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Edit File: basic_timed_mutex.hpp

#ifndef BOOST_BASIC_TIMED_MUTEX_WIN32_HPP
#define BOOST_BASIC_TIMED_MUTEX_WIN32_HPP

//  basic_timed_mutex_win32.hpp
//
//  (C) Copyright 2006-8 Anthony Williams
//  (C) Copyright 2011-2012 Vicente J. Botet Escriba
//
//  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)

#include <boost/assert.hpp>
#include <boost/thread/win32/thread_primitives.hpp>
#include <boost/thread/win32/interlocked_read.hpp>
#include <boost/thread/thread_time.hpp>
#if defined BOOST_THREAD_USES_DATETIME
#include <boost/thread/xtime.hpp>
#endif
#include <boost/detail/interlocked.hpp>
#ifdef BOOST_THREAD_USES_CHRONO
#include <boost/chrono/system_clocks.hpp>
#include <boost/chrono/ceil.hpp>
#endif
#include <boost/thread/detail/platform_time.hpp>

#include <boost/config/abi_prefix.hpp>

namespace boost
{
    namespace detail
    {
        struct basic_timed_mutex
        {
            BOOST_STATIC_CONSTANT(unsigned char,lock_flag_bit=31);
            BOOST_STATIC_CONSTANT(unsigned char,event_set_flag_bit=30);
            BOOST_STATIC_CONSTANT(long,lock_flag_value=1<<lock_flag_bit);
            BOOST_STATIC_CONSTANT(long,event_set_flag_value=1<<event_set_flag_bit);
            long active_count;
            void* event;

void initialize()
            {
                active_count=0;
                event=0;
            }

void destroy()
            {
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4312)
#endif
                void* const old_event=BOOST_INTERLOCKED_EXCHANGE_POINTER(&event,0);
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
                if(old_event)
                {
                    winapi::CloseHandle(old_event);
                }
            }

// Take the lock flag if it's available
            bool try_lock() BOOST_NOEXCEPT
            {
                return !win32::interlocked_bit_test_and_set(&active_count,lock_flag_bit);
            }

void lock()
            {
                if(try_lock())
                {
                    return;
                }
                long old_count=active_count;
                mark_waiting_and_try_lock(old_count);

if(old_count&lock_flag_value)
                {
                    void* const sem=get_event();

do
                    {
                        if(winapi::WaitForSingleObjectEx(sem,::boost::detail::win32::infinite,0)==0)
                        {
                            clear_waiting_and_try_lock(old_count);
                        }
                    }
                    while(old_count&lock_flag_value);
                }
            }

// Loop until the number of waiters has been incremented or we've taken the lock flag
            // The loop is necessary since this function may be called by multiple threads simultaneously
            void mark_waiting_and_try_lock(long& old_count)
            {
                for(;;)
                {
                    bool const was_locked=(old_count&lock_flag_value) ? true : false;
                    long const new_count=was_locked?(old_count+1):(old_count|lock_flag_value);
                    long const current=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&active_count,new_count,old_count);
                    if(current==old_count)
                    {
                        if(was_locked)
                            old_count=new_count;
                        // else we've taken the lock flag
                            // don't update old_count so that the calling function can see that
                            // the old lock flag was 0 and know that we've taken the lock flag
                        break;
                    }
                    old_count=current;
                }
            }

// Loop until someone else has taken the lock flag and cleared the event set flag or
            // until we've taken the lock flag and cleared the event set flag and decremented the
            // number of waiters
            // The loop is necessary since this function may be called by multiple threads simultaneously
            void clear_waiting_and_try_lock(long& old_count)
            {
                old_count&=~lock_flag_value;
                old_count|=event_set_flag_value;
                for(;;)
                {
                    long const new_count=((old_count&lock_flag_value)?old_count:((old_count-1)|lock_flag_value))&~event_set_flag_value;
                    long const current=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&active_count,new_count,old_count);
                    if(current==old_count)
                    {
                        // if someone else has taken the lock flag
                            // no need to update old_count since old_count == new_count (ignoring
                            // event_set_flag_value which the calling function doesn't care about)
                        // else we've taken the lock flag
                            // don't update old_count so that the calling function can see that
                            // the old lock flag was 0 and know that we've taken the lock flag
                        break;
                    }
                    old_count=current;
                }
            }

private:
            unsigned long getMs(detail::platform_duration const& d)
            {
                return static_cast<unsigned long>(d.getMs());
            }

template <typename Duration>
            unsigned long getMs(Duration const& d)
            {
                return static_cast<unsigned long>(chrono::ceil<chrono::milliseconds>(d).count());
            }

template <typename Clock, typename Timepoint, typename Duration>
            bool do_lock_until(Timepoint const& t, Duration const& max)
            {
                if(try_lock())
                {
                    return true;
                }

long old_count=active_count;
                mark_waiting_and_try_lock(old_count);

if(old_count&lock_flag_value)
                {
                    void* const sem=get_event();

