encoding.mjs

Functions

Imports

It imports no other module of this repo. No module of this repo imports it.

Source

1/**
2 * Byte encodings, once, for every repo: hex, base64, base64url and a SHA-256 hex digest. Each site had its own copy, a
3 * few on `jose` or Buffer (which a Worker has only with nodejs_compat). Web APIs only.
4 *
5 * Every encoder takes bytes (a Uint8Array or ArrayBuffer) or a string, which is encoded as UTF-8 first.
6 */
7
8/** @param {Uint8Array | ArrayBuffer | string} input */
9function bytesOf(input) {
10  return typeof input === "string" ? new TextEncoder().encode(input) : new Uint8Array(input);
11}
12
13/**
14 * Lowercase hex, two digits a byte.
15 * @param {Uint8Array | ArrayBuffer | string} input
16 * @returns {string}
17 */
18export function toHex(input) {
19  return Array.from(bytesOf(input), (b) => b.toString(16).padStart(2, "0")).join("");
20}
21
22/**
23 * The bytes of a hex string, either case. Throws on an odd length or a character that is not hex.
24 * @param {string} hex
25 * @returns {Uint8Array<ArrayBuffer>}
26 */
27export function fromHex(hex) {
28  if (hex.length % 2 || /[^0-9a-f]/i.test(hex)) throw new TypeError("not a hex string");
29  return Uint8Array.from(hex.match(/../g) ?? [], (pair) => Number.parseInt(pair, 16));
30}
31
32/**
33 * Standard base64, padded (GitHub's contents API, data: URLs).
34 * @param {Uint8Array | ArrayBuffer | string} input
35 * @returns {string}
36 */
37export function toBase64(input) {
38  let binary = "";
39  for (const byte of bytesOf(input)) binary += String.fromCharCode(byte);
40  return btoa(binary);
41}
42
43/**
44 * The bytes of standard base64. Whitespace is dropped first, since GitHub wraps its base64 in lines and `atob` throws
45 * on it; anything else that is not base64 throws.
46 * @param {string} text
47 * @returns {Uint8Array<ArrayBuffer>}
48 */
49export function fromBase64(text) {
50  return Uint8Array.from(atob(text.replace(/\s+/g, "")), (c) => c.charCodeAt(0));
51}
52
53/**
54 * URL-safe base64 with no padding (RFC 4648 section 5): tokens, JWT parts, VAPID keys.
55 * @param {Uint8Array | ArrayBuffer | string} input
56 * @returns {string}
57 */
58export function base64url(input) {
59  return toBase64(input).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
60}
61
62/**
63 * The bytes of URL-safe base64, padded or not.
64 * @param {string} text
65 * @returns {Uint8Array<ArrayBuffer>}
66 */
67export function fromBase64url(text) {
68  const plain = text.replace(/-/g, "+").replace(/_/g, "/");
69  return fromBase64(plain + "=".repeat((4 - (plain.length % 4)) % 4));
70}
71
72/**
73 * The SHA-256 digest of `input`, as lowercase hex.
74 * @param {Uint8Array | ArrayBuffer | string} input
75 * @returns {Promise<string>}
76 */
77export async function sha256Hex(input) {
78  return toHex(await crypto.subtle.digest("SHA-256", bytesOf(input)));
79}