| ////////////////////////////////////////////////////////////////////////////// |
| // |
| // (C) Copyright Ion Gaztanaga 2005-2009. 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) |
| // |
| // See http://www.boost.org/libs/interprocess for documentation. |
| // |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| #ifndef BOOST_INTERPROCESS_DETAIL_EMULATION_MUTEX_HPP |
| #define BOOST_INTERPROCESS_DETAIL_EMULATION_MUTEX_HPP |
| |
| #if (defined _MSC_VER) && (_MSC_VER >= 1200) |
| # pragma once |
| #endif |
| |
| #include <boost/interprocess/detail/config_begin.hpp> |
| #include <boost/interprocess/detail/workaround.hpp> |
| #include <boost/interprocess/detail/posix_time_types_wrk.hpp> |
| #include <boost/assert.hpp> |
| #include <boost/interprocess/detail/atomic.hpp> |
| #include <boost/cstdint.hpp> |
| #include <boost/interprocess/detail/os_thread_functions.hpp> |
| |
| namespace boost { |
| namespace interprocess { |
| namespace detail { |
| |
| class emulation_mutex |
| { |
| emulation_mutex(const emulation_mutex &); |
| emulation_mutex &operator=(const emulation_mutex &); |
| public: |
| |
| emulation_mutex(); |
| ~emulation_mutex(); |
| |
| void lock(); |
| bool try_lock(); |
| bool timed_lock(const boost::posix_time::ptime &abs_time); |
| void unlock(); |
| void take_ownership(){}; |
| private: |
| volatile boost::uint32_t m_s; |
| }; |
| |
| inline emulation_mutex::emulation_mutex() |
| : m_s(0) |
| { |
| //Note that this class is initialized to zero. |
| //So zeroed memory can be interpreted as an |
| //initialized mutex |
| } |
| |
| inline emulation_mutex::~emulation_mutex() |
| { |
| //Trivial destructor |
| } |
| |
| inline void emulation_mutex::lock(void) |
| { |
| do{ |
| boost::uint32_t prev_s = detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_s), 1, 0); |
| |
| if (m_s == 1 && prev_s == 0){ |
| break; |
| } |
| // relinquish current timeslice |
| detail::thread_yield(); |
| }while (true); |
| } |
| |
| inline bool emulation_mutex::try_lock(void) |
| { |
| boost::uint32_t prev_s = detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_s), 1, 0); |
| return m_s == 1 && prev_s == 0; |
| } |
| |
| inline bool emulation_mutex::timed_lock(const boost::posix_time::ptime &abs_time) |
| { |
| if(abs_time == boost::posix_time::pos_infin){ |
| this->lock(); |
| return true; |
| } |
| //Obtain current count and target time |
| boost::posix_time::ptime now = microsec_clock::universal_time(); |
| |
| if(now >= abs_time) return false; |
| |
| do{ |
| if(this->try_lock()){ |
| break; |
| } |
| now = microsec_clock::universal_time(); |
| |
| if(now >= abs_time){ |
| return false; |
| } |
| // relinquish current time slice |
| detail::thread_yield(); |
| }while (true); |
| |
| return true; |
| } |
| |
| inline void emulation_mutex::unlock(void) |
| { detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_s), 0, 1); } |
| |
| } //namespace detail { |
| } //namespace interprocess { |
| } //namespace boost { |
| |
| #endif //BOOST_INTERPROCESS_DETAIL_EMULATION_MUTEX_HPP |