// If the clock is the system clock, it may jump while this function
                    // is waiting. To compensate for this and time out near the correct
                    // time, we call WaitForSingleObjectEx() in a loop with a short
                    // timeout and recheck the time remaining each time through the loop.
                    do
                    {
                        Duration d(t - Clock::now());
                        if(d <= Duration::zero()) // timeout occurred
                        {
                            BOOST_INTERLOCKED_DECREMENT(&active_count);
                            return false;
                        }
                        if(max != Duration::zero())
                        {
                            d = (std::min)(d, max);
                        }
                        if(winapi::WaitForSingleObjectEx(sem,getMs(d),0)==0)
                        {
                            clear_waiting_and_try_lock(old_count);
                        }
                    }
                    while(old_count&lock_flag_value);
                }
                return true;
            }
        public:

#if defined BOOST_THREAD_USES_DATETIME
            bool timed_lock(::boost::system_time const& wait_until)
            {
                const detail::real_platform_timepoint t(wait_until);
                return do_lock_until<detail::real_platform_clock>(t, detail::platform_milliseconds(BOOST_THREAD_POLL_INTERVAL_MILLISECONDS));
            }

template<typename Duration>
            bool timed_lock(Duration const& timeout)
            {
                const detail::mono_platform_timepoint t(detail::mono_platform_clock::now() + detail::platform_duration(timeout));
                // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max)
                return do_lock_until<detail::mono_platform_clock>(t, detail::platform_duration::zero());
            }

bool timed_lock(boost::xtime const& timeout)
            {
                return timed_lock(boost::system_time(timeout));
            }
#endif
#ifdef BOOST_THREAD_USES_CHRONO
            template <class Rep, class Period>
            bool try_lock_for(const chrono::duration<Rep, Period>& rel_time)
            {
                const chrono::steady_clock::time_point t(chrono::steady_clock::now() + rel_time);
                typedef typename chrono::duration<Rep, Period> Duration;
                typedef typename common_type<Duration, typename chrono::steady_clock::duration>::type common_duration;
                // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max)
                return do_lock_until<chrono::steady_clock>(t, common_duration::zero());
            }
            template <class Duration>
            bool try_lock_until(const chrono::time_point<chrono::steady_clock, Duration>& t)
            {
                typedef typename common_type<Duration, typename chrono::steady_clock::duration>::type common_duration;
                // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max)
                return do_lock_until<chrono::steady_clock>(t, common_duration::zero());
            }
            template <class Clock, class Duration>
            bool try_lock_until(const chrono::time_point<Clock, Duration>& t)
            {
                typedef typename common_type<Duration, typename Clock::duration>::type common_duration;
                return do_lock_until<Clock>(t, common_duration(chrono::milliseconds(BOOST_THREAD_POLL_INTERVAL_MILLISECONDS)));
            }
#endif

void unlock()
            {
                // Clear the lock flag using atomic addition (works since long is always 32 bits on Windows)
                long const old_count=BOOST_INTERLOCKED_EXCHANGE_ADD(&active_count,lock_flag_value);
                // If someone is waiting to take the lock, set the event set flag and, if
                // the event set flag hadn't already been set, send an event.
                if(!(old_count&event_set_flag_value) && (old_count>lock_flag_value))
                {
                    if(!win32::interlocked_bit_test_and_set(&active_count,event_set_flag_bit))
                    {
                        winapi::SetEvent(get_event());
                    }
                }
            }

private:
            // Create an event in a thread-safe way
            // The first thread to create the event wins and all other thread will use that event
            void* get_event()
            {
                void* current_event=::boost::detail::interlocked_read_acquire(&event);

if(!current_event)
                {
                    void* const new_event=win32::create_anonymous_event(win32::auto_reset_event,win32::event_initially_reset);
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4311)
#pragma warning(disable:4312)
#endif
                    void* const old_event=BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(&event,new_event,0);
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
                    if(old_event!=0)
                    {
                        winapi::CloseHandle(new_event);
                        return old_event;
                    }
                    else
                    {
                        return new_event;
                    }
                }
                return current_event;
            }

};

}
}

#define BOOST_BASIC_TIMED_MUTEX_INITIALIZER {0}

#include <boost/config/abi_suffix.hpp>

#endif