1  /*!
   2   * The buffer module from node.js, for the browser.
   3   *
   4   * @author   Feross Aboukhadijeh <https://feross.org>
   5   * @license  MIT
   6   */
   7  /* eslint-disable no-proto */
   8  
   9  'use strict'
  10  
  11  var base64 = require('base64-js')
  12  var ieee754 = require('ieee754')
  13  var customInspectSymbol =
  14    (typeof Symbol === 'function' && typeof Symbol['for'] === 'function') // eslint-disable-line dot-notation
  15      ? Symbol['for']('nodejs.util.inspect.custom') // eslint-disable-line dot-notation
  16      : null
  17  
  18  exports.Buffer = Buffer
  19  exports.SlowBuffer = SlowBuffer
  20  exports.INSPECT_MAX_BYTES = 50
  21  
  22  var K_MAX_LENGTH = 0x7fffffff
  23  exports.kMaxLength = K_MAX_LENGTH
  24  
  25  /**
  26   * If `Buffer.TYPED_ARRAY_SUPPORT`:
  27   *   === true    Use Uint8Array implementation (fastest)
  28   *   === false   Print warning and recommend using `buffer` v4.x which has an Object
  29   *               implementation (most compatible, even IE6)
  30   *
  31   * Browsers that support typed arrays are IE 10+, Firefox 4+, Chrome 7+, Safari 5.1+,
  32   * Opera 11.6+, iOS 4.2+.
  33   *
  34   * We report that the browser does not support typed arrays if the are not subclassable
  35   * using __proto__. Firefox 4-29 lacks support for adding new properties to `Uint8Array`
  36   * (See: https://bugzilla.mozilla.org/show_bug.cgi?id=695438). IE 10 lacks support
  37   * for __proto__ and has a buggy typed array implementation.
  38   */
  39  Buffer.TYPED_ARRAY_SUPPORT = typedArraySupport()
  40  
  41  if (!Buffer.TYPED_ARRAY_SUPPORT && typeof console !== 'undefined' &&
  42      typeof console.error === 'function') {
  43    console.error(
  44      'This browser lacks typed array (Uint8Array) support which is required by ' +
  45      '`buffer` v5.x. Use `buffer` v4.x if you require old browser support.'
  46    )
  47  }
  48  
  49  function typedArraySupport () {
  50    // Can typed array instances can be augmented?
  51    try {
  52      var arr = new Uint8Array(1)
  53      var proto = { foo: function () { return 42 } }
  54      Object.setPrototypeOf(proto, Uint8Array.prototype)
  55      Object.setPrototypeOf(arr, proto)
  56      return arr.foo() === 42
  57    } catch (e) {
  58      return false
  59    }
  60  }
  61  
  62  Object.defineProperty(Buffer.prototype, 'parent', {
  63    enumerable: true,
  64    get: function () {
  65      if (!Buffer.isBuffer(this)) return undefined
  66      return this.buffer
  67    }
  68  })
  69  
  70  Object.defineProperty(Buffer.prototype, 'offset', {
  71    enumerable: true,
  72    get: function () {
  73      if (!Buffer.isBuffer(this)) return undefined
  74      return this.byteOffset
  75    }
  76  })
  77  
  78  function createBuffer (length) {
  79    if (length > K_MAX_LENGTH) {
  80      throw new RangeError('The value "' + length + '" is invalid for option "size"')
  81    }
  82    // Return an augmented `Uint8Array` instance
  83    var buf = new Uint8Array(length)
  84    Object.setPrototypeOf(buf, Buffer.prototype)
  85    return buf
  86  }
  87  
  88  /**
  89   * The Buffer constructor returns instances of `Uint8Array` that have their
  90   * prototype changed to `Buffer.prototype`. Furthermore, `Buffer` is a subclass of
  91   * `Uint8Array`, so the returned instances will have all the node `Buffer` methods
  92   * and the `Uint8Array` methods. Square bracket notation works as expected -- it
  93   * returns a single octet.
  94   *
  95   * The `Uint8Array` prototype remains unmodified.
  96   */
  97  
  98  function Buffer (arg, encodingOrOffset, length) {
  99    // Common case.
 100    if (typeof arg === 'number') {
 101      if (typeof encodingOrOffset === 'string') {
 102        throw new TypeError(
 103          'The "string" argument must be of type string. Received type number'
 104        )
 105      }
 106      return allocUnsafe(arg)
 107    }
 108    return from(arg, encodingOrOffset, length)
 109  }
 110  
 111  Buffer.poolSize = 8192 // not used by this implementation
 112  
 113  function from (value, encodingOrOffset, length) {
 114    if (typeof value === 'string') {
 115      return fromString(value, encodingOrOffset)
 116    }
 117  
 118    if (ArrayBuffer.isView(value)) {
 119      return fromArrayView(value)
 120    }
 121  
 122    if (value == null) {
 123      throw new TypeError(
 124        'The first argument must be one of type string, Buffer, ArrayBuffer, Array, ' +
 125        'or Array-like Object. Received type ' + (typeof value)
 126      )
 127    }
 128  
 129    if (isInstance(value, ArrayBuffer) ||
 130        (value && isInstance(value.buffer, ArrayBuffer))) {
 131      return fromArrayBuffer(value, encodingOrOffset, length)
 132    }
 133  
 134    if (typeof SharedArrayBuffer !== 'undefined' &&
 135        (isInstance(value, SharedArrayBuffer) ||
 136        (value && isInstance(value.buffer, SharedArrayBuffer)))) {
 137      return fromArrayBuffer(value, encodingOrOffset, length)
 138    }
 139  
 140    if (typeof value === 'number') {
 141      throw new TypeError(
 142        'The "value" argument must not be of type number. Received type number'
 143      )
 144    }
 145  
 146    var valueOf = value.valueOf && value.valueOf()
 147    if (valueOf != null && valueOf !== value) {
 148      return Buffer.from(valueOf, encodingOrOffset, length)
 149    }
 150  
 151    var b = fromObject(value)
 152    if (b) return b
 153  
 154    if (typeof Symbol !== 'undefined' && Symbol.toPrimitive != null &&
 155        typeof value[Symbol.toPrimitive] === 'function') {
 156      return Buffer.from(
 157        value[Symbol.toPrimitive]('string'), encodingOrOffset, length
 158      )
 159    }
 160  
 161    throw new TypeError(
 162      'The first argument must be one of type string, Buffer, ArrayBuffer, Array, ' +
 163      'or Array-like Object. Received type ' + (typeof value)
 164    )
 165  }
 166  
 167  /**
 168   * Functionally equivalent to Buffer(arg, encoding) but throws a TypeError
 169   * if value is a number.
 170   * Buffer.from(str[, encoding])
 171   * Buffer.from(array)
 172   * Buffer.from(buffer)
 173   * Buffer.from(arrayBuffer[, byteOffset[, length]])
 174   **/
 175  Buffer.from = function (value, encodingOrOffset, length) {
 176    return from(value, encodingOrOffset, length)
 177  }
 178  
 179  // Note: Change prototype *after* Buffer.from is defined to workaround Chrome bug:
 180  // https://github.com/feross/buffer/pull/148
 181  Object.setPrototypeOf(Buffer.prototype, Uint8Array.prototype)
 182  Object.setPrototypeOf(Buffer, Uint8Array)
 183  
 184  function assertSize (size) {
 185    if (typeof size !== 'number') {
 186      throw new TypeError('"size" argument must be of type number')
 187    } else if (size < 0) {
 188      throw new RangeError('The value "' + size + '" is invalid for option "size"')
 189    }
 190  }
 191  
 192  function alloc (size, fill, encoding) {
 193    assertSize(size)
 194    if (size <= 0) {
 195      return createBuffer(size)
 196    }
 197    if (fill !== undefined) {
 198      // Only pay attention to encoding if it's a string. This
 199      // prevents accidentally sending in a number that would
 200      // be interpreted as a start offset.
