bool _M_singular() const throw (); /** Can we compare this iterator to the given iterator @p __x? Returns true if both iterators are nonsingular and reference the same sequence. */ _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw (); /** Invalidate the iterator, making it singular. */ void _M_invalidate() { _M_version = 0; } /** Reset all member variables */ void _M_reset() throw (); /** Unlink itself */ void _M_unlink() throw () { if (_M_prior) _M_prior->_M_next = _M_next; if (_M_next) _M_next->_M_prior = _M_prior; } }; /** Iterators that derive from _Safe_iterator_base can be determined singular * or non-singular. **/ inline bool __check_singular_aux(const _Safe_iterator_base* __x) { return __x->_M_singular(); } /** * @brief Base class that supports tracking of iterators that * reference a sequence. * * The %_Safe_sequence_base class provides basic support for * tracking iterators into a sequence. Sequences that track * iterators must derived from %_Safe_sequence_base publicly, so * that safe iterators (which inherit _Safe_iterator_base) can * attach to them. This class contains two linked lists of * iterators, one for constant iterators and one for mutable * iterators, and a version number that allows very fast * invalidation of all iterators that reference the container. * * This class must ensure that no operation on it may throw an * exception, otherwise @a safe sequences may fail to provide the * exception-safety guarantees required by the C++ standard. */ class _Safe_sequence_base { friend class _Safe_iterator_base; public: /// The list of mutable iterators that reference this container _Safe_iterator_base* _M_iterators; /// The list of constant iterators that reference this container _Safe_iterator_base* _M_const_iterators; /// The container version number. This number may never be 0. mutable unsigned int _M_version; protected: // Initialize with a version number of 1 and no iterators _Safe_sequence_base() _GLIBCXX_NOEXCEPT : _M_iterators(0), _M_const_iterators(0), _M_version(1) { } #if __cplusplus >= 201103L _Safe_sequence_base(const _Safe_sequence_base&) noexcept : _Safe_sequence_base() { } // Move constructor swap iterators. _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept : _Safe_sequence_base() { _M_swap(__seq); } #endif /** Notify all iterators that reference this sequence that the sequence is being destroyed. */ ~_Safe_sequence_base() { this->_M_detach_all(); } /** Detach all iterators, leaving them singular. */ void _M_detach_all(); /** Detach all singular iterators. * @post for all iterators i attached to this sequence, * i->_M_version == _M_version. */ void _M_detach_singular(); /** Revalidates all attached singular iterators. This method may * be used to validate iterators that were invalidated before * (but for some reason, such as an exception, need to become * valid again). */ void _M_revalidate_singular(); /** Swap this sequence with the given sequence. This operation * also swaps ownership of the iterators, so that when the * operation is complete all iterators that originally referenced * one container now reference the other container. */ void _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT; /** For use in _Safe_sequence. */ __gnu_cxx::__mutex& _M_get_mutex() throw (); /** Invalidates all iterators. */ void _M_invalidate_all() const { if (++_M_version == 0) _M_version = 1; } private: /** Attach an iterator to this sequence. */ void _M_attach(_Safe_iterator_base* __it, bool __constant); /** Likewise but not thread safe. */ void _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw (); /** Detach an iterator from this sequence */ void _M_detach(_Safe_iterator_base* __it); /** Likewise but not thread safe. */ void _M_detach_single(_Safe_iterator_base* __it) throw (); }; } // namespace __gnu_debug #endif