diff --git a/src/time/Calendar.hxx b/src/time/Calendar.hxx new file mode 100644 index 000000000..c8a0983f1 --- /dev/null +++ b/src/time/Calendar.hxx @@ -0,0 +1,53 @@ +/* + * Copyright 2012-2019 Max Kellermann + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the + * distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#pragma once + +constexpr bool +IsLeapYear(unsigned y) noexcept +{ + return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0); +} + +constexpr unsigned +DaysInFebruary(unsigned year) noexcept +{ + return IsLeapYear(year) ? 29 : 28; +} + +constexpr unsigned +DaysInMonth(unsigned month, unsigned year) noexcept +{ + if (month == 4 || month == 6 || month == 9 || month == 11) + return 30; + else if (month != 2) + return 31; + else + return DaysInFebruary(year); +} diff --git a/src/time/Math.cxx b/src/time/Math.cxx new file mode 100644 index 000000000..28d04bae7 --- /dev/null +++ b/src/time/Math.cxx @@ -0,0 +1,115 @@ +/* + * Copyright 2007-2020 CM4all GmbH + * All rights reserved. + * + * author: Max Kellermann + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the + * distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "Math.hxx" +#include "Calendar.hxx" +#include "Convert.hxx" + +#include + +std::chrono::system_clock::time_point +PrecedingMidnightLocal(std::chrono::system_clock::time_point t) noexcept +try { + auto tm = LocalTime(t); + tm.tm_sec = 0; + tm.tm_min = 0; + tm.tm_hour = 0; + return MakeTime(tm); +} catch (...) { + /* best-effort fallback for this exotic error condition */ + return t; + } + +static void +IncrementMonth(struct tm &tm) noexcept +{ + ++tm.tm_mon; + + if (tm.tm_mon >= 12) { + /* roll over to next year */ + tm.tm_mon = 0; + ++tm.tm_year; + } +} + +void +EndOfMonth(struct tm &tm) noexcept +{ + tm.tm_sec = 0; + tm.tm_min = 0; + tm.tm_hour = 0; + tm.tm_mday = 1; + IncrementMonth(tm); +} + +void +IncrementDay(struct tm &tm) noexcept +{ + const unsigned max_day = DaysInMonth(tm.tm_mon + 1, tm.tm_year + 1900); + + ++tm.tm_mday; + + if ((unsigned)tm.tm_mday > max_day) { + /* roll over to next month */ + tm.tm_mday = 1; + IncrementMonth(tm); + } + + ++tm.tm_wday; + if (tm.tm_wday >= 7) + tm.tm_wday = 0; +} + +void +DecrementDay(struct tm &tm) noexcept +{ + --tm.tm_mday; + + if (tm.tm_mday < 1) { + /* roll over to previous month */ + + --tm.tm_mon; + if (tm.tm_mon < 0) { + /* roll over to previous eyar */ + tm.tm_mon = 11; + --tm.tm_year; + } + + const unsigned max_day = DaysInMonth(tm.tm_mon + 1, + tm.tm_year + 1900); + tm.tm_mday = max_day; + } + + --tm.tm_wday; + if (tm.tm_wday < 0) + tm.tm_wday = 6; +} diff --git a/src/time/Math.hxx b/src/time/Math.hxx new file mode 100644 index 000000000..891049947 --- /dev/null +++ b/src/time/Math.hxx @@ -0,0 +1,73 @@ +/* + * Copyright 2007-2020 CM4all GmbH + * All rights reserved. + * + * author: Max Kellermann + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the + * distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#pragma once + +#include "util/Compiler.h" + +#include + +struct tm; + +/** + * Calculates the preceding midnight time point in the current time + * zone. + */ +gcc_const +std::chrono::system_clock::time_point +PrecedingMidnightLocal(std::chrono::system_clock::time_point t) noexcept; + +/** + * Calculate the end of the current month (i.e. midnight on the 1st of + * the following month). Does NOT keeps the tm_wday and tm_yday + * attributes updated, and ignores day light saving transitions. + */ +void +EndOfMonth(struct tm &tm) noexcept; + +/** + * Calculate the next day, keeping month/year wraparounds and leap + * days in mind. Keeps the tm_wday attribute updated, but not other + * derived attributes such as tm_yday, and ignores day light saving + * transitions. + */ +void +IncrementDay(struct tm &tm) noexcept; + +/** + * Calculate the previous day, keeping month/year wraparounds and leap + * days in mind. Keeps the tm_wday attribute updated, but not other + * derived attributes such as tm_yday, and ignores day light saving + * transitions. + */ +void +DecrementDay(struct tm &tm) noexcept; diff --git a/src/time/meson.build b/src/time/meson.build index 2c53f7848..276bac22d 100644 --- a/src/time/meson.build +++ b/src/time/meson.build @@ -3,6 +3,7 @@ time = static_library( 'Parser.cxx', 'Convert.cxx', 'ISO8601.cxx', + 'Math.cxx', include_directories: inc, )