 201      return typeof encoding === 'string'
 202        ? createBuffer(size).fill(fill, encoding)
 203        : createBuffer(size).fill(fill)
 204    }
 205    return createBuffer(size)
 206  }
 207  
 208  /**
 209   * Creates a new filled Buffer instance.
 210   * alloc(size[, fill[, encoding]])
 211   **/
 212  Buffer.alloc = function (size, fill, encoding) {
 213    return alloc(size, fill, encoding)
 214  }
 215  
 216  function allocUnsafe (size) {
 217    assertSize(size)
 218    return createBuffer(size < 0 ? 0 : checked(size) | 0)
 219  }
 220  
 221  /**
 222   * Equivalent to Buffer(num), by default creates a non-zero-filled Buffer instance.
 223   * */
 224  Buffer.allocUnsafe = function (size) {
 225    return allocUnsafe(size)
 226  }
 227  /**
 228   * Equivalent to SlowBuffer(num), by default creates a non-zero-filled Buffer instance.
 229   */
 230  Buffer.allocUnsafeSlow = function (size) {
 231    return allocUnsafe(size)
 232  }
 233  
 234  function fromString (string, encoding) {
 235    if (typeof encoding !== 'string' || encoding === '') {
 236      encoding = 'utf8'
 237    }
 238  
 239    if (!Buffer.isEncoding(encoding)) {
 240      throw new TypeError('Unknown encoding: ' + encoding)
 241    }
 242  
 243    var length = byteLength(string, encoding) | 0
 244    var buf = createBuffer(length)
 245  
 246    var actual = buf.write(string, encoding)
 247  
 248    if (actual !== length) {
 249      // Writing a hex string, for example, that contains invalid characters will
 250      // cause everything after the first invalid character to be ignored. (e.g.
 251      // 'abxxcd' will be treated as 'ab')
 252      buf = buf.slice(0, actual)
 253    }
 254  
 255    return buf
 256  }
 257  
 258  function fromArrayLike (array) {
 259    var length = array.length < 0 ? 0 : checked(array.length) | 0
 260    var buf = createBuffer(length)
 261    for (var i = 0; i < length; i += 1) {
 262      buf[i] = array[i] & 255
 263    }
 264    return buf
 265  }
 266  
 267  function fromArrayView (arrayView) {
 268    if (isInstance(arrayView, Uint8Array)) {
 269      var copy = new Uint8Array(arrayView)
 270      return fromArrayBuffer(copy.buffer, copy.byteOffset, copy.byteLength)
 271    }
 272    return fromArrayLike(arrayView)
 273  }
 274  
 275  function fromArrayBuffer (array, byteOffset, length) {
 276    if (byteOffset < 0 || array.byteLength < byteOffset) {
 277      throw new RangeError('"offset" is outside of buffer bounds')
 278    }
 279  
 280    if (array.byteLength < byteOffset + (length || 0)) {
 281      throw new RangeError('"length" is outside of buffer bounds')
 282    }
 283  
 284    var buf
 285    if (byteOffset === undefined && length === undefined) {
 286      buf = new Uint8Array(array)
 287    } else if (length === undefined) {
 288      buf = new Uint8Array(array, byteOffset)
 289    } else {
 290      buf = new Uint8Array(array, byteOffset, length)
 291    }
 292  
 293    // Return an augmented `Uint8Array` instance
 294    Object.setPrototypeOf(buf, Buffer.prototype)
 295  
 296    return buf
 297  }
 298  
 299  function fromObject (obj) {
 300    if (Buffer.isBuffer(obj)) {
 301      var len = checked(obj.length) | 0
 302      var buf = createBuffer(len)
 303  
 304      if (buf.length === 0) {
 305        return buf
 306      }
 307  
 308      obj.copy(buf, 0, 0, len)
 309      return buf
 310    }
 311  
 312    if (obj.length !== undefined) {
 313      if (typeof obj.length !== 'number' || numberIsNaN(obj.length)) {
 314        return createBuffer(0)
 315      }
 316      return fromArrayLike(obj)
 317    }
 318  
 319    if (obj.type === 'Buffer' && Array.isArray(obj.data)) {
 320      return fromArrayLike(obj.data)
 321    }
 322  }
 323  
 324  function checked (length) {
 325    // Note: cannot use `length < K_MAX_LENGTH` here because that fails when
 326    // length is NaN (which is otherwise coerced to zero.)
 327    if (length >= K_MAX_LENGTH) {
 328      throw new RangeError('Attempt to allocate Buffer larger than maximum ' +
 329                           'size: 0x' + K_MAX_LENGTH.toString(16) + ' bytes')
 330    }
 331    return length | 0
 332  }
 333  
 334  function SlowBuffer (length) {
 335    if (+length != length) { // eslint-disable-line eqeqeq
 336      length = 0
 337    }
 338    return Buffer.alloc(+length)
 339  }
 340  
 341  Buffer.isBuffer = function isBuffer (b) {
 342    return b != null && b._isBuffer === true &&
 343      b !== Buffer.prototype // so Buffer.isBuffer(Buffer.prototype) will be false
 344  }
 345  
 346  Buffer.compare = function compare (a, b) {
 347    if (isInstance(a, Uint8Array)) a = Buffer.from(a, a.offset, a.byteLength)
 348    if (isInstance(b, Uint8Array)) b = Buffer.from(b, b.offset, b.byteLength)
 349    if (!Buffer.isBuffer(a) || !Buffer.isBuffer(b)) {
 350      throw new TypeError(
 351        'The "buf1", "buf2" arguments must be one of type Buffer or Uint8Array'
 352      )
 353    }
 354  
 355    if (a === b) return 0
 356  
 357    var x = a.length
 358    var y = b.length
 359  
 360    for (var i = 0, len = Math.min(x, y); i < len; ++i) {
 361      if (a[i] !== b[i]) {
 362        x = a[i]
 363        y = b[i]
 364        break
 365      }
 366    }
 367  
 368    if (x < y) return -1
 369    if (y < x) return 1
 370    return 0
 371  }
 372  
 373  Buffer.isEncoding = function isEncoding (encoding) {
 374    switch (String(encoding).toLowerCase()) {
 375      case 'hex':
 376      case 'utf8':
 377      case 'utf-8':
 378      case 'ascii':
 379      case 'latin1':
 380      case 'binary':
 381      case 'base64':
 382      case 'ucs2':
 383      case 'ucs-2':
 384      case 'utf16le':
 385      case 'utf-16le':
 386        return true
 387      default:
 388        return false
 389    }
 390  }
 391  
 392  Buffer.concat = function concat (list, length) {
 393    if (!Array.isArray(list)) {
 394      throw new TypeError('"list" argument must be an Array of Buffers')
 395    }
 396  
 397    if (list.length === 0) {
 398      return Buffer.alloc(0)
 399    }
 400  
 401    var i
 402    if (length === undefined) {
 403      length = 0
 404      for (i = 0; i < list.length; ++i) {
 405        length += list[i].length
 406      }
 407    }
 408  
 409    var buffer = Buffer.allocUnsafe(length)
 410    var pos = 0
 411    for (i = 0; i < list.length; ++i) {
 412      var buf = list[i]
 413      if (isInstance(buf, Uint8Array)) {
 414        if (pos + buf.length > buffer.length) {
 415          Buffer.from(buf).copy(buffer, pos)
 416        } else {
 417          Uint8Array.prototype.set.call(
 418            buffer,
 419            buf,
 420            pos
 421          )
 422        }
 423      } else if (!Buffer.isBuffer(buf)) {
 424        throw new TypeError('"list" argument must be an Array of Buffers')
 425      } else {
 426        buf.copy(buffer, pos)
 427      }
 428      pos += buf.length
 429    }
 430    return buffer
 431  }
 432  
 433  function byteLength (string, encoding) {
 434    if (Buffer.isBuffer(string)) {
 435      return string.length
 436    }
 437    if (ArrayBuffer.isView(string) || isInstance(string, ArrayBuffer)) {
 438      return string.byteLength
 439    }
 440    if (typeof string !== 'string') {
 441      throw new TypeError(
 442        'The "string" argument must be one of type string, Buffer, or ArrayBuffer. ' +
 443        'Received type ' + typeof string
 444      )
 445    }
 446  
 447    var len = string.length
 448    var mustMatch = (arguments.length > 2 && arguments[2] === true)
 449    if (!mustMatch && len === 0) return 0
 450  
