include/comphelper/date.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
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   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
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   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
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  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19 #pragma once
  20
  21 #include <sal/config.h>
  22 #include <sal/types.h>
  23 #include <comphelper/comphelperdllapi.h>
  24
  25 #include <cassert>
  26
  27 namespace comphelper::date
  28 {
  29 /** Days until start of year from zero, so month and day of month can be added.
  30
  31     year 1 => 0 days, year 2 => 365 days, ...
  32     year -1 => -366 days, year -2 => -731 days, ...
  33
  34     @param  nYear
  35             MUST be != 0.
  36  */
  37 constexpr inline sal_Int32 YearToDays(sal_Int16 nYear)
  38 {
  39     assert(nYear != 0);
  40     auto val = [](int off, int y) { return off + y * 365 + y / 4 - y / 100 + y / 400; };
  41     return nYear < 0 ? val(-366, nYear + 1) : val(0, nYear - 1);
  42 }
  43
  44 /** Whether year is a leap year.
  45
  46     Leap years BCE are -1, -5, -9, ...
  47     See
  48     https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar#Usage
  49     https://en.wikipedia.org/wiki/0_(year)#History_of_astronomical_usage
  50
  51     @param  nYear
  52             MUST be != 0.
  53  */
  54 constexpr inline bool isLeapYear(sal_Int16 nYear)
  55 {
  56     assert(nYear != 0);
  57     if (nYear < 0)
  58         nYear = -nYear - 1;
  59     return (((nYear % 4) == 0) && ((nYear % 100) != 0)) || ((nYear % 400) == 0);
  60 }
  61
  62 /** Get number of days in month of year.
  63
  64     @param  nYear
  65             MUST be != 0.
  66  */
  67 constexpr inline sal_uInt16 getDaysInMonth(sal_uInt16 nMonth, sal_Int16 nYear)
  68 {
  69     assert(1 <= nMonth && nMonth <= 12);
  70     if (nMonth < 1 || 12 < nMonth)
  71         return 0;
  72
  73     constexpr sal_uInt16 aDaysInMonth[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
  74     sal_uInt16 n = aDaysInMonth[nMonth - 1];
  75     return nMonth == 2 && isLeapYear(nYear) ? n + 1 : n;
  76 }
  77
  78 /** Obtain days from zero for a given date, without normalizing.
  79
  80     nDay, nMonth, nYear MUST form a valid proleptic Gregorian calendar date.
  81  */
  82 constexpr inline sal_Int32 convertDateToDays(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
  83 {
  84     sal_Int32 nDays = YearToDays(nYear);
  85     for (sal_uInt16 i = 1; i < nMonth; ++i)
  86         nDays += getDaysInMonth(i, nYear);
  87     nDays += nDay;
  88     return nDays;
  89 }
  90
  91 /** Obtain days from zero for a given date, with normalizing.
  92
  93     nDay, nMonth, nYear may be out-of-bounds and are adjusted/normalized.
  94
  95     @param  nYear
  96             Must be != 0, unless nMonth > 12.
  97  */
  98 COMPHELPER_DLLPUBLIC sal_Int32 convertDateToDaysNormalizing(sal_uInt16 nDay, sal_uInt16 nMonth,
  99                                                             sal_Int16 nYear);
 100
 101 /** Whether date is a valid date.
 102  */
 103 COMPHELPER_DLLPUBLIC bool isValidDate(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear);
 104
 105 /** Obtain date for a days from zero value.
 106  */
 107 COMPHELPER_DLLPUBLIC void convertDaysToDate(sal_Int32 nDays, sal_uInt16& rDay, sal_uInt16& rMonth,
 108                                             sal_Int16& rYear);
 109
 110 /** Normalize date, i.e. add days or months to form a proper proleptic
 111     Gregorian calendar date, unless all values are 0.
 112
 113     @param  rYear
 114             Must be != 0, unless rMonth > 12.
 115
 116     @return <TRUE/> if date was normalized, <FALSE/> if it was valid already
 117     or empty (all values 0).
 118  */
 119 COMPHELPER_DLLPUBLIC bool normalize(sal_uInt16& rDay, sal_uInt16& rMonth, sal_Int16& rYear);
 120
 121 } // namespace comphelper::date
 122
 123 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */