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>

1 files changed, 26 insertions, 10 deletions

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;