 451    // Use a for loop to avoid recursion
 452    var loweredCase = false
 453    for (;;) {
 454      switch (encoding) {
 455        case 'ascii':
 456        case 'latin1':
 457        case 'binary':
 458          return len
 459        case 'utf8':
 460        case 'utf-8':
 461          return utf8ToBytes(string).length
 462        case 'ucs2':
 463        case 'ucs-2':
 464        case 'utf16le':
 465        case 'utf-16le':
 466          return len * 2
 467        case 'hex':
 468          return len >>> 1
 469        case 'base64':
 470          return base64ToBytes(string).length
 471        default:
 472          if (loweredCase) {
 473            return mustMatch ? -1 : utf8ToBytes(string).length // assume utf8
 474          }
 475          encoding = ('' + encoding).toLowerCase()
 476          loweredCase = true
 477      }
 478    }
 479  }
 480  Buffer.byteLength = byteLength
 481  
 482  function slowToString (encoding, start, end) {
 483    var loweredCase = false
 484  
 485    // No need to verify that "this.length <= MAX_UINT32" since it's a read-only
 486    // property of a typed array.
 487  
 488    // This behaves neither like String nor Uint8Array in that we set start/end
 489    // to their upper/lower bounds if the value passed is out of range.
 490    // undefined is handled specially as per ECMA-262 6th Edition,
 491    // Section 13.3.3.7 Runtime Semantics: KeyedBindingInitialization.
 492    if (start === undefined || start < 0) {
 493      start = 0
 494    }
 495    // Return early if start > this.length. Done here to prevent potential uint32
 496    // coercion fail below.
 497    if (start > this.length) {
 498      return ''
 499    }
 500  
 501    if (end === undefined || end > this.length) {
 502      end = this.length
 503    }
 504  
 505    if (end <= 0) {
 506      return ''
 507    }
 508  
 509    // Force coercion to uint32. This will also coerce falsey/NaN values to 0.
 510    end >>>= 0
 511    start >>>= 0
 512  
 513    if (end <= start) {
 514      return ''
 515    }
 516  
 517    if (!encoding) encoding = 'utf8'
 518  
 519    while (true) {
 520      switch (encoding) {
 521        case 'hex':
 522          return hexSlice(this, start, end)
 523  
 524        case 'utf8':
 525        case 'utf-8':
 526          return utf8Slice(this, start, end)
 527  
 528        case 'ascii':
 529          return asciiSlice(this, start, end)
 530  
 531        case 'latin1':
 532        case 'binary':
 533          return latin1Slice(this, start, end)
 534  
 535        case 'base64':
 536          return base64Slice(this, start, end)
 537  
 538        case 'ucs2':
 539        case 'ucs-2':
 540        case 'utf16le':
 541        case 'utf-16le':
 542          return utf16leSlice(this, start, end)
 543  
 544        default:
 545          if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
 546          encoding = (encoding + '').toLowerCase()
 547          loweredCase = true
 548      }
 549    }
 550  }
 551  
 552  // This property is used by `Buffer.isBuffer` (and the `is-buffer` npm package)
 553  // to detect a Buffer instance. It's not possible to use `instanceof Buffer`
 554  // reliably in a browserify context because there could be multiple different
 555  // copies of the 'buffer' package in use. This method works even for Buffer
 556  // instances that were created from another copy of the `buffer` package.
 557  // See: https://github.com/feross/buffer/issues/154
 558  Buffer.prototype._isBuffer = true
 559  
 560  function swap (b, n, m) {
 561    var i = b[n]
 562    b[n] = b[m]
 563    b[m] = i
 564  }
 565  
 566  Buffer.prototype.swap16 = function swap16 () {
 567    var len = this.length
 568    if (len % 2 !== 0) {
 569      throw new RangeError('Buffer size must be a multiple of 16-bits')
 570    }
 571    for (var i = 0; i < len; i += 2) {
 572      swap(this, i, i + 1)
 573    }
 574    return this
 575  }
 576  
 577  Buffer.prototype.swap32 = function swap32 () {
 578    var len = this.length
 579    if (len % 4 !== 0) {
 580      throw new RangeError('Buffer size must be a multiple of 32-bits')
 581    }
 582    for (var i = 0; i < len; i += 4) {
 583      swap(this, i, i + 3)
 584      swap(this, i + 1, i + 2)
 585    }
 586    return this
 587  }
 588  
 589  Buffer.prototype.swap64 = function swap64 () {
 590    var len = this.length
 591    if (len % 8 !== 0) {
 592      throw new RangeError('Buffer size must be a multiple of 64-bits')
 593    }
 594    for (var i = 0; i < len; i += 8) {
 595      swap(this, i, i + 7)
 596      swap(this, i + 1, i + 6)
 597      swap(this, i + 2, i + 5)
 598      swap(this, i + 3, i + 4)
 599    }
 600    return this
 601  }
 602  
 603  Buffer.prototype.toString = function toString () {
 604    var length = this.length
 605    if (length === 0) return ''
 606    if (arguments.length === 0) return utf8Slice(this, 0, length)
 607    return slowToString.apply(this, arguments)
 608  }
 609  
 610  Buffer.prototype.toLocaleString = Buffer.prototype.toString
 611  
 612  Buffer.prototype.equals = function equals (b) {
 613    if (!Buffer.isBuffer(b)) throw new TypeError('Argument must be a Buffer')
 614    if (this === b) return true
 615    return Buffer.compare(this, b) === 0
 616  }
 617  
 618  Buffer.prototype.inspect = function inspect () {
 619    var str = ''
 620    var max = exports.INSPECT_MAX_BYTES
 621    str = this.toString('hex', 0, max).replace(/(.{2})/g, '$1 ').trim()
 622    if (this.length > max) str += ' ... '
 623    return '<Buffer ' + str + '>'
 624  }
 625  if (customInspectSymbol) {
 626    Buffer.prototype[customInspectSymbol] = Buffer.prototype.inspect
 627  }
 628  
 629  Buffer.prototype.compare = function compare (target, start, end, thisStart, thisEnd) {
 630    if (isInstance(target, Uint8Array)) {
 631      target = Buffer.from(target, target.offset, target.byteLength)
 632    }
 633    if (!Buffer.isBuffer(target)) {
 634      throw new TypeError(
 635        'The "target" argument must be one of type Buffer or Uint8Array. ' +
 636        'Received type ' + (typeof target)
 637      )
 638    }
 639  
 640    if (start === undefined) {
 641      start = 0
 642    }
 643    if (end === undefined) {
 644      end = target ? target.length : 0
 645    }
 646    if (thisStart === undefined) {
 647      thisStart = 0
 648    }
 649    if (thisEnd === undefined) {
 650      thisEnd = this.length
 651    }
 652  
 653    if (start < 0 || end > target.length || thisStart < 0 || thisEnd > this.length) {
 654      throw new RangeError('out of range index')
 655    }
 656  
 657    if (thisStart >= thisEnd && start >= end) {
 658      return 0
 659    }
 660    if (thisStart >= thisEnd) {
 661      return -1
 662    }
 663    if (start >= end) {
 664      return 1
 665    }
 666  
 667    start >>>= 0
 668    end >>>= 0
 669    thisStart >>>= 0
 670    thisEnd >>>= 0
 671  
 672    if (this === target) return 0
 673  
 674    var x = thisEnd - thisStart
 675    var y = end - start
 676    var len = Math.min(x, y)
 677  
 678    var thisCopy = this.slice(thisStart, thisEnd)
 679    var targetCopy = target.slice(start, end)
 680  
 681    for (var i = 0; i < len; ++i) {
 682      if (thisCopy[i] !== targetCopy[i]) {
 683        x = thisCopy[i]
 684        y = targetCopy[i]
 685        break
 686      }
 687    }
 688  
 689    if (x < y) return -1
 690    if (y < x) return 1
 691    return 0
 692  }
 693  
 694  // Finds either the first index of `val` in `buffer` at offset >= `byteOffset`,
 695  // OR the last index of `val` in `buffer` at offset <= `byteOffset`.
