jiff Integration

Enable with features = ["jiff"]. Bundles the IANA timezone database (tzdb-bundle-always) — no system tzdata required. Coexists with the time feature.

🔗Type mapping

All scalar types support Option<T>, Vec<T>, and Vec<Option<T>> variants.

🔗Timezone policy

• Zoned → R: writes the IANA name from time_zone().iana_name() into the tzone attribute. Fixed-offset zones without an IANA name fall back to "UTC".
• R → Zoned: unknown tzone → SexpError::InvalidValue. No silent UTC fallback — unlike the time feature, jiff can represent real IANA zones, so losing them is an error.
• Empty or missing tzone: treated as UTC.
• Vec<Zoned> → R: a single tzone attribute applies to the whole vector; the first element’s timezone is used. Mixed-timezone vectors log a warning (requires log feature).

🔗Fractional seconds

Floor-based split into whole seconds + nanoseconds, matching time_impl.rs. Correct for negative timestamps: -1.2s → -2s + 800_000_000ns.

🔗Adapter traits

For types with no base-R scalar analog, wrap in #[derive(ExternalPtr)] and implement the relevant trait:

• RSpan — component getters (years/months/weeks/days/hours/minutes/seconds/ms/µs/ns), is_zero, is_negative, negate, abs
• RDateTime — year/month/day/hour/minute/second, to_date, to_time, in_tz
• RTime — hour/minute/second/subsec_nanosecond, on
• RTimestamp — as_second, as_millisecond, subsec_nanosecond, to_zoned_in, strftime
• RZoned — year/month/day/hour/minute/second, iana_name, in_tz, start_of_day, strftime
• RDate — year/month/day/weekday/day_of_year, first_of_month, last_of_month, tomorrow, yesterday, strftime
• RSignedDuration — as_seconds_f64, as_milliseconds, whole_seconds/minutes/hours/days, subsec_nanoseconds, is_negative, is_zero, abs

🔗ALTREP

JiffTimestampVec — lazy REALSXP backed by Arc<Vec<Timestamp>>. Elements are projected to seconds-since-epoch on access; no upfront conversion. Apply POSIXct class after construction.

JiffZonedVec — lazy REALSXP backed by Arc<Vec<Zoned>>, single-timezone strict. Constructor (JiffZonedVec::new) validates that all elements share the same IANA timezone name; returns Err if any element differs. On success, into_sexp() produces a POSIXct ALTREP with class = c("POSIXct", "POSIXt") and tzone = <iana>. TryFromSexp reconstructs each element using the SEXP’s tzone attribute.

🔗vctrs rcrd constructors

Requires features = ["jiff", "vctrs"]. Public helpers in jiff_impl::vctrs_support:

• span_vec_to_rcrd(&[Span]) -> SEXP — fields: years/months/weeks/days/hours/minutes/seconds/ms/µs/ns (all INTSXP)
• zoned_vec_to_rcrd(&[Zoned]) -> SEXP — fields: timestamp (REALSXP, seconds-since-epoch), tz (STRSXP)
• datetime_vec_to_rcrd(&[DateTime]) -> SEXP — fields: year/month/day/hour/minute/second/subsec_nanosecond
• time_vec_to_rcrd(&[Time]) -> SEXP — fields: hour/minute/second/subsec_nanosecond

All constructors return vctrs rcrd SEXPs with class c("<type>", "vctrs_rcrd", "vctrs_vctr").

🔗Follow-ups

• #305 — expand adapter-trait test coverage (formatting/arithmetic methods, ALTREP laziness counter)