ClickHouse/base/common/DateLUTImpl.cpp
2021-08-09 16:16:17 +02:00

239 lines
8.6 KiB
C++

#include "DateLUTImpl.h"
#include <cctz/civil_time.h>
#include <cctz/time_zone.h>
#include <cctz/zone_info_source.h>
#include <common/getResource.h>
#include <Poco/Exception.h>
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cstring>
#include <iostream>
#include <memory>
namespace
{
UInt8 getDayOfWeek(const cctz::civil_day & date)
{
cctz::weekday day_of_week = cctz::get_weekday(date);
switch (day_of_week)
{
case cctz::weekday::monday: return 1;
case cctz::weekday::tuesday: return 2;
case cctz::weekday::wednesday: return 3;
case cctz::weekday::thursday: return 4;
case cctz::weekday::friday: return 5;
case cctz::weekday::saturday: return 6;
case cctz::weekday::sunday: return 7;
}
__builtin_unreachable();
}
}
__attribute__((__weak__)) extern bool inside_main;
DateLUTImpl::DateLUTImpl(const std::string & time_zone_)
: time_zone(time_zone_)
{
/// DateLUT should not be initialized in global constructors for the following reasons:
/// 1. It is too heavy.
if (&inside_main)
assert(inside_main);
cctz::time_zone cctz_time_zone;
if (!cctz::load_time_zone(time_zone, &cctz_time_zone))
throw Poco::Exception("Cannot load time zone " + time_zone_);
constexpr cctz::civil_day epoch{1970, 1, 1};
constexpr cctz::civil_day lut_start{DATE_LUT_MIN_YEAR, 1, 1};
time_t start_of_day;
/// Note: it's validated against all timezones in the system.
static_assert((epoch - lut_start) == daynum_offset_epoch);
offset_at_start_of_epoch = cctz_time_zone.lookup(cctz_time_zone.lookup(epoch).pre).offset;
offset_at_start_of_lut = cctz_time_zone.lookup(cctz_time_zone.lookup(lut_start).pre).offset;
offset_is_whole_number_of_hours_during_epoch = true;
offset_is_whole_number_of_minutes_during_epoch = true;
cctz::civil_day date = lut_start;
UInt32 i = 0;
do
{
cctz::time_zone::civil_lookup lookup = cctz_time_zone.lookup(date);
/// Ambiguity is possible if time was changed backwards at the midnight
/// or after midnight time has been changed back to midnight, for example one hour backwards at 01:00
/// or after midnight time has been changed to the previous day, for example two hours backwards at 01:00
/// Then midnight appears twice. Usually time change happens exactly at 00:00 or 01:00.
/// If transition did not involve previous day, we should use the first midnight as the start of the day,
/// otherwise it's better to use the second midnight.
std::chrono::time_point start_of_day_time_point = lookup.trans < lookup.post
? lookup.post /* Second midnight appears after transition, so there was a piece of previous day after transition */
: lookup.pre;
start_of_day = std::chrono::system_clock::to_time_t(start_of_day_time_point);
Values & values = lut[i];
values.year = date.year();
values.month = date.month();
values.day_of_month = date.day();
values.day_of_week = getDayOfWeek(date);
values.date = start_of_day;
assert(values.year >= DATE_LUT_MIN_YEAR && values.year <= DATE_LUT_MAX_YEAR + 1);
assert(values.month >= 1 && values.month <= 12);
assert(values.day_of_month >= 1 && values.day_of_month <= 31);
assert(values.day_of_week >= 1 && values.day_of_week <= 7);
if (values.day_of_month == 1)
{
cctz::civil_month month(date);
values.days_in_month = cctz::civil_day(month + 1) - cctz::civil_day(month);
}
else
values.days_in_month = i != 0 ? lut[i - 1].days_in_month : 31;
values.time_at_offset_change_value = 0;
values.amount_of_offset_change_value = 0;
if (offset_is_whole_number_of_hours_during_epoch && start_of_day > 0 && start_of_day % 3600)
offset_is_whole_number_of_hours_during_epoch = false;
if (offset_is_whole_number_of_minutes_during_epoch && start_of_day > 0 && start_of_day % 60)
offset_is_whole_number_of_minutes_during_epoch = false;
/// If UTC offset was changed this day.