 696  //
 697  // Arguments:
 698  // - buffer - a Buffer to search
 699  // - val - a string, Buffer, or number
 700  // - byteOffset - an index into `buffer`; will be clamped to an int32
 701  // - encoding - an optional encoding, relevant is val is a string
 702  // - dir - true for indexOf, false for lastIndexOf
 703  function bidirectionalIndexOf (buffer, val, byteOffset, encoding, dir) {
 704    // Empty buffer means no match
 705    if (buffer.length === 0) return -1
 706  
 707    // Normalize byteOffset
 708    if (typeof byteOffset === 'string') {
 709      encoding = byteOffset
 710      byteOffset = 0
 711    } else if (byteOffset > 0x7fffffff) {
 712      byteOffset = 0x7fffffff
 713    } else if (byteOffset < -0x80000000) {
 714      byteOffset = -0x80000000
 715    }
 716    byteOffset = +byteOffset // Coerce to Number.
 717    if (numberIsNaN(byteOffset)) {
 718      // byteOffset: it it's undefined, null, NaN, "foo", etc, search whole buffer
 719      byteOffset = dir ? 0 : (buffer.length - 1)
 720    }
 721  
 722    // Normalize byteOffset: negative offsets start from the end of the buffer
 723    if (byteOffset < 0) byteOffset = buffer.length + byteOffset
 724    if (byteOffset >= buffer.length) {
 725      if (dir) return -1
 726      else byteOffset = buffer.length - 1
 727    } else if (byteOffset < 0) {
 728      if (dir) byteOffset = 0
 729      else return -1
 730    }
 731  
 732    // Normalize val
 733    if (typeof val === 'string') {
 734      val = Buffer.from(val, encoding)
 735    }
 736  
 737    // Finally, search either indexOf (if dir is true) or lastIndexOf
 738    if (Buffer.isBuffer(val)) {
 739      // Special case: looking for empty string/buffer always fails
 740      if (val.length === 0) {
 741        return -1
 742      }
 743      return arrayIndexOf(buffer, val, byteOffset, encoding, dir)
 744    } else if (typeof val === 'number') {
 745      val = val & 0xFF // Search for a byte value [0-255]
 746      if (typeof Uint8Array.prototype.indexOf === 'function') {
 747        if (dir) {
 748          return Uint8Array.prototype.indexOf.call(buffer, val, byteOffset)
 749        } else {
 750          return Uint8Array.prototype.lastIndexOf.call(buffer, val, byteOffset)
 751        }
 752      }
 753      return arrayIndexOf(buffer, [val], byteOffset, encoding, dir)
 754    }
 755  
 756    throw new TypeError('val must be string, number or Buffer')
 757  }
 758  
 759  function arrayIndexOf (arr, val, byteOffset, encoding, dir) {
 760    var indexSize = 1
 761    var arrLength = arr.length
 762    var valLength = val.length
 763  
 764    if (encoding !== undefined) {
 765      encoding = String(encoding).toLowerCase()
 766      if (encoding === 'ucs2' || encoding === 'ucs-2' ||
 767          encoding === 'utf16le' || encoding === 'utf-16le') {
 768        if (arr.length < 2 || val.length < 2) {
 769          return -1
 770        }
 771        indexSize = 2
 772        arrLength /= 2
 773        valLength /= 2
 774        byteOffset /= 2
 775      }
 776    }
 777  
 778    function read (buf, i) {
 779      if (indexSize === 1) {
 780        return buf[i]
 781      } else {
 782        return buf.readUInt16BE(i * indexSize)
 783      }
 784    }
 785  
 786    var i
 787    if (dir) {
 788      var foundIndex = -1
 789      for (i = byteOffset; i < arrLength; i++) {
 790        if (read(arr, i) === read(val, foundIndex === -1 ? 0 : i - foundIndex)) {
 791          if (foundIndex === -1) foundIndex = i
 792          if (i - foundIndex + 1 === valLength) return foundIndex * indexSize
 793        } else {
 794          if (foundIndex !== -1) i -= i - foundIndex
 795          foundIndex = -1
 796        }
 797      }
 798    } else {
 799      if (byteOffset + valLength > arrLength) byteOffset = arrLength - valLength
 800      for (i = byteOffset; i >= 0; i--) {
 801        var found = true
 802        for (var j = 0; j < valLength; j++) {
 803          if (read(arr, i + j) !== read(val, j)) {
 804            found = false
 805            break
 806          }
 807        }
 808        if (found) return i
 809      }
 810    }
 811  
 812    return -1
 813  }
 814  
 815  Buffer.prototype.includes = function includes (val, byteOffset, encoding) {
 816    return this.indexOf(val, byteOffset, encoding) !== -1
 817  }
 818  
 819  Buffer.prototype.indexOf = function indexOf (val, byteOffset, encoding) {
 820    return bidirectionalIndexOf(this, val, byteOffset, encoding, true)
 821  }
 822  
 823  Buffer.prototype.lastIndexOf = function lastIndexOf (val, byteOffset, encoding) {
 824    return bidirectionalIndexOf(this, val, byteOffset, encoding, false)
 825  }
 826  
 827  function hexWrite (buf, string, offset, length) {
 828    offset = Number(offset) || 0
 829    var remaining = buf.length - offset
 830    if (!length) {
 831      length = remaining
 832    } else {
 833      length = Number(length)
 834      if (length > remaining) {
 835        length = remaining
 836      }
 837    }
 838  
 839    var strLen = string.length
 840  
 841    if (length > strLen / 2) {
 842      length = strLen / 2
 843    }
 844    for (var i = 0; i < length; ++i) {
 845      var parsed = parseInt(string.substr(i * 2, 2), 16)
 846      if (numberIsNaN(parsed)) return i
 847      buf[offset + i] = parsed
 848    }
 849    return i
 850  }
 851  
 852  function utf8Write (buf, string, offset, length) {
 853    return blitBuffer(utf8ToBytes(string, buf.length - offset), buf, offset, length)
 854  }
 855  
 856  function asciiWrite (buf, string, offset, length) {
 857    return blitBuffer(asciiToBytes(string), buf, offset, length)
 858  }
 859  
 860  function base64Write (buf, string, offset, length) {
 861    return blitBuffer(base64ToBytes(string), buf, offset, length)
 862  }
 863  
 864  function ucs2Write (buf, string, offset, length) {
 865    return blitBuffer(utf16leToBytes(string, buf.length - offset), buf, offset, length)
 866  }
 867  
