uint64.js

var v0 = 0 // represent the first 24bit of an uint64
var v1 = 0 // next 8bit
var v2 = 0 // final 32bit

function addUint64 (b0, b1, b2) {
  v0 = (v0 & 0xffffff) + b0 // cast to 24bit and add b0
  v1 = (v1 & 0xff) + b1 + (v0 >>> 24) // cast to 8bit, add b1 one plus the carry from v0
  v2 = (v2 + b2 + (v1 >>> 8)) | 0 // add b2 and carry from v1. cast to int to make v8 happy
}

function toUint32LEArray () {
  return new Uint32Array([(v1 << 24) | v0, v2])
}