sysl.time.tzif

Index

abbrev_at is_dst_at offset_at parse TzifError Zone Display for TzifError

Functions

abbrev_at

abbrev_at(z: Zone, t: Instant) -> Result[string, TzifError]

The abbreviation the zone used at that instant – EST, EDT, +0545.

It is here because the file already carries it, and it is the one thing a host’s tm_gmtoff route cannot answer without a second call. It is a display string and nothing else: CST names three different offsets around the world, so a timestamp that has to be read back carries the number instead, which is what timestamp_text writes.

is_dst_at

is_dst_at(z: Zone, t: Instant) -> Result[bool, TzifError]

Whether daylight saving was in force at that instant, as the file records it.

offset_at

offset_at(z: Zone, t: Instant) -> Result[Offset, TzifError]

How far this zone’s clocks were set from UTC at that instant.

This is the shape sysl.time.resolve takes, which is the whole point of it: a zone read from a file, a zone talking to a chip and a zone written out by hand are one thing to everything above.

parse

parse(data: []const u8) -> Result[Zone, TzifError]

Reads a zone out of the bytes of a TZif file.

The Zone borrows data – see the note above about what that costs.

A version 2 or later file carries its table twice: once with 4-byte transition times for a reader that predates the format’s second version, and then again with 8-byte ones. The first is stepped over rather than read, which is why the length of it has to be worked out even though nothing in it is wanted.

Types

TzifError

enum TzifError
    BadMagic
    BadVersion(saw: u8)
    Truncated(needed: usize)
    NoTypes

Why a decode refused, at the granularity a caller can act on.

The shape is sysl.encoding.DecodeError‘s and for its reason: the variants are separated by what a caller would do about each. BadMagic is a file that is not one of these at all – the usual cause being a path that named something else. Truncated carries the length that would have been enough, so a caller reading in pieces knows how much more to get rather than doubling until it fits.

Zone

struct Zone
    data: []const u8
    trans_at: usize
    types_at: usize
    ttinfo_at: usize
    desig_at: usize
    timecnt: usize
    typecnt: usize
    wide: bool

A zone, as a view of the bytes it was decoded from.

Implementations

Display for TzifError

impl Display for TzifError