Check on a few billions values that the optimised version of h3IsValid returns the same result as the reference implementation.

check.rs

fn main() {
    let mut valid = 0;
    let mut invalid = 0;

    for i in 0..=0x7fff_ffff_u32 {
        let cell = 0x0880_0000_001f_ffff | (u64::from(i) << 21);
        let result = h3cell::is_valid_h3(cell);
        let expected = unsafe { h3ron_h3_sys::h3IsValid(cell) != 0 };

        valid += expected as usize;
        invalid += !expected as usize;

        assert_eq!(
            result, expected,
            "{}: sanic={}, h3ron={}",
            cell, result, expected
        );

        if i % 1_000_000 == 0 {
            eprintln!("{}/{}", i, 0x7fff_ffff);
        }
    }
    println!("{} valid, {} invalid", valid, invalid);
}