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authorJohn Layt <jlayt@kde.org>2011-08-25 07:54:16 +0100
committerQt by Nokia <qt-info@nokia.com>2012-02-05 00:26:07 +0100
commit8327fa7c11f6c84ccc66be4365ee282a76288788 (patch)
tree680f7ef682a3beddc90106769664934cacd402c2 /src/corelib
parent31b4c5aa05376c2270122679c97a5727dc743d92 (diff)
QDateTime: Store Julian Day as qint64
Store the QDate Julian Day number as an qint64 instead of uint32 to enable support for dates before 2 January 4713 BCE. This changes the possible date range to be approx 2.5 Quadrillion BC to 2.5 Quadrillion AD. A qint32 was not used as it only covers 5 million BCE to 5 million CE which does include Geological or Astronomical time. The effective supported date range is currently 4800 BCE to 1.4 million CE due to restrictions in existing conversion formulas. The effective range will be extended later with new formulas. Change-Id: Ib4345369455b31d4edae8c933b7721e76414e914 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib')
-rw-r--r--src/corelib/tools/qdatetime.cpp145
-rw-r--r--src/corelib/tools/qdatetime.h36
2 files changed, 112 insertions, 69 deletions
diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
index f34176ca55..e05eb371dd 100644
--- a/src/corelib/tools/qdatetime.cpp
+++ b/src/corelib/tools/qdatetime.cpp
@@ -76,9 +76,6 @@
QT_BEGIN_NAMESPACE
enum {
- FIRST_YEAR = -4713,
- FIRST_MONTH = 1,
- FIRST_DAY = 2, // ### Qt 5: make FIRST_DAY = 1, by support jd == 0 as valid
SECS_PER_DAY = 86400,
MSECS_PER_DAY = 86400000,
SECS_PER_HOUR = 3600,
@@ -95,7 +92,7 @@ static inline QDate fixedDate(int y, int m, int d)
return result;
}
-static inline uint julianDayFromGregorianDate(int year, int month, int day)
+static inline qint64 julianDayFromGregorianDate(qint64 year, int month, int day)
{
// Gregorian calendar starting from October 15, 1582
// Algorithm from Henry F. Fliegel and Thomas C. Van Flandern
@@ -105,35 +102,34 @@ static inline uint julianDayFromGregorianDate(int year, int month, int day)
+ day - 32075;
}
-static uint julianDayFromDate(int year, int month, int day)
+static qint64 julianDayFromDate(qint64 year, int month, int day)
{
- if (year < 0)
- ++year;
-
if (year > 1582 || (year == 1582 && (month > 10 || (month == 10 && day >= 15)))) {
return julianDayFromGregorianDate(year, month, day);
} else if (year < 1582 || (year == 1582 && (month < 10 || (month == 10 && day <= 4)))) {
// Julian calendar until October 4, 1582
// Algorithm from Frequently Asked Questions about Calendars by Claus Toendering
+ if (year < 0)
+ ++year;
int a = (14 - month) / 12;
return (153 * (month + (12 * a) - 3) + 2) / 5
+ (1461 * (year + 4800 - a)) / 4
+ day - 32083;
} else {
// the day following October 4, 1582 is October 15, 1582
- return 0;
+ return std::numeric_limits<qint64>::min(); // i.e. nullJd()
}
}
-static void getDateFromJulianDay(uint julianDay, int *year, int *month, int *day)
+static void getDateFromJulianDay(qint64 julianDay, int *year, int *month, int *day)
{
int y, m, d;
if (julianDay >= 2299161) {
// Gregorian calendar starting from October 15, 1582
// This algorithm is from Henry F. Fliegel and Thomas C. Van Flandern
- qulonglong ell, n, i, j;
- ell = qulonglong(julianDay) + 68569;
+ qint64 ell, n, i, j; //TODO These will need to be bigger to prevent overflow!!!
+ ell = julianDay + 68569;
n = (4 * ell) / 146097;
ell = ell - (146097 * n + 3) / 4;
i = (4000 * (ell + 1)) / 1461001;
@@ -147,9 +143,9 @@ static void getDateFromJulianDay(uint julianDay, int *year, int *month, int *day
// Julian calendar until October 4, 1582
// Algorithm from Frequently Asked Questions about Calendars by Claus Toendering
julianDay += 32082;
- int dd = (4 * julianDay + 3) / 1461;
- int ee = julianDay - (1461 * dd) / 4;
- int mm = ((5 * ee) + 2) / 153;
+ qint64 dd = (4 * julianDay + 3) / 1461; //TODO These may need to be bigger to prevent overflow!!!
