234 lines
8.8 KiB
Plaintext
234 lines
8.8 KiB
Plaintext
// boost/chrono/system_clocks.hpp --------------------------------------------------------------//
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// Copyright 2008 Howard Hinnant
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// Copyright 2008 Beman Dawes
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// Copyright 2009-2011 Vicente J. Botet Escriba
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// Distributed under the Boost Software License, Version 1.0.
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// See http://www.boost.org/LICENSE_1_0.txt
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/*
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This code was derived by Beman Dawes from Howard Hinnant's time2_demo prototype.
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Many thanks to Howard for making his code available under the Boost license.
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The original code was modified to conform to Boost conventions and to section
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20.9 Time utilities [time] of the C++ committee's working paper N2798.
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See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2798.pdf.
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time2_demo contained this comment:
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Much thanks to Andrei Alexandrescu,
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Walter Brown,
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Peter Dimov,
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Jeff Garland,
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Terry Golubiewski,
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Daniel Krugler,
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Anthony Williams.
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*/
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/*
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TODO:
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* Fully implement error handling, with test cases.
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* Consider issues raised by Michael Marcin:
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> In the past I've seen QueryPerformanceCounter give incorrect results,
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> especially with SpeedStep processors on laptops. This was many years ago and
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> might have been fixed by service packs and drivers.
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>
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> Typically you check the results of QPC against GetTickCount to see if the
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> results are reasonable.
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> http://support.microsoft.com/kb/274323
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>
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> I've also heard of problems with QueryPerformanceCounter in multi-processor
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> systems.
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>
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> I know some people SetThreadAffinityMask to 1 for the current thread call
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> their QueryPerformance* functions then restore SetThreadAffinityMask. This
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> seems horrible to me because it forces your program to jump to another
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> physical processor if it isn't already on cpu0 but they claim it worked well
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> in practice because they called the timing functions infrequently.
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>
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> In the past I have chosen to use timeGetTime with timeBeginPeriod(1) for
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> high resolution timers to avoid these issues.
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*/
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#ifndef BOOST_CHRONO_SYSTEM_CLOCKS_HPP
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#define BOOST_CHRONO_SYSTEM_CLOCKS_HPP
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#include <boost/chrono/config.hpp>
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#include <boost/chrono/duration.hpp>
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#include <boost/chrono/time_point.hpp>
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#include <boost/chrono/detail/system.hpp>
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#include <boost/chrono/clock_string.hpp>
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#include <ctime>
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# if defined( BOOST_CHRONO_POSIX_API )
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# if ! defined(CLOCK_REALTIME) && ! defined (__hpux__)
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# error <time.h> does not supply CLOCK_REALTIME
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# endif
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# endif
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#ifdef BOOST_CHRONO_WINDOWS_API
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// The system_clock tick is 100 nanoseconds
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# define BOOST_SYSTEM_CLOCK_DURATION boost::chrono::duration<boost::int_least64_t, ratio<BOOST_RATIO_INTMAX_C(1), BOOST_RATIO_INTMAX_C(10000000)> >
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#else
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# define BOOST_SYSTEM_CLOCK_DURATION boost::chrono::nanoseconds
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#endif
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// this must occur after all of the includes and before any code appears:
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#ifndef BOOST_CHRONO_HEADER_ONLY
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#include <boost/config/abi_prefix.hpp> // must be the last #include
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#endif
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//----------------------------------------------------------------------------//
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// //
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// 20.9 Time utilities [time] //
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// synopsis //
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// //
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//----------------------------------------------------------------------------//
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namespace boost {
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namespace chrono {
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// Clocks
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class BOOST_CHRONO_DECL system_clock;
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#ifdef BOOST_CHRONO_HAS_CLOCK_STEADY
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class BOOST_CHRONO_DECL steady_clock;
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#endif
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#ifdef BOOST_CHRONO_HAS_CLOCK_STEADY
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typedef steady_clock high_resolution_clock; // as permitted by [time.clock.hires]
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#else
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typedef system_clock high_resolution_clock; // as permitted by [time.clock.hires]
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#endif
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//----------------------------------------------------------------------------//
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// //
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// 20.9.5 Clocks [time.clock] //
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// //
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//----------------------------------------------------------------------------//
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// If you're porting, clocks are the system-specific (non-portable) part.
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// You'll need to know how to get the current time and implement that under now().
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// You'll need to know what units (tick period) and representation makes the most
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// sense for your clock and set those accordingly.
