Conversion between IPv6 addresses and their network-order wire bytes.

This module reads an address straight out of a packet buffer and writes it straight back into one, with no string round-trip. It is the byte-form counterpart of the ipv6 submodule: addressv6FromBytes is to parseAddressv6 what addressv6ToBytes is to stringifyAddressv6.

Addresses keep the numeric representation of the rest of the package — a bigint holding a 128-bit unsigned integer. Bytes are a conversion, not a second representation.

Byte order

Always network order (big-endian), on both the read and the write side. There is no option, because an IP address has exactly one wire order.

Widths and offsets

Both functions are fixed at 16 bytes, and offset selects where in the buffer that span sits, never how wide it is. A span that runs past the end of the buffer throws a RangeError rather than reading undefined and quietly decoding as ::.

IPv4-mapped byte sequences (::ffff:x.x.x.x) stay 128-bit values here; they are never unwrapped to a number.

For IPv4 see bytesv4; for the version-detecting pair see bytes.

import { assertEquals } from "@std/assert";
import { addressv6FromBytes } from "@hertzg/ip/bytesv6";
import { stringifyAddressv6 } from "@hertzg/ip/addressv6";

// deno-fmt-ignore
const packet = new Uint8Array([
  0x60, 0x00, 0x00, 0x00, 0x00, 0x14, 0x06, 0x40,
  0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
]);

assertEquals(stringifyAddressv6(addressv6FromBytes(packet, 8)), "2001:db8::1");

import { assertEquals } from "@std/assert";
import { addressv6FromBytes, addressv6ToBytes } from "@hertzg/ip/bytesv6";
import { parseAddressv6 } from "@hertzg/ip/addressv6";

const frame = new Uint8Array(40);
addressv6ToBytes(parseAddressv6("2001:db8::1").address, frame, 8);
addressv6ToBytes(parseAddressv6("2001:db8::2").address, frame, 24);

assertEquals(addressv6FromBytes(frame, 24), parseAddressv6("2001:db8::2").address);