+ qint64 ee = julianDay - (1461 * dd) / 4; //TODO These may need to be bigger to prevent overflow!!!
+ qint64 mm = ((5 * ee) + 2) / 153; //TODO These may need to be bigger to prevent overflow!!!
d = ee - (153 * mm + 2) / 5 + 1;
m = mm + 3 - 12 * (mm / 10);
y = dd - 4800 + (mm / 10);
@@ -261,16 +257,27 @@ static QString fmtDateTime(const QString& f, const QTime* dt = 0, const QDate* d
There is no year 0. Dates in that year are considered invalid. The
year -1 is the year "1 before Christ" or "1 before current era."
- The day before 0001-01-01 is December 31st, 1 BCE.
+ The day before 1 January 1 CE is 31 December 1 BCE.
\section2 Range of Valid Dates
- The range of valid dates is from January 2nd, 4713 BCE, to
- sometime in the year 11 million CE. The Julian Day returned by
- QDate::toJulianDay() is a number in the contiguous range from 1 to
- \e{overflow}, even across QDateTime's "date holes". It is suitable
- for use in applications that must convert a QDateTime to a date in
- another calendar system, e.g., Hebrew, Islamic or Chinese.
+ Dates are stored internally as a Julian Day number, an interger count of
+ every day in a contiguous range, with 24 November 4714 BCE in the Gregorian
+ calendar being Julian Day 0 (1 January 4713 BCE in the Julian calendar).
+ As well as being an efficient and accurate way of storing an absolute date,
+ it is suitable for converting a Date into other calendar systems such as
+ Hebrew, Islamic or Chinese. The Julian Day number can be obtained using
+ QDate::toJulianDay() and can be set using QDate::fromJulianDay().
+
+ The range of dates able to be stored by QDate as a Julian Day number is
+ limited for convenience from std::numeric_limits<qint64>::min() / 2 to
+ std::numeric_limits<qint64>::max() / 2, which on most platforms means
+ from around 2.5 quadrillion BCE to around 2.5 quadrillion CE, effectively
+ covering the full range of astronomical time. The range of Julian Days
+ able to be accurately converted to and from valid YMD form Dates is
+ restricted to 1 January 4800 BCE to 31 December 1400000 CE due to
+ shortcomings in the available conversion formulas. Conversions outside this
+ range are not guaranteed to be correct. This may change in the future.
\sa QTime, QDateTime, QDateEdit, QDateTimeEdit, QCalendarWidget
*/
@@ -287,8 +294,7 @@ static QString fmtDateTime(const QString& f, const QTime* dt = 0, const QDate* d
Constructs a date with year \a y, month \a m and day \a d.
If the specified date is invalid, the date is not set and
- isValid() returns false. A date before 2 January 4713 B.C. is
- considered invalid.
+ isValid() returns false.
\warning Years 0 to 99 are interpreted as is, i.e., years
0-99.
@@ -315,20 +321,17 @@ QDate::QDate(int y, int m, int d)
/*!
+ \fn bool isValid() const
+
Returns true if this date is valid; otherwise returns false.
\sa isNull()
*/
-bool QDate::isValid() const
-{
- return !isNull();
-}
-
/*!
Returns the year of this date. Negative numbers indicate years
- before 1 A.D. = 1 C.E., such that year -44 is 44 B.C.
+ before 1 CE, such that year -44 is 44 BCE.
Returns 0 if the date is invalid.
@@ -410,7 +413,10 @@ int QDate::dayOfWeek() const
if (isNull())
return 0;
- return (jd % 7) + 1;
+ if (jd >= 0)
+ return (jd % 7) + 1;
+ else
+ return ((jd + 1) % 7) + 7;
}
/*!
@@ -896,19 +902,21 @@ QString QDate::toString(const QString& format) const
the date is valid; otherwise returns false.
If the specified date is invalid, the QDate object is set to be
- invalid. Any date before 2 January 4713 B.C. is considered
invalid.
+ Note that any date before 4800 BCE or after about 1.4 million CE
+ may not be accurately stored.
+
\sa isValid()
*/
bool QDate::setDate(int year, int month, int day)
{
- if (!isValid(year, month, day)) {
- jd = 0;
- } else {
+ if (isValid(year, month, day))
jd = julianDayFromDate(year, month, day);
- }
- return jd != 0;
+ else
+ jd = nullJd();
+
+ return isValid();
}
/*!
@@ -919,6 +927,9 @@ bool QDate::setDate(int year, int month, int day)
Returns 0 if the date is invalid.
+ Note that any date before 4800 BCE or after about 1.4 million CE
+ may not be accurately stored.