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// If you know how to map this clock to time_t (perhaps your clock is std::time, which
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// makes that trivial), then you can fill out system_clock's to_time_t() and from_time_t().
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//----------------------------------------------------------------------------//
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// 20.9.5.1 Class system_clock [time.clock.system] //
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//----------------------------------------------------------------------------//
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class BOOST_CHRONO_DECL system_clock
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{
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public:
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typedef BOOST_SYSTEM_CLOCK_DURATION duration;
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typedef duration::rep rep;
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typedef duration::period period;
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typedef chrono::time_point<system_clock> time_point;
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BOOST_STATIC_CONSTEXPR bool is_steady = false;
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static BOOST_CHRONO_INLINE time_point now() BOOST_NOEXCEPT;
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#if !defined BOOST_CHRONO_DONT_PROVIDE_HYBRID_ERROR_HANDLING
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static BOOST_CHRONO_INLINE time_point now(system::error_code & ec);
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#endif
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static BOOST_CHRONO_INLINE std::time_t to_time_t(const time_point& t) BOOST_NOEXCEPT;
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static BOOST_CHRONO_INLINE time_point from_time_t(std::time_t t) BOOST_NOEXCEPT;
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};
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//----------------------------------------------------------------------------//
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// 20.9.5.2 Class steady_clock [time.clock.steady] //
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//----------------------------------------------------------------------------//
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// As permitted by [time.clock.steady]
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// The class steady_clock is conditionally supported.
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#ifdef BOOST_CHRONO_HAS_CLOCK_STEADY
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class BOOST_CHRONO_DECL steady_clock
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{
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public:
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typedef nanoseconds duration;
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typedef duration::rep rep;
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typedef duration::period period;
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typedef chrono::time_point<steady_clock> time_point;
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BOOST_STATIC_CONSTEXPR bool is_steady = true;
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static BOOST_CHRONO_INLINE time_point now() BOOST_NOEXCEPT;
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#if !defined BOOST_CHRONO_DONT_PROVIDE_HYBRID_ERROR_HANDLING
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static BOOST_CHRONO_INLINE time_point now(system::error_code & ec);
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#endif
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};
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#endif
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//----------------------------------------------------------------------------//
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// 20.9.5.3 Class high_resolution_clock [time.clock.hires] //
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//----------------------------------------------------------------------------//
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// As permitted, steady_clock or system_clock is a typedef for high_resolution_clock.
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// See synopsis.
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template<class CharT>
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struct clock_string<system_clock, CharT>
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{
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static std::basic_string<CharT> name()
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{
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static const CharT u[] =
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{ 's', 'y', 's', 't', 'e', 'm', '_', 'c', 'l', 'o', 'c', 'k' };
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static const std::basic_string<CharT> str(u, u + sizeof(u)
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/ sizeof(u[0]));
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return str;
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}
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static std::basic_string<CharT> since()
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{
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static const CharT
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u[] =
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{ ' ', 's', 'i', 'n', 'c', 'e', ' ', 'J', 'a', 'n', ' ', '1', ',', ' ', '1', '9', '7', '0' };
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static const std::basic_string<CharT> str(u, u + sizeof(u)
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/ sizeof(u[0]));
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return str;
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}
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};
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#ifdef BOOST_CHRONO_HAS_CLOCK_STEADY
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template<class CharT>
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struct clock_string<steady_clock, CharT>
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{
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static std::basic_string<CharT> name()
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{
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static const CharT
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u[] =
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{ 's', 't', 'e', 'a', 'd', 'y', '_', 'c', 'l', 'o', 'c', 'k' };
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static const std::basic_string<CharT> str(u, u + sizeof(u)
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/ sizeof(u[0]));
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return str;
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}
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static std::basic_string<CharT> since()
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{
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const CharT u[] =
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{ ' ', 's', 'i', 'n', 'c', 'e', ' ', 'b', 'o', 'o', 't' };
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const std::basic_string<CharT> str(u, u + sizeof(u) / sizeof(u[0]));
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return str;
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}
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};
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#endif
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} // namespace chrono
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} // namespace boost
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#ifndef BOOST_CHRONO_HEADER_ONLY
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// the suffix header occurs after all of our code:
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#include <boost/config/abi_suffix.hpp> // pops abi_prefix.hpp pragmas
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#else
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#include <boost/chrono/detail/inlined/chrono.hpp>
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#endif
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#endif // BOOST_CHRONO_SYSTEM_CLOCKS_HPP
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