 868  Buffer.prototype.write = function write (string, offset, length, encoding) {
 869    // Buffer#write(string)
 870    if (offset === undefined) {
 871      encoding = 'utf8'
 872      length = this.length
 873      offset = 0
 874    // Buffer#write(string, encoding)
 875    } else if (length === undefined && typeof offset === 'string') {
 876      encoding = offset
 877      length = this.length
 878      offset = 0
 879    // Buffer#write(string, offset[, length][, encoding])
 880    } else if (isFinite(offset)) {
 881      offset = offset >>> 0
 882      if (isFinite(length)) {
 883        length = length >>> 0
 884        if (encoding === undefined) encoding = 'utf8'
 885      } else {
 886        encoding = length
 887        length = undefined
 888      }
 889    } else {
 890      throw new Error(
 891        'Buffer.write(string, encoding, offset[, length]) is no longer supported'
 892      )
 893    }
 894  
 895    var remaining = this.length - offset
 896    if (length === undefined || length > remaining) length = remaining
 897  
 898    if ((string.length > 0 && (length < 0 || offset < 0)) || offset > this.length) {
 899      throw new RangeError('Attempt to write outside buffer bounds')
 900    }
 901  
 902    if (!encoding) encoding = 'utf8'
 903  
 904    var loweredCase = false
 905    for (;;) {
 906      switch (encoding) {
 907        case 'hex':
 908          return hexWrite(this, string, offset, length)
 909  
 910        case 'utf8':
 911        case 'utf-8':
 912          return utf8Write(this, string, offset, length)
 913  
 914        case 'ascii':
 915        case 'latin1':
 916        case 'binary':
 917          return asciiWrite(this, string, offset, length)
 918  
 919        case 'base64':
 920          // Warning: maxLength not taken into account in base64Write
 921          return base64Write(this, string, offset, length)
 922  
 923        case 'ucs2':
 924        case 'ucs-2':
 925        case 'utf16le':
 926        case 'utf-16le':
 927          return ucs2Write(this, string, offset, length)
 928  
 929        default:
 930          if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
 931          encoding = ('' + encoding).toLowerCase()
 932          loweredCase = true
 933      }
 934    }
 935  }
 936  
 937  Buffer.prototype.toJSON = function toJSON () {
 938    return {
 939      type: 'Buffer',
 940      data: Array.prototype.slice.call(this._arr || this, 0)
 941    }
 942  }
 943  
 944  function base64Slice (buf, start, end) {
 945    if (start === 0 && end === buf.length) {
 946      return base64.fromByteArray(buf)
 947    } else {
 948      return base64.fromByteArray(buf.slice(start, end))
 949    }
 950  }
 951  
 952  function utf8Slice (buf, start, end) {
 953    end = Math.min(buf.length, end)
 954    var res = []
 955  
 956    var i = start
 957    while (i < end) {
 958      var firstByte = buf[i]
 959      var codePoint = null
 960      var bytesPerSequence = (firstByte > 0xEF)
 961        ? 4
 962        : (firstByte > 0xDF)
 963            ? 3
 964            : (firstByte > 0xBF)
 965                ? 2
 966                : 1
 967  
 968      if (i + bytesPerSequence <= end) {
 969        var secondByte, thirdByte, fourthByte, tempCodePoint
 970  
 971        switch (bytesPerSequence) {
 972          case 1:
 973            if (firstByte < 0x80) {
 974              codePoint = firstByte
 975            }
 976            break
 977          case 2:
 978            secondByte = buf[i + 1]
 979            if ((secondByte & 0xC0) === 0x80) {
 980              tempCodePoint = (firstByte & 0x1F) << 0x6 | (secondByte & 0x3F)
 981              if (tempCodePoint > 0x7F) {
 982                codePoint = tempCodePoint
 983              }
 984            }
 985            break
 986          case 3:
 987            secondByte = buf[i + 1]
 988            thirdByte = buf[i + 2]
 989            if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80) {
 990              tempCodePoint = (firstByte & 0xF) << 0xC | (secondByte & 0x3F) << 0x6 | (thirdByte & 0x3F)
 991              if (tempCodePoint > 0x7FF && (tempCodePoint < 0xD800 || tempCodePoint > 0xDFFF)) {
 992                codePoint = tempCodePoint
 993              }
 994            }
 995            break
 996          case 4:
 997            secondByte = buf[i + 1]
 998            thirdByte = buf[i + 2]
 999            fourthByte = buf[i + 3]
1000            if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80 && (fourthByte & 0xC0) === 0x80) {
1001              tempCodePoint = (firstByte & 0xF) << 0x12 | (secondByte & 0x3F) << 0xC | (thirdByte & 0x3F) << 0x6 | (fourthByte & 0x3F)
1002              if (tempCodePoint > 0xFFFF && tempCodePoint < 0x110000) {
1003                codePoint = tempCodePoint
1004              }
1005            }
1006        }
1007      }
1008  
1009      if (codePoint === null) {
1010        // we did not generate a valid codePoint so insert a
1011        // replacement char (U+FFFD) and advance only 1 byte
1012        codePoint = 0xFFFD
1013        bytesPerSequence = 1
1014      } else if (codePoint > 0xFFFF) {
1015        // encode to utf16 (surrogate pair dance)
1016        codePoint -= 0x10000
1017        res.push(codePoint >>> 10 & 0x3FF | 0xD800)
1018        codePoint = 0xDC00 | codePoint & 0x3FF
1019      }
1020  
1021      res.push(codePoint)
1022      i += bytesPerSequence
1023    }
1024  
1025    return decodeCodePointsArray(res)
1026  }
1027  
1028  // Based on http://stackoverflow.com/a/22747272/680742, the browser with
1029  // the lowest limit is Chrome, with 0x10000 args.
1030  // We go 1 magnitude less, for safety
1031  var MAX_ARGUMENTS_LENGTH = 0x1000
1032  
1033  function decodeCodePointsArray (codePoints) {
1034    var len = codePoints.length
1035    if (len <= MAX_ARGUMENTS_LENGTH) {
1036      return String.fromCharCode.apply(String, codePoints) // avoid extra slice()
1037    }
1038  
1039    // Decode in chunks to avoid "call stack size exceeded".
