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Fix Posix::time_zone for southern hemisphere

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* The get_info functions were not prepared for the case where the start
  and end times of a rule are chronologically reversed for a year.  I.e.
  the daylight saving start comes later in the year than the daylight
  saving end.  When save is positive, this happens in the southern
  hemisphere (e.g. "Australia/Sydney" -> "AEST-10AEDT,M10.1.0,M4.1.0/3").
  It also happens in the nothern hemisphere when the save is negative
  (e.g. "Europe/Dublin" -> "IST-1GMT0,M10.5.0,M3.5.0/1").

* Added tests for Posix::time_zone.
This commit is contained in:
Howard Hinnant
2021-04-09 11:08:12 -04:00
parent 156e0a786e
commit ae017078c9
2 changed files with 246 additions and 66 deletions
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include/date/ptz.h
+138 -66
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@@ -269,8 +269,76 @@ public:
std::string name() const;
friend bool operator==(const time_zone& x, const time_zone& y);
private:
date::sys_seconds get_start(date::year y) const;
date::sys_seconds get_prev_start(date::year y) const;
date::sys_seconds get_next_start(date::year y) const;
date::sys_seconds get_end(date::year y) const;
date::sys_seconds get_prev_end(date::year y) const;
date::sys_seconds get_next_end(date::year y) const;
date::sys_info contant_offset() const;
};
inline
date::sys_seconds
time_zone::get_start(date::year y) const
{
return date::sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
}
inline
date::sys_seconds
time_zone::get_prev_start(date::year y) const
{
return date::sys_seconds{(start_rule_(--y) - offset_).time_since_epoch()};
}
inline
date::sys_seconds
time_zone::get_next_start(date::year y) const
{
return date::sys_seconds{(start_rule_(++y) - offset_).time_since_epoch()};
}
inline
date::sys_seconds
time_zone::get_end(date::year y) const
{
return date::sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
}
inline
date::sys_seconds
time_zone::get_prev_end(date::year y) const
{
return date::sys_seconds{(end_rule_(--y) - (offset_ + save_)).time_since_epoch()};
}
inline
date::sys_seconds
time_zone::get_next_end(date::year y) const
{
return date::sys_seconds{(end_rule_(++y) - (offset_ + save_)).time_since_epoch()};
}
date::sys_info
time_zone::contant_offset() const
{
using date::year;
using date::sys_info;
using date::sys_days;
using date::January;
using date::December;
using date::last;
sys_info r;
r.begin = sys_days{year::min()/January/1};
r.end = sys_days{year::max()/December/last};
r.abbrev = std_abbrev_;
r.offset = offset_;
return r;
}
inline
time_zone::time_zone(const detail::string_t& s)
{
@@ -313,12 +381,10 @@ time_zone::get_info(date::sys_time<Duration> st) const
{
using date::sys_info;
using date::year_month_day;
using date::sys_seconds;
using date::sys_days;
using date::floor;
using date::ceil;
using date::days;
using date::years;
using date::year;
using date::January;
using date::December;
@@ -329,36 +395,59 @@ time_zone::get_info(date::sys_time<Duration> st) const
if (start_rule_.ok())
{
auto y = year_month_day{floor<days>(st)}.year();
auto start = sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
auto end = sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
if (start <= st && st < end)
auto start = get_start(y);
auto end = get_end(y);
if (start <= end) // (northern hemisphere)
{
r.begin = start;
r.end = end;
r.offset += save_;
r.save = ceil<minutes>(save_);
r.abbrev = dst_abbrev_;
if (start <= st && st < end)
{
r.begin = start;
r.end = end;
r.offset += save_;
r.save = ceil<minutes>(save_);
r.abbrev = dst_abbrev_;
}
else if (st < start)
{
r.begin = get_prev_end(y);
