1#ifndef DATE_TIME_HIGHRES_TIME_CLOCK_HPP___
2#define DATE_TIME_HIGHRES_TIME_CLOCK_HPP___
3
4/* Copyright (c) 2002,2003,2005 CrystalClear Software, Inc.
5 * Use, modification and distribution is subject to the
6 * Boost Software License, Version 1.0. (See accompanying
7 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
8 * Author: Jeff Garland, Bart Garst
9 * $Date$
10 */
11
12
13/*! @file microsec_time_clock.hpp
14 This file contains a high resolution time clock implementation.
15*/
16
17#include <boost/cstdint.hpp>
18#include <boost/shared_ptr.hpp>
19#include <boost/detail/workaround.hpp>
20#include <boost/date_time/compiler_config.hpp>
21#include <boost/date_time/c_time.hpp>
22#include <boost/date_time/time_clock.hpp>
23#if defined(BOOST_HAS_FTIME)
24#include <boost/winapi/time.hpp>
25#endif
26
27#ifdef BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK
28
29namespace boost {
30namespace date_time {
31
32 //! A clock providing microsecond level resolution
33 /*! A high precision clock that measures the local time
34 * at a resolution up to microseconds and adjusts to the
35 * resolution of the time system. For example, for the
36 * a library configuration with nano second resolution,
37 * the last 3 places of the fractional seconds will always
38 * be 000 since there are 1000 nano-seconds in a micro second.
39 */
40 template<class time_type>
41 class microsec_clock
42 {
43 private:
44 //! Type for the function used to convert time_t to tm
45 typedef std::tm* (*time_converter)(const std::time_t*, std::tm*);
46
47 public:
48 typedef typename time_type::date_type date_type;
49 typedef typename time_type::time_duration_type time_duration_type;
50 typedef typename time_duration_type::rep_type resolution_traits_type;
51
52 //! return a local time object for the given zone, based on computer clock
53 //JKG -- looks like we could rewrite this against universal_time
54 template<class time_zone_type>
55 static time_type local_time(shared_ptr<time_zone_type> tz_ptr)
56 {
57 typedef typename time_type::utc_time_type utc_time_type;
58 typedef second_clock<utc_time_type> second_clock;
59 // we'll need to know the utc_offset this machine has
60 // in order to get a utc_time_type set to utc
61 utc_time_type utc_time = second_clock::universal_time();
62 time_duration_type utc_offset = second_clock::local_time() - utc_time;
63 // use micro clock to get a local time with sub seconds
64 // and adjust it to get a true utc time reading with sub seconds
65 utc_time = microsec_clock<utc_time_type>::local_time() - utc_offset;
66 return time_type(utc_time, tz_ptr);
67 }
68
69 //! Returns the local time based on computer clock settings
70 static time_type local_time()
71 {
72 return create_time(converter: &c_time::localtime);
73 }
74
75 //! Returns the UTC time based on computer settings
76 static time_type universal_time()
77 {
78 return create_time(converter: &c_time::gmtime);
79 }
80
81 private:
82 static time_type create_time(time_converter converter)
83 {
84#ifdef BOOST_HAS_GETTIMEOFDAY
85 timeval tv;
86 gettimeofday(tv: &tv, tz: 0); //gettimeofday does not support TZ adjust on Linux.
87 std::time_t t = tv.tv_sec;
88 boost::uint32_t sub_sec = tv.tv_usec;
89#elif defined(BOOST_HAS_FTIME)
90 boost::winapi::FILETIME_ ft;
91 boost::winapi::GetSystemTimeAsFileTime(&ft);
92#if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3205))
93 // Some runtime library implementations expect local times as the norm for ctime functions.
94 {
95 boost::winapi::FILETIME_ local_ft;
96 boost::winapi::FileTimeToLocalFileTime(&ft, &local_ft);
97 ft = local_ft;
98 }
99#endif
100
101 boost::uint64_t micros = file_time_to_microseconds(ft); // it will not wrap, since ft is the current time
102 // and cannot be before 1970-Jan-01
103 std::time_t t = static_cast<std::time_t>(micros / 1000000UL); // seconds since epoch
104 // microseconds -- static casts suppress warnings
105 boost::uint32_t sub_sec = static_cast<boost::uint32_t>(micros % 1000000UL);
106#else
107#error Internal Boost.DateTime error: BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK is defined, however neither gettimeofday nor FILETIME support is detected.
108#endif
109
110 std::tm curr;
111 std::tm* curr_ptr = converter(&t, &curr);
112 date_type d(static_cast< typename date_type::year_type::value_type >(curr_ptr->tm_year + 1900),
113 static_cast< typename date_type::month_type::value_type >(curr_ptr->tm_mon + 1),
114 static_cast< typename date_type::day_type::value_type >(curr_ptr->tm_mday));
115
116 //The following line will adjust the fractional second tick in terms
117 //of the current time system. For example, if the time system
118 //doesn't support fractional seconds then res_adjust returns 0
119 //and all the fractional seconds return 0.
120 int adjust = static_cast< int >(resolution_traits_type::res_adjust() / 1000000);
121
122 time_duration_type td(static_cast< typename time_duration_type::hour_type >(curr_ptr->tm_hour),
123 static_cast< typename time_duration_type::min_type >(curr_ptr->tm_min),
124 static_cast< typename time_duration_type::sec_type >(curr_ptr->tm_sec),
125 sub_sec * adjust);
126
127 return time_type(d,td);
128 }
129
130#if defined(BOOST_HAS_FTIME)
131 /*!
132 * The function converts file_time into number of microseconds elapsed since 1970-Jan-01
133 *
134 * \note Only dates after 1970-Jan-01 are supported. Dates before will be wrapped.
135 */
136 static boost::uint64_t file_time_to_microseconds(boost::winapi::FILETIME_ const& ft)
137 {
138 // shift is difference between 1970-Jan-01 & 1601-Jan-01
139 // in 100-nanosecond units
140 const boost::uint64_t shift = 116444736000000000ULL; // (27111902 << 32) + 3577643008
141
142 // 100-nanos since 1601-Jan-01
143 boost::uint64_t ft_as_integer = (static_cast< boost::uint64_t >(ft.dwHighDateTime) << 32) | static_cast< boost::uint64_t >(ft.dwLowDateTime);
144
145 ft_as_integer -= shift; // filetime is now 100-nanos since 1970-Jan-01
146 return (ft_as_integer / 10U); // truncate to microseconds
147 }
148#endif
149 };
150
151
152} } //namespace date_time
153
154#endif //BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK
155
156
157#endif
158
159

source code of boost/libs/date_time/include/boost/date_time/microsec_time_clock.hpp