1040    var res = ''
1041    var i = 0
1042    while (i < len) {
1043      res += String.fromCharCode.apply(
1044        String,
1045        codePoints.slice(i, i += MAX_ARGUMENTS_LENGTH)
1046      )
1047    }
1048    return res
1049  }
1050  
1051  function asciiSlice (buf, start, end) {
1052    var ret = ''
1053    end = Math.min(buf.length, end)
1054  
1055    for (var i = start; i < end; ++i) {
1056      ret += String.fromCharCode(buf[i] & 0x7F)
1057    }
1058    return ret
1059  }
1060  
1061  function latin1Slice (buf, start, end) {
1062    var ret = ''
1063    end = Math.min(buf.length, end)
1064  
1065    for (var i = start; i < end; ++i) {
1066      ret += String.fromCharCode(buf[i])
1067    }
1068    return ret
1069  }
1070  
1071  function hexSlice (buf, start, end) {
1072    var len = buf.length
1073  
1074    if (!start || start < 0) start = 0
1075    if (!end || end < 0 || end > len) end = len
1076  
1077    var out = ''
1078    for (var i = start; i < end; ++i) {
1079      out += hexSliceLookupTable[buf[i]]
1080    }
1081    return out
1082  }
1083  
1084  function utf16leSlice (buf, start, end) {
1085    var bytes = buf.slice(start, end)
1086    var res = ''
1087    // If bytes.length is odd, the last 8 bits must be ignored (same as node.js)
1088    for (var i = 0; i < bytes.length - 1; i += 2) {
1089      res += String.fromCharCode(bytes[i] + (bytes[i + 1] * 256))
1090    }
1091    return res
1092  }
1093  
1094  Buffer.prototype.slice = function slice (start, end) {
1095    var len = this.length
1096    start = ~~start
1097    end = end === undefined ? len : ~~end
1098  
1099    if (start < 0) {
1100      start += len
1101      if (start < 0) start = 0
1102    } else if (start > len) {
1103      start = len
1104    }
1105  
1106    if (end < 0) {
1107      end += len
1108      if (end < 0) end = 0
1109    } else if (end > len) {
1110      end = len
1111    }
1112  
1113    if (end < start) end = start
1114  
1115    var newBuf = this.subarray(start, end)
1116    // Return an augmented `Uint8Array` instance
1117    Object.setPrototypeOf(newBuf, Buffer.prototype)
1118  
1119    return newBuf
1120  }
1121  
1122  /*
1123   * Need to make sure that buffer isn't trying to write out of bounds.
1124   */
1125  function checkOffset (offset, ext, length) {
1126    if ((offset % 1) !== 0 || offset < 0) throw new RangeError('offset is not uint')
1127    if (offset + ext > length) throw new RangeError('Trying to access beyond buffer length')
1128  }
1129  
1130  Buffer.prototype.readUintLE =
1131  Buffer.prototype.readUIntLE = function readUIntLE (offset, byteLength, noAssert) {
1132    offset = offset >>> 0
1133    byteLength = byteLength >>> 0
1134    if (!noAssert) checkOffset(offset, byteLength, this.length)
1135  
1136    var val = this[offset]
1137    var mul = 1
1138    var i = 0
1139    while (++i < byteLength && (mul *= 0x100)) {
1140      val += this[offset + i] * mul
1141    }
1142  
1143    return val
1144  }
1145  
1146  Buffer.prototype.readUintBE =
1147  Buffer.prototype.readUIntBE = function readUIntBE (offset, byteLength, noAssert) {
1148    offset = offset >>> 0
1149    byteLength = byteLength >>> 0
1150    if (!noAssert) {
1151      checkOffset(offset, byteLength, this.length)
1152    }
1153  
1154    var val = this[offset + --byteLength]
1155    var mul = 1
1156    while (byteLength > 0 && (mul *= 0x100)) {
1157      val += this[offset + --byteLength] * mul
1158    }
1159  
1160    return val
1161  }
1162  
1163  Buffer.prototype.readUint8 =
1164  Buffer.prototype.readUInt8 = function readUInt8 (offset, noAssert) {
1165    offset = offset >>> 0
1166    if (!noAssert) checkOffset(offset, 1, this.length)
1167    return this[offset]
1168  }
1169  
1170  Buffer.prototype.readUint16LE =
1171  Buffer.prototype.readUInt16LE = function readUInt16LE (offset, noAssert) {
1172    offset = offset >>> 0
1173    if (!noAssert) checkOffset(offset, 2, this.length)
1174    return this[offset] | (this[offset + 1] << 8)
1175  }
1176  
1177  Buffer.prototype.readUint16BE =
1178  Buffer.prototype.readUInt16BE = function readUInt16BE (offset, noAssert) {
1179    offset = offset >>> 0
1180    if (!noAssert) checkOffset(offset, 2, this.length)
1181    return (this[offset] << 8) | this[offset + 1]
1182  }
1183  
1184  Buffer.prototype.readUint32LE =
1185  Buffer.prototype.readUInt32LE = function readUInt32LE (offset, noAssert) {
1186    offset = offset >>> 0
1187    if (!noAssert) checkOffset(offset, 4, this.length)
1188  
1189    return ((this[offset]) |
1190        (this[offset + 1] << 8) |
1191        (this[offset + 2] << 16)) +
1192        (this[offset + 3] * 0x1000000)
1193  }
1194  
1195  Buffer.prototype.readUint32BE =
1196  Buffer.prototype.readUInt32BE = function readUInt32BE (offset, noAssert) {
1197    offset = offset >>> 0
1198    if (!noAssert) checkOffset(offset, 4, this.length)
1199  
1200    return (this[offset] * 0x1000000) +
1201      ((this[offset + 1] << 16) |
1202      (this[offset + 2] << 8) |
1203      this[offset + 3])
1204  }
1205  
1206  Buffer.prototype.readIntLE = function readIntLE (offset, byteLength, noAssert) {
1207    offset = offset >>> 0
1208    byteLength = byteLength >>> 0
1209    if (!noAssert) checkOffset(offset, byteLength, this.length)
1210  
1211    var val = this[offset]
1212    var mul = 1
1213    var i = 0
1214    while (++i < byteLength && (mul *= 0x100)) {
1215      val += this[offset + i] * mul
1216    }
1217    mul *= 0x80
1218  
1219    if (val >= mul) val -= Math.pow(2, 8 * byteLength)
1220  
1221    return val
1222  }
1223  
1224  Buffer.prototype.readIntBE = function readIntBE (offset, byteLength, noAssert) {
1225    offset = offset >>> 0
1226    byteLength = byteLength >>> 0
1227    if (!noAssert) checkOffset(offset, byteLength, this.length)
1228  
1229    var i = byteLength
1230    var mul = 1
1231    var val = this[offset + --i]
1232    while (i > 0 && (mul *= 0x100)) {
1233      val += this[offset + --i] * mul
1234    }
1235    mul *= 0x80
1236  
1237    if (val >= mul) val -= Math.pow(2, 8 * byteLength)
1238  
1239    return val
1240  }
1241  
1242  Buffer.prototype.readInt8 = function readInt8 (offset, noAssert) {
1243    offset = offset >>> 0
1244    if (!noAssert) checkOffset(offset, 1, this.length)
1245    if (!(this[offset] & 0x80)) return (this[offset])
1246    return ((0xff - this[offset] + 1) * -1)
1247  }
1248  
1249  Buffer.prototype.readInt16LE = function readInt16LE (offset, noAssert) {
1250    offset = offset >>> 0
1251    if (!noAssert) checkOffset(offset, 2, this.length)
1252    var val = this[offset] | (this[offset + 1] << 8)
1253    return (val & 0x8000) ? val | 0xFFFF0000 : val
1254  }
1255  
1256  Buffer.prototype.readInt16BE = function readInt16BE (offset, noAssert) {
1257    offset = offset >>> 0
1258    if (!noAssert) checkOffset(offset, 2, this.length)
