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//! This modules implements some math helper functions.

/// Returns ceil(log2(d)) but panics if d = 0.
pub fn ceil_log2(d: usize) -> usize {
    // NOTE: should this really be usize, since usize is depended on the underlying system architecture?

    assert!(d != 0);
    let mut pow2 = 1;
    let mut ceil_log2 = 0;
    while d > pow2 {
        ceil_log2 += 1;
        pow2 = match pow2.checked_mul(2) {
            Some(x) => x,
            None => break,
        }
    }
    ceil_log2
}

/// This function is bound to be stable soon. See <https://github.com/rust-lang/rust/issues/88581>
pub fn div_ceil(a: usize, b: usize) -> usize {
    (a + b - 1) / b
}