time.bend source
time.bend on the hub · documented module
# Clocks, Duration and Instant, Gregorian dates, RFC 3339 and HTTP-date text, and TZif time zones. Source: https://github.com/paymog/bend-kit/tree/main/timeimport Baseimport bend-kit-int@0.2.0.0/int.bend as Intimport bend-kit-fmt@0.1.0.0/fmt.bend as Fmt# bend-kit-bytes@0.3.0.0import 0x49814d83de8f70993a43e1002be29ecd/bytes.bend as Bytes# secs + nanos / 10^9 seconds, with nanos below 10^9: -0.5 s is Duration{-1, 500000000}.type Duration is Data: Duration{secs: Int.I64, nanos: U32}# A Duration since 1970-01-01T00:00:00Z. Days are 86400 s: there are no leap seconds.type Instant is Data: Instant{secs: Int.I64, nanos: U32}# A proleptic Gregorian date. The conversions and formats cover years 0 to 9999.type Date is Data: Date{year: U32, month: U32, day: U32}type DateTime is Data: DateTime{date: Date, hour: U32, min: U32, sec: U32, nanos: U32}def i64(x: U32) -> Int.I64: Int.I64.from_u32(x)# The signed 32-bit value of x, widened.def i64s(x: U32) -> Int.I64: match x: case U32{w}: Int.I64{Int.Int.sext(64n, 32n, w)}# hi * 2^32 + lo, as the bits of an I64.def i64.of(hi: U32, lo: U32) -> Int.I64: Int.I64.or(Int.I64.shl(i64(hi), 32n), i64(lo))# Duration# --------def Duration.zero() -> Duration: Duration{i64(0), 0}def Duration.of_secs(s: Int.I64) -> Duration: Duration{s, 0}def Duration.of_ms(+ms: U32) -> Duration: Duration{i64((ms / 1000 : U32)), ((ms % 1000 : U32) * 1000000 : U32)}# Whole milliseconds, rounded down.def Duration.to_ms(d: Duration) -> Int.I64: match d: case Duration{s, n}: Int.I64.add(Int.I64.mul(s, i64(1000)), i64((n / 1000000 : U32)))def Duration.carry(c: Bool, s: Int.I64, +n: U32) -> Duration: match c: case True{}: Duration{Int.I64.add(s, i64(1)), (n - 1000000000 : U32)} case False{}: Duration{s, n}def Duration.add(a: Duration, b: Duration) -> Duration: match a b: case Duration{sa, na} Duration{sb, nb}: +n = (na + nb : U32) Duration.carry(U32.is_ge(n, 1000000000), Int.I64.add(sa, sb), n)# n is na - nb, wrapped when na < nb.def Duration.borrow(c: Bool, s: Int.I64, +n: U32) -> Duration: match c: case True{}: Duration{Int.I64.sub(s, i64(1)), (n + 1000000000 : U32)} case False{}: Duration{s, n}def Duration.sub(a: Duration, b: Duration) -> Duration: match a b: case Duration{sa, +na} Duration{sb, +nb}: Duration.borrow(U32.is_lt(na, nb), Int.I64.sub(sa, sb), (na - nb : U32))def Duration.neg(d: Duration) -> Duration: Duration.sub(Duration.zero(), d)def Duration.cmp.then(c: Cmp, +na: U32, +nb: U32) -> Cmp: match c: case EQ{}: U32.cmp(na, nb) case LT{}: LT{} case GT{}: GT{}def Duration.cmp(a: Duration, b: Duration) -> Cmp: match a b: case Duration{sa, na} Duration{sb, nb}: Duration.cmp.then(Int.I64.cmp(sa, sb), na, nb)# Instant# -------def Instant.epoch() -> Instant: Instant{i64(0), 0}def Instant.of_unix(s: Int.I64) -> Instant: Instant{s, 0}def Instant.of(d: Duration) -> Instant: