ref: a51d1fcf9346ae3d9e6418f568fa6a06d4111ea8
dir: /lib/date/date.myr/
use std
use "types.use"
use "zoneinfo.use"
pkg date =
/* useful constructors */
const utcnow : (-> instant)
const now : (tz : byte[:] -> instant)
const tozone : (d : instant, zone : byte[:] -> instant)
const mkdate : (y : int, m : int, day : int, zone : byte[:] -> instant)
const mkdatetime : (year : int, mon : int, day : int, \
h : int, m : int, s : int, zone : byte[:] -> instant)
const mkinstant : (tm : std.time, zone : byte[:] -> instant)
const localoff : (tm : std.time -> duration)
const tzoff : (tzname : byte[:], tm : std.time -> duration)
const tzname : (tzoff : int -> byte[:])
const isleap : (d : instant -> bool)
/* date differences */
const add : (d : instant, dt : duration -> instant)
const sub : (d : instant, dt : duration -> instant)
const addperiod : (d : instant, dt : period -> instant)
const subperiod : (d : instant, dt : period -> instant)
const duration : (a : instant, b : instant -> duration)
pkglocal const recalc : (inst : instant# -> std.time)
;;
const Days400y = 365*400 + 4*25 - 3
const Days4y = 365*4 + 1
const DayUsec = (24*60*60*1_000_000)
const Mdays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
const utcnow = {
-> mkinstant(std.now(), "")
}
const now = {tz : byte[:]
var tm
tm = std.now()
-> mkinstant(tm, tz)
}
const tozone = {d, tz
-> mkinstant(d.actual, tz)
}
const mkdate = {y, m, d, tz
-> mkinstant(recalc(&[.year=y, .mon=m, .day=d]), tz)
}
const mkdatetime = {year, mon, day, h, m, s, tz
-> mkinstant(recalc(&[
.year=year, .mon=mon, .day=day,
.h=h, .m=m, .s=s
]), tz)
}
const mkinstant = {tm, tz
var j, y, m, d
var t, e
var inst
inst.actual = tm
/* time zones */
std.assert(tz.len <= inst._tzbuf.len, "time zone name too long\n")
match _zoneinfo.findtzoff(tz, tm)
| `std.Some o: inst.tzoff = o
| `std.None: std.fatal("no zone named {}\n", tz)
;;
std.slcp(inst._tzbuf[:tz.len], tz)
inst.tzname = inst._tzbuf[:tz.len]
tm += inst.tzoff castto(std.time)
/* break up time */
t = tm % DayUsec /* time */
e = tm / DayUsec /* epoch day */
if t < 0
t += DayUsec
e -= 1
;;
/* microseconds, seconds, minutes, hours */
inst.us = (t % 1_000_000) castto(int)
t /= 1_000_000
inst.s = (t % 60) castto(int)
t /= 60
inst.m = (t % 60) castto(int)
t /= 60
inst.h = t castto(int)
/* weekday */
inst.wday = ((e + 4) % 7) castto(int) /* the world started on Thursday */
/*
split up year, month, day.
Implemented according to "Algorithm 199, conversions between calendar
date and Julian day number", Robert G. Tantzen, Air Force Missile Development
Center, Holloman AFB, New Mex.
Lots of magic. Yer a wizard, 'arry.
*/
j = (tm + 2440588 * DayUsec) / DayUsec
j -= 1721119
y = (4 * j - 1) / Days400y
j = 4 * j - 1 - Days400y * y
d = j / 4
j = (4 * d + 3) / Days4y
d = 4 * d + 3 - Days4y * j
d = (d + 4) / 4 ;
m = (5 * d - 3) / 153
d = 5 * d - 3 - 153 * m
d = (d + 5) / 5
y = 100 * y + j
if m < 10
m += 3
else
m -= 9
y++
;;
/* there's no year 0 */
if y <= 0
y--
;;
/* and if j negative, the day and month are also negative */
if m < 0
m += 12
;;
if d < 0
d += Mdays[m - 1]
;;
inst.year = y castto(int)
inst.mon = m castto(int)
inst.day = d castto(int)
-> inst
}
const localoff = {tm
-> tzoff("local", tm)
}
const tzoff = {tz, tm
match _zoneinfo.findtzoff(tz, tm)
| `std.Some dt: -> dt
| `std.None: std.fatal("unable to load zoneinfo\n")
;;
}
const isleap = {d
-> d.year % 4 == 0 && (d.year % 100 != 0 || d.year % 400 == 0)
}
const add = {d, dt
-> mkinstant(d.actual + (dt castto(std.time)), d.tzname)
}
const sub = {d, dt
-> mkinstant(d.actual - (dt castto(std.time)), d.tzname)
}
const addperiod = {inst, p
match p
| `Year y: inst.year += y
| `Month m: inst.mon += m
| `Day d: inst.day += d
| `Hour h: inst.h += h
| `Minute m: inst.m += m
| `Second s: inst.s += s
;;
-> mkinstant(recalc(&inst), inst.tzname)
}
const subperiod = {inst, p
match p
| `Year y: inst.year -= y
| `Month m: inst.mon -= m
| `Day d: inst.day -= d
| `Hour h: inst.h -= h
| `Minute m: inst.m -= m
| `Second s: inst.s -= s
;;
-> mkinstant(recalc(&inst), inst.tzname)
}
const duration = {a, b
-> (b.actual - a.actual) castto(duration)
}
const recalc = {inst
var c, ya, j, tm
var y, m, d
if inst.mon > 2
m = (inst.mon - 3) castto(std.time)
y = inst.year castto(std.time)
else
m = (inst.mon + 9) castto(std.time)
y = (inst.year - 1) castto(std.time)
;;
d = inst.day castto(std.time)
c = y / 100
ya = y - 100 * c
j = c * Days400y / 4 + \
Days4y * ya / 4 + \
(153 * m + 2)/5 + d - \
719469
tm = j * DayUsec
tm += (inst.h castto(std.time)) * 3600*1_000_000
tm += (inst.m castto(std.time)) * 60*1_000_000
tm += (inst.s castto(std.time)) * 1_000_000
tm += (inst.us castto(std.time))
-> tm
}