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Use QTimeZone to determine offsets outside the system-function range 

Follow up on some comments saying "TODO Use QTimeZone when available"
in converting times, outside the range supported by the system's
time_t functions, between local or zone time and UTC.  Since this
required two formerly static functions in qdatetime.cpp to access
QTimeZone's d-ptr, turn those into methods of QTZ's friend QDTPrivate.

Change-Id: I27fe03d8eff9f4e98661263b1a1d4d830f4e7459
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
This commit is contained in:
Edward Welbourne 2021-02-18 18:33:18 +01:00
parent b4a875544b
commit 530e0bd469
2 changed files with 61 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
src/corelib/time/qdatetime.cpp
View File

@ -2638,8 +2638,8 @@ static inline bool millisInSystemRange(qint64 millis, qint64 slack = 0)
}
// Convert an MSecs Since Epoch into Local Time
static bool epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTime,
QDateTimePrivate::DaylightStatus *daylightStatus = nullptr)
bool QDateTimePrivate::epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTime,
QDateTimePrivate::DaylightStatus *daylightStatus)
{
if (msecs < 0) {
// Docs state any LocalTime before 1970-01-01 will *not* have any Daylight Time applied
@ -2654,9 +2654,23 @@ static bool epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTi
if (!millisInSystemRange(msecs)) {
// Docs state any LocalTime after 2038-01-18 *will* have any DST applied.
// When this falls outside the supported range, we need to fake it.
// Use existing method to fake the conversion, but this is deeply flawed as it may
// apply the conversion from the wrong day number, e.g. if rule is last Sunday of month
// TODO Use QTimeZone when available to apply the future rule correctly
#if QT_CONFIG(timezone)
// Use the system time-zone.
const auto sys = QTimeZone::systemTimeZone();
if (daylightStatus) {
*daylightStatus = sys.d->isDaylightTime(msecs)
? QDateTimePrivate::DaylightTime
: QDateTimePrivate::StandardTime;
}
if (add_overflow(msecs, sys.d->offsetFromUtc(msecs) * MSECS_PER_SEC, &msecs))
return false;
msecsToTime(msecs, localDate, localTime);
return true;
#else // Kludge
// Use existing method to fake the conversion (this is deeply flawed
// as it may apply the conversion from the wrong day number, e.g. if
// rule is last Sunday of month).
QDate utcDate;
QTime utcTime;
msecsToTime(msecs, &utcDate, &utcTime);
@ -2670,6 +2684,7 @@ static bool epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTi
bool res = qt_localtime(fakeMsecs, localDate, localTime, daylightStatus);
*localDate = localDate->addDays(fakeDate.daysTo(utcDate));
return res;
#endif // timezone
}
// Falls inside time_t supported range so can use localtime
@ -2679,10 +2694,10 @@ static bool epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTi
// Convert a LocalTime expressed in local msecs encoding and the corresponding
// DST status into a UTC epoch msecs. Optionally populate the returned
// values from mktime for the adjusted local date and time.
static qint64 localMSecsToEpochMSecs(qint64 localMsecs,
QDateTimePrivate::DaylightStatus *daylightStatus,
QDate *localDate = nullptr, QTime *localTime = nullptr,
QString *abbreviation = nullptr)
qint64 QDateTimePrivate::localMSecsToEpochMSecs(qint64 localMsecs,
QDateTimePrivate::DaylightStatus *daylightStatus,
QDate *localDate, QTime *localTime,
QString *abbreviation)
{
QDate dt;
QTime tm;
@ -2703,15 +2718,15 @@ static qint64 localMSecsToEpochMSecs(qint64 localMsecs,
}
// Restore dt and tm, after qt_mktime() stomped them:
msecsToTime(localMsecs, &dt, &tm);
} else {
// If we don't call mktime then we need to call tzset to set up local zone data:
} else if (localMsecs < MSECS_PER_DAY) {
// Didn't call mktime(), but the pre-epoch code below needs mktime()'s
// implicit tzset() call to have happened.
qTzSet();
}
if (localMsecs <= MSECS_PER_DAY) {
// Would have been caught above if after UTC epoch, so is before.
// Docs state any LocalTime before 1970-01-01 will *not* have any DST applied
// Time is clearly before 1970-01-01 so just use standard offset to convert
const qint64 utcMsecs = localMsecs + qt_timezone() * MSECS_PER_SEC;
if (localDate || localTime)
msecsToTime(localMsecs, localDate, localTime);
@ -2723,9 +2738,25 @@ static qint64 localMSecsToEpochMSecs(qint64 localMsecs,