r.end = start;
r.abbrev = std_abbrev_;
}
else // st >= end
{
r.begin = end;
r.end = get_next_start(y);
r.abbrev = std_abbrev_;
}
}
else if (st < start)
else // end < start (southern hemisphere)
{
r.begin = sys_seconds{(end_rule_(y-years{1}) -
(offset_ + save_)).time_since_epoch()};
r.end = start;
r.abbrev = std_abbrev_;
}
else // st >= end
{
r.begin = end;
r.end = sys_seconds{(start_rule_(y+years{1}) - offset_).time_since_epoch()};
r.abbrev = std_abbrev_;
if (end <= st && st < start)
{
r.begin = end;
r.end = start;
r.abbrev = std_abbrev_;
}
else if (st < end)
{
r.begin = get_prev_start(y);
r.end = end;
r.offset += save_;
r.save = ceil<minutes>(save_);
r.abbrev = dst_abbrev_;
}
else // st >= start
{
r.begin = start;
r.end = get_next_end(y);
r.offset += save_;
r.save = ceil<minutes>(save_);
r.abbrev = dst_abbrev_;
}
}
}
else // constant offset
{
r.begin = sys_days{year::min()/January/1};
r.end = sys_days{year::max()/December/last};
r.abbrev = std_abbrev_;
}
else
r = contant_offset();
return r;
}
@@ -371,7 +460,6 @@ time_zone::get_info(date::local_time<Duration> tp) const
using date::days;
using date::sys_days;
using date::sys_seconds;
using date::years;
using date::year;
using date::ceil;
using date::January;
@@ -384,19 +472,25 @@ time_zone::get_info(date::local_time<Duration> tp) const
if (start_rule_.ok())
{
auto y = year_month_day{floor<days>(tp)}.year();
auto start = sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
auto end = sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
auto start = get_start(y);
auto end = get_end(y);
auto utcs = sys_seconds{floor<seconds>(tp - offset_).time_since_epoch()};
auto utcd = sys_seconds{floor<seconds>(tp - (offset_ + save_)).time_since_epoch()};
auto northern = start <= end;
if ((utcs < start) != (utcd < start))
{
r.first.begin = sys_seconds{(end_rule_(y-years{1}) -
(offset_ + save_)).time_since_epoch()};
if (northern)
r.first.begin = get_prev_end(y);
else
r.first.begin = end;
r.first.end = start;
r.first.offset = offset_;
r.first.abbrev = std_abbrev_;
r.second.begin = start;
r.second.end = end;
if (northern)
r.second.end = end;
else
r.second.end = get_next_end(y);
r.second.abbrev = dst_abbrev_;
r.second.offset = offset_ + save_;
r.second.save = ceil<minutes>(save_);
@@ -405,51 +499,29 @@ time_zone::get_info(date::local_time<Duration> tp) const
}
else if ((utcs < end) != (utcd < end))
{
r.first.begin = start;
if (northern)
r.first.begin = start;
else
r.first.begin = get_prev_start(y);
r.first.end = end;
r.first.offset = offset_ + save_;
r.first.save = ceil<minutes>(save_);
r.first.abbrev = dst_abbrev_;
r.second.begin = end;
r.second.end = sys_seconds{(start_rule_(y+years{1}) -
offset_).time_since_epoch()};
if (northern)
r.second.end = get_next_start(y);
else
r.second.end = start;
r.second.abbrev = std_abbrev_;
r.second.offset = offset_;
r.result = save_ > seconds{0} ? local_info::ambiguous
: local_info::nonexistent;
}
else if (utcs < start)
{
r.first.begin = sys_seconds{(end_rule_(y-years{1}) -
(offset_ + save_)).time_since_epoch()};
r.first.end = start;
r.first.offset = offset_;
r.first.abbrev = std_abbrev_;
}
else if (utcs < end)
{
r.first.begin = start;
r.first.end = end;
r.first.offset = offset_ + save_;
r.first.save = ceil<minutes>(save_);
r.first.abbrev = dst_abbrev_;
}
else
{
r.first.begin = end;
r.first.end = sys_seconds{(start_rule_(y+years{1}) -
offset_).time_since_epoch()};
r.first.abbrev = std_abbrev_;
r.first.offset = offset_;
}
}
else // constant offset
{
r.first.begin = sys_days{year::min()/January/1};
r.first.end = sys_days{year::max()/December/last};
r.first.abbrev = std_abbrev_;
r.first.offset = offset_;
r.first = get_info(utcs);
}
else
r.first = contant_offset();
return r;
}