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44 lines
1.3 KiB
44 lines
1.3 KiB
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) |
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return pool.subarray(poolOffset - bytes, poolOffset) |
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} |
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let customRandom = (alphabet, size, 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 * size) / alphabet.length) |
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return () => { |
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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) => customRandom(alphabet, size, random) |
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let nanoid = (size = 21) => { |
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fillPool(size) |
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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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