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1 // Copyright (c) 2014 Google Inc. (contributed by Remy Blank <rblank@google.com>)
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2 // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
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3 // Licensed under the MIT License:
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4 //
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5 // Permission is hereby granted, free of charge, to any person obtaining a copy
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6 // of this software and associated documentation files (the "Software"), to deal
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7 // in the Software without restriction, including without limitation the rights
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8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 // copies of the Software, and to permit persons to whom the Software is
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10 // furnished to do so, subject to the following conditions:
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11 //
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12 // The above copyright notice and this permission notice shall be included in
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13 // all copies or substantial portions of the Software.
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14 //
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15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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21 // THE SOFTWARE.
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22
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23 #pragma once
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24
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25 #include "units.h"
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26 #include <inttypes.h>
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27 #include "string.h"
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28
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29 KJ_BEGIN_HEADER
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30
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31 namespace kj {
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32 namespace _ { // private
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33
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34 class NanosecondLabel;
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35 class TimeLabel;
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36 class DateLabel;
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37
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38 static constexpr size_t TIME_STR_LEN = sizeof(int64_t) * 3 + 8;
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39 // Maximum length of a stringified time. 3 digits per byte of integer, plus 8 digits to cover
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40 // negative sign, decimal point, unit, NUL terminator, and anything else that might sneak in.
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41
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42 } // namespace _ (private)
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43
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44 using Duration = Quantity<int64_t, _::NanosecondLabel>;
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45 // A time value, in nanoseconds.
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46
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47 constexpr Duration NANOSECONDS = unit<Duration>();
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48 constexpr Duration MICROSECONDS = 1000 * NANOSECONDS;
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49 constexpr Duration MILLISECONDS = 1000 * MICROSECONDS;
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50 constexpr Duration SECONDS = 1000 * MILLISECONDS;
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51 constexpr Duration MINUTES = 60 * SECONDS;
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52 constexpr Duration HOURS = 60 * MINUTES;
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53 constexpr Duration DAYS = 24 * HOURS;
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54
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55 using TimePoint = Absolute<Duration, _::TimeLabel>;
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56 // An absolute time measured by some particular instance of `Timer` or `MonotonicClock`. `Time`s
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57 // from two different `Timer`s or `MonotonicClock`s may be measured from different origins and so
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58 // are not necessarily compatible.
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59
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60 using Date = Absolute<Duration, _::DateLabel>;
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61 // A point in real-world time, measured relative to the Unix epoch (Jan 1, 1970 00:00:00 UTC).
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62
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63 CappedArray<char, _::TIME_STR_LEN> KJ_STRINGIFY(TimePoint);
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64 CappedArray<char, _::TIME_STR_LEN> KJ_STRINGIFY(Date);
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65 CappedArray<char, _::TIME_STR_LEN> KJ_STRINGIFY(Duration);
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66
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67 constexpr Date UNIX_EPOCH = origin<Date>();
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68 // The `Date` representing Jan 1, 1970 00:00:00 UTC.
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69
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70 class Clock {
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71 // Interface to read the current date and time.
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72 public:
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73 virtual Date now() const = 0;
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74 };
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75
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76 class MonotonicClock {
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77 // Interface to read time in a way that increases as real-world time increases, independent of
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78 // any manual changes to the calendar date/time. Such a clock never "goes backwards" even if the
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79 // system administrator changes the calendar time or suspends the system. However, this clock's
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80 // time points are only meaningful in comparison to other time points from the same clock, and
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81 // cannot be used to determine the current calendar date.
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82
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83 public:
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84 virtual TimePoint now() const = 0;
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85 };
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86
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87 const Clock& nullClock();
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88 // A clock which always returns UNIX_EPOCH as the current time. Useful when you don't care about
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89 // time.
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90
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91 const Clock& systemCoarseCalendarClock();
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92 const Clock& systemPreciseCalendarClock();
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93 // A clock that reads the real system time.
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94 //
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95 // In well-designed code, this should only be called by the top-level dependency injector. All
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96 // other modules should request that the caller provide a Clock so that alternate clock
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97 // implementations can be injected for testing, simulation, reproducibility, and other purposes.
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98 //
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99 // The "coarse" version has precision around 1-10ms, while the "precise" version has precision
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100 // better than 1us. The "precise" version may be slightly slower, though on modern hardware and
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101 // a reasonable operating system the difference is usually negligible.
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102 //
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103 // Note: On Windows prior to Windows 8, there is no precise calendar clock; the "precise" clock
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104 // will be no more precise than the "coarse" clock in this case.
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105
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106 const MonotonicClock& systemCoarseMonotonicClock();
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107 const MonotonicClock& systemPreciseMonotonicClock();
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108 // A MonotonicClock that reads the real system time.
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109 //
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110 // In well-designed code, this should only be called by the top-level dependency injector. All
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111 // other modules should request that the caller provide a Clock so that alternate clock
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112 // implementations can be injected for testing, simulation, reproducibility, and other purposes.
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113 //
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114 // The "coarse" version has precision around 1-10ms, while the "precise" version has precision
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115 // better than 1us. The "precise" version may be slightly slower, though on modern hardware and
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116 // a reasonable operating system the difference is usually negligible.
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117 } // namespace kj
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118
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119 KJ_END_HEADER
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