Attempt to multiply with overflow

[azzamsa]

Hi,

I wanted to port my Chrono code to jiff, but I got attempt to multiply with overflow.
The Chrono part works just fine.

pub fn hijri_to_julian_chrono(date: chrono::NaiveDate) -> i32 {
    ((((11 * date.year() + 3) / 30) as f32).floor()
        + ((354 * date.year()) as f32).floor()
        + ((30 * date.month() as u8) as f32).floor()
        - (((date.month() as u8 - 1) / 2) as f32).floor()
        + date.day() as f32
        + 1_948_440.0
        - 385.0) as i32
}

pub fn hijri_to_julian_jiff(date: jiff::civil::Date) -> i32 {
    ((((11 * date.year() + 3) / 30) as f32).floor()
        + ((354 * date.year()) as f32).floor()
        + ((30 * date.month() as u8) as f32).floor()
        - (((date.month() as u8 - 1) / 2) as f32).floor()
        + date.day() as f32
        + 1_948_440.0
        - 385.0) as i32
}

fn main() {
    assert_eq!(
        hijri_to_julian_chrono(chrono::NaiveDate::from_ymd_opt(1442, 8, 25).unwrap()),
        2459313
    );
    assert_eq!(
        hijri_to_julian_jiff(jiff::civil::date(1442, 8, 25)),
        2459313
    );
}

The original python code is here

[BurntSushi]

date.year() returns an i16. In this case, 1442. Multiplying that by 354 gives 510468, which overflows i16. Chrono's date.year() returns an i32, which doesn't result in an overflow here. So a simple fix is to convert to i32 and then multiply: ((354 * i32::from(date.year())).

[azzamsa]

Would you be able to explain why jiff uses i16 for the year?
What the migration would be at i16:MAX? 😀

[BurntSushi]

The minimum and maximum years supported by Jiff are -9999 and 9999, respectively. Those fit in an i16.