Function write_decimal

src/sponge.rs:104–148

(out: &mut [u8], mut x: u64)

/// This function is unsafe because it uses `copy_nonoverlapping`.
#[inline(always)]
unsafe fn write_decimal<const N: usize>(out: &mut [u8], mut x: u64) -> usize {
    let mut buf = [0u8; 64];

    let buf_ptr = if N == 0 {
        buf.as_mut_ptr()
    } else {
        out.as_mut_ptr().add(32)
    };
    let lut_ptr = DEC_DIGITS_LUT.as_ptr();

    let mut curr = 32;

    while x >= 10000 {
        let rem = (x % 10000) as usize;
        x /= 10000;

        let d1 = (rem / 100) << 1;
        let d2 = (rem % 100) << 1;
        curr -= 4;

        std::ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
        std::ptr::copy_nonoverlapping(lut_ptr.add(d2), buf_ptr.add(curr + 2), 2);
    }

    let mut x = x as usize;

    if x >= 100 {
        let d1 = (x % 100) << 1;
        x /= 100;
        curr -= 2;
        std::ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
    }

    if x < 10 {
        curr -= 1;
        *buf_ptr.add(curr) = (x as u8) + b'0';
    } else {
        let d1 = x << 1;
        curr -= 2;
        std::ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
    }

    std::ptr::copy_nonoverlapping(buf_ptr.add(curr), out.as_mut_ptr(), 32);
    32 - curr
}