Related: tdf#152114 Move some tools' Date class algorithms to comphelper::date

So they can be reused, specifically in
connectivity/source/commontools/dbconversion.cxx

Change-Id: I8b2b59e3cb078a73d5f670f0756404471009cf9b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143114
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins

2 files changed, 263 insertions, 0 deletions

diff --git a/comphelper/Library_comphelper.mk b/comphelper/Library_comphelper.mk
index 6d0536058882..0bad46866d54 100644
--- a/comphelper/Library_comphelper.mk
+++ b/comphelper/Library_comphelper.mk
@@ -97,6 +97,7 @@ $(eval $(call gb_Library_add_exception_objects,comphelper,\
     comphelper/source/misc/componentbase \
     comphelper/source/misc/configuration \
     comphelper/source/misc/configurationhelper \
+    comphelper/source/misc/date \
     comphelper/source/misc/debuggerinfo \
     comphelper/source/misc/diagnose_ex \
     comphelper/source/misc/DirectoryHelper \
diff --git a/comphelper/source/misc/date.cxx b/comphelper/source/misc/date.cxx
new file mode 100644
index 000000000000..ea8a588dbabd
--- /dev/null
+++ b/comphelper/source/misc/date.cxx
@@ -0,0 +1,262 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <comphelper/date.hxx>
+
+#include <cassert>
+
+namespace comphelper::date
+{
+// Once upon a time the number of days we internally handled in tools' class
+// Date was limited to MAX_DAYS 3636532. That changed with a full 16-bit year.
+// Assuming the first valid positive date in a proleptic Gregorian calendar is
+// 0001-01-01, this resulted in an end date of 9957-06-26.
+// Hence we documented that years up to and including 9956 are handled.
+/* XXX: it is unclear history why this value was chosen, the representable
+ * 9999-12-31 would be 3652060 days from 0001-01-01. Even 9998-12-31 to
+ * distinguish from a maximum possible date would be 3651695.
+ * There is connectivity/source/commontools/dbconversion.cxx that still has the
+ * same value to calculate with css::util::Date */
+/* XXX can that dbconversion cope with years > 9999 or negative years at all?
+ * Database fields may be limited to positive 4 digits. */
+
+constexpr sal_Int32 MIN_DAYS = -11968265; // -32768-01-01
+constexpr sal_Int32 MAX_DAYS = 11967900; //  32767-12-31
+
+constexpr sal_Int16 kYearMax = SAL_MAX_INT16;
+constexpr sal_Int16 kYearMin = SAL_MIN_INT16;
+
+sal_Int32 YearToDays(sal_Int16 nYear)
+{
+    assert(nYear != 0);
+    sal_Int32 nOffset;
+    sal_Int32 nYr;
+    if (nYear < 0)
+    {
+        nOffset = -366;
+        nYr = nYear + 1;
+    }
+    else
+    {
+        nOffset = 0;
+        nYr = nYear - 1;
+    }
+    return nOffset + nYr * 365 + nYr / 4 - nYr / 100 + nYr / 400;
+}
+
+bool isLeapYear(sal_Int16 nYear)
+{
+    assert(nYear != 0);
+    if (nYear < 0)
+        nYear = -nYear - 1;
+    return (((nYear % 4) == 0) && ((nYear % 100) != 0)) || ((nYear % 400) == 0);
+}
+
+sal_uInt16 getDaysInMonth(sal_uInt16 nMonth, sal_Int16 nYear)
+{
+    assert(1 <= nMonth && nMonth <= 12);
+    if (nMonth < 1 || 12 < nMonth)
+        return 0;
+
+    constexpr sal_uInt16 aDaysInMonth[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+    if (nMonth != 2)
+        return aDaysInMonth[nMonth - 1];
+    else
+    {
+        if (isLeapYear(nYear))
+            return aDaysInMonth[nMonth - 1] + 1;
+        else
+            return aDaysInMonth[nMonth - 1];
+    }
+}
+
+sal_Int32 convertDateToDays(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
+{
+    sal_Int32 nDays = YearToDays(nYear);
+    for (sal_uInt16 i = 1; i < nMonth; ++i)
+        nDays += getDaysInMonth(i, nYear);
+    nDays += nDay;
+    return nDays;
+}
+
+sal_Int32 convertDateToDaysNormalizing(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
+{
+    // Speed-up the common null-date 1899-12-30.
