Step by Step solution about How to resolve the algorithm Canonicalize CIDR step by step in the JavaScript programming language

The provided JavaScript code defines a function called canonicalize that takes a string representing an IP address and a CIDR (Classless Inter-Domain Routing) prefix length and returns a canonicalized form of the IP address. Here's how this code works:

1. Data Preparation:

   • It starts by creating a DataView over a 16-byte ArrayBuffer, which is initially filled with zeros.
   • The input string is split into two parts: ip (the IP address) and cidr (the CIDR prefix length). If the cidr component is missing, it defaults to 32.
   • The ip component is split further into individual octets (IPv4 address parts), and each octet is parsed as an integer. If an octet is missing, it defaults to 0. The parsed octets are stored in the DataView buffer.

2. IP Address Normalization:

   • The code then retrieves the IP address as a 32-bit unsigned integer (ipAsInt) from the DataView buffer.
   • It shifts the ipAsInt value to the left by the number of bits specified by the cidrInt to zero out the lower bits of the IP address, effectively normalizing the IP address to the specified CIDR prefix length.
   • The normalized IP address is then stored back in the DataView buffer.

3. Canonical IP Address Representation:

   • The DataView buffer is read to obtain each of the octets of the normalized IP address. These octets are joined together with dots to form a string representation of the canonical IP address.

4. CIDR Prefix Attachment:

   • The canonical IP address is combined with the cidrInt value using a slash ("/") separator. This results in the canonicalized form of the IP address with the CIDR prefix length.

5. Testing:

   • The provided test cases demonstrate how to use the canonicalize function to normalize and canonicalize various IP addresses with different CIDR prefix lengths. Each test case is printed along with its canonicalized result. Here are a few examples:

   • 255.255.255.255/10 -> 0.0.0.0/10

   • 87.70.141.1/22 -> 87.70.140.0/22

   • 10.207.219.251 -> 10.207.219.251/32

In summary, this JavaScript code provides a function that transforms IP addresses into their canonicalized form based on a specified CIDR prefix length. It follows a structured approach to normalize the IP address, convert it into a canonical representation, and attach the appropriate CIDR prefix length.

const canonicalize = s => {

    // Prepare a DataView over a 16 Byte Array buffer.
    // Initialised to all zeros.
    const dv = new DataView(new ArrayBuffer(16));

    // Get the ip-address and cidr components
    const [ip, cidr] = s.split('/');

    // Make sure the cidr component is a usable int, and
    // default to 32 if it does not exist.
    const cidrInt = parseInt(cidr || 32, 10);

    // Populate the buffer with uint8 ip address components.
    // Use zero as the default for shorthand pool definitions.
    ip.split('.').forEach(
        (e, i) => dv.setUint8(i, parseInt(e || 0, 10))
    );

    // Grab the whole buffer as a uint32
    const ipAsInt = dv.getUint32(0);

    // Zero out the lower bits as per the CIDR number.
    const normIpInt = (ipAsInt >> 32 - cidrInt) << 32 - cidrInt;

    // Plonk it back into the buffer
    dv.setUint32(0, normIpInt);

    // Read each of the uint8 slots in the buffer and join them with a dot.
    const canonIp = [...'0123'].map((e, i) => dv.getUint8(i)).join('.');

    // Attach the cidr number to the back of the normalised IP address.
    return [canonIp, cidrInt].join('/');
  }

  const test = s => console.log(s, '->', canonicalize(s));
  [
    '255.255.255.255/10',
    '87.70.141.1/22',
    '36.18.154.103/12',
    '62.62.197.11/29',
    '67.137.119.181/4',
    '161.214.74.21/24',
    '184.232.176.184/18',
    '10.207.219.251/32',
    '10.207.219.251',
    '110.200.21/4',
    '10..55/8',
    '10.../8'
  ].forEach(test)