cidr-calc

# CIDR Calculator Given an IP address in CIDR notation, compute all subnet parameters: network address, broadcast, host range, subnet mask, wildcard mask, host counts, IP class, and binary representation. ## Input - A CIDR notation string in the format `A.B.C.D/N` (e.g. `192.168.1.0/24`) ## Output A structured result with these fields: - CIDR Notation (normalized) - Network Address - Broadcast Address - Subnet Mask - Wildcard Mask - First Usable Host - Last Usable Host - Total Hosts (2^(32-N)) - Usable Hosts - IP Class (A / B / C / D Multicast / E Reserved) - Network Type (Private / Public) - Binary Representation of the IP ## Instructions 1. Validate the input. It must match `\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\/\d{1,2}`. Each octet must be 0–255. Prefix must be 0–32. 2. Compute values using standard subnet math: - `maskNum = (0xFFFFFFFF << (32 - prefix)) >>> 0` - `wildcardNum = ~maskNum >>> 0` - `networkNum = (ipNum & maskNum) >>> 0` - `broadcastNum = (networkNum | wildcardNum) >>> 0` - `totalHosts = 2^(32 - prefix)` - `usableHosts`: if prefix == 32 → 1; if prefix == 31 → 2; else `totalHosts - 2` 3. Determine IP class from first octet: - 1–126 → A; 128–191 → B; 192–223 → C; 224–239 → D (Multicast); 240–255 → E (Reserved); 127 → Loopback 4. Determine private vs public: - Private: 10.x.x.x, 172.16–31.x.x, 192.168.x.x, 127.x.x.x (loopback) 5. Compute binary as four 8-bit groups joined by dots. 6. Present results in a clear labeled format. ### Quick CIDR reference | CIDR | Subnet Mask | Total Hosts | |------|-------------------|-------------| | /8 | 255.0.0.0 | 16,777,216 | | /16 | 255.255.0.0 | 65,536 | | /20 | 255.255.240.0 | 4,096 | | /22 | 255.255.252.0 | 1,024 | | /24 | 255.255.255.0 | 256 | | /28 | 255.255.255.240 | 16 | | /30 | 255.255.255.252 | 4 | | /32 | 255.255.255.255 | 1 | ## Options - Input is always a single CIDR string; no additional options. ## Examples **Input:** `192.168.1.0/24` **Output:** ``` CIDR Notation: 192.168.1.0/24 Network Address: 192.168.1.0 Broadcast: 192.168.1.255 Subnet Mask: 255.255.255.0 Wildcard Mask: 0.0.0.255 First Host: 192.168.1.1 Last Host: 192.168.1.254 Total Hosts: 256 Usable Hosts: 254 IP Class: C Network Type: Private Binary: 11000000.10101000.00000001.00000000 ``` **Input:** `10.0.0.0/8` **Output:** ``` CIDR Notation: 10.0.0.0/8 Network Address: 10.0.0.0 Broadcast: 10.255.255.255 Subnet Mask: 255.0.0.0 Wildcard Mask: 0.255.255.255 First Host: 10.0.0.1 Last Host: 10.255.255.254 Total Hosts: 16,777,216 Usable Hosts: 16,777,214 IP Class: A Network Type: Private Binary: 00001010.00000000.00000000.00000000 ``` ## Error Handling - If the input is not valid CIDR notation, say so and provide the expected format (`A.B.C.D/N`). - If an octet exceeds 255 or the prefix exceeds 32, explain the validation error. - If the user provides an IP without a prefix (e.g. `192.168.1.1`), ask for the prefix length or assume /32.