cidrFirstAddress - cidr.ts - @hertzg/ip documentation

function cidrFirstAddress



cidrFirstAddress<T extends Cidr>(cidr: T): T extends Cidrv6 ? bigint : number

Returns the first address of a CIDR block.

Dispatches to cidrv4FirstAddress or cidrv6FirstAddress based on the address type. Masking a non-canonical block through this is the version-agnostic way to canonicalize it.

There is deliberately no universal cidrFirstUsableAddress: the addresses an operator may assign differ per version, and IPv6 has no library-wide rule to apply. The usable-address vocabulary is IPv4-only — see cidrv4FirstUsableAddress.

Examples

Example 1

import { assertEquals } from "@std/assert";
import { cidrFirstAddress, parseCidr } from "@hertzg/ip/cidr";
import { stringifyAddress } from "@hertzg/ip/address";

assertEquals(stringifyAddress(cidrFirstAddress(parseCidr("192.168.1.0/24"))), "192.168.1.0");
assertEquals(stringifyAddress(cidrFirstAddress(parseCidr("2001:db8::/32"))), "2001:db8::");

Sorting blocks by their first address

import { assertEquals } from "@std/assert";
import { cidrFirstAddress, parseCidr, stringifyCidr } from "@hertzg/ip/cidr";

const blocks = [
  parseCidr("10.0.2.0/24"),
  parseCidr("10.0.0.0/24"),
  parseCidr("10.0.1.0/24"),
];
blocks.sort((a, b) => Number(cidrFirstAddress(a)) - Number(cidrFirstAddress(b)));

assertEquals(blocks.map(stringifyCidr), [
  "10.0.0.0/24",
  "10.0.1.0/24",
  "10.0.2.0/24",
]);

Type Parameters



T extends Cidr

Parameters



cidr: T

The CIDR block

Return Type

T extends Cidrv6 ? bigint : number

The first address (number for IPv4, bigint for IPv6)