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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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