Function format_duration

cel/src/duration.rs:100–176

Formats a [`Duration`] into a string. String returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0s. This is a direct port of the Go version of the time.Duration(0).St

(d: &Duration)

///
/// This is a direct port of the Go version of the time.Duration(0).String() function.
pub fn format_duration(d: &Duration) -> String {
    let buf = &mut [0u8; 32];
    let mut w = buf.len();

    let mut neg = false;
    let mut u = d
        .num_nanoseconds()
        .map(|n| {
            if n < 0 {
                neg = true;
            }
            n as u64
        })
        .unwrap_or_else(|| {
            let s = d.num_seconds();
            if s < 0 {
                neg = true;
            }
            s as u64 * SECOND
        });

    if u < SECOND {
        // Special case: if duration is smaller than a second,
        // use smaller units, like 1.2ms
        let mut _prec = 0;
        w -= 1;
        buf[w] = b's';
        w -= 1;

        if u == 0 {
            return "0s".to_string();
        } else if u < MICROSECOND {
            _prec = 0;
            buf[w] = b'n';
        } else if u < MILLISECOND {
            _prec = 3;
            // U+00B5 'µ' micro sign == 0xC2 0xB5
            buf[w] = 0xB5;
            w -= 1;
            buf[w] = 0xC2;
        } else {
            _prec = 6;
            buf[w] = b'm';
        }
        (w, u) = format_float(&mut buf[..w], u, _prec);
        w = format_int(&mut buf[..w], u);
    } else {
        w -= 1;
        buf[w] = b's';
        (w, u) = format_float(&mut buf[..w], u, 9);

        // u is now integer number of seconds
        w = format_int(&mut buf[..w], u % 60);
        u /= 60;

        // u is now integer number of minutes
        if u > 0 {
            w -= 1;