1259    var val = this[offset + 1] | (this[offset] << 8)
1260    return (val & 0x8000) ? val | 0xFFFF0000 : val
1261  }
1262  
1263  Buffer.prototype.readInt32LE = function readInt32LE (offset, noAssert) {
1264    offset = offset >>> 0
1265    if (!noAssert) checkOffset(offset, 4, this.length)
1266  
1267    return (this[offset]) |
1268      (this[offset + 1] << 8) |
1269      (this[offset + 2] << 16) |
1270      (this[offset + 3] << 24)
1271  }
1272  
1273  Buffer.prototype.readInt32BE = function readInt32BE (offset, noAssert) {
1274    offset = offset >>> 0
1275    if (!noAssert) checkOffset(offset, 4, this.length)
1276  
1277    return (this[offset] << 24) |
1278      (this[offset + 1] << 16) |
1279      (this[offset + 2] << 8) |
1280      (this[offset + 3])
1281  }
1282  
1283  Buffer.prototype.readFloatLE = function readFloatLE (offset, noAssert) {
1284    offset = offset >>> 0
1285    if (!noAssert) checkOffset(offset, 4, this.length)
1286    return ieee754.read(this, offset, true, 23, 4)
1287  }
1288  
1289  Buffer.prototype.readFloatBE = function readFloatBE (offset, noAssert) {
1290    offset = offset >>> 0
1291    if (!noAssert) checkOffset(offset, 4, this.length)
1292    return ieee754.read(this, offset, false, 23, 4)
1293  }
1294  
1295  Buffer.prototype.readDoubleLE = function readDoubleLE (offset, noAssert) {
1296    offset = offset >>> 0
1297    if (!noAssert) checkOffset(offset, 8, this.length)
1298    return ieee754.read(this, offset, true, 52, 8)
1299  }
1300  
1301  Buffer.prototype.readDoubleBE = function readDoubleBE (offset, noAssert) {
1302    offset = offset >>> 0
1303    if (!noAssert) checkOffset(offset, 8, this.length)
1304    return ieee754.read(this, offset, false, 52, 8)
1305  }
1306  
1307  function checkInt (buf, value, offset, ext, max, min) {
1308    if (!Buffer.isBuffer(buf)) throw new TypeError('"buffer" argument must be a Buffer instance')
1309    if (value > max || value < min) throw new RangeError('"value" argument is out of bounds')
1310    if (offset + ext > buf.length) throw new RangeError('Index out of range')
1311  }
1312  
1313  Buffer.prototype.writeUintLE =
1314  Buffer.prototype.writeUIntLE = function writeUIntLE (value, offset, byteLength, noAssert) {
1315    value = +value
1316    offset = offset >>> 0
1317    byteLength = byteLength >>> 0
1318    if (!noAssert) {
1319      var maxBytes = Math.pow(2, 8 * byteLength) - 1
1320      checkInt(this, value, offset, byteLength, maxBytes, 0)
1321    }
1322  
1323    var mul = 1
1324    var i = 0
1325    this[offset] = value & 0xFF
1326    while (++i < byteLength && (mul *= 0x100)) {
1327      this[offset + i] = (value / mul) & 0xFF
1328    }
1329  
1330    return offset + byteLength
1331  }
1332  
1333  Buffer.prototype.writeUintBE =
1334  Buffer.prototype.writeUIntBE = function writeUIntBE (value, offset, byteLength, noAssert) {
1335    value = +value
1336    offset = offset >>> 0
1337    byteLength = byteLength >>> 0
1338    if (!noAssert) {
1339      var maxBytes = Math.pow(2, 8 * byteLength) - 1
1340      checkInt(this, value, offset, byteLength, maxBytes, 0)
1341    }
1342  
1343    var i = byteLength - 1
1344    var mul = 1
1345    this[offset + i] = value & 0xFF
1346    while (--i >= 0 && (mul *= 0x100)) {
1347      this[offset + i] = (value / mul) & 0xFF
1348    }
1349  
1350    return offset + byteLength
1351  }
1352  
1353  Buffer.prototype.writeUint8 =
1354  Buffer.prototype.writeUInt8 = function writeUInt8 (value, offset, noAssert) {
1355    value = +value
1356    offset = offset >>> 0
1357    if (!noAssert) checkInt(this, value, offset, 1, 0xff, 0)
1358    this[offset] = (value & 0xff)
1359    return offset + 1
1360  }
1361  
1362  Buffer.prototype.writeUint16LE =
1363  Buffer.prototype.writeUInt16LE = function writeUInt16LE (value, offset, noAssert) {
1364    value = +value
1365    offset = offset >>> 0
1366    if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0)
1367    this[offset] = (value & 0xff)
1368    this[offset + 1] = (value >>> 8)
1369    return offset + 2
1370  }
1371  
1372  Buffer.prototype.writeUint16BE =
1373  Buffer.prototype.writeUInt16BE = function writeUInt16BE (value, offset, noAssert) {
1374    value = +value
1375    offset = offset >>> 0
1376    if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0)
1377    this[offset] = (value >>> 8)
1378    this[offset + 1] = (value & 0xff)
1379    return offset + 2
1380  }
1381  
1382  Buffer.prototype.writeUint32LE =
1383  Buffer.prototype.writeUInt32LE = function writeUInt32LE (value, offset, noAssert) {
1384    value = +value
1385    offset = offset >>> 0
1386    if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0)
1387    this[offset + 3] = (value >>> 24)
1388    this[offset + 2] = (value >>> 16)
1389    this[offset + 1] = (value >>> 8)
1390    this[offset] = (value & 0xff)
1391    return offset + 4
1392  }
1393  
1394  Buffer.prototype.writeUint32BE =
1395  Buffer.prototype.writeUInt32BE = function writeUInt32BE (value, offset, noAssert) {
1396    value = +value
1397    offset = offset >>> 0
1398    if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0)
1399    this[offset] = (value >>> 24)
1400    this[offset + 1] = (value >>> 16)
1401    this[offset + 2] = (value >>> 8)
1402    this[offset + 3] = (value & 0xff)
1403    return offset + 4
1404  }
1405  
1406  Buffer.prototype.writeIntLE = function writeIntLE (value, offset, byteLength, noAssert) {
1407    value = +value
1408    offset = offset >>> 0
1409    if (!noAssert) {
1410      var limit = Math.pow(2, (8 * byteLength) - 1)
1411  
1412      checkInt(this, value, offset, byteLength, limit - 1, -limit)
1413    }
1414  
1415    var i = 0
1416    var mul = 1
1417    var sub = 0
1418    this[offset] = value & 0xFF
1419    while (++i < byteLength && (mul *= 0x100)) {
1420      if (value < 0 && sub === 0 && this[offset + i - 1] !== 0) {
1421        sub = 1
1422      }
1423      this[offset + i] = ((value / mul) >> 0) - sub & 0xFF
1424    }
1425  
1426    return offset + byteLength
1427  }
1428  
1429  Buffer.prototype.writeIntBE = function writeIntBE (value, offset, byteLength, noAssert) {
1430    value = +value
1431    offset = offset >>> 0
1432    if (!noAssert) {
1433      var limit = Math.pow(2, (8 * byteLength) - 1)
1434  
1435      checkInt(this, value, offset, byteLength, limit - 1, -limit)
1436    }
1437  
1438    var i = byteLength - 1
1439    var mul = 1
1440    var sub = 0
1441    this[offset + i] = value & 0xFF
1442    while (--i >= 0 && (mul *= 0x100)) {
1443      if (value < 0 && sub === 0 && this[offset + i + 1] !== 0) {
1444        sub = 1
1445      }
1446      this[offset + i] = ((value / mul) >> 0) - sub & 0xFF
1447    }
1448  
1449    return offset + byteLength
1450  }
1451  
1452  Buffer.prototype.writeInt8 = function writeInt8 (value, offset, noAssert) {
