@naturalcycles/nodejs-lib
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Standard library for Node.js
93 lines (90 loc) • 4.32 kB
JavaScript
/*
This file is "vendored" from Nanoid, all credit is to Nanoid authors:
https://github.com/ai/nanoid/
*/
// oxlint-disable no-bitwise -- NanoID implementation relies on bitwise operations
import { randomFillSync } from 'node:crypto';
export const ALPHABET_NONAMBIGUOUS = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';
export const ALPHABET_NUMBER = '0123456789';
export const ALPHABET_LOWERCASE = 'abcdefghijklmnopqrstuvwxyz';
export const ALPHABET_UPPERCASE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
export const ALPHABET_ALPHANUMERIC_LOWERCASE = [ALPHABET_NUMBER, ALPHABET_LOWERCASE].join('');
export const ALPHABET_ALPHANUMERIC_UPPERCASE = [ALPHABET_NUMBER, ALPHABET_UPPERCASE].join('');
export const ALPHABET_ALPHANUMERIC = [ALPHABET_NUMBER, ALPHABET_LOWERCASE, ALPHABET_UPPERCASE].join('');
export const ALPHABET_BASE64 = [ALPHABET_ALPHANUMERIC, '+/'].join('');
export const ALPHABET_BASE64_URL = [ALPHABET_ALPHANUMERIC, '-_'].join('');
// It is best to make fewer, larger requests to the crypto module to
// avoid system call overhead. So, random numbers are generated in a
// pool. The pool is a Buffer that is larger than the initial random
// request size by this multiplier. The pool is enlarged if subsequent
// requests exceed the maximum buffer size.
const POOL_SIZE_MULTIPLIER = 128;
let pool;
let poolOffset;
function fillPool(bytes) {
if (!pool || pool.length < bytes) {
pool = Buffer.allocUnsafe(bytes * POOL_SIZE_MULTIPLIER);
randomFillSync(pool);
poolOffset = 0;
}
else if (poolOffset + bytes > pool.length) {
randomFillSync(pool);
poolOffset = 0;
}
poolOffset += bytes;
}
function random(bytes) {
// `-=` convert `bytes` to number to prevent `valueOf` abusing
fillPool((bytes -= 0));
return pool.subarray(poolOffset - bytes, poolOffset);
}
function customRandom(alphabet, defaultSize, getRandom) {
// First, a bitmask is necessary to generate the ID. The bitmask makes bytes
// values closer to the alphabet size. The bitmask calculates the closest
// `2^31 - 1` number, which exceeds the alphabet size.
// For example, the bitmask for the alphabet size 30 is 31 (00011111).
const mask = (2 << (31 - Math.clz32((alphabet.length - 1) | 1))) - 1;
// Though, the bitmask solution is not perfect since the bytes exceeding
// the alphabet size are refused. Therefore, to reliably generate the ID,
// the random bytes redundancy has to be satisfied.
// Note: every hardware random generator call is performance expensive,
// because the system call for entropy collection takes a lot of time.
// So, to avoid additional system calls, extra bytes are requested in advance.
// Next, a step determines how many random bytes to generate.
// The number of random bytes gets decided upon the ID size, mask,
// alphabet size, and magic number 1.6 (using 1.6 peaks at performance
// according to benchmarks).
const step = Math.ceil((1.6 * mask * defaultSize) / alphabet.length);
return (size = defaultSize) => {
let id = '';
while (true) {
const bytes = getRandom(step);
// A compact alternative for `for (let i = 0; i < step; i++)`.
let i = step;
while (i--) {
// Adding `|| ''` refuses a random byte that exceeds the alphabet size.
id += alphabet[bytes[i] & mask] || '';
if (id.length === size)
return id;
}
}
};
}
export function nanoIdCustomAlphabet(alphabet, size = 21) {
return customRandom(alphabet, size, random);
}
export function nanoid(size = 21) {
// `-=` convert `size` to number to prevent `valueOf` abusing
fillPool((size -= 0));
let id = '';
// We are reading directly from the random pool to avoid creating new array
for (let i = poolOffset - size; i < poolOffset; i++) {
// It is incorrect to use bytes exceeding the alphabet size.
// The following mask reduces the random byte in the 0-255 value
// range to the 0-63 value range. Therefore, adding hacks, such
// as empty string fallback or magic numbers, is unneccessary because
// the bitmask trims bytes down to the alphabet size.
id += ALPHABET_BASE64_URL[pool[i] & 63];
}
return id;
}