+
\sa year(), month(), day(), isValid()
*/
void QDate::getDate(int *year, int *month, int *day)
@@ -945,17 +956,24 @@ void QDate::getDate(int *year, int *month, int *day)
\sa addMonths() addYears() daysTo()
*/
-QDate QDate::addDays(int ndays) const
+QDate QDate::addDays(qint64 ndays) const
{
if (isNull())
return QDate();
QDate d;
+ quint64 diff = 0;
+
// this is basically "d.jd = jd + ndays" with checks for integer overflow
+ // Due to limits on minJd() and maxJd() we know diff will never overflow
if (ndays >= 0)
- d.jd = (jd + ndays >= jd) ? jd + ndays : 0;
+ diff = maxJd() - jd;
else
- d.jd = (jd + ndays < jd) ? jd + ndays : 0;
+ diff = jd - minJd();
+
+ if (abs(ndays) <= diff)
+ d.jd = jd + ndays;
+
return d;
}
@@ -1072,11 +1090,12 @@ QDate QDate::addYears(int nyears) const
\sa addDays()
*/
-int QDate::daysTo(const QDate &d) const
+qint64 QDate::daysTo(const QDate &d) const
{
if (isNull() || d.isNull())
return 0;
+ // Due to limits on minJd() and maxJd() we know this will never overflow
return d.jd - jd;
}
@@ -1313,16 +1332,13 @@ QDate QDate::fromString(const QString &string, const QString &format)
bool QDate::isValid(int year, int month, int day)
{
- if (year < FIRST_YEAR
- || (year == FIRST_YEAR &&
- (month < FIRST_MONTH
- || (month == FIRST_MONTH && day < FIRST_DAY)))
- || year == 0) // there is no year 0 in the Julian calendar
+ // there is no year 0 in the Julian calendar
+ if (year == 0)
return false;
// passage from Julian to Gregorian calendar
if (year == 1582 && month == 10 && day > 4 && day < 15)
- return 0;
+ return false;
return (day > 0 && month > 0 && month <= 12) &&
(day <= monthDays[month] || (day == 29 && month == 2 && isLeapYear(year)));
@@ -2096,16 +2112,27 @@ int QTime::elapsed() const
There is no year 0. Dates in that year are considered invalid. The
year -1 is the year "1 before Christ" or "1 before current era."
- The day before 0001-01-01 is December 31st, 1 BCE.
+ The day before 1 January 1 CE is 31 December 1 BCE.
\section2 Range of Valid Dates
- The range of valid dates is from January 2nd, 4713 BCE, to
- sometime in the year 11 million CE. The Julian Day returned by
- QDate::toJulianDay() is a number in the contiguous range from 1 to
- \e{overflow}, even across QDateTime's "date holes". It is suitable
- for use in applications that must convert a QDateTime to a date in
- another calendar system, e.g., Hebrew, Islamic or Chinese.
+ Dates are stored internally as a Julian Day number, an interger count of
+ every day in a contiguous range, with 24 November 4714 BCE in the Gregorian
+ calendar being Julian Day 0 (1 January 4713 BCE in the Julian calendar).
+ As well as being an efficient and accurate way of storing an absolute date,
+ it is suitable for converting a Date into other calendar systems such as
+ Hebrew, Islamic or Chinese. The Julian Day number can be obtained using
+ QDate::toJulianDay() and can be set using QDate::fromJulianDay().
+
+ The range of dates able to be stored by QDate as a Julian Day number is
+ limited for convenience from std::numeric_limits<qint64>::min() / 2 to
+ std::numeric_limits<qint64>::max() / 2, which on most platforms means
+ from around 2.5 quadrillion BCE to around 2.5 quadrillion CE, effectively
+ covering the full range of astronomical time. The range of Julian Days
+ able to be accurately converted to and from valid YMD form Dates is
+ restricted to 1 January 4800 BCE to 31 December 1400000 CE due to
+ shortcomings in the available conversion formulas. Conversions outside this
+ range are not guaranteed to be correct. This may change in the future.
