diff options
Diffstat (limited to 'absl/time/internal/cctz/src/time_zone_libc.cc')
| -rw-r--r-- | absl/time/internal/cctz/src/time_zone_libc.cc | 200 |
1 files changed, 164 insertions, 36 deletions
diff --git a/absl/time/internal/cctz/src/time_zone_libc.cc b/absl/time/internal/cctz/src/time_zone_libc.cc index e35fa18b7733..6db519e165cf 100644 --- a/absl/time/internal/cctz/src/time_zone_libc.cc +++ b/absl/time/internal/cctz/src/time_zone_libc.cc @@ -20,6 +20,7 @@ #include <chrono> #include <ctime> +#include <limits> #include <tuple> #include <utility> @@ -85,6 +86,76 @@ OffsetAbbr get_offset_abbr(const T& tm, decltype(&T::__tm_gmtoff) = nullptr, #endif // !defined(__tm_gmtoff) && !defined(__tm_zone) #endif +inline std::tm* gm_time(const std::time_t *timep, std::tm *result) { +#if defined(_WIN32) || defined(_WIN64) + return gmtime_s(result, timep) ? nullptr : result; +#else + return gmtime_r(timep, result); +#endif +} + +inline std::tm* local_time(const std::time_t *timep, std::tm *result) { +#if defined(_WIN32) || defined(_WIN64) + return localtime_s(result, timep) ? nullptr : result; +#else + return localtime_r(timep, result); +#endif +} + +// Converts a civil second and "dst" flag into a time_t and UTC offset. +// Returns false if time_t cannot represent the requested civil second. +// Caller must have already checked that cs.year() will fit into a tm_year. +bool make_time(const civil_second& cs, int is_dst, std::time_t* t, int* off) { + std::tm tm; + tm.tm_year = static_cast<int>(cs.year() - year_t{1900}); + tm.tm_mon = cs.month() - 1; + tm.tm_mday = cs.day(); + tm.tm_hour = cs.hour(); + tm.tm_min = cs.minute(); + tm.tm_sec = cs.second(); + tm.tm_isdst = is_dst; + *t = std::mktime(&tm); + if (*t == std::time_t{-1}) { + std::tm tm2; + const std::tm* tmp = local_time(t, &tm2); + if (tmp == nullptr || tmp->tm_year != tm.tm_year || + tmp->tm_mon != tm.tm_mon || tmp->tm_mday != tm.tm_mday || + tmp->tm_hour != tm.tm_hour || tmp->tm_min != tm.tm_min || + tmp->tm_sec != tm.tm_sec) { + // A true error (not just one second before the epoch). + return false; + } + } + *off = get_offset_abbr(tm).first; + return true; +} + +// Find the least time_t in [lo:hi] where local time matches offset, given: +// (1) lo doesn't match, (2) hi does, and (3) there is only one transition. +std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) { + std::tm tm; + while (lo + 1 != hi) { + const std::time_t mid = lo + (hi - lo) / 2; + if (std::tm* tmp = local_time(&mid, &tm)) { + if (get_offset_abbr(*tmp).first == offset) { + hi = mid; + } else { + lo = mid; + } + } else { + // If std::tm cannot hold some result we resort to a linear search, + // ignoring all failed conversions. Slow, but never really happens. + while (++lo != hi) { + if (std::tm* tmp = local_time(&lo, &tm)) { + if (get_offset_abbr(*tmp).first == offset) break; + } + } + return lo; + } + } + return hi; +} + } // namespace TimeZoneLibC::TimeZoneLibC(const std::string& name) @@ -93,50 +164,107 @@ TimeZoneLibC::TimeZoneLibC(const std::string& name) time_zone::absolute_lookup TimeZoneLibC::BreakTime( const time_point<seconds>& tp) const { time_zone::absolute_lookup al; - std::time_t t = ToUnixSeconds(tp); + al.offset = 0; + al.is_dst = false; + al.abbr = "-00"; + + const std::int_fast64_t s = ToUnixSeconds(tp); + + // If std::time_t cannot hold the input we saturate the output. + if (s < std::numeric_limits<std::time_t>::min()) { + al.cs = civil_second::min(); + return al; + } + if (s > std::numeric_limits<std::time_t>::max()) { + al.cs = civil_second::max(); + return al; + } + + const std::time_t t = static_cast<std::time_t>(s); std::tm tm; - if (local_) { -#if defined(_WIN32) || defined(_WIN64) - localtime_s(&tm, &t); -#else - localtime_r(&t, &tm); -#endif - std::tie(al.offset, al.abbr) = get_offset_abbr(tm); - } else { -#if defined(_WIN32) || defined(_WIN64) - gmtime_s(&tm, &t); -#else - gmtime_r(&t, &tm); -#endif - al.offset = 0; - al.abbr = "UTC"; + std::tm* tmp = local_ ? local_time(&t, &tm) : gm_time(&t, &tm); + + // If std::tm cannot hold the result we saturate the output. + if (tmp == nullptr) { + al.cs = (s < 0) ? civil_second::min() : civil_second::max(); + return al; } - al.cs = civil_second(tm.tm_year + year_t{1900}, tm.tm_mon + 1, tm.tm_mday, - tm.tm_hour, tm.tm_min, tm.tm_sec); - al.is_dst = tm.tm_isdst > 0; + + const year_t year = tmp->tm_year + year_t{1900}; + al.cs = civil_second(year, tmp->tm_mon + 1, tmp->tm_mday, + tmp->tm_hour, tmp->tm_min, tmp->tm_sec); + std::tie(al.offset, al.abbr) = get_offset_abbr(*tmp); + if (!local_) al.abbr = "UTC"; // as expected by cctz + al.is_dst = tmp->tm_isdst > 0; return al; } time_zone::civil_lookup TimeZoneLibC::MakeTime(const civil_second& cs) const { - time_zone::civil_lookup cl; - std::time_t t; - if (local_) { - // Does not handle SKIPPED/AMBIGUOUS or huge years. - std::tm tm; - tm.tm_year = static_cast<int>(cs.year() - 1900); - tm.tm_mon = cs.month() - 1; - tm.tm_mday = cs.day(); - tm.tm_hour = cs.hour(); - tm.tm_min = cs.minute(); - tm.tm_sec = cs.second(); - tm.tm_isdst = -1; - t = std::mktime(&tm); + if (!local_) { + // If time_point<seconds> cannot hold the result we saturate. + static const civil_second min_tp_cs = + civil_second() + ToUnixSeconds(time_point<seconds>::min()); + static const civil_second max_tp_cs = + civil_second() + ToUnixSeconds(time_point<seconds>::max()); + const time_point<seconds> tp = + (cs < min_tp_cs) + ? time_point<seconds>::min() + : (cs > max_tp_cs) ? time_point<seconds>::max() + : FromUnixSeconds(cs - civil_second()); + return {time_zone::civil_lookup::UNIQUE, tp, tp, tp}; + } + + // If tm_year cannot hold the requested year we saturate the result. + if (cs.year() < 0) { + if (cs.year() < std::numeric_limits<int>::min() + year_t{1900}) { + const time_point<seconds> tp = time_point<seconds>::min(); + return {time_zone::civil_lookup::UNIQUE, tp, tp, tp}; + } } else { - t = cs - civil_second(); + if (cs.year() - year_t{1900} > std::numeric_limits<int>::max()) { + const time_point<seconds> tp = time_point<seconds>::max(); + return {time_zone::civil_lookup::UNIQUE, tp, tp, tp}; + } + } + + // We probe with "is_dst" values of 0 and 1 to try to distinguish unique + // civil seconds from skipped or repeated ones. This is not always possible + // however, as the "dst" flag does not change over some offset transitions. + // We are also subject to the vagaries of mktime() implementations. + std::time_t t0, t1; + int offset0, offset1; + if (make_time(cs, 0, &t0, &offset0) && make_time(cs, 1, &t1, &offset1)) { + if (t0 == t1) { + // The civil time was singular (pre == trans == post). + const time_point<seconds> tp = FromUnixSeconds(t0); + return {time_zone::civil_lookup::UNIQUE, tp, tp, tp}; + } + + if (t0 > t1) { + std::swap(t0, t1); + std::swap(offset0, offset1); + } + const std::time_t tt = find_trans(t0, t1, offset1); + const time_point<seconds> trans = FromUnixSeconds(tt); + + if (offset0 < offset1) { + // The civil time did not exist (pre >= trans > post). + const time_point<seconds> pre = FromUnixSeconds(t1); + const time_point<seconds> post = FromUnixSeconds(t0); + return {time_zone::civil_lookup::SKIPPED, pre, trans, post}; + } + + // The civil time was ambiguous (pre < trans <= post). + const time_point<seconds> pre = FromUnixSeconds(t0); + const time_point<seconds> post = FromUnixSeconds(t1); + return {time_zone::civil_lookup::REPEATED, pre, trans, post}; } - cl.kind = time_zone::civil_lookup::UNIQUE; - cl.pre = cl.trans = cl.post = FromUnixSeconds(t); - return cl; + + // make_time() failed somehow so we saturate the result. + const time_point<seconds> tp = (cs < civil_second()) + ? time_point<seconds>::min() + : time_point<seconds>::max(); + return {time_zone::civil_lookup::UNIQUE, tp, tp, tp}; } bool TimeZoneLibC::NextTransition(const time_point<seconds>& tp, |