time/Math: new library
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Max Kellermann
parent
273771ffec
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764eaadd25
53
src/time/Calendar.hxx
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53
src/time/Calendar.hxx
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/*
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* Copyright 2012-2019 Max Kellermann <max.kellermann@gmail.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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constexpr bool
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IsLeapYear(unsigned y) noexcept
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{
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return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0);
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}
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constexpr unsigned
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DaysInFebruary(unsigned year) noexcept
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{
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return IsLeapYear(year) ? 29 : 28;
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}
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constexpr unsigned
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DaysInMonth(unsigned month, unsigned year) noexcept
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{
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if (month == 4 || month == 6 || month == 9 || month == 11)
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return 30;
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else if (month != 2)
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return 31;
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else
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return DaysInFebruary(year);
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}
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115
src/time/Math.cxx
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115
src/time/Math.cxx
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/*
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* Copyright 2007-2020 CM4all GmbH
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* All rights reserved.
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*
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* author: Max Kellermann <mk@cm4all.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "Math.hxx"
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#include "Calendar.hxx"
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#include "Convert.hxx"
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#include <time.h>
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std::chrono::system_clock::time_point
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PrecedingMidnightLocal(std::chrono::system_clock::time_point t) noexcept
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try {
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auto tm = LocalTime(t);
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tm.tm_sec = 0;
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tm.tm_min = 0;
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tm.tm_hour = 0;
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return MakeTime(tm);
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} catch (...) {
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/* best-effort fallback for this exotic error condition */
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return t;
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}
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static void
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IncrementMonth(struct tm &tm) noexcept
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{
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++tm.tm_mon;
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if (tm.tm_mon >= 12) {
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/* roll over to next year */
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tm.tm_mon = 0;
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++tm.tm_year;
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}
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}
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void
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EndOfMonth(struct tm &tm) noexcept
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{
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tm.tm_sec = 0;
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tm.tm_min = 0;
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tm.tm_hour = 0;
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tm.tm_mday = 1;
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IncrementMonth(tm);
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}
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void
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IncrementDay(struct tm &tm) noexcept
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{
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const unsigned max_day = DaysInMonth(tm.tm_mon + 1, tm.tm_year + 1900);
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++tm.tm_mday;
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if ((unsigned)tm.tm_mday > max_day) {
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/* roll over to next month */
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tm.tm_mday = 1;
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IncrementMonth(tm);
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}
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++tm.tm_wday;
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if (tm.tm_wday >= 7)
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tm.tm_wday = 0;
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}
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void
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DecrementDay(struct tm &tm) noexcept
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{
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--tm.tm_mday;
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if (tm.tm_mday < 1) {
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/* roll over to previous month */
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--tm.tm_mon;
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if (tm.tm_mon < 0) {
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/* roll over to previous eyar */
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tm.tm_mon = 11;
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--tm.tm_year;
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}
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const unsigned max_day = DaysInMonth(tm.tm_mon + 1,
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tm.tm_year + 1900);
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tm.tm_mday = max_day;
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}
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--tm.tm_wday;
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if (tm.tm_wday < 0)
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tm.tm_wday = 6;
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}
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73
src/time/Math.hxx
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73
src/time/Math.hxx
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@ -0,0 +1,73 @@
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/*
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* Copyright 2007-2020 CM4all GmbH
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* All rights reserved.
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*
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* author: Max Kellermann <mk@cm4all.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "util/Compiler.h"
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#include <chrono>
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struct tm;
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/**
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* Calculates the preceding midnight time point in the current time
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* zone.
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*/
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gcc_const
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std::chrono::system_clock::time_point
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PrecedingMidnightLocal(std::chrono::system_clock::time_point t) noexcept;
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/**
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* Calculate the end of the current month (i.e. midnight on the 1st of
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* the following month). Does NOT keeps the tm_wday and tm_yday
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* attributes updated, and ignores day light saving transitions.
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*/
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void
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EndOfMonth(struct tm &tm) noexcept;
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/**
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* Calculate the next day, keeping month/year wraparounds and leap
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* days in mind. Keeps the tm_wday attribute updated, but not other
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* derived attributes such as tm_yday, and ignores day light saving
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* transitions.
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*/
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void
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IncrementDay(struct tm &tm) noexcept;
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/**
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* Calculate the previous day, keeping month/year wraparounds and leap
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* days in mind. Keeps the tm_wday attribute updated, but not other
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* derived attributes such as tm_yday, and ignores day light saving
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* transitions.
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*/
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void
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DecrementDay(struct tm &tm) noexcept;
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@ -3,6 +3,7 @@ time = static_library(
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'Parser.cxx',
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'Convert.cxx',
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'ISO8601.cxx',
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'Math.cxx',
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include_directories: inc,
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)
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