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Diffstat (limited to 'src/corelib/time/qgregoriancalendar.cpp')
| -rw-r--r-- | src/corelib/time/qgregoriancalendar.cpp | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/src/corelib/time/qgregoriancalendar.cpp b/src/corelib/time/qgregoriancalendar.cpp new file mode 100644 index 0000000000..633b1ea94e --- /dev/null +++ b/src/corelib/time/qgregoriancalendar.cpp @@ -0,0 +1,175 @@ +/**************************************************************************** +** +** Copyright (C) 2019 The Qt Company Ltd. +** Contact: https://www.qt.io/licensing/ +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/contact-us. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 3 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL3 included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 3 requirements +** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 2.0 or (at your option) the GNU General +** Public license version 3 or any later version approved by the KDE Free +** Qt Foundation. The licenses are as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 +** included in the packaging of this file. Please review the following +** information to ensure the GNU General Public License requirements will +** be met: https://www.gnu.org/licenses/gpl-2.0.html and +** https://www.gnu.org/licenses/gpl-3.0.html. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include "qgregoriancalendar_p.h" +#include "qcalendarmath_p.h" +#include <QtCore/qdatetime.h> + +QT_BEGIN_NAMESPACE + +using namespace QRoundingDown; + +/*! + \since 5.14 + + \class QGregorianCalendar + \inmodule QtCore + \brief The QGregorianCalendar class implements the Gregorian calendar. + + \section1 The Gregorian Calendar + + The Gregorian calendar is a refinement of the earlier Julian calendar, + itself a late form of the Roman calendar. It is widely used. + + \sa QRomanCalendar, QJulianCalendar, QCalendar +*/ + +QGregorianCalendar::QGregorianCalendar() + : QRomanCalendar(QStringLiteral("Gregorian"), QCalendar::System::Gregorian) +{ + registerAlias(QStringLiteral("gregory")); +} + +QString QGregorianCalendar::name() const +{ + return QStringLiteral("Gregorian"); +} + +QCalendar::System QGregorianCalendar::calendarSystem() const +{ + return QCalendar::System::Gregorian; +} + +bool QGregorianCalendar::isLeapYear(int year) const +{ + return leapTest(year); +} + +bool QGregorianCalendar::leapTest(int year) +{ + if (year == QCalendar::Unspecified) + return false; + + // No year 0 in Gregorian calendar, so -1, -5, -9 etc are leap years + if (year < 1) + ++year; + + return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0); +} + +// Duplicating code from QRomanCalendar, but inlining isLeapYear() as leapTest(): +int QGregorianCalendar::monthLength(int month, int year) +{ + if (month < 1 || month > 12) + return 0; + + if (month == 2) + return leapTest(year) ? 29 : 28; + + return 30 | ((month & 1) ^ (month >> 3)); +} + +bool QGregorianCalendar::validParts(int year, int month, int day) +{ + return year && 0 < day && day <= monthLength(month, year); +} + +int QGregorianCalendar::weekDayOfJulian(qint64 jd) +{ + return qMod(jd, 7) + 1; +} + +bool QGregorianCalendar::dateToJulianDay(int year, int month, int day, qint64 *jd) const +{ + return julianFromParts(year, month, day, jd); +} + +bool QGregorianCalendar::julianFromParts(int year, int month, int day, qint64 *jd) +{ + Q_ASSERT(jd); + if (!validParts(year, month, day)) + return false; + + if (year < 0) + ++year; + + /* + * Math from The Calendar FAQ at http://www.tondering.dk/claus/cal/julperiod.php + * This formula is correct for all julian days, when using mathematical integer + * division (round to negative infinity), not c++11 integer division (round to zero) + */ + int a = month < 3 ? 1 : 0; + qint64 y = qint64(year) + 4800 - a; + int m = month + 12 * a - 3; + *jd = day + qDiv(153 * m + 2, 5) - 32045 + + 365 * y + qDiv(y, 4) - qDiv(y, 100) + qDiv(y, 400); + return true; +} + +QCalendar::YearMonthDay QGregorianCalendar::julianDayToDate(qint64 jd) const +{ + return partsFromJulian(jd); +} + +QCalendar::YearMonthDay QGregorianCalendar::partsFromJulian(qint64 jd) +{ + /* + * Math from The Calendar FAQ at http://www.tondering.dk/claus/cal/julperiod.php + * This formula is correct for all julian days, when using mathematical integer + * division (round to negative infinity), not c++11 integer division (round to zero) + */ + qint64 a = jd + 32044; + qint64 b = qDiv(4 * a + 3, 146097); + int c = a - qDiv(146097 * b, 4); + + int d = qDiv(4 * c + 3, 1461); + int e = c - qDiv(1461 * d, 4); + int m = qDiv(5 * e + 2, 153); + + int y = 100 * b + d - 4800 + qDiv(m, 10); + + // Adjust for no year 0 + int year = y > 0 ? y : y - 1; + int month = m + 3 - 12 * qDiv(m, 10); + int day = e - qDiv(153 * m + 2, 5) + 1; + + return QCalendar::YearMonthDay(year, month, day); +} + +QT_END_NAMESPACE |