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Replace look-up array with simple arithmetic

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QDate looked up lengths of months in an array.  Change it to use some
simple arithmetic instead.  Benchmark result unchanged:
RESULT : tst_QDate::monthLengths():
     0.33 msecs per iteration (total: 87, iterations: 256)

Change-Id: I1ab0fa3b97e6716598e50d643a498e0b01c04a96
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
This commit is contained in:
Edward Welbourne 2019-05-15 15:54:37 +02:00
parent 7efce5d510
commit 070517f628
1 changed files with 13 additions and 12 deletions
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25
src/corelib/tools/qdatetime.cpp
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@ -172,8 +172,6 @@ static ParsedDate getDateFromJulianDay(qint64 julianDay)
Date/Time formatting helper functions
*****************************************************************************/
static const char monthDays[] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
#if QT_CONFIG(textdate)
static const char qt_shortMonthNames[][4] = {
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
@ -305,6 +303,12 @@ static int fromOffsetString(const QStringRef &offsetString, bool *valid) noexcep
}
#endif // datestring
static constexpr int daysInUsualMonth(int month) // (February isn't usual.)
{
// Long if odd up to July = 7, or if even from 8 = August onwards:
return Q_ASSERT(month != 2 && month > 0 && month <= 12), 30 | ((month & 1) ^ (month >> 3));
}
/*****************************************************************************
QDate member functions
*****************************************************************************/
@ -546,10 +550,10 @@ int QDate::daysInMonth() const
return 0;
const ParsedDate pd = getDateFromJulianDay(jd);
if (pd.month == 2 && isLeapYear(pd.year))
return 29;
else
return monthDays[pd.month];
if (pd.month == 2)
return isLeapYear(pd.year) ? 29 : 28;
return daysInUsualMonth(pd.month);
}
/*!
@ -1635,12 +1639,9 @@ QDate QDate::fromString(const QString &string, const QString &format)
bool QDate::isValid(int year, int month, int day)
{
// there is no year 0 in the Gregorian calendar
if (year == 0)
return false;
return (day > 0 && month > 0 && month <= 12) &&
(day <= monthDays[month] || (day == 29 && month == 2 && isLeapYear(year)));
// There is no year 0 in the Gregorian calendar.
return year && day > 0 && month > 0 && month <= 12 &&
day <= (month == 2 ? isLeapYear(year) ? 29 : 28 : daysInUsualMonth(month));
}
/*!