+    if (nYear == 1899 && nDay == 30 && nMonth == 12)
+    {
+        assert(convertDateToDays(nDay, nMonth, nYear) == 693594);
+        return 693594;
+    }
+    normalize(nDay, nMonth, nYear);
+    return convertDateToDays(nDay, nMonth, nYear);
+}
+
+bool isValidDate(sal_uInt16 nDay, sal_uInt16 nMonth, sal_Int16 nYear)
+{
+    if (nYear == 0)
+        return false;
+    if (nMonth < 1 || 12 < nMonth)
+        return false;
+    if (nDay < 1 || (nDay > comphelper::date::getDaysInMonth(nMonth, nYear)))
+        return false;
+    return true;
+}
+
+void convertDaysToDate(sal_Int32 nDays, sal_uInt16& rDay, sal_uInt16& rMonth, sal_Int16& rYear)
+{
+    if (nDays <= MIN_DAYS)
+    {
+        rDay = 1;
+        rMonth = 1;
+        rYear = kYearMin;
+        return;
+    }
+    if (nDays >= MAX_DAYS)
+    {
+        rDay = 31;
+        rMonth = 12;
+        rYear = kYearMax;
+        return;
+    }
+
+    // Day 0 is -0001-12-31, day 1 is 0001-01-01
+    const sal_Int16 nSign = (nDays <= 0 ? -1 : 1);
+    sal_Int32 nTempDays;
+    sal_Int32 i = 0;
+    bool bCalc;
+
+    do
+    {
+        rYear = static_cast<sal_Int16>((nDays / 365) - (i * nSign));
+        if (rYear == 0)
+            rYear = nSign;
+        nTempDays = nDays - YearToDays(rYear);
+        bCalc = false;
+        if (nTempDays < 1)
+        {
+            i += nSign;
+            bCalc = true;
+        }
+        else
+        {
+            if (nTempDays > 365)
+            {
+                if ((nTempDays != 366) || !isLeapYear(rYear))
+                {
+                    i -= nSign;
+                    bCalc = true;
+                }
+            }
+        }
+    } while (bCalc);
+
+    rMonth = 1;
+    while (nTempDays > getDaysInMonth(rMonth, rYear))
+    {
+        nTempDays -= getDaysInMonth(rMonth, rYear);
+        ++rMonth;
+    }
+
+    rDay = static_cast<sal_uInt16>(nTempDays);
+}
+
+bool normalize(sal_uInt16& rDay, sal_uInt16& rMonth, sal_Int16& rYear)
+{
+    if (isValidDate(rDay, rMonth, rYear))
+        return false;
+
+    if (rDay == 0 && rMonth == 0 && rYear == 0)
+        return false; // empty date
+
+    if (rDay == 0)
+    {
+        if (rMonth == 0)
+            ; // nothing, handled below
+        else
+            --rMonth;
+        // Last day of month is determined at the end.
+    }
+
+    if (rMonth > 12)
+    {
+        rYear += rMonth / 12;
+        rMonth = rMonth % 12;
+        if (rYear == 0)
+            rYear = 1;
+    }
+    if (rMonth == 0)
+    {
+        --rYear;
+        if (rYear == 0)
+            rYear = -1;
+        rMonth = 12;
+    }
+
+    if (rYear < 0)
+    {
+        sal_uInt16 nDays;
+        while (rDay > (nDays = getDaysInMonth(rMonth, rYear)))
+        {
+            rDay -= nDays;
+            if (rMonth > 1)
+                --rMonth;
+            else
+            {
+                if (rYear == kYearMin)
+                {
+                    rDay = 1;
+                    rMonth = 1;
+                    return true;
+                }
+                --rYear;
+                rMonth = 12;
+            }
+        }
+    }
+    else
+    {
+        sal_uInt16 nDays;
+        while (rDay > (nDays = getDaysInMonth(rMonth, rYear)))
+        {
+            rDay -= nDays;
+            if (rMonth < 12)
+                ++rMonth;
+            else
+            {
+                if (rYear == kYearMax)
+                {
+                    rDay = 31;
+                    rMonth = 12;
+                    return true;
+                }
+                ++rYear;
+                rMonth = 1;
+            }
+        }
+    }
+
+    if (rDay == 0)
+        rDay = getDaysInMonth(rMonth, rYear);
+
+    return true;
+}
+
+} // namespace comphelper::date
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */