var dz = require('dezalgo')

var cache = {}
function maybeSync(arg, cb) {
  cb = dz(cb)

  // this will actually defer to nextTick
  if (cache[arg]) cb(null, cache[arg])

  fs.readFile(arg, function (er, data) {
    // since this is *already* defered, it will call immediately
    if (er) cb(er)
    cb(null, cache[arg] = data)
  })
}