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//! Epoch reference times in terms of their difference from
//! UTC 1970-01-01 in seconds.
const std = @import("../std.zig");
const testing = std.testing;
const math = std.math;
/// Jan 01, 1970 AD
pub const posix = 0;
/// Jan 01, 1980 AD
pub const dos = 315532800;
/// Jan 01, 2001 AD
pub const ios = 978307200;
/// Nov 17, 1858 AD
pub const openvms = -3506716800;
/// Jan 01, 1900 AD
pub const zos = -2208988800;
/// Jan 01, 1601 AD
pub const windows = -11644473600;
/// Jan 01, 1978 AD
pub const amiga = 252460800;
/// Dec 31, 1967 AD
pub const pickos = -63244800;
/// Jan 06, 1980 AD
pub const gps = 315964800;
/// Jan 01, 0001 AD
pub const clr = -62135769600;
pub const unix = posix;
pub const android = posix;
pub const os2 = dos;
pub const bios = dos;
pub const vfat = dos;
pub const ntfs = windows;
pub const ntp = zos;
pub const jbase = pickos;
pub const aros = amiga;
pub const morphos = amiga;
pub const brew = gps;
pub const atsc = gps;
pub const go = clr;
/// The type that holds the current year, i.e. 2016
pub const Year = u16;
pub const epoch_year = 1970;
pub const secs_per_day: u17 = 24 * 60 * 60;
pub fn isLeapYear(year: Year) bool {
if (@mod(year, 4) != 0)
return false;
if (@mod(year, 100) != 0)
return true;
return (0 == @mod(year, 400));
}
test isLeapYear {
try testing.expectEqual(false, isLeapYear(2095));
try testing.expectEqual(true, isLeapYear(2096));
try testing.expectEqual(false, isLeapYear(2100));
try testing.expectEqual(true, isLeapYear(2400));
}
pub fn getDaysInYear(year: Year) u9 {
return if (isLeapYear(year)) 366 else 365;
}
pub const Month = enum(u4) {
jan = 1,
feb,
mar,
apr,
may,
jun,
jul,
aug,
sep,
oct,
nov,
dec,
/// return the numeric calendar value for the given month
/// i.e. jan=1, feb=2, etc
pub fn numeric(self: Month) u4 {
return @intFromEnum(self);
}
};
/// Get the number of days in the given month and year
pub fn getDaysInMonth(year: Year, month: Month) u5 {
return switch (month) {
.jan => 31,
.feb => @as(u5, switch (isLeapYear(year)) {
true => 29,
false => 28,
}),
.mar => 31,
.apr => 30,
.may => 31,
.jun => 30,
.jul => 31,
.aug => 31,
.sep => 30,
.oct => 31,
.nov => 30,
.dec => 31,
};
}
pub const YearAndDay = struct {
year: Year,
/// The number of days into the year (0 to 365)
day: u9,
pub fn calculateMonthDay(self: YearAndDay) MonthAndDay {
var month: Month = .jan;
var days_left = self.day;
while (true) {
const days_in_month = getDaysInMonth(self.year, month);
if (days_left < days_in_month)
break;
days_left -= days_in_month;
month = @as(Month, @enumFromInt(@intFromEnum(month) + 1));
}
return .{ .month = month, .day_index = @as(u5, @intCast(days_left)) };
}
};
pub const MonthAndDay = struct {
month: Month,
day_index: u5, // days into the month (0 to 30)
};
/// days since epoch Jan 1, 1970
pub const EpochDay = struct {
day: u47, // u47 = u64 - u17 (because day = sec(u64) / secs_per_day(u17)
pub fn calculateYearDay(self: EpochDay) YearAndDay {
var year_day = self.day;
var year: Year = epoch_year;
while (true) {
const year_size = getDaysInYear(year);
if (year_day < year_size)
break;
year_day -= year_size;
year += 1;
}
return .{ .year = year, .day = @as(u9, @intCast(year_day)) };
}
};
/// seconds since start of day
pub const DaySeconds = struct {
secs: u17, // max is 24*60*60 = 86400
/// the number of hours past the start of the day (0 to 23)
pub fn getHoursIntoDay(self: DaySeconds) u5 {
return @as(u5, @intCast(@divTrunc(self.secs, 3600)));
}
/// the number of minutes past the hour (0 to 59)
pub fn getMinutesIntoHour(self: DaySeconds) u6 {
return @as(u6, @intCast(@divTrunc(@mod(self.secs, 3600), 60)));
}
/// the number of seconds past the start of the minute (0 to 59)
pub fn getSecondsIntoMinute(self: DaySeconds) u6 {
return math.comptimeMod(self.secs, 60);
}
};
/// seconds since epoch Jan 1, 1970 at 12:00 AM
pub const EpochSeconds = struct {
secs: u64,
/// Returns the number of days since the epoch as an EpochDay.
/// Use EpochDay to get information about the day of this time.
pub fn getEpochDay(self: EpochSeconds) EpochDay {
return EpochDay{ .day = @as(u47, @intCast(@divTrunc(self.secs, secs_per_day))) };
}
/// Returns the number of seconds into the day as DaySeconds.
/// Use DaySeconds to get information about the time.
pub fn getDaySeconds(self: EpochSeconds) DaySeconds {
return DaySeconds{ .secs = math.comptimeMod(self.secs, secs_per_day) };
}
};
fn testEpoch(secs: u64, expected_year_day: YearAndDay, expected_month_day: MonthAndDay, expected_day_seconds: struct {
/// 0 to 23
hours_into_day: u5,
/// 0 to 59
minutes_into_hour: u6,
/// 0 to 59
seconds_into_minute: u6,
}) !void {
const epoch_seconds = EpochSeconds{ .secs = secs };
const epoch_day = epoch_seconds.getEpochDay();
const day_seconds = epoch_seconds.getDaySeconds();
const year_day = epoch_day.calculateYearDay();
try testing.expectEqual(expected_year_day, year_day);
try testing.expectEqual(expected_month_day, year_day.calculateMonthDay());
try testing.expectEqual(expected_day_seconds.hours_into_day, day_seconds.getHoursIntoDay());
try testing.expectEqual(expected_day_seconds.minutes_into_hour, day_seconds.getMinutesIntoHour());
try testing.expectEqual(expected_day_seconds.seconds_into_minute, day_seconds.getSecondsIntoMinute());
}
test "epoch decoding" {
try testEpoch(0, .{ .year = 1970, .day = 0 }, .{
.month = .jan,
.day_index = 0,
}, .{ .hours_into_day = 0, .minutes_into_hour = 0, .seconds_into_minute = 0 });
try testEpoch(31535999, .{ .year = 1970, .day = 364 }, .{
.month = .dec,
.day_index = 30,
}, .{ .hours_into_day = 23, .minutes_into_hour = 59, .seconds_into_minute = 59 });
try testEpoch(1622924906, .{ .year = 2021, .day = 31 + 28 + 31 + 30 + 31 + 4 }, .{
.month = .jun,
.day_index = 4,
}, .{ .hours_into_day = 20, .minutes_into_hour = 28, .seconds_into_minute = 26 });
try testEpoch(1625159473, .{ .year = 2021, .day = 31 + 28 + 31 + 30 + 31 + 30 }, .{
.month = .jul,
.day_index = 0,
}, .{ .hours_into_day = 17, .minutes_into_hour = 11, .seconds_into_minute = 13 });
}
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