match d: case Duration{s, n}: Instant{s, n}def Instant.since_epoch(i: Instant) -> Duration: match i: case Instant{s, n}: Duration{s, n}def Instant.add(i: Instant, d: Duration) -> Instant: Instant.of(Duration.add(Instant.since_epoch(i), d))# a - b.def Instant.since(a: Instant, b: Instant) -> Duration: Duration.sub(Instant.since_epoch(a), Instant.since_epoch(b))def Instant.cmp(a: Instant, b: Instant) -> Cmp: Duration.cmp(Instant.since_epoch(a), Instant.since_epoch(b))# Clocks# ------# (secs hi, secs lo, nanos) of CLOCK_MONOTONIC, from an unspecified start.def mono.raw() -> IO(U32 & U32 & U32): import "./effs/time.c" import "./effs/time.js"# (secs hi, secs lo, nanos) of CLOCK_REALTIME, since the Unix epoch.def wall.raw() -> IO(U32 & U32 & U32): import "./effs/time.c" import "./effs/time.js"def raw.dur(r: U32 & U32 & U32) -> Duration: (hi, lo, n) = r Duration{i64.of(hi, lo), n}# Time since an unspecified start that never goes back. Use it to measure spans.def mono() -> IO(Duration): do IO<Duration>: r : U32 & U32 & U32 <- mono.raw() return raw.dur(r)# The wall clock. It can jump when the system time is set.def now() -> IO(Instant): do IO<Instant>: r : U32 & U32 & U32 <- wall.raw() return Instant.of(raw.dur(r))# Dates# -----def Date.is_leap(+y: U32) -> Bool: Bool.and(U32.is_eq((y % 4 : U32), 0), Bool.or(U32.is_ne((y % 100 : U32), 0), U32.is_eq((y % 400 : U32), 0)))# 0 for a month outside 1 to 12.def Date.days_in_month(+y: U32, +m: U32) -> U32: Bool.pick(U32, U32.is_eq(m, 2), Bool.pick(U32, Date.is_leap(y), 29, 28), Bool.pick(U32, Bool.and(U32.is_ge(m, 1), U32.is_le(m, 12)), (30 + ((m + (m >> 3n)) .&. 1) : U32), 0))def Date.valid(d: Date) -> Bool: match d: case Date{+y, +m, +dd}: Bool.and(U32.is_le(y, 9999), Bool.and(U32.is_ge(dd, 1), U32.is_le(dd, Date.days_in_month(y, m))))# z counts days from -0400-03-01, so every date from year 0 has z > 0 in a U32.# The civil-days algorithm is Howard Hinnant's, with the year starting in March.def Z.EPOCH() -> U32: 865565def Date.to_z.at(+y: U32, +mp: U32, +d: U32) -> U32: +era = (y / 400 : U32) +yoe = (y - era * 400 : U32) +doy = ((153 * mp + 2) / 5 + d - 1 : U32) (era * 146097 + yoe * 365 + yoe / 4 - yoe / 100 + doy : U32)def Date.to_z.go(jf: Bool, +y: U32, +m: U32, +d: U32) -> U32: match jf: case True{}: Date.to_z.at((y + 399 : U32), (m + 9 : U32), d) case False{}: Date.to_z.at((y + 400 : U32), (m - 3 : U32), d)def Date.to_z(d: Date) -> U32: match d: case Date{+y, +m, +dd}: Date.to_z.go(U32.is_le(m, 2), y, m, dd)def Date.of_z.fin(lo: Bool, +y: U32, +mp: U32, +d: U32) -> Date: match lo: case True{}: Date{(y - 400 : U32), (mp + 3 : U32), d} case False{}: Date{(y - 399 : U32), (mp - 9 : U32), d}def Date.of_z(+z: U32) -> Date: +era = (z / 146097 : U32) +doe = (z - era * 146097 : U32) +yoe = ((doe - doe / 1460 + doe / 36524 - doe / 146096) / 365 : U32) +doy = (doe - (365 * yoe + yoe / 4 - yoe / 100) : U32) +mp = ((5 * doy + 2) / 153 : U32) Date.of_z.fin(U32.is_lt(mp, 10), (yoe + era * 400 : U32), mp, (doy - (153 * mp + 2) / 5 + 1 : U32))# Days since 1970-01-01.def Date.to_days(d: Date) -> Int.I64: Int.I64.sub(i64(Date.to_z(d)), i64(Z.EPOCH()))def Date.of_z.if(ok: Bool, +z: U32) -> Maybe<&2, Date>: match ok: case True{}: Some{Date.of_z(z)} case False{}: None{}# The date days after 1970-01-01, or None outside 0000-01-01 to 9999-12-31.def Date.of_days(days: Int.I64) -> Maybe<&2, Date>: +z = Int.I64.add(days, i64(Z.EPOCH())) Date.of_z.if(Bool.and(Int.I64.is_ge(z, i64(146037)), Int.I64.is_le(z, i64(3798461))), Int.I64.to_u32(z))# 1 for Monday to 7 for Sunday, as in ISO 8601.def Date.weekday(d: Date) -> U32: ((Date.to_z(d) + 2) % 7 + 1 : U32)# Date and time# -------------def DateTime.valid(t: DateTime) -> Bool: match t: case DateTime{d, h, mi, s, n}: Bool.and(Date.valid(d), Bool.and(U32.is_le(h, 23), Bool.and(U32.is_le(mi, 59), Bool.and(U32.is_le(s, 59), U32.is_lt(n, 1000000000)))))# The instant of a UTC date and time. It does not check t; see DateTime.valid.def DateTime.to_instant(t: DateTime) -> Instant: match t: case DateTime{d, h, mi, s, n}: Instant{Int.I64.add(Int.I64.mul(Date.to_days(d), i64(86400)), i64((h * 3600 + mi * 60 + s : U32))), n}def DateTime.at(m: Maybe<&2, Date>, +sod: U32, n: U32) -> Maybe<&2, DateTime>: match m: case None{}: None{} case Some{d}: Some{DateTime{d, (sod / 3600 : U32), (sod / 60 % 60 : U32), (sod % 60 : U32), n}}# r is secs % 86400, which has the sign of secs.def DateTime.floor(neg: Bool, q: Int.I64, r: Int.I64, n: U32) -> Maybe<&2, DateTime>: match neg: case True{}: DateTime.at(Date.of_days(Int.I64.sub(q, i64(1))), (Int.I64.to_u32(r) + 86400 : U32), n) case False{}: DateTime.at(Date.of_days(q), Int.I64.to_u32(r), n)# The UTC date and time of i, or None outside years 0 to 9999.def DateTime.of_instant(i: Instant) -> Maybe<&2, DateTime>: match i: case Instant{+s, n}: +r = Int.I64.mod(s, i64(86400)) DateTime.floor(Int.I64.is_neg(r), Int.I64.div(s, i64(86400)), r, n)# Text# ----def pad(+x: U32, w: Nat) -> String: Fmt.Fmt.pad_left(U32.show(x), w, '0')# Milliseconds with six decimal places.def Duration.show_ms.pos(d: Duration) -> String: match d: case Duration{s, +n}: Int.I64.show(Duration.to_ms(Duration{s, n})) ++ "." ++ pad((n % 1000000 : U32), 6n)def Duration.show_ms.sign(neg: Bool, d: Duration) -> String: match neg: case True{}: "-" ++ Duration.show_ms.pos(Duration.neg(d)) case False{}: Duration.show_ms.pos(d)def Duration.show_ms(d: Duration) -> String: match d: case Duration{+s, n}: Duration.show_ms.sign(Int.I64.is_neg(s), Duration{s, n})# The digits of n / 10^(9 - w), with trailing zeros cut. n is not 0.def frac.go(f: Nat, z: Bool, +n: U32, +w: Nat) -> String: match f: case 0n: pad(n, w) case 1n+g: match z: case True{}: +m = (n / 10 : U32) frac.go(g, U32.is_eq((m % 10 : U32), 0), m, (w - 1n : Nat)) case False{}: pad(n, w)def frac(+n: U32) -> String: Bool.pick(String, U32.is_eq(n, 0), "", SCon{'.', frac.go(8n, U32.is_eq((n % 10 : U32), 0), n, 9n)})def DateTime.rfc3339(t: DateTime) -> String: match t: case DateTime{Date{y, mo, d}, h, mi, s, n}: String.concat([pad(y, 4n), "-", pad(mo, 2n), "-", pad(d, 2n), "T", pad(h, 2n), ":", pad(mi, 2n), ":", pad(s, 2n), frac(n), "Z"])def fmt.map(~f: DateTime -> String, m: Maybe<&2, DateTime>) -> Maybe<&2, String>: match m: case None{}: None{} case Some{t}: Some{f(t)}# RFC 3339 in UTC, such as 1985-04-12T23:20:50.52Z. The fraction has no trailing zeros, and is left out when 0.def rfc3339(i: Instant) -> Maybe<&2, String>: fmt.map(~DateTime.rfc3339, DateTime.of_instant(i))def WEEKDAYS() -> List<&2, String>: ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]def MONTHS() -> List<&2, String>: ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]def name(xs: List<&2, String>, +i: U32) -> String: Maybe.default(&2, String, List.get(&2, String, xs, U32.to_nat(i)), "")def DateTime.http_date(t: DateTime) -> String: match t: case DateTime{+date, h, mi, s, n}: Date{y, mo, d} = date String.concat([name(WEEKDAYS(), (Date.weekday(date) - 1 : U32)), ", ", pad(d, 2n), " ", name(MONTHS(), (mo - 1 : U32)), " ", pad(y, 4n), " ", pad(h, 2n), ":", pad(mi, 2n), ":", pad(s, 2n), " GMT"])# IMF-fixdate (RFC 9110 §5.6.7), such as Sun, 06 Nov 1994 08:49:37 GMT. It drops the fraction of a second.def http_date(i: Instant) -> Maybe<&2, String>: fmt.map(~DateTime.http_date, DateTime.of_instant(i))# Parsers# -------# A parser state: the numbers read so far, newest first, and the text left.type P is Data: P{vals: List<&2, U32>, rest: String}def is_digit(+c: U32) -> Bool: Bool.and(U32.is_ge(c, 48), U32.is_le(c, 57))def digits.go(n: Nat, s: String, +acc: U32, ok: Bool) -> Maybe<&1, U32 & String>: match n: case 0n: match ok: case True{}: Some{(acc, s)} case False{}: None{} case 1n+k: match s: case SNil{}: None{} case SCon{Chr{+c}, t}: digits.go(k, t, (acc * 10 + c - 48 : U32), Bool.and(ok, is_digit(c)))def push(vs: List<&2, U32>, r: Maybe<&1, U32 & String>) -> Maybe<&2, P>: match r: case None{}: None{} case Some{(v, t)}: Some{P{Con{v, vs}, t}}# Exactly n digits.def num(n: Nat, p: P) -> Maybe<&2, P>: match p: case P{vs, s}: push(vs, digits.go(n, s, 0, True{}))def lit.if(ok: Bool, vs: List<&2, U32>, t: String) -> Maybe<&2, P>: match ok: case True{}: Some{P{vs, t}} case False{}: None{}# One char that is a or b.def lit2(+a: U32, +b: U32, p: P) -> Maybe<&2, P>: match p: case P{vs, s}: match s: case SNil{}: None{} case SCon{Chr{+c}, t}: lit.if(Bool.or(U32.is_eq(c, a), U32.is_eq(c, b)), vs, t)def lit(+c: U32, p: P) -> Maybe<&2, P>: lit2(c, c, p)def text(+w: String, p: P) -> Maybe<&2, P>: match p: case P{vs, +s}: +n = String.length(w) lit.if(String.eq(String.take(s, n), w), vs, String.drop(s, n))def at.head(+s: