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let crypto = require('crypto') let { urlAlphabet } = require('./url-alphabet/index.cjs') const POOL_SIZE_MULTIPLIER = 128 let pool, poolOffset let fillPool = bytes => { if (!pool || pool.length < bytes) { pool = Buffer.allocUnsafe(bytes * POOL_SIZE_MULTIPLIER) crypto.randomFillSync(pool) poolOffset = 0 } else if (poolOffset + bytes > pool.length) { crypto.randomFillSync(pool) poolOffset = 0 } poolOffset += bytes } let random = bytes => { fillPool((bytes -= 0)) return pool.subarray(poolOffset - bytes, poolOffset) } let customRandom = (alphabet, defaultSize, getRandom) => { let mask = (2 << (31 - Math.clz32((alphabet.length - 1) | 1))) - 1 let step = Math.ceil((1.6 * mask * defaultSize) / alphabet.length) return (size = defaultSize) => { let id = '' while (true) { let bytes = getRandom(step) let i = step while (i--) { id += alphabet[bytes[i] & mask] || '' if (id.length === size) return id } } } } let customAlphabet = (alphabet, size = 21) => customRandom(alphabet, size, random) let nanoid = (size = 21) => { fillPool((size -= 0)) let id = '' for (let i = poolOffset - size; i < poolOffset; i++) { id += urlAlphabet[pool[i] & 63] } return id } module.exports = { nanoid, customAlphabet, customRandom, urlAlphabet, random }
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