ref: cebd9262172a94782ffadd1ebc2bf66dfee971e1
dir: /lib/date/date.myr/
use std
use "types"
use "zoneinfo"
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 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 = {
-> mkinstantoff(std.now(), "", 0)
}
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
var tm
tm = recalc(&[.year=year, .mon=mon, .day=day,
.h=h, .m=m, .s=s,])
match _zoneinfo.findtzoff(tz, tm)
| `std.Some off:
-> mkinstantoff(tm, tz, off)
| `std.None:
std.fatal("invalid timezone {}\n", tz)
;;
}
const mkinstant = {tm, tz
match _zoneinfo.findtzoff(tz, tm)
| `std.Some o: -> mkinstantoff(tm, tz, o)
| `std.None: std.fatal("no zone named {}\n", tz)
;;
}
const mkinstantoff = {tm, tz, tzoff
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")
std.slcp(inst._tzbuf[:tz.len], tz)
inst.tzname = inst._tzbuf[:tz.len]
inst.tzoff = tzoff
tm += (inst.tzoff : 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 : int)
t /= 1_000_000
inst.s = (t % 60 : int)
t /= 60
inst.m = (t % 60 : int)
t /= 60
inst.h = (t : int)
/* weekday */
inst.wday = ((e + 4) % 7 : 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 : int)
inst.mon = (m : int)
inst.day = (d : 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
-> mkinstantoff(d.actual + (dt : std.time), d.tzname, d.tzoff)
}
const sub = {d, dt
-> mkinstantoff(d.actual - (dt : std.time), d.tzname, d.tzoff)
}
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
;;
-> mkinstantoff(recalc(&inst), inst.tzname, inst.tzoff)
}
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
;;
-> mkinstantoff(recalc(&inst), inst.tzname, inst.tzoff)
}
const duration = {a, b
-> (b.actual - a.actual : duration)
}
const recalc = {inst
var c, ya, j, tm
var y, m, d
if inst.mon > 2
m = (inst.mon - 3 : std.time)
y = (inst.year : std.time)
else
m = (inst.mon + 9 : std.time)
y = (inst.year - 1 : std.time)
;;
d = (inst.day : 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 : std.time) * 3600*1_000_000
tm += (inst.m : std.time) * 60*1_000_000
tm += (inst.s : std.time) * 1_000_000
tm += (inst.us : std.time)
-> tm
}