From a4a7efaf5f7688a45a78da92a14b79e2ec11d60c Mon Sep 17 00:00:00 2001 From: Timothy Flynn Date: Tue, 2 Aug 2022 08:42:58 -0400 Subject: [PATCH] LibC+LibCore: Use tm_isdst to handle time zone offsets in DST Previously, we were incorrectly assuming that the daylight global variable indicated whether the current time zone is in DST. In reality, the daylight variable only indicates whether a time zone *can* be in DST. Instead, the tm structure has a tm_isdst member that should be used for this purpose. Ensure our LibC handles tm_isdst, and avoid errant usage of the daylight variable in Core::DateTime. --- Userland/Libraries/LibC/time.cpp | 31 ++++++++++++++++++------- Userland/Libraries/LibCore/DateTime.cpp | 20 +++++++--------- 2 files changed, 30 insertions(+), 21 deletions(-) diff --git a/Userland/Libraries/LibC/time.cpp b/Userland/Libraries/LibC/time.cpp index c1df69c6a56..a1591c80512 100644 --- a/Userland/Libraries/LibC/time.cpp +++ b/Userland/Libraries/LibC/time.cpp @@ -112,13 +112,18 @@ static bool is_valid_time(time_t timestamp) return (timestamp >= smallest_possible_time) && (timestamp <= biggest_possible_time); } -static struct tm* time_to_tm(struct tm* tm, time_t t) +static struct tm* time_to_tm(struct tm* tm, time_t t, StringView time_zone) { if (!is_valid_time(t)) { errno = EOVERFLOW; return nullptr; } + if (auto offset = TimeZone::get_time_zone_offset(time_zone, AK::Time::from_seconds(t)); offset.has_value()) { + tm->tm_isdst = offset->in_dst == TimeZone::InDST::Yes; + t += offset->seconds; + } + int year = 1970; for (; t >= days_in_year(year) * __seconds_per_day; ++year) t -= days_in_year(year) * __seconds_per_day; @@ -146,7 +151,7 @@ static struct tm* time_to_tm(struct tm* tm, time_t t) return tm; } -static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds) +static time_t tm_to_time(struct tm* tm, StringView time_zone) { // "The original values of the tm_wday and tm_yday components of the structure are ignored, // and the original values of the other components are not restricted to the ranges described in . @@ -156,8 +161,6 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds) // but with their values forced to the ranges indicated in the entry; // the final value of tm_mday shall not be set until tm_mon and tm_year are determined." - // FIXME: Handle tm_isdst eventually. - tm->tm_year += tm->tm_mon / 12; tm->tm_mon %= 12; if (tm->tm_mon < 0) { @@ -167,7 +170,17 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds) tm->tm_yday = day_of_year(1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday); time_t days_since_epoch = years_to_days_since_epoch(1900 + tm->tm_year) + tm->tm_yday; - auto timestamp = ((days_since_epoch * 24 + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec + timezone_adjust_seconds; + auto timestamp = ((days_since_epoch * 24 + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec; + + if (tm->tm_isdst < 0) { + if (auto offset = TimeZone::get_time_zone_offset(time_zone, AK::Time::from_seconds(timestamp)); offset.has_value()) + timestamp -= offset->seconds; + } else { + auto index = tm->tm_isdst == 0 ? 0 : 1; + + if (auto offsets = TimeZone::get_named_time_zone_offsets(time_zone, AK::Time::from_seconds(timestamp)); offsets.has_value()) + timestamp -= offsets->at(index).seconds; + } if (!is_valid_time(timestamp)) { errno = EOVERFLOW; @@ -180,7 +193,7 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds) time_t mktime(struct tm* tm) { tzset(); - return tm_to_time(tm, daylight ? altzone : timezone); + return tm_to_time(tm, __tzname); } struct tm* localtime(time_t const* t) @@ -196,12 +209,12 @@ struct tm* localtime_r(time_t const* t, struct tm* tm) if (!t) return nullptr; - return time_to_tm(tm, *t - (daylight ? altzone : timezone)); + return time_to_tm(tm, *t, __tzname); } time_t timegm(struct tm* tm) { - return tm_to_time(tm, 0); + return tm_to_time(tm, { __utc, __builtin_strlen(__utc) }); } struct tm* gmtime(time_t const* t) @@ -214,7 +227,7 @@ struct tm* gmtime_r(time_t const* t, struct tm* tm) { if (!t) return nullptr; - return time_to_tm(tm, *t); + return time_to_tm(tm, *t, { __utc, __builtin_strlen(__utc) }); } char* asctime(const struct tm* tm) diff --git a/Userland/Libraries/LibCore/DateTime.cpp b/Userland/Libraries/LibCore/DateTime.cpp index bf09253f77c..350e0766582 100644 --- a/Userland/Libraries/LibCore/DateTime.cpp +++ b/Userland/Libraries/LibCore/DateTime.cpp @@ -92,13 +92,13 @@ String DateTime::to_string(StringView format) const int const format_len = format.length(); auto format_time_zone_offset = [&](bool with_separator) { -#if defined(__serenity__) - auto offset_seconds = daylight ? -altzone : -timezone; -#elif !defined(__FreeBSD__) - auto offset_seconds = -timezone; -#else - auto offset_seconds = 0; -#endif + struct tm gmt_tm; + gmtime_r(&m_timestamp, &gmt_tm); + + gmt_tm.tm_isdst = -1; + auto gmt_timestamp = mktime(&gmt_tm); + + auto offset_seconds = static_cast(difftime(m_timestamp, gmt_timestamp)); StringView offset_sign; if (offset_seconds >= 0) { @@ -251,11 +251,7 @@ String DateTime::to_string(StringView format) const format_time_zone_offset(true); break; case 'Z': { -#ifndef __FreeBSD__ - auto const* timezone_name = tzname[daylight]; -#else - auto const* timezone_name = tzname[0]; -#endif + auto const* timezone_name = tzname[tm.tm_isdst == 0 ? 0 : 1]; builder.append({ timezone_name, strlen(timezone_name) }); break; }