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109 lines
2.7 KiB
V
109 lines
2.7 KiB
V
// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module time
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pub fn unix(abs int) Time {
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// Split into day and time
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mut day_offset := abs / seconds_per_day
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if abs % seconds_per_day < 0 {
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// Compensate for round towards zero on integers as we want floored instead
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day_offset--
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}
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year,month,day := calculate_date_from_offset(day_offset)
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hr,min,sec := calculate_time_from_offset(abs % seconds_per_day)
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return Time{
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year: year
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month: month
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day: day
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hour: hr
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minute: min
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second: sec
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unix: abs
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}
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}
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[inline]
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fn calculate_date_from_offset(day_offset_ int) (int,int,int) {
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mut day_offset := day_offset_
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// Move offset to year 2001 as it's the start of a new 400-year cycle
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// Code below this rely on the fact that the day_offset is lined up with the 400-year cycle
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// 1970-2000 (inclusive) has 31 years (8 of which are leap years)
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mut year := 2001
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day_offset -= 31 * 365 + 8
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// Account for 400 year cycle
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year += (day_offset / days_per_400_years) * 400
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day_offset %= days_per_400_years
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// Account for 100 year cycle
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if day_offset == days_per_100_years * 4 {
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year += 300
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day_offset -= days_per_100_years * 3
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}
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else {
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year += (day_offset / days_per_100_years) * 100
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day_offset %= days_per_100_years
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}
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// Account for 4 year cycle
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if day_offset == days_per_4_years * 25 {
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year += 96
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day_offset -= days_per_4_years * 24
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}
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else {
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year += (day_offset / days_per_4_years) * 4
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day_offset %= days_per_4_years
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}
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// Account for every year
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if day_offset == 365 * 4 {
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year += 3
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day_offset -= 365 * 3
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}
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else {
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year += (day_offset / 365)
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day_offset %= 365
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}
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if day_offset < 0 {
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year--
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if is_leap_year(year) {
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day_offset += 366
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}
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else {
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day_offset += 365
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}
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}
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if is_leap_year(year) {
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if day_offset > 31 + 29 - 1 {
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// After leap day; pretend it wasn't there.
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day_offset--
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}
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else if day_offset == 31 + 29 - 1 {
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// Leap day.
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return year,2,29
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}
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}
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mut estimated_month := day_offset / 31
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for day_offset >= days_before[estimated_month + 1] {
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estimated_month++
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}
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for day_offset < days_before[estimated_month] {
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if estimated_month == 0 {
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break
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}
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estimated_month--
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}
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day_offset -= days_before[estimated_month]
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return year,estimated_month + 1,day_offset + 1
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}
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[inline]
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fn calculate_time_from_offset(second_offset_ int) (int,int,int) {
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mut second_offset := second_offset_
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if second_offset < 0 {
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second_offset += seconds_per_day
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}
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hour := second_offset / seconds_per_hour
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second_offset %= seconds_per_hour
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min := second_offset / seconds_per_minute
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second_offset %= seconds_per_minute
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return hour,min,second_offset
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}
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