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Module

std/ulid/_util.ts

Deno standard library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
/** Type for a ULID generator function. */export type ULID = (seedTime?: number) => string;
// These values should NEVER change. If// they do, we're no longer making ulids!export const ENCODING = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"; // Crockford's Base32export const ENCODING_LEN = ENCODING.length;export const TIME_MAX = Math.pow(2, 48) - 1;export const TIME_LEN = 10;export const RANDOM_LEN = 16;
function replaceCharAt(str: string, index: number, char: string) { return str.substring(0, index) + char + str.substring(index + 1);}
export function encodeTime(now: number, len: number = TIME_LEN): string { if (!Number.isInteger(now) || now < 0 || now > TIME_MAX) { throw new Error("Time must be a positive integer less than " + TIME_MAX); } let str = ""; for (; len > 0; len--) { const mod = now % ENCODING_LEN; str = ENCODING[mod] + str; now = (now - mod) / ENCODING_LEN; } return str;}
export function encodeRandom(len: number): string { let str = ""; const randomBytes = crypto.getRandomValues(new Uint8Array(len)); for (const randomByte of randomBytes) { str += ENCODING[randomByte % ENCODING_LEN]; } return str;}
export function incrementBase32(str: string): string { let index = str.length; let char; let charIndex; const maxCharIndex = ENCODING_LEN - 1; while (--index >= 0) { char = str[index]!; charIndex = ENCODING.indexOf(char); if (charIndex === -1) { throw new Error("incorrectly encoded string"); } if (charIndex === maxCharIndex) { str = replaceCharAt(str, index, ENCODING[0]!); continue; } return replaceCharAt(str, index, ENCODING[charIndex + 1]!); } throw new Error("cannot increment this string");}
/** Generates a monotonically increasing ULID. */export function monotonicFactory(encodeRand = encodeRandom): ULID { let lastTime = 0; let lastRandom: string; return function ulid(seedTime: number = Date.now()): string { if (seedTime <= lastTime) { const incrementedRandom = (lastRandom = incrementBase32(lastRandom)); return encodeTime(lastTime, TIME_LEN) + incrementedRandom; } lastTime = seedTime; const newRandom = (lastRandom = encodeRand(RANDOM_LEN)); return encodeTime(seedTime, TIME_LEN) + newRandom; };}