}
// Otherwise, after the end of the system range.
// Use existing method to fake the conversion, but this is deeply flawed as it may
// apply the conversion from the wrong day number, e.g. if rule is last Sunday of month
// TODO Use QTimeZone when available to apply the future rule correctly
#if QT_CONFIG(timezone)
// Use the system zone:
const auto sys = QTimeZone::systemTimeZone();
const qint64 utcMsecs =
QDateTimePrivate::zoneMSecsToEpochMSecs(localMsecs, sys,
QDateTimePrivate::UnknownDaylightTime,
localDate, localTime);
if (abbreviation)
*abbreviation = sys.d->abbreviation(utcMsecs);
if (daylightStatus) {
*daylightStatus = sys.d->isDaylightTime(utcMsecs)
? QDateTimePrivate::DaylightTime
: QDateTimePrivate::StandardTime;
}
return utcMsecs;
#else // Kludge
// Use existing method to fake the conversion (this is deeply flawed as it
// may apply the conversion from the wrong day number, e.g. if rule is last
// Sunday of month).
int year, month, day;
dt.getDate(&year, &month, &day);
// 2037 is not a leap year, so make sure date isn't Feb 29
@ -2744,6 +2775,7 @@ static qint64 localMSecsToEpochMSecs(qint64 localMsecs,
QTime utcTime;
msecsToTime(utcMsecs, &utcDate, &utcTime);
return timeToMSecs(utcDate.addDays(fakeDiff), utcTime);
#endif
}
static inline bool specCanBeSmall(Qt::TimeSpec spec)
@ -2874,7 +2906,8 @@ static void refreshZonedDateTime(QDateTimeData &d, Qt::TimeSpec spec)
QTime testTime;
auto dstStatus = extractDaylightStatus(status);
if (spec == Qt::LocalTime) {
epochMSecs = localMSecsToEpochMSecs(msecs, &dstStatus, &testDate, &testTime);
epochMSecs =
QDateTimePrivate::localMSecsToEpochMSecs(msecs, &dstStatus, &testDate, &testTime);
#if QT_CONFIG(timezone)
// else spec == Qt::TimeZone, so check zone is valid:
} else if (d->m_timeZone.isValid()) {
@ -3678,7 +3711,7 @@ QString QDateTime::timeZoneAbbreviation() const
case Qt::LocalTime: {
QString abbrev;
auto status = extractDaylightStatus(getStatus(d));
localMSecsToEpochMSecs(getMSecs(d), &status, nullptr, nullptr, &abbrev);
QDateTimePrivate::localMSecsToEpochMSecs(getMSecs(d), &status, nullptr, nullptr, &abbrev);
return abbrev;
}
}
@ -3715,7 +3748,7 @@ bool QDateTime::isDaylightTime() const
case Qt::LocalTime: {
auto status = extractDaylightStatus(getStatus(d));
if (status == QDateTimePrivate::UnknownDaylightTime)
localMSecsToEpochMSecs(getMSecs(d), &status);
QDateTimePrivate::localMSecsToEpochMSecs(getMSecs(d), &status);
return (status == QDateTimePrivate::DaylightTime);
}
}
@ -3858,7 +3891,7 @@ qint64 QDateTime::toMSecsSinceEpoch() const
if (!d.isShort())
return d->m_msecs - d->m_offsetFromUtc * MSECS_PER_SEC;
// Offset from UTC not recorded: need to recompute.
return localMSecsToEpochMSecs(getMSecs(d), &status);
return QDateTimePrivate::localMSecsToEpochMSecs(getMSecs(d), &status);
}
case Qt::TimeZone:
@ -3950,7 +3983,7 @@ void QDateTime::setMSecsSinceEpoch(qint64 msecs)
QDate dt;
QTime tm;
QDateTimePrivate::DaylightStatus dstStatus;
epochMSecsToLocalTime(msecs, &dt, &tm, &dstStatus);
QDateTimePrivate::epochMSecsToLocalTime(msecs, &dt, &tm, &dstStatus);
setDateTime(d, dt, tm);
refreshZonedDateTime(d, spec); // FIXME: we do this again, below
msecs = getMSecs(d);
@ -4158,7 +4191,7 @@ static inline void massageAdjustedDateTime(QDateTimeData &d, QDate date, QTime t
auto spec = getSpec(d);
if (spec == Qt::LocalTime) {
QDateTimePrivate::DaylightStatus status = QDateTimePrivate::UnknownDaylightTime;
localMSecsToEpochMSecs(timeToMSecs(date, time), &status, &date, &time);
QDateTimePrivate::localMSecsToEpochMSecs(timeToMSecs(date, time), &status, &date, &time);
#if QT_CONFIG(timezone)
} else if (spec == Qt::TimeZone && d->m_timeZone.isValid()) {
QDateTimePrivate::zoneMSecsToEpochMSecs(timeToMSecs(date, time),

7
src/corelib/time/qdatetime_p.h
View File

@ -118,6 +118,13 @@ public:
static QDateTime::Data create(QDate toDate, QTime toTime, const QTimeZone & timeZone);
#endif // timezone
static bool epochMSecsToLocalTime(qint64 msecs, QDate *localDate, QTime *localTime,
QDateTimePrivate::DaylightStatus *daylightStatus = nullptr);
static qint64 localMSecsToEpochMSecs(qint64 localMsecs,
QDateTimePrivate::DaylightStatus *daylightStatus,
QDate *localDate = nullptr, QTime *localTime = nullptr,
QString *abbreviation = nullptr);
StatusFlags m_status = StatusFlag(Qt::LocalTime << TimeSpecShift);
qint64 m_msecs = 0;
int m_offsetFromUtc = 0;