fn rand_fixed_hex32(buffer: MutSpan<u8>, value: u32) -> Maybe<Span<u8>> {
    if std.mem.len(buffer) < 8 {
        return null
    }
    var place: u32 = 268435456_u32
    var index: usize = 0
    while index < 8 {
        let digit: u8 = ((value / place) % 16_u32) as u8
        if digit < 10_u8 {
            buffer[index] = 48_u8 + digit
        } else {
            buffer[index] = 87_u8 + digit
        }
        place = place / 16_u32
        index = index + 1
    }
    return buffer[..8]
}

fn rand_entropy_hex32(buffer: MutSpan<u8>) -> Maybe<Span<u8>> {
    return rand_fixed_hex32(buffer, std.rand.entropyU32())
}