The Gregorian calendar was introduced in different places around
the world on different dates. QDateTime uses QDate to store the
@@ -2656,7 +2683,7 @@ QString QDateTime::toString(const QString& format) const
\sa daysTo(), addMonths(), addYears(), addSecs()
*/
-QDateTime QDateTime::addDays(int ndays) const
+QDateTime QDateTime::addDays(qint64 ndays) const
{
return QDateTime(d->date.addDays(ndays), d->time, timeSpec());
}
@@ -2707,7 +2734,7 @@ QDateTime QDateTimePrivate::addMSecs(const QDateTime &dt, qint64 msecs)
*/
void QDateTimePrivate::addMSecs(QDate &utcDate, QTime &utcTime, qint64 msecs)
{
- int dd = utcDate.toJulianDay();
+ qint64 dd = utcDate.toJulianDay();
int tt = QTime(0, 0, 0).msecsTo(utcTime);
int sign = 1;
if (msecs < 0) {
@@ -2767,7 +2794,7 @@ QDateTime QDateTime::addMSecs(qint64 msecs) const
\sa addDays(), secsTo(), msecsTo()
*/
-int QDateTime::daysTo(const QDateTime &other) const
+qint64 QDateTime::daysTo(const QDateTime &other) const
{
return d->date.daysTo(other.d->date);
}
@@ -3577,7 +3604,7 @@ void QDateTime::detach()
QDataStream &operator<<(QDataStream &out, const QDate &date)
{
- return out << (quint32)(date.jd);
+ return out << (qint64)(date.jd);
}
/*!
@@ -3590,7 +3617,7 @@ QDataStream &operator<<(QDataStream &out, const QDate &date)
QDataStream &operator>>(QDataStream &in, QDate &date)
{
- quint32 jd;
+ qint64 jd;
in >> jd;
date.jd = jd;
return in;
diff --git a/src/corelib/tools/qdatetime.h b/src/corelib/tools/qdatetime.h
index 056b0debf1..af257eaa40 100644
--- a/src/corelib/tools/qdatetime.h
+++ b/src/corelib/tools/qdatetime.h
@@ -46,6 +46,17 @@
#include <QtCore/qnamespace.h>
#include <QtCore/qsharedpointer.h>
+// windows.h defines these identifiers, so undefine it
+// ### figure out where in Qt we include it too soon
+#ifdef max
+# undef max
+#endif
+#ifdef min
+# undef min
+#endif
+
+#include <limits>
+
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
@@ -59,11 +70,11 @@ public:
StandaloneFormat
};
public:
- QDate() { jd = 0; }
+ QDate() { jd = nullJd(); }
QDate(int y, int m, int d);
- bool isNull() const { return jd == 0; }
- bool isValid() const;
+ bool isNull() const { return !isValid(); }
+ bool isValid() const { return jd >= minJd() && jd <= maxJd(); }
int year() const;
int month() const;
@@ -93,10 +104,10 @@ QT_DEPRECATED inline bool setYMD(int y, int m, int d)
void getDate(int *year, int *month, int *day);
- QDate addDays(int days) const;
+ QDate addDays(qint64 days) const;
QDate addMonths(int months) const;
QDate addYears(int years) const;
- int daysTo(const QDate &) const;
+ qint64 daysTo(const QDate &) const;
bool operator==(const QDate &other) const { return jd == other.jd; }
bool operator!=(const QDate &other) const { return jd != other.jd; }
@@ -113,11 +124,16 @@ QT_DEPRECATED inline bool setYMD(int y, int m, int d)
static bool isValid(int y, int m, int d);
static bool isLeapYear(int year);
- static inline QDate fromJulianDay(int jd) { QDate d; d.jd = jd; return d; }
- inline int toJulianDay() const { return jd; }
+ static inline QDate fromJulianDay(qint64 jd)
+ { QDate d; if (jd >= minJd() && jd <= maxJd()) d.jd = jd; return d; }
+ inline qint64 toJulianDay() const { return jd; }
private:
- uint jd;
+ static inline qint64 nullJd() { return std::numeric_limits<qint64>::min(); }
+ static inline qint64 minJd() { return std::numeric_limits<qint64>::min() / 2; }
+ static inline qint64 maxJd() { return (std::numeric_limits<qint64>::max()) / 2; }
+
+ qint64 jd;
friend class QDateTime;
friend class QDateTimePrivate;
@@ -220,7 +236,7 @@ public:
QString toString(Qt::DateFormat f = Qt::TextDate) const;
QString toString(const QString &format) const;
#endif
- QDateTime addDays(int days) const;
+ QDateTime addDays(qint64 days) const;
QDateTime addMonths(int months) const;
QDateTime addYears(int years) const;
QDateTime addSecs(int secs) const;
@@ -228,7 +244,7 @@ public:
QDateTime toTimeSpec(Qt::TimeSpec spec) const;
inline QDateTime toLocalTime() const { return toTimeSpec(Qt::LocalTime); }
inline QDateTime toUTC() const { return toTimeSpec(Qt::UTC); }
- int daysTo(const QDateTime &) const;
+ qint64 daysTo(const QDateTime &) const;
int secsTo(const QDateTime &) const;
qint64 msecsTo(const QDateTime &) const;