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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 } | |