text: import * as Expo from 'expo'
  import base64 from 'base64-js'
  
  export default function getTusFileReader (file, chunkSize, cb) {
    Expo.FileSystem.getInfoAsync(file.uri, { size: true }).then((info) => {
      cb(null, new TusFileReader(file, info.size))
    }).catch(cb)
  }
  
  class TusFileReader {
    constructor (file, size) {
      this.file = file
      this.size = size
    }
  
    slice (start, end, cb) {
      end = Math.min(end, this.size)
      const options = {
        encoding: Expo.FileSystem.EncodingTypes.Base64,
        length: end - start,
        postion: start
      }
      Expo.FileSystem.readAsStringAsync(this.file.uri, options).then((data) => {
        cb(null, base64.toByteArray(data))
      }).catch(cb)
    }
  
    close () {
  
    }
  }
  