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2d03d330bc
The Year 1925 is a starting point because most of the timezones switched to saner (mostly 15-minutes based) offsets somewhere during 1924 or before. And that significantly simplifies implementation. 2238 is to simplify arithmetics for sanitizing LUT index access; there are less than 0x1ffff days from 1925. * Extended DateLUTImpl internal LUT to 0x1ffff items, some of which represent negative (pre-1970) time values. As a collateral benefit, Date now correctly supports dates up to 2149 (instead of 2106). * Added a new strong typedef ExtendedDayNum, which represents dates pre-1970 and post 2149. * Functions that used to return DayNum now return ExtendedDayNum. * Refactored DateLUTImpl to untie DayNum from the dual role of being a value and an index (due to negative time). Index is now a different type LUTIndex with explicit conversion functions from DatNum, time_t, and ExtendedDayNum. * Updated DateLUTImpl to properly support values close to epoch start (1970-01-01 00:00), including negative ones. * Reduced resolution of DateLUTImpl::Values::time_at_offset_change to multiple of 15-minutes to allow storing 64-bits of time_t in DateLUTImpl::Value while keeping same size. * Minor performance updates to DateLUTImpl when building month LUT by skipping non-start-of-month days. * Fixed extractTimeZoneFromFunctionArguments to work correctly with DateTime64. * New unit-tests and stateless integration tests for both DateTime and DateTime64.
58 lines
1.6 KiB
C++
58 lines
1.6 KiB
C++
#pragma once
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#include "DateLUTImpl.h"
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#include "defines.h"
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#include <boost/noncopyable.hpp>
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#include <atomic>
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#include <memory>
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#include <mutex>
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#include <unordered_map>
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/// This class provides lazy initialization and lookup of singleton DateLUTImpl objects for a given timezone.
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class DateLUT : private boost::noncopyable
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{
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public:
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/// Return singleton DateLUTImpl instance for the default time zone.
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static ALWAYS_INLINE const DateLUTImpl & instance()
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{
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const auto & date_lut = getInstance();
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return *date_lut.default_impl.load(std::memory_order_acquire);
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}
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/// Return singleton DateLUTImpl instance for a given time zone.
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static ALWAYS_INLINE const DateLUTImpl & instance(const std::string & time_zone)
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{
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const auto & date_lut = getInstance();
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if (time_zone.empty())
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return *date_lut.default_impl.load(std::memory_order_acquire);
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return date_lut.getImplementation(time_zone);
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}
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static void setDefaultTimezone(const std::string & time_zone)
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{
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auto & date_lut = getInstance();
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const auto & impl = date_lut.getImplementation(time_zone);
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date_lut.default_impl.store(&impl, std::memory_order_release);
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}
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protected:
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DateLUT();
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private:
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static DateLUT & getInstance();
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const DateLUTImpl & getImplementation(const std::string & time_zone) const;
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using DateLUTImplPtr = std::unique_ptr<DateLUTImpl>;
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/// Time zone name -> implementation.
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mutable std::unordered_map<std::string, DateLUTImplPtr> impls;
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mutable std::mutex mutex;
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std::atomic<const DateLUTImpl *> default_impl;
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};
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