String) -> Bool: match s: case SNil{}: False{} case SCon{Chr{+c}, t}: is_digit(c)# Digits after the first nine are read and dropped. d says whether s starts with a digit.def secfrac.go(s: String, d: Bool, +mul: U32, +acc: U32, +k: U32) -> U32 & U32 & String: match s: case SNil{}: (k, acc, SNil{}) case SCon{Chr{+c}, +t}: match d: case True{}: secfrac.go(t, at.head(t), (mul / 10 : U32), (acc + (c - 48) * mul : U32), (k + 1 : U32)) case False{}: (k, acc, SCon{Chr{c}, t})def secfrac.fin(vs: List<&2, U32>, r: U32 & U32 & String) -> Maybe<&2, P>: (k, n, t) = r lit.if(U32.is_gt(k, 0), Con{n, vs}, t)def secfrac.if(dot: Bool, vs: List<&2, U32>, +s: String) -> Maybe<&2, P>: match dot: case True{}: +t = String.drop(s, 1n) secfrac.fin(vs, secfrac.go(t, at.head(t), 100000000, 0, 0)) case False{}: Some{P{Con{0, vs}, s}}# An optional '.' and one or more digits, as nanoseconds.def secfrac(p: P) -> Maybe<&2, P>: match p: case P{vs, +s}: secfrac.if(String.starts_with(s, "."), vs, s)def zone.num(+neg: U32, vs: List<&2, U32>, t: String) -> Maybe<&2, P>: do Maybe<&2, P>: a : P <- num(2n, P{Con{neg, vs}, t}) b : P <- lit(58, a) num(2n, b)def zone.if(z: Bool, plus: Bool, minus: Bool, vs: List<&2, U32>, t: String) -> Maybe<&2, P>: match z: case True{}: Some{P{Con{0, Con{0, Con{0, vs}}}, t}} case False{}: match plus: case True{}: zone.num(0, vs, t) case False{}: match minus: case True{}: zone.num(1, vs, t) case False{}: None{}# Z, or +hh:mm or -hh:mm, as (sign, hh, mm) with sign 1 for west of UTC.def zone(p: P) -> Maybe<&2, P>: match p: case P{vs, s}: match s: case SNil{}: None{} case SCon{Chr{+c}, t}: zone.if(Bool.or(U32.is_eq(c, 90), U32.is_eq(c, 122)), U32.is_eq(c, 43), U32.is_eq(c, 45), vs, t)def index.go(xs: List<&2, String>, +w: String, +i: U32) -> U32: match xs: case Nil{}: i case Con{x, rest}: Bool.pick(U32, String.eq(x, w), i, index.go(rest, w, (i + 1 : U32)))# One of names, as its index.def word(+names: List<&2, String>, p: P) -> Maybe<&2, P>: match p: case P{vs, +s}: +i = index.go(names, String.take(s, 3n), 0) lit.if(U32.is_lt(i, U32.from_nat(List.length(&2, String, names))), Con{i, vs}, String.drop(s, 3n))def mk.if(ok: Bool, t: DateTime) -> Maybe<&2, Instant>: match ok: case True{}: Some{DateTime.to_instant(t)} case False{}: None{}def mk(+t: DateTime) -> Maybe<&2, Instant>: mk.if(DateTime.valid(t), t)def rfc3339.shift(m: Maybe<&2, Instant>, +west: U32, +hh: U32, +mm: U32) -> Maybe<&2, Instant>: match m: case None{}: None{} case Some{i}: +off = Duration.of_secs(i64((hh * 3600 + mm * 60 : U32))) Bool.pick(Maybe<&2, Instant>, Bool.and(U32.is_le(hh, 23), U32.is_le(mm, 59)), Some{Instant.add(i, Bool.pick(Duration, U32.is_eq(west, 1), off, Duration.neg(off)))}, None{})def rfc3339.fin(p: P) -> Maybe<&2, Instant>: match p: case P{Con{mm, Con{hh, Con{west, Con{n, Con{s, Con{mi, Con{h, Con{d, Con{mo, Con{y, Nil{}}}}}}}}}}}, SNil{}}: rfc3339.shift(mk(DateTime{Date{y, mo, d}, h, mi, s, n}), west, hh, mm) case _: None{}# An RFC 3339 date-time (§5.6), such as 1985-04-12T23:20:50.52Z or 1996-12-19T16:39:57-08:00.