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QTimeZone: Add back-end based on std::chrono::tzdb
Implement QTimeZone back-end based on C++20 std::chrono::tzdb; requires GCC libstdc++ 14, Clang libc++ 19 or MSVC STL 19.29. Fixes: QTBUG-68812 Change-Id: I6581b3fe908c2318befa8f421c4ca8bf7c51a760 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
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Magdalena Stojek
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Oct 3, 2024
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| Original file line number | Diff line number | Diff line change |
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| // Copyright (C) 2024 The Qt Company Ltd. | ||
| // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only | ||
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| #include "qtimezoneprivate_p.h" | ||
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| #include <chrono> | ||
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| QT_BEGIN_NAMESPACE | ||
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| using namespace std::chrono; | ||
| using namespace std::chrono_literals; | ||
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| #define EXCEPTION_CHECKED(expression, fallback) \ | ||
| QT_TRY { \ | ||
| expression; \ | ||
| } QT_CATCH (const std::runtime_error &) { \ | ||
| fallback; \ | ||
| } | ||
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| static std::chrono::sys_time<std::chrono::milliseconds> | ||
| chronoForEpochMillis(qint64 millis) | ||
| { | ||
| return sys_time<milliseconds>(milliseconds(millis)); | ||
| } | ||
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| static std::optional<std::chrono::sys_info> | ||
| infoAtEpochMillis(const std::chrono::time_zone *zone, qint64 millis) | ||
| { | ||
| EXCEPTION_CHECKED(return zone->get_info(chronoForEpochMillis(millis)), return std::nullopt); | ||
| } | ||
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| static const std::chrono::time_zone *idToZone(std::string_view id) | ||
| { | ||
| EXCEPTION_CHECKED(return get_tzdb().locate_zone(id), return nullptr); | ||
| } | ||
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| static QChronoTimeZonePrivate::Data | ||
| fromSysInfo(std::chrono::sys_info info, qint64 atMSecsSinceEpoch) | ||
| { | ||
| QString abbreviation = QString::fromLatin1(info.abbrev); | ||
| int offsetFromUtc = info.offset.count(); | ||
| // offset is in seconds, save is in minutes | ||
| int standardTimeOffset = offsetFromUtc - seconds(info.save).count(); | ||
| return QChronoTimeZonePrivate::Data(abbreviation, atMSecsSinceEpoch, | ||
| offsetFromUtc, standardTimeOffset); | ||
| } | ||
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| QChronoTimeZonePrivate::QChronoTimeZonePrivate() | ||
| : m_timeZone(std::chrono::current_zone()) | ||
| { | ||
| if (m_timeZone) | ||
| m_id.assign(m_timeZone->name()); | ||
| } | ||
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| QChronoTimeZonePrivate::QChronoTimeZonePrivate(QByteArrayView id) | ||
| : m_timeZone(idToZone(std::string_view(id.data(), id.size()))) | ||
| { | ||
| if (m_timeZone) | ||
| m_id.assign(m_timeZone->name()); | ||
| } | ||
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| QChronoTimeZonePrivate::~QChronoTimeZonePrivate() | ||
| = default; | ||
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| QString QChronoTimeZonePrivate::abbreviation(qint64 atMSecsSinceEpoch) const | ||
| { | ||
| if (auto info = infoAtEpochMillis(m_timeZone, atMSecsSinceEpoch)) | ||
| return fromSysInfo(*info, atMSecsSinceEpoch).abbreviation; | ||
| return {}; | ||
| } | ||
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| int QChronoTimeZonePrivate::offsetFromUtc(qint64 atMSecsSinceEpoch) const | ||
| { | ||
| if (auto info = infoAtEpochMillis(m_timeZone, atMSecsSinceEpoch)) | ||
| return fromSysInfo(*info, atMSecsSinceEpoch).offsetFromUtc; | ||
| return invalidSeconds(); | ||
| } | ||
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| int QChronoTimeZonePrivate::standardTimeOffset(qint64 atMSecsSinceEpoch) const | ||
| { | ||
| // Subtracting minutes from seconds will convert the minutes to seconds. | ||
| if (auto info = infoAtEpochMillis(m_timeZone, atMSecsSinceEpoch)) | ||
| return int((info->offset - info->save).count()); | ||
| return invalidSeconds(); | ||
| } | ||
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| int QChronoTimeZonePrivate::daylightTimeOffset(qint64 atMSecsSinceEpoch) const | ||
| { | ||
| if (auto info = infoAtEpochMillis(m_timeZone, atMSecsSinceEpoch)) | ||
| return int(std::chrono::seconds(info->save).count()); | ||
| return invalidSeconds(); | ||
| } | ||
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| bool QChronoTimeZonePrivate::hasDaylightTime() const | ||
| { | ||
| Data data = QTimeZonePrivate::data(QTimeZone::DaylightTime); | ||
| return data.daylightTimeOffset != 0 | ||
| && data.daylightTimeOffset != invalidSeconds(); | ||
| } | ||
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| bool QChronoTimeZonePrivate::isDaylightTime(qint64 atMSecsSinceEpoch) const | ||
| { | ||
| if (auto info = infoAtEpochMillis(m_timeZone, atMSecsSinceEpoch)) | ||
| return info->save != 0min; | ||
| return false; | ||
| } | ||
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| QChronoTimeZonePrivate::Data | ||
| QChronoTimeZonePrivate::data(qint64 forMSecsSinceEpoch) const | ||
| { | ||
| if (auto info = infoAtEpochMillis(m_timeZone, forMSecsSinceEpoch)) | ||
| return fromSysInfo(*info, forMSecsSinceEpoch); | ||
| return {}; | ||
| } | ||
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| bool QChronoTimeZonePrivate::hasTransitions() const | ||
| { | ||
| return true; | ||
| } | ||
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| QChronoTimeZonePrivate::Data | ||
| QChronoTimeZonePrivate::nextTransition(qint64 afterMSecsSinceEpoch) const | ||
| { | ||
| if (const auto info = infoAtEpochMillis(m_timeZone, afterMSecsSinceEpoch)) { | ||
| const auto tran = info->end; | ||
| qint64 when = milliseconds(tran.time_since_epoch()).count(); | ||
| if (when > afterMSecsSinceEpoch) { | ||
| return fromSysInfo(*info, afterMSecsSinceEpoch); | ||
| } // else we were already at (or after) the end-of-time "transition" | ||
| } | ||
| return {}; | ||
| } | ||
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| QChronoTimeZonePrivate::Data | ||
| QChronoTimeZonePrivate::previousTransition(qint64 beforeMSecsSinceEpoch) const | ||
| { | ||
| if (const auto info = infoAtEpochMillis(m_timeZone, beforeMSecsSinceEpoch - 1)) { | ||
| qint64 when = milliseconds(info->begin.time_since_epoch()).count(); | ||
| if (when < beforeMSecsSinceEpoch) { | ||
| return fromSysInfo(*info, beforeMSecsSinceEpoch); | ||
| } // else we were already at (or before) the start-of-time "transition" | ||
| } | ||
| return {}; | ||
| } | ||
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| QT_END_NAMESPACE |
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