QWinTimeZonePrivate: make transition searches more efficient
Iterate rules (now that there's fewer of them than years) with only a secondary iteration on years (when needed - in which case it should never need more than two iterations). In particular, avoid iterating years to the MIN_YEAR and MAX_YEAR extremes on failure; fail faster ! Change-Id: I354af8e0cb1e484c8abda279991e6e1824f9f7d4 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Edward Welbourne
parent
a99c773972
commit
88d5ba5409
@ -401,9 +401,6 @@ struct TransitionTimePair
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{
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// Transition times after the epoch, in ms:
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qint64 std, dst;
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TransitionTimePair()
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: std(QTimeZonePrivate::invalidMSecs()), dst(QTimeZonePrivate::invalidMSecs())
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{}
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TransitionTimePair(const QWinTimeZonePrivate::QWinTransitionRule &rule, int year)
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// The local time in Daylight Time of the switch to Standard Time
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: std(calculateTransitionForYear(rule.standardTimeRule, year,
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@ -660,39 +657,37 @@ bool QWinTimeZonePrivate::isDaylightTime(qint64 atMSecsSinceEpoch) const
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QTimeZonePrivate::Data QWinTimeZonePrivate::data(qint64 forMSecsSinceEpoch) const
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{
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// Convert MSecs to year to get transitions for, assumes no transitions around 31 Dec/1 Jan
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int year = msecsToDate(forMSecsSinceEpoch).year();
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qint64 first;
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qint64 second;
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qint64 next = maxMSecs();
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TransitionTimePair pair;
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Q_ASSERT(next != pair.dst); // so break on first iteration gets standard time
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QWinTransitionRule rule;
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do {
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// Convert the transition rules into msecs for the year we want to try
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rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
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// If no transition rules to calculate then no DST, so just use rule for std
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if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0)
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break;
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pair = TransitionTimePair(rule, year);
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if (pair.std < pair.dst) {
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first = pair.std;
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second = pair.dst;
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for (int ruleIndex = ruleIndexForYear(m_tranRules, year);
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ruleIndex >= 0; --ruleIndex) {
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const QWinTransitionRule &rule = m_tranRules.at(ruleIndex);
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// Does this rule's period include any transition at all ?
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if (rule.standardTimeRule.wMonth > 0 || rule.daylightTimeRule.wMonth > 0) {
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const int endYear = qMax(rule.startYear, year - 1);
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while (year >= endYear) {
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const TransitionTimePair pair(rule, year);
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bool isDst = false;
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if (pair.std <= forMSecsSinceEpoch) {
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isDst = pair.std < pair.dst && pair.dst <= forMSecsSinceEpoch;
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} else if (pair.dst <= forMSecsSinceEpoch) {
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isDst = true;
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} else {
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--year; // Try an earlier year for this rule (once).
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continue;
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}
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return ruleToData(rule, forMSecsSinceEpoch,
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isDst ? QTimeZone::DaylightTime : QTimeZone::StandardTime);
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}
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// Fell off start of rule, try previous rule.
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} else {
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first = pair.dst;
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second = pair.std;
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// No transition, no DST, use the year's standard time.
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return ruleToData(rule, forMSecsSinceEpoch, QTimeZone::StandardTime);
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}
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if (forMSecsSinceEpoch >= second && second != invalidMSecs())
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next = second;
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else if (forMSecsSinceEpoch >= first && first != invalidMSecs())
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next = first;
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// If didn't fall in this year, try the previous
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--year;
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} while (next == maxMSecs() && year >= MIN_YEAR);
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return ruleToData(rule, forMSecsSinceEpoch, (next == pair.dst) ? QTimeZone::DaylightTime : QTimeZone::StandardTime);
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if (year >= rule.startYear)
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year = rule.startYear - 1; // Seek last transition in new rule.
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}
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// We don't have relevant data :-(
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return invalidData();
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}
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bool QWinTimeZonePrivate::hasTransitions() const
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@ -706,107 +701,70 @@ bool QWinTimeZonePrivate::hasTransitions() const
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QTimeZonePrivate::Data QWinTimeZonePrivate::nextTransition(qint64 afterMSecsSinceEpoch) const
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{
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// Convert MSecs to year to get transitions for, assumes no transitions around 31 Dec/1 Jan
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int year = msecsToDate(afterMSecsSinceEpoch).year();
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for (int ruleIndex = ruleIndexForYear(m_tranRules, year);
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ruleIndex < m_tranRules.count(); ++ruleIndex) {
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const QWinTransitionRule &rule = m_tranRules.at(ruleIndex);
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// Does this rule's period include any transition at all ?
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if (rule.standardTimeRule.wMonth > 0 || rule.daylightTimeRule.wMonth > 0) {
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if (year < rule.startYear)
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year = rule.startYear; // Seek first transition in this rule.
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const int endYear = ruleIndex + 1 < m_tranRules.count()
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? qMin(m_tranRules.at(ruleIndex + 1).startYear, year + 2) : (year + 2);
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while (year < endYear) {
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const TransitionTimePair pair(rule, year);
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bool isDst = false;
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if (pair.std > afterMSecsSinceEpoch) {
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isDst = pair.std > pair.dst && pair.dst > afterMSecsSinceEpoch;
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} else if (pair.dst > afterMSecsSinceEpoch) {
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isDst = true;
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} else {
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++year; // Try a later year for this rule (once).
