comphelper/source/misc/date.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
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   9  * This file incorporates work covered by the following license notice:
  10  *
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  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
  20 #include <comphelper/date.hxx>
  21
  22 #include <cassert>
  23
  24 namespace comphelper::date
  25 {
  26 // Once upon a time the number of days we internally handled in tools' class
  27 // Date was limited to MAX_DAYS 3636532. That changed with a full 16-bit year.
  28 // Assuming the first valid positive date in a proleptic Gregorian calendar is
  29 // 0001-01-01, this resulted in an end date of 9957-06-26.
  30 // Hence we documented that years up to and including 9956 are handled.
  31 /* XXX: it is unclear history why this value was chosen, the representable
  32  * 9999-12-31 would be 3652060 days from 0001-01-01. Even 9998-12-31 to
  33  * distinguish from a maximum possible date would be 3651695.
  34  * There is connectivity/source/commontools/dbconversion.cxx that still has the
  35  * same value to calculate with css::util::Date */
  36 /* XXX can that dbconversion cope with years > 9999 or negative years at all?
  37  * Database fields may be limited to positive 4 digits. */
  38
  39 constexpr sal_Int32 MIN_DAYS = -11968265; // -32768-01-01
  40 constexpr sal_Int32 MAX_DAYS = 11967900; //  32767-12-31
  41
  42 constexpr sal_Int16 kYearMax = SAL_MAX_INT16;
  43 constexpr sal_Int16 kYearMin = SAL_MIN_INT16;
  44
  45 constexpr sal_Int32 nNullDateDays = convertDateToDays(30, 12, 1899);
  46 static_assert(nNullDateDays == 693594);
  47
  48 sal_Int32 convertDateToDaysNormalizing(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
  49 {
  50     // Speed-up the common null-date 1899-12-30.
  51     if (nYear == 1899 && nMonth == 12 && nDay == 30)
  52         return nNullDateDays;
  53
  54     normalize(nDay, nMonth, nYear);
  55     return convertDateToDays(nDay, nMonth, nYear);
  56 }
  57
  58 bool isValidDate(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
  59 {
  60     if (nYear == 0)
  61         return false;
  62     if (nMonth < 1 || 12 < nMonth)
  63         return false;
  64     if (nDay < 1 || (nDay > comphelper::date::getDaysInMonth(nMonth, nYear)))
  65         return false;
  66     return true;
  67 }
  68
  69 void convertDaysToDate(sal_Int32 nDays, sal_uInt16& rDay, sal_uInt16& rMonth, sal_Int16& rYear)
  70 {
  71     if (nDays <= MIN_DAYS)
  72     {
  73         rDay = 1;
  74         rMonth = 1;
  75         rYear = kYearMin;
  76         return;
  77     }
  78     if (nDays >= MAX_DAYS)
  79     {
  80         rDay = 31;
  81         rMonth = 12;
  82         rYear = kYearMax;
  83         return;
  84     }
  85
  86     // Day 0 is -0001-12-31, day 1 is 0001-01-01
  87     const sal_Int16 nSign = (nDays <= 0 ? -1 : 1);
  88     sal_Int32 nTempDays;
  89     sal_Int32 i = 0;
  90     bool bCalc;
  91
  92     do
  93     {
  94         rYear = static_cast<sal_Int16>((nDays / 365) - (i * nSign));
  95         if (rYear == 0)
  96             rYear = nSign;
  97         nTempDays = nDays - YearToDays(rYear);
  98         bCalc = false;
  99         if (nTempDays < 1)
 100         {
 101             i += nSign;
 102             bCalc = true;
 103         }
 104         else
 105         {
 106             if (nTempDays > 365)
 107             {
 108                 if ((nTempDays != 366) || !isLeapYear(rYear))
 109                 {
 110                     i -= nSign;
 111                     bCalc = true;
 112                 }
 113             }
 114         }
 115     } while (bCalc);
 116
 117     rMonth = 1;
 118     while (nTempDays > getDaysInMonth(rMonth, rYear))
 119     {
 120         nTempDays -= getDaysInMonth(rMonth, rYear);
 121         ++rMonth;
 122     }
 123
 124     rDay = static_cast<sal_uInt16>(nTempDays);
 125 }
 126
 127 bool normalize(sal_uInt16& rDay, sal_uInt16& rMonth, sal_Int16& rYear)
 128 {
 129     if (isValidDate(rDay, rMonth, rYear))
 130         return false;
 131
 132     if (rDay == 0 && rMonth == 0 && rYear == 0)
 133         return false; // empty date
 134
 135     if (rDay == 0)
 136     {
 137         if (rMonth == 0)
 138             ; // nothing, handled below
 139         else
 140             --rMonth;
 141         // Last day of month is determined at the end.
 142     }
 143
 144     if (rMonth > 12)
 145     {
 146         rYear += rMonth / 12;
 147         rMonth = rMonth % 12;
 148         if (rYear == 0)
 149             rYear = 1;
 150     }
 151     if (rMonth == 0)
 152     {
 153         --rYear;
 154         if (rYear == 0)
 155             rYear = -1;
 156         rMonth = 12;
 157     }
 158
 159     if (rYear < 0)
 160     {
 161         sal_uInt16 nDays;
 162         while (rDay > (nDays = getDaysInMonth(rMonth, rYear)))
 163         {
 164             rDay -= nDays;
 165             if (rMonth > 1)
 166                 --rMonth;
 167             else
 168             {
 169                 if (rYear == kYearMin)
 170                 {
 171                     rDay = 1;
 172                     rMonth = 1;
 173                     return true;
 174                 }
 175                 --rYear;
 176                 rMonth = 12;
 177             }
 178         }
 179     }
 180     else
 181     {
 182         sal_uInt16 nDays;
 183         while (rDay > (nDays = getDaysInMonth(rMonth, rYear)))
 184         {
 185             rDay -= nDays;
 186             if (rMonth < 12)
 187                 ++rMonth;
 188             else
 189             {
 190                 if (rYear == kYearMax)
 191                 {
 192                     rDay = 31;
 193                     rMonth = 12;
 194                     return true;
 195                 }
 196                 ++rYear;
 197                 rMonth = 1;
 198             }
 199         }
 200     }
 201
 202     if (rDay == 0)
 203         rDay = getDaysInMonth(rMonth, rYear);
 204
 205     return true;
 206 }
 207
 208 } // namespace comphelper::date
 209
 210 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */