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| import { randomBytes } from 'node:crypto'; | |
| const ENCODING = '0123456789ABCDEFGHJKMNPQRSTVWXYZ'; | |
| const TIME_LEN = 10; | |
| const RANDOM_LEN = 16; | |
| function encodeTime(ms: number): string { | |
| let out = ''; | |
| let t = ms; | |
| for (let i = 0; i < TIME_LEN; i++) { | |
| out = ENCODING[t % 32] + out; | |
| t = Math.floor(t / 32); | |
| } | |
| return out; | |
| } | |
| function randomDigits(): number[] { | |
| const bytes = randomBytes(RANDOM_LEN); | |
| return Array.from(bytes, (b) => b % 32); | |
| } | |
| function incrementDigits(digits: number[]): void { | |
| for (let i = digits.length - 1; i >= 0; i--) { | |
| if (digits[i] < 31) { | |
| digits[i]++; | |
| return; | |
| } | |
| digits[i] = 0; | |
| } | |
| throw new Error('ULID random component overflow'); | |
| } | |
| /** | |
| * Returns a monotonic ULID generator: ids created in the same millisecond | |
| * strictly increase, so lexical order equals creation order within a process. | |
| */ | |
| export function createUlidFactory(now: () => number = Date.now): () => string { | |
| let lastTime = -1; | |
| let lastRandom: number[] | null = null; | |
| return () => { | |
| const t = Math.floor(now()); | |
| if (lastRandom !== null && t <= lastTime) { | |
| incrementDigits(lastRandom); | |
| } else { | |
| lastTime = t; | |
| lastRandom = randomDigits(); | |
| } | |
| return encodeTime(lastTime) + lastRandom.map((d) => ENCODING[d]).join(''); | |
| }; | |
| } | |
| export const ulid = createUlidFactory(); | |