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continue;
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}
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QWinTransitionRule rule;
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// If the required year falls after the last rule start year and the last rule has no
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// valid future transition calculations then there is no next transition
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if (year > m_tranRules.last().startYear) {
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rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
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// If the rules have either a fixed year, or no month, then no future trans
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if (rule.standardTimeRule.wYear != 0 || rule.daylightTimeRule.wYear != 0
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|| rule.standardTimeRule.wMonth == 0 || rule.daylightTimeRule.wMonth == 0) {
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return invalidData();
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}
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if (isDst)
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return ruleToData(rule, pair.dst, QTimeZone::DaylightTime);
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return ruleToData(rule, pair.std, QTimeZone::StandardTime);
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}
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// Fell off end of rule, try next rule.
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} // else: no transition during rule's period
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}
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// Otherwise we have a valid rule for the required year that can be used
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// to calculate this year or next
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qint64 first;
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qint64 second;
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qint64 next = minMSecs();
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TransitionTimePair pair;
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do {
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// Convert the transition rules into msecs for the year we want to try
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rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
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// If there's no transition this year, check for a later year:
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if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0) {
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++year;
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continue;
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}
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pair = TransitionTimePair(rule, year);
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// Find the first and second transition for the year
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if (pair.std < pair.dst) {
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first = pair.std;
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second = pair.dst;
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} else {
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first = pair.dst;
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second = pair.std;
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}
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if (afterMSecsSinceEpoch < first)
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next = first;
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else if (afterMSecsSinceEpoch < second)
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next = second;
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// If didn't fall in this year, try the next
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++year;
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} while (next == minMSecs() && year <= MAX_YEAR);
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if (next == minMSecs() || next == invalidMSecs())
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return invalidData();
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return ruleToData(rule, next, (next == pair.dst) ? QTimeZone::DaylightTime : QTimeZone::StandardTime);
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// Apparently no transition after the given time:
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return invalidData();
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}
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QTimeZonePrivate::Data QWinTimeZonePrivate::previousTransition(qint64 beforeMSecsSinceEpoch) const
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{
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// Convert MSecs to year to get transitions for, assumes no transitions around 31 Dec/1 Jan
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int year = msecsToDate(beforeMSecsSinceEpoch).year();
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QWinTransitionRule rule;
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// If the required year falls before the first rule start year and the first rule has no
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// valid transition calculations then there is no previous transition
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if (year < m_tranRules.first().startYear) {
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rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
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// If the rules have either a fixed year, or no month, then no previous trans
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if (rule.standardTimeRule.wYear != 0 || rule.daylightTimeRule.wYear != 0
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|| rule.standardTimeRule.wMonth == 0 || rule.daylightTimeRule.wMonth == 0) {
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return invalidData();
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}
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for (int ruleIndex = ruleIndexForYear(m_tranRules, year);
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ruleIndex >= 0; --ruleIndex) {
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const QWinTransitionRule &rule = m_tranRules.at(ruleIndex);
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// Does this rule's period include any transition at all ?
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if (rule.standardTimeRule.wMonth > 0 || rule.daylightTimeRule.wMonth > 0) {
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const int endYear = qMax(rule.startYear, year - 1);
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while (year >= endYear) {
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const TransitionTimePair pair(rule, year);
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bool isDst = false;
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if (pair.std < beforeMSecsSinceEpoch) {
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isDst = pair.std < pair.dst && pair.dst < beforeMSecsSinceEpoch;
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} else if (pair.dst < beforeMSecsSinceEpoch) {
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isDst = true;
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} else {
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--year; // Try an earlier year for this rule (once).
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continue;
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}
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if (isDst)
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return ruleToData(rule, pair.dst, QTimeZone::DaylightTime);
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return ruleToData(rule, pair.std, QTimeZone::StandardTime);
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}
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// Fell off start of rule, try previous rule.
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} // else: no transition during rule's period
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if (year >= rule.startYear)
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year = rule.startYear - 1; // Seek last transition in new rule
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}
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qint64 first;
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qint64 second;
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qint64 next = maxMSecs();
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TransitionTimePair pair;
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do {
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// Convert the transition rules into msecs for the year we want to try
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rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
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// If there's no transition this year, check for an earlier year:
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if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0) {
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--year;
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continue;
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}
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pair = TransitionTimePair(rule, year);
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if (pair.std < pair.dst) {
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first = pair.std;
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second = pair.dst;
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} else {
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first = pair.dst;
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second = pair.std;
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}
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if (beforeMSecsSinceEpoch > second && second != invalidMSecs())
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next = second;
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else if (beforeMSecsSinceEpoch > first && first != invalidMSecs())
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next = first;
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// If didn't fall in this year, try the previous
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--year;
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} while (next == maxMSecs() && year >= MIN_YEAR);
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if (next == maxMSecs())
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return invalidData();
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return ruleToData(rule, next, (next == pair.dst) ? QTimeZone::DaylightTime : QTimeZone::StandardTime);
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// Apparently no transition before the given time:
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return invalidData();
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}
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QByteArray QWinTimeZonePrivate::systemTimeZoneId() const
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