2019-10-29 00:13:20 +04:00

127 lines
3.9 KiB
Swift

import Foundation
public struct DateTime {
public let seconds: Int32 // 0 ... 59
public let minutes: Int32 // 0 ... 59
public let hours: Int32 // 0 ... 23
public let dayOfMonth: Int32 // 1 ... 31
public let month: Int32 // 0 ... 11
public let year: Int32 // since 1900
public let dayOfWeek: Int32 // 0 ... 6
public let dayOfYear: Int32 // 0 ... 365
}
private let daysSinceJan1st: [[UInt32]] =
[
[0,31,59,90,120,151,181,212,243,273,304,334,365], // 365 days, non-leap
[0,31,60,91,121,152,182,213,244,274,305,335,366] // 366 days, leap
]
public func secondsSinceEpochToDateTime(_ secondsSinceEpoch: Int64) -> DateTime {
var sec: UInt64
let quadricentennials: UInt32
var centennials: UInt32
var quadrennials: UInt32
var annuals: UInt32
let year: UInt32
let leap: UInt32
let yday: UInt32
let hour: UInt32
let min: UInt32
var month: UInt32
var mday: UInt32
let wday: UInt32
/*
400 years:
1st hundred, starting immediately after a leap year that's a multiple of 400:
n n n l \
n n n l } 24 times
... /
n n n l /
n n n n
2nd hundred:
n n n l \
n n n l } 24 times
... /
n n n l /
n n n n
3rd hundred:
n n n l \
n n n l } 24 times
... /
n n n l /
n n n n
4th hundred:
n n n l \
n n n l } 24 times
... /
n n n l /
n n n L <- 97'th leap year every 400 years
*/
// Re-bias from 1970 to 1601:
// 1970 - 1601 = 369 = 3*100 + 17*4 + 1 years (incl. 89 leap days) =
// (3*100*(365+24/100) + 17*4*(365+1/4) + 1*365)*24*3600 seconds
sec = UInt64(secondsSinceEpoch) + (11644473600 as UInt64)
wday = (uint)((sec / 86400 + 1) % 7); // day of week
// Remove multiples of 400 years (incl. 97 leap days)
quadricentennials = UInt32((UInt64(sec) / (12622780800 as UInt64))) // 400*365.2425*24*3600
sec %= 12622780800 as UInt64
// Remove multiples of 100 years (incl. 24 leap days), can't be more than 3
// (because multiples of 4*100=400 years (incl. leap days) have been removed)
centennials = UInt32(UInt64(sec) / (3155673600 as UInt64)) // 100*(365+24/100)*24*3600
if centennials > 3 {
centennials = 3
}
sec -= UInt64(centennials) * (3155673600 as UInt64)
// Remove multiples of 4 years (incl. 1 leap day), can't be more than 24
// (because multiples of 25*4=100 years (incl. leap days) have been removed)
quadrennials = UInt32((UInt64(sec) / (126230400 as UInt64))) // 4*(365+1/4)*24*3600
if quadrennials > 24 {
quadrennials = 24
}
sec -= UInt64(quadrennials) * (126230400 as UInt64)
// Remove multiples of years (incl. 0 leap days), can't be more than 3
// (because multiples of 4 years (incl. leap days) have been removed)
annuals = UInt32(sec / (31536000 as UInt64)) // 365*24*3600
if annuals > 3 {
annuals = 3
}
sec -= UInt64(annuals) * (31536000 as UInt64)
// Calculate the year and find out if it's leap
year = 1601 + quadricentennials * 400 + centennials * 100 + quadrennials * 4 + annuals;
leap = (!(year % UInt32(4) != 0) && ((year % UInt32(100) != 0) || !(year % UInt32(400) != 0))) ? 1 : 0
// Calculate the day of the year and the time
yday = UInt32(sec / (86400 as UInt64))
sec %= 86400;
hour = UInt32(sec / 3600);
sec %= 3600;
min = UInt32(sec / 60);
sec %= 60;
mday = 1
month = 1
while month < 13 {
if (yday < daysSinceJan1st[Int(leap)][Int(month)]) {
mday += yday - daysSinceJan1st[Int(leap)][Int(month - 1)]
break
}
month += 1
}
return DateTime(seconds: Int32(sec), minutes: Int32(min), hours: Int32(hour), dayOfMonth: Int32(mday), month: Int32(month - 1), year: Int32(year - 1900), dayOfWeek: Int32(wday), dayOfYear: Int32(yday))
}