| #ifndef BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_HPP_INCLUDED | |
| #define BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_HPP_INCLUDED | |
| // MS compatible compilers support #pragma once | |
| #if defined(_MSC_VER) && (_MSC_VER >= 1020) | |
| # pragma once | |
| #endif | |
| // | |
| // boost/detail/atomic_count.hpp - thread/SMP safe reference counter | |
| // | |
| // Copyright (c) 2001, 2002 Peter Dimov and Multi Media Ltd. | |
| // | |
| // 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) | |
| // | |
| // typedef <implementation-defined> boost::detail::atomic_count; | |
| // | |
| // atomic_count a(n); | |
| // | |
| // (n is convertible to long) | |
| // | |
| // Effects: Constructs an atomic_count with an initial value of n | |
| // | |
| // a; | |
| // | |
| // Returns: (long) the current value of a | |
| // | |
| // ++a; | |
| // | |
| // Effects: Atomically increments the value of a | |
| // Returns: (long) the new value of a | |
| // | |
| // --a; | |
| // | |
| // Effects: Atomically decrements the value of a | |
| // Returns: (long) the new value of a | |
| // | |
| // Important note: when --a returns zero, it must act as a | |
| // read memory barrier (RMB); i.e. the calling thread must | |
| // have a synchronized view of the memory | |
| // | |
| // On Intel IA-32 (x86) memory is always synchronized, so this | |
| // is not a problem. | |
| // | |
| // On many architectures the atomic instructions already act as | |
| // a memory barrier. | |
| // | |
| // This property is necessary for proper reference counting, since | |
| // a thread can update the contents of a shared object, then | |
| // release its reference, and another thread may immediately | |
| // release the last reference causing object destruction. | |
| // | |
| // The destructor needs to have a synchronized view of the | |
| // object to perform proper cleanup. | |
| // | |
| // Original example by Alexander Terekhov: | |
| // | |
| // Given: | |
| // | |
| // - a mutable shared object OBJ; | |
| // - two threads THREAD1 and THREAD2 each holding | |
| // a private smart_ptr object pointing to that OBJ. | |
| // | |
| // t1: THREAD1 updates OBJ (thread-safe via some synchronization) | |
| // and a few cycles later (after "unlock") destroys smart_ptr; | |
| // | |
| // t2: THREAD2 destroys smart_ptr WITHOUT doing any synchronization | |
| // with respect to shared mutable object OBJ; OBJ destructors | |
| // are called driven by smart_ptr interface... | |
| // | |
| #include <boost/config.hpp> | |
| #include <boost/smart_ptr/detail/sp_has_sync.hpp> | |
| #ifndef BOOST_HAS_THREADS | |
| namespace boost | |
| { | |
| namespace detail | |
| { | |
| typedef long atomic_count; | |
| } | |
| } | |
| #elif defined(BOOST_AC_USE_PTHREADS) | |
| # include <boost/smart_ptr/detail/atomic_count_pthreads.hpp> | |
| #elif defined( __GNUC__ ) && ( defined( __i386__ ) || defined( __x86_64__ ) ) | |
| # include <boost/smart_ptr/detail/atomic_count_gcc_x86.hpp> | |
| #elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__CYGWIN__) | |
| # include <boost/smart_ptr/detail/atomic_count_win32.hpp> | |
| #elif defined( BOOST_SP_HAS_SYNC ) | |
| # include <boost/smart_ptr/detail/atomic_count_sync.hpp> | |
| #elif defined(__GLIBCPP__) || defined(__GLIBCXX__) | |
| # include <boost/smart_ptr/detail/atomic_count_gcc.hpp> | |
| #elif defined(BOOST_HAS_PTHREADS) | |
| # define BOOST_AC_USE_PTHREADS | |
| # include <boost/smart_ptr/detail/atomic_count_pthreads.hpp> | |
| #else | |
| // Use #define BOOST_DISABLE_THREADS to avoid the error | |
| #error Unrecognized threading platform | |
| #endif | |
| #endif // #ifndef BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_HPP_INCLUDED |