Functions for working with IP addresses
-------------------------

IPv4NumToString(num)
~~~~~~~~~~~~~
Takes a UInt32 number. Interprets it as an IPv4 address in big endian. Returns a string containing the corresponding IPv4 address in the format A.B.C.d (dot-separated numbers in decimal form).

IPv4StringToNum(s)
~~~~~~~~
The reverse function of IPv4NumToString. If the IPv4 address has an invalid format, it returns 0.

IPv4NumToStringClassC(num)
~~~~~~~~~~~
Similar to IPv4NumToString, but using ``xxx`` instead of the last octet. 

Example:

.. code-block:: sql

  SELECT
      IPv4NumToStringClassC(ClientIP) AS k,
      count() AS c
  FROM test.hits
  GROUP BY k
  ORDER BY c DESC
  LIMIT 10
  
  ┌─k──────────────┬─────c─┐
  │ 83.149.9.xxx   │ 26238 │
  │ 217.118.81.xxx │ 26074 │
  │ 213.87.129.xxx │ 25481 │
  │ 83.149.8.xxx   │ 24984 │
  │ 217.118.83.xxx │ 22797 │
  │ 78.25.120.xxx  │ 22354 │
  │ 213.87.131.xxx │ 21285 │
  │ 78.25.121.xxx  │ 20887 │
  │ 188.162.65.xxx │ 19694 │
  │ 83.149.48.xxx  │ 17406 │
  └────────────────┴───────┘

Since using ``'xxx'`` is highly unusual, this may be changed in the future. We recommend that you don't rely on the exact format of this fragment.

IPv6NumToString(x)
~~~~~~~~~~~~
Accepts a FixedString(16) value containing the IPv6 address in binary format. Returns a string containing this address in text format.
IPv6-mapped IPv4 addresses are output in the format ``::ffff:111.222.33.44``. Examples:

.. code-block:: sql

  SELECT IPv6NumToString(toFixedString(unhex('2A0206B8000000000000000000000011'), 16)) AS addr
  
  ┌─addr─────────┐
  │ 2a02:6b8::11 │
  └──────────────┘
  SELECT
      IPv6NumToString(ClientIP6 AS k),
      count() AS c
  FROM hits_all
  WHERE EventDate = today() AND substring(ClientIP6, 1, 12) != unhex('00000000000000000000FFFF')
  GROUP BY k
  ORDER BY c DESC
  LIMIT 10
  
  ┌─IPv6NumToString(ClientIP6)──────────────┬─────c─┐
  │ 2a02:2168:aaa:bbbb::2                   │ 24695 │
  │ 2a02:2698:abcd:abcd:abcd:abcd:8888:5555 │ 22408 │
  │ 2a02:6b8:0:fff::ff                      │ 16389 │
  │ 2a01:4f8:111:6666::2                    │ 16016 │
  │ 2a02:2168:888:222::1                    │ 15896 │
  │ 2a01:7e00::ffff:ffff:ffff:222           │ 14774 │
  │ 2a02:8109:eee:ee:eeee:eeee:eeee:eeee    │ 14443 │
  │ 2a02:810b:8888:888:8888:8888:8888:8888  │ 14345 │
  │ 2a02:6b8:0:444:4444:4444:4444:4444      │ 14279 │
  │ 2a01:7e00::ffff:ffff:ffff:ffff          │ 13880 │
  └─────────────────────────────────────────┴───────┘
  SELECT
      IPv6NumToString(ClientIP6 AS k),
      count() AS c
  FROM hits_all
  WHERE EventDate = today()
  GROUP BY k
  ORDER BY c DESC
  LIMIT 10
  
  ┌─IPv6NumToString(ClientIP6)─┬──────c─┐
  │ ::ffff:94.26.111.111       │ 747440 │
  │ ::ffff:37.143.222.4        │ 529483 │
  │ ::ffff:5.166.111.99        │ 317707 │
  │ ::ffff:46.38.11.77         │ 263086 │
  │ ::ffff:79.105.111.111      │ 186611 │
  │ ::ffff:93.92.111.88        │ 176773 │
  │ ::ffff:84.53.111.33        │ 158709 │
  │ ::ffff:217.118.11.22       │ 154004 │
  │ ::ffff:217.118.11.33       │ 148449 │
  │ ::ffff:217.118.11.44       │ 148243 │
  └────────────────────────────┴────────┘

IPv6StringToNum(s)
~~~~~~~~
The reverse function of IPv6NumToString. If the IPv6 address has an invalid format, it returns a string of null bytes.
HEX can be uppercase or lowercase.