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95 lines
2.2 KiB
C++
95 lines
2.2 KiB
C++
#ifndef BOOST_DETAIL_LWM_WIN32_HPP_INCLUDED
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#define BOOST_DETAIL_LWM_WIN32_HPP_INCLUDED
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#if _MSC_VER >= 1020
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#pragma once
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#endif
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//
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// boost/detail/lwm_win32.hpp
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//
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// Copyright (c) 2002 Peter Dimov and Multi Media Ltd.
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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#include <boost/detail/winapi.hpp>
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#ifdef __BORLANDC__
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# pragma warn -8027 // Functions containing while are not expanded inline
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#endif
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namespace boost
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{
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namespace detail
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{
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class lightweight_mutex
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{
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private:
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long l_;
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lightweight_mutex(lightweight_mutex const &);
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lightweight_mutex & operator=(lightweight_mutex const &);
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public:
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lightweight_mutex(): l_(0)
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{
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}
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class scoped_lock;
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friend class scoped_lock;
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class scoped_lock
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{
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private:
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lightweight_mutex & m_;
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scoped_lock(scoped_lock const &);
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scoped_lock & operator=(scoped_lock const &);
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public:
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explicit scoped_lock(lightweight_mutex & m): m_(m)
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{
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while( winapi::InterlockedExchange(&m_.l_, 1) )
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{
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// Note: changed to Sleep(1) from Sleep(0).
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// According to MSDN, Sleep(0) will never yield
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// to a lower-priority thread, whereas Sleep(1)
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// will. Performance seems not to be affected.
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winapi::Sleep(1);
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}
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}
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~scoped_lock()
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{
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winapi::InterlockedExchange(&m_.l_, 0);
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// Note: adding a yield here will make
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// the spinlock more fair and will increase the overall
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// performance of some applications substantially in
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// high contention situations, but will penalize the
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// low contention / single thread case up to 5x
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}
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};
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};
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} // namespace detail
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} // namespace boost
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#ifdef __BORLANDC__
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# pragma warn .8027 // Functions containing while are not expanded inline
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#endif
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#endif // #ifndef BOOST_DETAIL_LWM_WIN32_HPP_INCLUDED
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