BigNumber.js vs Long for UInt64 serialization

benchmark.js

const Benchmark = require('benchmark')
const BigNumber = require('bignumber.js').BigNumber
const Long = require('long')

const ITERATIONS_PER_CALL = 1000

const TEST_DATA_STRINGS = new Array(ITERATIONS_PER_CALL).fill(null).map((v, i) => String(i))
const TEST_DATA_BUFFERS = TEST_DATA_STRINGS.map(str => Buffer.from(new BigNumber(str).toString(16).padStart(16, '0'), 'hex'))

const HIGH_WORD_MULTIPLIER = 0x100000000

const target = new Buffer(8)

const suite = new Benchmark.Suite()
suite
  .add('Long serialize', function () {
    for (let i = 0; i < ITERATIONS_PER_CALL; i++) {
      const amount = Long.fromString(TEST_DATA_STRINGS[i], true)
      target.writeUInt32BE(amount.getHighBitsUnsigned())
      target.writeUInt32BE(amount.getLowBitsUnsigned(), 4)
    }
  })
  .add('Bignumber.js serialize', function () {
    for (let i = 0; i < ITERATIONS_PER_CALL; i++) {
      const uint64 = new BigNumber(TEST_DATA_STRINGS[i])
      target.writeUInt32BE(uint64.dividedToIntegerBy(HIGH_WORD_MULTIPLIER).toNumber())
      target.writeUInt32BE(uint64.modulo(HIGH_WORD_MULTIPLIER).toNumber(), 4)
    }
  })
  .add('Long deserialize', function () {
    for (let i = 0; i < ITERATIONS_PER_CALL; i++) {
      const highBits = TEST_DATA_BUFFERS[i].readUInt32BE()
      const lowBits = TEST_DATA_BUFFERS[i].readUInt32BE(4)
      Long.fromBits(+lowBits, +highBits, true).toString()
    }
  })
  .add('Bignumber.js deserialize', function () {
    for (let i = 0; i < ITERATIONS_PER_CALL; i++) {
      const highBits = TEST_DATA_BUFFERS[i].readUInt32BE()
      const lowBits = TEST_DATA_BUFFERS[i].readUInt32BE(4)
      const uint64 = new BigNumber(highBits).times(HIGH_WORD_MULTIPLIER).plus(lowBits)
      uint64.toString(10)
    }
  })
  .on('cycle', function(event) {
    console.log(String(event.target))
  })
  .on('complete', function() {
    console.log('Fastest is ' + this.filter('fastest').map('name'));
  })
  .on('error', function (err) {
    console.log('Error:', err)
  })
  .run({ async: true })

Results on my machine:

Long x 5,546 ops/sec ±2.75% (84 runs sampled)
Bignumber.js x 165 ops/sec ±1.94% (74 runs sampled)
Fastest is Long

Results with deserialization:

Long serialize x 8,195 ops/sec ±3.41% (81 runs sampled)
Bignumber.js serialize x 136 ops/sec ±9.00% (63 runs sampled)
Long deserialize x 7,317 ops/sec ±2.83% (81 runs sampled)
Bignumber.js deserialize x 708 ops/sec ±1.95% (83 runs sampled)