util.rs

use core::ops::{Bound, RangeBounds, RangeInclusive};

/// Returns the container key and the index
/// in this container for a given integer.
#[inline]
pub fn split(value: u32) -> (u16, u16) {
    ((value >> 16) as u16, value as u16)
}

/// Returns the original integer from the container
/// key and the index of it in the container.
#[inline]
pub fn join(high: u16, low: u16) -> u32 {
    (u32::from(high) << 16) + u32::from(low)
}

/// Convert a `RangeBounds<u32>` object to `RangeInclusive<u32>`,
pub fn convert_range_to_inclusive<R>(range: R) -> Option<RangeInclusive<u32>>
where
    R: RangeBounds<u32>,
{
    let start: u32 = match range.start_bound() {
        Bound::Included(&i) => i,
        Bound::Excluded(&i) => i.checked_add(1)?,
        Bound::Unbounded => 0,
    };
    let end: u32 = match range.end_bound() {
        Bound::Included(&i) => i,
        Bound::Excluded(&i) => i.checked_sub(1)?,
        Bound::Unbounded => u32::MAX,
    };
    if end < start {
        return None;
    }
    Some(start..=end)
}

#[cfg(test)]
mod test {
    use super::{convert_range_to_inclusive, join, split};
    use core::ops::Bound;

    #[test]
    fn test_split_u32() {
        assert_eq!((0x0000u16, 0x0000u16), split(0x0000_0000u32));
        assert_eq!((0x0000u16, 0x0001u16), split(0x0000_0001u32));
        assert_eq!((0x0000u16, 0xFFFEu16), split(0x0000_FFFEu32));
        assert_eq!((0x0000u16, 0xFFFFu16), split(0x0000_FFFFu32));
        assert_eq!((0x0001u16, 0x0000u16), split(0x0001_0000u32));
        assert_eq!((0x0001u16, 0x0001u16), split(0x0001_0001u32));
        assert_eq!((0xFFFFu16, 0xFFFEu16), split(0xFFFF_FFFEu32));
        assert_eq!((0xFFFFu16, 0xFFFFu16), split(0xFFFF_FFFFu32));
    }

    #[test]
    fn test_join_u32() {
        assert_eq!(0x0000_0000u32, join(0x0000u16, 0x0000u16));
        assert_eq!(0x0000_0001u32, join(0x0000u16, 0x0001u16));
        assert_eq!(0x0000_FFFEu32, join(0x0000u16, 0xFFFEu16));
        assert_eq!(0x0000_FFFFu32, join(0x0000u16, 0xFFFFu16));
        assert_eq!(0x0001_0000u32, join(0x0001u16, 0x0000u16));
        assert_eq!(0x0001_0001u32, join(0x0001u16, 0x0001u16));
        assert_eq!(0xFFFF_FFFEu32, join(0xFFFFu16, 0xFFFEu16));
        assert_eq!(0xFFFF_FFFFu32, join(0xFFFFu16, 0xFFFFu16));
    }

    #[test]
    #[allow(clippy::reversed_empty_ranges)]
    fn test_convert_range_to_inclusive() {
        assert_eq!(Some(1..=5), convert_range_to_inclusive(1..6));
        assert_eq!(Some(1..=u32::MAX), convert_range_to_inclusive(1..));
        assert_eq!(Some(0..=u32::MAX), convert_range_to_inclusive(..));
        assert_eq!(Some(16..=16), convert_range_to_inclusive(16..=16));
        assert_eq!(
            Some(11..=19),
            convert_range_to_inclusive((Bound::Excluded(10), Bound::Excluded(20)))
        );

        assert_eq!(None, convert_range_to_inclusive(0..0));
        assert_eq!(None, convert_range_to_inclusive(5..5));
        assert_eq!(None, convert_range_to_inclusive(1..0));
        assert_eq!(None, convert_range_to_inclusive(10..5));
        assert_eq!(
            None,
            convert_range_to_inclusive((Bound::Excluded(u32::MAX), Bound::Included(u32::MAX)))
        );
        assert_eq!(
            None,
            convert_range_to_inclusive((Bound::Excluded(u32::MAX), Bound::Included(u32::MAX)))
        );
        assert_eq!(None, convert_range_to_inclusive((Bound::Excluded(0), Bound::Included(0))));
    }
}