index.cjs 1.4 KB

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  1. let crypto = require('crypto')
  2. let { urlAlphabet } = require('./url-alphabet/index.cjs')
  3. const POOL_SIZE_MULTIPLIER = 128
  4. let pool, poolOffset
  5. let fillPool = bytes => {
  6. if (bytes < 0 || bytes > 1024) throw new RangeError('Wrong ID size')
  7. if (!pool || pool.length < bytes) {
  8. pool = Buffer.allocUnsafe(bytes * POOL_SIZE_MULTIPLIER)
  9. crypto.randomFillSync(pool)
  10. poolOffset = 0
  11. } else if (poolOffset + bytes > pool.length) {
  12. crypto.randomFillSync(pool)
  13. poolOffset = 0
  14. }
  15. poolOffset += bytes
  16. }
  17. let random = bytes => {
  18. fillPool((bytes |= 0))
  19. return pool.subarray(poolOffset - bytes, poolOffset)
  20. }
  21. let customRandom = (alphabet, defaultSize, getRandom) => {
  22. let mask = (2 << (31 - Math.clz32((alphabet.length - 1) | 1))) - 1
  23. let step = Math.ceil((1.6 * mask * defaultSize) / alphabet.length)
  24. return (size = defaultSize) => {
  25. if (size <= 0) return ''
  26. let id = ''
  27. while (true) {
  28. let bytes = getRandom(step)
  29. let i = step
  30. while (i--) {
  31. id += alphabet[bytes[i] & mask] || ''
  32. if (id.length === size) return id
  33. }
  34. }
  35. }
  36. }
  37. let customAlphabet = (alphabet, size = 21) =>
  38. customRandom(alphabet, size, random)
  39. let nanoid = (size = 21) => {
  40. fillPool((size |= 0))
  41. let id = ''
  42. for (let i = poolOffset - size; i < poolOffset; i++) {
  43. id += urlAlphabet[pool[i] & 63]
  44. }
  45. return id
  46. }
  47. module.exports = { nanoid, customAlphabet, customRandom, urlAlphabet, random }