pub fn highlight(code: &str) -> String {
    unsafe {
        let mut buf = Vec::new();
        buf.reserve(
            2usize
                .pow(1 + (code.len() as f32).log2().ceil() as u32)
                .max(1024),
        );
        let used = highlight_swift(
            code.as_ptr(),
            code.len() as u64,
            buf.as_mut_ptr(),
            buf.capacity() as u64,
        );
        buf.set_len(used as usize);
        String::from_utf8_unchecked(buf)
    }
}

extern "C" {
    fn highlight_swift(code_ptr: *const u8, code_len: u64, out_ptr: *mut u8, max_len: u64) -> u64;
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_highlight() {
        let result = super::highlight("1+1");
        assert_eq!(
            result,
            r#"<span class="hl-num">1</span>+<span class="hl-num">1</span>"#
        );
    }
}