# T and Z may be lowercase. A leap second (:60) is refused, as Instant has none.def rfc3339.parse(s: String) -> Maybe<&2, Instant>: do Maybe<&2, Instant>: a : P <- num(4n, P{Nil{}, s}) b : P <- lit(45, a) c : P <- num(2n, b) d : P <- lit(45, c) e : P <- num(2n, d) f : P <- lit2(84, 116, e) g : P <- num(2n, f) h : P <- lit(58, g) i : P <- num(2n, h) j : P <- lit(58, i) k : P <- num(2n, j) l : P <- secfrac(k) m : P <- zone(l) rfc3339.fin(m)def http_date.fin(p: P) -> Maybe<&2, Instant>: match p: case P{Con{s, Con{mi, Con{h, Con{y, Con{mo, Con{d, Con{wd, Nil{}}}}}}}}, SNil{}}: mk(DateTime{Date{y, (mo + 1 : U32), d}, h, mi, s, 0}) case _: None{}# An IMF-fixdate (RFC 9110 §5.6.7), such as Sun, 06 Nov 1994 08:49:37 GMT.# The day name must be one of the seven, but it is not checked against the date.def http_date.parse(s: String) -> Maybe<&2, Instant>: do Maybe<&2, Instant>: a : P <- word(WEEKDAYS(), P{Nil{}, s}) b : P <- text(", ", a) c : P <- num(2n, b) d : P <- lit(32, c) e : P <- word(MONTHS(), d) f : P <- lit(32, e) g : P <- num(4n, f) h : P <- lit(32, g) i : P <- num(2n, h) j : P <- lit(58, i) k : P <- num(2n, j) l : P <- lit(58, k) m : P <- num(2n, l) n : P <- text(" GMT", m) http_date.fin(n)# Time zones# ----------# A local time type: seconds east of UTC, whether it is daylight time, and its abbreviation.type Ttype is Data: Ttype{utoff: Int.I64, dst: Bool, abbr: String}# From at on, local time follows types[idx].type Trans is Data: Trans{at: Int.I64, idx: U32}# A TZif zone (RFC 8536): transitions in time order, local time types, and the footer TZ string ("" in version 1).type Zone is Data: Zone{trans: List<&2, Trans>, types: List<&2, Ttype>, tz: String}# n bytes of a byte string, big-endian.def be(n: Nat, s: String, +acc: U32) -> U32: match n: case 0n: acc case 1n+k: match s: case SNil{}: acc case SCon{Chr{c}, t}: be(k, t, ((acc << 8n) .|. c : U32))def be32(+s: String, n: Nat) -> U32: be(4n, String.drop(s, n), 0)def u8(+s: String, n: Nat) -> U32: be(1n, String.drop(s, n), 0)def tzif.size(t8: Bool) -> Nat: match t8: case True{}: 8n case False{}: 4ndef tzif.time(t8: Bool, +s: String) -> Int.I64: match t8: case True{}: i64.of(be32(s, 0n), be32(s, 4n)) case False{}: i64s(be32(s, 0n))# ts holds the transition times and ks their type indexes.def tzif.trans(n: Nat, +t8: Bool, +ts: String, +ks: String) -> List<&2, Trans>: match n: case 0n: Nil{} case 1n+k: Con{Trans{tzif.time(t8, ts), u8(ks, 0n)}, tzif.trans(k, t8, String.drop(ts, tzif.size(t8)), String.drop(ks, 1n))}# The NUL-terminated abbreviation at byte i of chars.def tzif.abbr(chars: String, +i: U32) -> String: name(String.split(String.drop(chars, U32.to_nat(i)), Chr{0}), 0)def tzif.types(n: Nat, +s: String, +chars: