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

The provided Julia code performs a specific operation on IPv4 addresses in the form of Classless Inter-Domain Routing (CIDR) notation. Here's a step-by-step explanation of the code:

1. using Sockets: This line imports the Sockets module, which provides functionality for working with network sockets and IP addresses.

2. function canonCIDR(cidr::String): This defines a function named canonCIDR that takes a single argument cidr of type String. This function is designed to canonicalize (standardize) the given CIDR notation string.

3. Replace Operations: The function performs two replacement operations on the input cidr string using the replace function:

   • It replaces any occurrence of ".." (two consecutive periods) with ".0."
   • It replaces any occurrence of "..." (three consecutive periods) with ".0."

   These replacements are used to handle CIDR notations with missing octets, ensuring that the string is in a valid IPv4 CIDR format.

4. Splitting the CIDR: The function then splits the cidr string at the '/' character into two parts: ip and mask. ip contains the IPv4 address, while mask contains the subnet mask (if present).

5. Mask Calculation: It calculates the subnet mask dig based on the length of ip and the value in mask (if available). The subnet mask is used to determine the number of bits used for the network address.

6. IPv4 Conversion: The function converts the ip string to an IPv4 object, applies the subnet mask to it using the bitwise AND operation, and stores the result in ip4.

7. Output Formatting: Finally, depending on whether mask is present or not, the function formats the output in the following way:

   • If mask is present, the output is in the form "$ip4/$mask" (e.g., "87.70.141.1/22")
   • If mask is not present, the output is in the form "$ip4/32", representing a single IP address (e.g., "10.207.219.251/32")

8. Printing Results: The function prints the canonicalized CIDR notations for various input strings using the println function.

In summary, this code takes IPv4 addresses in CIDR notation, standardizes them, and prints the canonicalized representations.

using Sockets

function canonCIDR(cidr::String)
    cidr = replace(cidr, r"\.(\.|\/)" => s".0\1") # handle ..
    cidr = replace(cidr, r"\.(\.|\/)" => s".0\1") # handle ...
    ip = split(cidr, "/")
    dig = length(ip) > 1 ? 2^(32 - parse(UInt8, ip[2])) : 1
    ip4 = IPv4(UInt64(IPv4(ip[1])) & (0xffffffff - dig + 1))
    return length(ip) == 1 ? "$ip4/32" : "$ip4/$(ip[2])"
end

println(canonCIDR("87.70.141.1/22"))
println(canonCIDR("100.68.0.18/18"))
println(canonCIDR("10.4.30.77/30"))
println(canonCIDR("10.207.219.251/32"))
println(canonCIDR("10.207.219.251"))
println(canonCIDR("110.200.21/4"))
println(canonCIDR("10..55/8"))
println(canonCIDR("10.../8"))