Added matchesCidr utility

src/misc.ts

@@ -76,6 +76,23 @@ export function gravatar(email: string, def='mp') {
 	return `https://www.gravatar.com/avatar/${md5(email)}?d=${def}`;
 }
 
+/**
+ * Check if IP address falls within CIDR range
+ * @param {string} ip IPV4 to check (192.168.0.12)
+ * @param {string} cidr IP range to check against (example: 192.168.0.0/24)
+ * @returns {boolean} Whether IP address is within range
+ */
+export function matchesCidr(ip: string, cidr: string): boolean {
+	if(!cidr) return true;
+	if(!ip) return false;
+	if(!cidr?.includes('/')) return ip === cidr; // Single IP
+	const [range, bits] = cidr.split('/');
+	const mask = ~(2 ** (32 - parseInt(bits)) - 1);
+	const ipToInt = (str: string) => str.split('.')
+		.reduce((int, octet) => (int << 8) + parseInt(octet), 0) >>> 0;
+	return (ipToInt(ip) & mask) === (ipToInt(range) & mask);
+}
+
 /**
  * Convert IPv6 to v4 because who uses that, NAT4Life
  * @param {string} ip IPv6 address, e.g. 2001:0db8:85a3:0000:0000:8a2e:0370:7334