rangoo94/easen-tools

// Retrieve available Crypto API implementation
const crypto = require('./getCryptoInstance')()

// Configuration
const bufferSize = require('../shared/bufferSize')

// Initialize buffer for random bytes
let buffer = new Uint8Array(bufferSize)
let bufferIndex = bufferSize

/**
 * Generate binary UUID v4,
 * using 'crypto' with browser-compatible API.
 *
 * @returns {int[]}
 */
module.exports = function generateBinaryUuid () {
  // When there is not enough random bytes available, rebuild buffer
  if (bufferIndex + 16 > bufferSize) {
    buffer = new Uint8Array(bufferSize)
    bufferIndex = 0
    crypto.getRandomValues(buffer)
  }

  // Build array of UUID v4 bytes
  const value = [
    buffer[bufferIndex],
    buffer[bufferIndex + 1],
    buffer[bufferIndex + 2],
    buffer[bufferIndex + 3],
    buffer[bufferIndex + 4],
    buffer[bufferIndex + 5],
    (buffer[bufferIndex + 6] & 0x0f) | 0x40,
    buffer[bufferIndex + 7],
    (buffer[bufferIndex + 8] & 0x3f) | 0x80,
    buffer[bufferIndex + 9],
    buffer[bufferIndex + 10],
    buffer[bufferIndex + 11],
    buffer[bufferIndex + 12],
    buffer[bufferIndex + 13],
    buffer[bufferIndex + 14],
    buffer[bufferIndex + 15]
  ]

  // Move buffer index to next position
  bufferIndex += 16

  return value
}