/// Change in time zone without transition is possible, e.g. Moscow 1991 Sun, 31 Mar, 02:00 MSK to EEST
cctz::time_zone::civil_transition transition{};
if (cctz_time_zone.next_transition(start_of_day_time_point - std::chrono::seconds(1), &transition)
&& (cctz::civil_day(transition.from) == date || cctz::civil_day(transition.to) == date)
&& transition.from != transition.to)
{
values.time_at_offset_change_value = (transition.from - cctz::civil_second(date)) / Values::OffsetChangeFactor;
values.amount_of_offset_change_value = (transition.to - transition.from) / Values::OffsetChangeFactor;
// std::cerr << time_zone << ", " << date << ": change from " << transition.from << " to " << transition.to << "\n";
// std::cerr << time_zone << ", " << date << ": change at " << values.time_at_offset_change() << " with " << values.amount_of_offset_change() << "\n";
/// We don't support too large changes.
if (values.amount_of_offset_change_value > 24 * 4)
values.amount_of_offset_change_value = 24 * 4;
else if (values.amount_of_offset_change_value < -24 * 4)
values.amount_of_offset_change_value = -24 * 4;
/// We don't support cases when time change results in switching to previous day.
/// Shift the point of time change later.
if (values.time_at_offset_change_value + values.amount_of_offset_change_value < 0)
values.time_at_offset_change_value = -values.amount_of_offset_change_value;
}
/// Going to next day.
++date;
++i;
}
while (i < DATE_LUT_SIZE && lut[i - 1].year <= DATE_LUT_MAX_YEAR);
/// Fill excessive part of lookup table. This is needed only to simplify handling of overflow cases.
while (i < DATE_LUT_SIZE)
{
lut[i] = lut[i - 1];
++i;
}
/// Fill lookup table for years and months.
size_t year_months_lut_index = 0;
size_t first_day_of_last_month = 0;
for (size_t day = 0; day < DATE_LUT_SIZE; ++day)
{
const Values & values = lut[day];
if (values.day_of_month == 1)
{
if (values.month == 1)
years_lut[values.year - DATE_LUT_MIN_YEAR] = day;
year_months_lut_index = (values.year - DATE_LUT_MIN_YEAR) * 12 + values.month - 1;
years_months_lut[year_months_lut_index] = day;
first_day_of_last_month = day;
}
}
/// Fill the rest of lookup table with the same last month (2106-02-01).
for (; year_months_lut_index < DATE_LUT_YEARS * 12; ++year_months_lut_index)
{
years_months_lut[year_months_lut_index] = first_day_of_last_month;
}
}
#if !defined(ARCADIA_BUILD) /// Arcadia's variant of CCTZ already has the same implementation.
/// Prefer to load timezones from blobs linked to the binary.
/// The blobs are provided by "tzdata" library.
/// This allows to avoid dependency on system tzdata.
namespace cctz_extension
{
namespace
{
class Source : public cctz::ZoneInfoSource
{
public:
Source(const char * data_, size_t size_) : data(data_), size(size_) {}
size_t Read(void * buf, size_t bytes) override
{
if (bytes > size)
bytes = size;
memcpy(buf, data, bytes);
data += bytes;
size -= bytes;
return bytes;
}
int Skip(size_t offset) override
{
if (offset <= size)
{
data += offset;
size -= offset;
return 0;
}
else
{
errno = EINVAL;
return -1;
}
}
private:
const char * data;
size_t size;
};
std::unique_ptr<cctz::ZoneInfoSource> custom_factory(
const std::string & name,
const std::function<std::unique_ptr<cctz::ZoneInfoSource>(const std::string & name)> & fallback)
{
std::string_view resource = getResource(name);
if (!resource.empty())
return std::make_unique<Source>(resource.data(), resource.size());
return fallback(name);
}
}
ZoneInfoSourceFactory zone_info_source_factory = custom_factory;
}
#endif