time.unix-to-iso

pub fn unix_to_iso(seconds: i64) -> String

fune!(time.unix-to-iso@^1);  // then call unix_to_iso(…)

use super::funejson::Value;  ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::dates_add_days::iso_from_epoch_day;  ← from dates.add-days ^1.0.0 · built alongside by fune

/// 0001-01-01T00:00:00Z and 9999-12-31T23:59:59Z in Unix seconds.
const MIN_SECONDS: i64 = -62135596800;
const MAX_SECONDS: i64 = 253402300799;

/// Unix seconds as YYYY-MM-DDTHH:MM:SSZ. The day is floored (`div_euclid`),
/// so a negative time falls on the day before the epoch rather than rounding
/// towards it.
///
/// # Panics
/// Panics outside years 0001 to 9999.
pub fn unix_to_iso(seconds: i64) -> String {
    if !(MIN_SECONDS..=MAX_SECONDS).contains(&seconds) {
        panic!(
            "seconds must be from {} to {} (years 0001 to 9999), received {}",
            MIN_SECONDS, MAX_SECONDS, seconds
        );
    }
    let day = seconds.div_euclid(86400);
    let rest = seconds.rem_euclid(86400);
    format!(
        "{}T{:02}:{:02}:{:02}Z",
        iso_from_epoch_day(day),
        rest / 3600,
        (rest % 3600) / 60,
        rest % 60
    )
}

pub fn fune_vector(args: &[Value]) -> Value {
    let seconds = match &args[0] {
        Value::Int(i) => *i,
        other => panic!("seconds must be a whole number, received {}", other),
    };
    Value::str(&unix_to_iso(seconds))
}

Install

fune build

With that line in your source, in a Rust project (language rust in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the Rust package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. A crate’s build.rs runs it before every compile. Or pin a range in fune.project and build in one step:

fune add time.unix-to-iso

The manifest, vectors and README with only the Rust implementation. Install it without the registry with fune add ./time.unix-to-iso-1.0.0-rust.fune, or fetch it from a terminal with fune pull time.unix-to-iso@1.0.0:rust.

The whole function, every language, is one file too: time.unix-to-iso-1.0.0.fune, 8,080 bytes, sha256 5ece36497825e6cc03e39573f4f7148c832ce451c8951058ba30d1d63d3c1eed. It installs into a project of any language.

// fune: before time.unix-to-iso

// fune: after time.unix-to-iso

// fune: replace dates.add-days in time.unix-to-iso

// fune: step time.unix-to-iso after <n|label>

More from the author

Seconds before 1970 are negative and are floored, not truncated: `-1` is `1969-12-31T23:59:59Z`, where dividing by 86,400 and rounding towards zero would give a time on 1970-01-01. The calendar arithmetic is `dates.add-days`'s, so leap years (2000 was one, 2100 will not be) come from one place.

The range is what a four-digit year can write, 0001-01-01T00:00:00Z (-62135596800) to 9999-12-31T23:59:59Z (253402300799); anything outside it, or a fractional second count, is an error. Milliseconds (JavaScript's `Date.now()`) must be divided by 1000 and floored first; passing them unchanged lands in the year 58,000 and is refused.

Unix time does not count leap seconds (POSIX.1-2017, Base Definitions, 4.16 "Seconds Since the Epoch"), so neither does this.

Files