switch(len & 3)
{
case 3: k1 ^= tail[2] << 16;
case 2: k1 ^= tail[1] << 8;
case 1: k1 ^= tail[0];
        k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
};

'outer: {
  'case1: {
    'case2: {
      'case3: {
        match len & 3 {
          3 => break 'case3,
          2 => break 'case2,
          1 => break 'case1,
          _ => break 'outer,
        }
      } // 'case3:
      k1 ^= (tail[2] as u32) << 16;
    } // 'case2:
    k1 ^= (tail[1] as u32) << 8;
  } // case1:
  k1 ^= tail[0] as u32;
  k1 *= c1; k1 = k1.rotate_left(15); k1 *= c2; h1 ^= k1;
}