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