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