String) -> List<&2, Ttype>: match n: case 0n: Nil{} case 1n+k: Con{Ttype{i64s(be32(s, 0n)), U32.is_ne(u8(s, 4n), 0), tzif.abbr(chars, u8(s, 5n))}, tzif.types(k, String.drop(s, 6n), chars)}def tzif.if(ok: Bool, z: Zone) -> Maybe<&2, Zone>: match ok: case True{}: Some{z} case False{}: None{}# Header counts, in RFC 8536 order: isut, isstd, leap, time, type, char.def tzif.count(+h: String, i: Nat) -> Nat: U32.to_nat(be32(h, (20n + 4n * i : Nat)))# The data block's size in bytes, for header h.def tzif.bsize(+t8: Bool, +h: String) -> Nat: +tc = tzif.count(h, 3n) (tc * tzif.size(t8) + tc + tzif.count(h, 4n) * 6n + tzif.count(h, 5n) + tzif.count(h, 2n) * (tzif.size(t8) + 4n) + tzif.count(h, 1n) + tzif.count(h, 0n) : Nat)# h starts at a header; its data block follows it. Version 2+ blocks have 8-byte times and a footer.def tzif.block(+t8: Bool, +h: String) -> Maybe<&2, Zone>: +d = String.drop(h, 44n) +tc = tzif.count(h, 3n) +ty = tzif.count(h, 4n) +at = (tc * tzif.size(t8) + tc : Nat) +foot = String.drop(d, tzif.bsize(t8, h)) tzif.if(Bool.and(String.starts_with(h, "TZif"), Bool.and(Nat.is_gt(ty, 0n), Nat.is_le((44n + tzif.bsize(t8, h) : Nat), String.length(h)))), Zone{tzif.trans(tc, t8, d, String.drop(d, (tc * tzif.size(t8) : Nat))), tzif.types(ty, String.drop(d, at), String.take(String.drop(d, (at + ty * 6n : Nat)), tzif.count(h, 5n))), Bool.pick(String, t8, name(String.split(foot, '\n'), 1), "")})def tzif.go(v2: Bool, +s: String) -> Maybe<&2, Zone>: match v2: case True{}: tzif.block(True{}, String.drop(s, (44n + tzif.bsize(False{}, s) : Nat))) case False{}: tzif.block(False{}, s)# A TZif file, such as one from /usr/share/zoneinfo. Versions 2 and up use their 64-bit block.# ponytail: reads the bytes as a byte String; walk Bytes directly if zone files get big.def tzif.parse(b: Bytes.Bytes) -> Maybe<&2, Zone>: +s = Bytes.to_string(b) tzif.go(U32.is_ge(u8(s, 4n), 50), s)# The type index at secs: the last transition at or before it, or type 0 before the first.# ponytail: linear scan; bisect an Array if lookups get hot.def Zone.find(ts: List<&2, Trans>, +secs: Int.I64, +cur: U32) -> U32: match ts: case Nil{}: cur case Con{Trans{t, k}, rest}: Zone.find(rest, secs, Bool.pick(U32, Int.I64.is_le(t, secs), k, cur))# The local time type at i.# ponytail: past the last transition the last type holds; evaluate the footer TZ rule for slim files and years past 2037.def Zone.at(z: Zone, i: Instant) -> Maybe<&2, Ttype>: match z i: case Zone{ts, types, tz} Instant{s, n}: List.get(&2, Ttype, types, U32.to_nat(Zone.find(ts, s, 0)))def Zone.local.at(m: Maybe<&2, Ttype>, i: Instant) -> Maybe<&2, DateTime>: match m: case None{}: None{} case Some{Ttype{off, dst, abbr}}: DateTime.of_instant(Instant.add(i, Duration.of_secs(off)))# The local date and time at i in zone z.def Zone.local(z: Zone, +i: Instant) -> Maybe<&2, DateTime>: Zone.local.at(Zone.at(z, i), i)