io3fix/src/utils/array/decode-to-string.js

toolkit for interior apps

import runtime from '../../core/runtime.js'

// decodes Uint8Array to String

// TODO: use StringDecoder in Node environment

// from https://github.com/mrdoob/three.js/blob/master/examples/js/loaders/GLTFLoader.js
function decodeArrayToStringUtf8 (a) {
  // FIXME: give this some more testing (i.e. inside gblock component)
  // Avoid the String.fromCharCode.apply(null, array) shortcut, which
  // throws a "maximum call stack size exceeded" error for large arrays.
  for (var i = 0, l = a.length, s = ''; i < l; i++) s += String.fromCharCode(a[i])
  return s
}

function decodeArrayToStringUtf16 (a) {
  var
    s = '',
    // ignore any initial character other than '{' = 123 and '[' = 91 (>> bug #9818)
    i = a[0] === 123 || a[1] === 91 ? 0 : 1,
    l20 = a.length - 20,
    l2 = a.length
  // passing 20 arguments into fromCharCode function provides fastest performance
  // (based on practical performance testing)
  for (; i < l20; i += 20) {
    s += String.fromCharCode(
      a[i], a[i + 1], a[i + 2], a[i + 3], a[i + 4], a[i + 5], a[i + 6], a[i + 7], a[i + 8], a[i + 9],
      a[i + 10], a[i + 11], a[i + 12], a[i + 13], a[i + 14], a[i + 15], a[i + 16], a[i + 17], a[i + 18], a[i + 19]
    )
  }
  // the rest we do char by char
  for (; i < l2; i++) {
    s += String.fromCharCode(a[i])
  }
  return s
}

var decodeArrayToStringShims = {
  // UTF-8
  'utf-8': decodeArrayToStringUtf8,
  'UTF-8': decodeArrayToStringUtf8,
  // UTF-16
  'utf-16': decodeArrayToStringUtf16,
  'UTF-16': decodeArrayToStringUtf16
}

function makeArrayToStringDecoder (enc) {

  // use native decoder when available
  if (runtime.isBrowser && window.TextDecoder) {
    var textDecoderUtf16 = new window.TextDecoder(enc)
    return textDecoderUtf16.decode.bind(textDecoderUtf16)

  } else {
    // use shim
    return decodeArrayToStringShims[enc]
  }

}

// API

var decodeTextArray = {

  utf8: makeArrayToStringDecoder('utf-8'),
  utf16: makeArrayToStringDecoder('utf-16')

}

// expose API

export default decodeTextArray