Index

fn Index(comptime I: type) type {
    return extern struct {
        const Self = @This();

        /// The index of this entry in the backing store.  If the index is
        /// empty, this is empty_sentinel.
        entry_index: I,

        /// The distance between this slot and its ideal placement.  This is
        /// used to keep maximum scan length small.  This value is undefined
        /// if the index is empty.
        distance_from_start_index: I,

        /// The special entry_index value marking an empty slot.
        const empty_sentinel = ~@as(I, 0);

        /// A constant empty index
        const empty = Self{
            .entry_index = empty_sentinel,
            .distance_from_start_index = undefined,
        };

        /// Checks if a slot is empty
        fn isEmpty(idx: Self) bool {
            return idx.entry_index == empty_sentinel;
        }

        /// Sets a slot to empty
        fn setEmpty(idx: *Self) void {
            idx.entry_index = empty_sentinel;
            idx.distance_from_start_index = undefined;
        }
    };
}