Edit File: boost_sp_counted_base.h
// <tr1_impl/boost_sp_counted_base.h> -*- C++ -*- // Copyright (C) 2007, 2009 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/>. // shared_count.hpp // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd. // shared_ptr.hpp // Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes. // Copyright (C) 2001, 2002, 2003 Peter Dimov // weak_ptr.hpp // Copyright (C) 2001, 2002, 2003 Peter Dimov // enable_shared_from_this.hpp // Copyright (C) 2002 Peter Dimov // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) // GCC Note: based on version 1.32.0 of the Boost library. /** @file tr1_impl/boost_sp_counted_base.h * This is an internal header file, included by other library headers. * You should not attempt to use it directly. */ namespace std { _GLIBCXX_BEGIN_NAMESPACE_TR1 class bad_weak_ptr : public std::exception { public: virtual char const* what() const throw() #ifdef _GLIBCXX_INCLUDE_AS_CXX0X { return "std::bad_weak_ptr"; } #else { return "tr1::bad_weak_ptr"; } #endif }; // Substitute for bad_weak_ptr object in the case of -fno-exceptions. inline void __throw_bad_weak_ptr() { #if __EXCEPTIONS throw bad_weak_ptr(); #else __builtin_abort(); #endif } using __gnu_cxx::_Lock_policy; using __gnu_cxx::__default_lock_policy; using __gnu_cxx::_S_single; using __gnu_cxx::_S_mutex; using __gnu_cxx::_S_atomic; // Empty helper class except when the template argument is _S_mutex. template<_Lock_policy _Lp> class _Mutex_base { protected: // The atomic policy uses fully-fenced builtins, single doesn't care. enum { _S_need_barriers = 0 }; }; template<> class _Mutex_base<_S_mutex> : public __gnu_cxx::__mutex { protected: // This policy is used when atomic builtins are not available. // The replacement atomic operations might not have the necessary // memory barriers. enum { _S_need_barriers = 1 }; }; template<_Lock_policy _Lp = __default_lock_policy> class _Sp_counted_base : public _Mutex_base<_Lp> { public: _Sp_counted_base() : _M_use_count(1), _M_weak_count(1) { } virtual ~_Sp_counted_base() // nothrow { } // Called when _M_use_count drops to zero, to release the resources // managed by *this. virtual void _M_dispose() = 0; // nothrow // Called when _M_weak_count drops to zero. virtual void _M_destroy() // nothrow { delete this; } virtual void* _M_get_deleter(const std::type_info&) = 0; void _M_add_ref_copy() { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); } void _M_add_ref_lock(); void _M_release() // nothrow { if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1) { _M_dispose(); // There must be a memory barrier between dispose() and destroy() // to ensure that the effects of dispose() are observed in the // thread that runs destroy(). // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html if (_Mutex_base<_Lp>::_S_need_barriers) { _GLIBCXX_READ_MEM_BARRIER; _GLIBCXX_WRITE_MEM_BARRIER; } if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1) _M_destroy(); } } void _M_weak_add_ref() // nothrow { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); } void _M_weak_release() // nothrow { if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1) { if (_Mutex_base<_Lp>::_S_need_barriers) { // See _M_release(), // destroy() must observe results of dispose() _GLIBCXX_READ_MEM_BARRIER; _GLIBCXX_WRITE_MEM_BARRIER; } _M_destroy(); } } long _M_get_use_count() const // nothrow { // No memory barrier is used here so there is no synchronization // with other threads. return const_cast<const volatile _Atomic_word&>(_M_use_count); } private: _Sp_counted_base(_Sp_counted_base const&); _Sp_counted_base& operator=(_Sp_counted_base const&); _Atomic_word _M_use_count; // #shared _Atomic_word _M_weak_count; // #weak + (#shared != 0) }; template<> inline void _Sp_counted_base<_S_single>:: _M_add_ref_lock() { if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0) { _M_use_count = 0; __throw_bad_weak_ptr(); } } template<> inline void _Sp_counted_base<_S_mutex>:: _M_add_ref_lock() { __gnu_cxx::__scoped_lock sentry(*this); if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0) { _M_use_count = 0; __throw_bad_weak_ptr(); } } template<> inline void _Sp_counted_base<_S_atomic>:: _M_add_ref_lock() { // Perform lock-free add-if-not-zero operation. _Atomic_word __count; do { __count = _M_use_count; if (__count == 0) __throw_bad_weak_ptr(); // Replace the current counter value with the old value + 1, as // long as it's not changed meanwhile. } while (!__sync_bool_compare_and_swap(&_M_use_count, __count, __count + 1)); } _GLIBCXX_END_NAMESPACE_TR1 }
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