1453    value = +value
1454    offset = offset >>> 0
1455    if (!noAssert) checkInt(this, value, offset, 1, 0x7f, -0x80)
1456    if (value < 0) value = 0xff + value + 1
1457    this[offset] = (value & 0xff)
1458    return offset + 1
1459  }
1460  
1461  Buffer.prototype.writeInt16LE = function writeInt16LE (value, offset, noAssert) {
1462    value = +value
1463    offset = offset >>> 0
1464    if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000)
1465    this[offset] = (value & 0xff)
1466    this[offset + 1] = (value >>> 8)
1467    return offset + 2
1468  }
1469  
1470  Buffer.prototype.writeInt16BE = function writeInt16BE (value, offset, noAssert) {
1471    value = +value
1472    offset = offset >>> 0
1473    if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000)
1474    this[offset] = (value >>> 8)
1475    this[offset + 1] = (value & 0xff)
1476    return offset + 2
1477  }
1478  
1479  Buffer.prototype.writeInt32LE = function writeInt32LE (value, offset, noAssert) {
1480    value = +value
1481    offset = offset >>> 0
1482    if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
1483    this[offset] = (value & 0xff)
1484    this[offset + 1] = (value >>> 8)
1485    this[offset + 2] = (value >>> 16)
1486    this[offset + 3] = (value >>> 24)
1487    return offset + 4
1488  }
1489  
1490  Buffer.prototype.writeInt32BE = function writeInt32BE (value, offset, noAssert) {
1491    value = +value
1492    offset = offset >>> 0
1493    if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
1494    if (value < 0) value = 0xffffffff + value + 1
1495    this[offset] = (value >>> 24)
1496    this[offset + 1] = (value >>> 16)
1497    this[offset + 2] = (value >>> 8)
1498    this[offset + 3] = (value & 0xff)
1499    return offset + 4
1500  }
1501  
1502  function checkIEEE754 (buf, value, offset, ext, max, min) {
1503    if (offset + ext > buf.length) throw new RangeError('Index out of range')
1504    if (offset < 0) throw new RangeError('Index out of range')
1505  }
1506  
1507  function writeFloat (buf, value, offset, littleEndian, noAssert) {
1508    value = +value
1509    offset = offset >>> 0
1510    if (!noAssert) {
1511      checkIEEE754(buf, value, offset, 4, 3.4028234663852886e+38, -3.4028234663852886e+38)
1512    }
1513    ieee754.write(buf, value, offset, littleEndian, 23, 4)
1514    return offset + 4
1515  }
1516  
1517  Buffer.prototype.writeFloatLE = function writeFloatLE (value, offset, noAssert) {
1518    return writeFloat(this, value, offset, true, noAssert)
1519  }
1520  
1521  Buffer.prototype.writeFloatBE = function writeFloatBE (value, offset, noAssert) {
1522    return writeFloat(this, value, offset, false, noAssert)
1523  }
1524  
1525  function writeDouble (buf, value, offset, littleEndian, noAssert) {
1526    value = +value
1527    offset = offset >>> 0
1528    if (!noAssert) {
1529      checkIEEE754(buf, value, offset, 8, 1.7976931348623157E+308, -1.7976931348623157E+308)
1530    }
1531    ieee754.write(buf, value, offset, littleEndian, 52, 8)
1532    return offset + 8
1533  }
1534  
1535  Buffer.prototype.writeDoubleLE = function writeDoubleLE (value, offset, noAssert) {
1536    return writeDouble(this, value, offset, true, noAssert)
1537  }
1538  
1539  Buffer.prototype.writeDoubleBE = function writeDoubleBE (value, offset, noAssert) {
1540    return writeDouble(this, value, offset, false, noAssert)
1541  }
1542  
1543  // copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
1544  Buffer.prototype.copy = function copy (target, targetStart, start, end) {
1545    if (!Buffer.isBuffer(target)) throw new TypeError('argument should be a Buffer')
1546    if (!start) start = 0
1547    if (!end && end !== 0) end = this.length
1548    if (targetStart >= target.length) targetStart = target.length
1549    if (!targetStart) targetStart = 0
1550    if (end > 0 && end < start) end = start
1551  
1552    // Copy 0 bytes; we're done
1553    if (end === start) return 0
1554    if (target.length === 0 || this.length === 0) return 0
1555  
1556    // Fatal error conditions
1557    if (targetStart < 0) {
1558      throw new RangeError('targetStart out of bounds')
1559    }
1560    if (start < 0 || start >= this.length) throw new RangeError('Index out of range')
1561    if (end < 0) throw new RangeError('sourceEnd out of bounds')
1562  
1563    // Are we oob?
1564    if (end > this.length) end = this.length
1565    if (target.length - targetStart < end - start) {
1566      end = target.length - targetStart + start
1567    }
1568  
1569    var len = end - start
1570  
1571    if (this === target && typeof Uint8Array.prototype.copyWithin === 'function') {
1572      // Use built-in when available, missing from IE11
1573      this.copyWithin(targetStart, start, end)
1574    } else {
1575      Uint8Array.prototype.set.call(
1576        target,
1577        this.subarray(start, end),
1578        targetStart
1579      )
1580    }
1581  
1582    return len
1583  }
1584  
1585  // Usage:
1586  //    buffer.fill(number[, offset[, end]])
1587  //    buffer.fill(buffer[, offset[, end]])
1588  //    buffer.fill(string[, offset[, end]][, encoding])
1589  Buffer.prototype.fill = function fill (val, start, end, encoding) {
1590    // Handle string cases:
1591    if (typeof val === 'string') {
1592      if (typeof start === 'string') {
1593        encoding = start
1594        start = 0
1595        end = this.length
1596      } else if (typeof end === 'string') {
1597        encoding = end
1598        end = this.length
1599      }
1600      if (encoding !== undefined && typeof encoding !== 'string') {
1601        throw new TypeError('encoding must be a string')
1602      }
1603      if (typeof encoding === 'string' && !Buffer.isEncoding(encoding)) {
1604        throw new TypeError('Unknown encoding: ' + encoding)
1605      }
1606      if (val.length === 1) {
1607        var code = val.charCodeAt(0)
1608        if ((encoding === 'utf8' && code < 128) ||
1609            encoding === 'latin1') {
1610          // Fast path: If `val` fits into a single byte, use that numeric value.
1611          val = code
1612        }
1613      }
1614    } else if (typeof val === 'number') {
1615      val = val & 255
1616    } else if (typeof val === 'boolean') {
1617      val = Number(val)
1618    }
1619  
1620    // Invalid ranges are not set to a default, so can range check early.
1621    if (start < 0 || this.length < start || this.length < end) {
1622      throw new RangeError('Out of range index')
1623    }
1624  
1625    if (end <= start) {
1626      return this
1627    }
1628  
1629    start = start >>> 0
1630    end = end === undefined ? this.length : end >>> 0
1631  
1632    if (!val) val = 0
1633  
1634    var i
1635    if (typeof val === 'number') {
1636      for (i = start; i < end; ++i) {
1637        this[i] = val
1638      }
1639    } else {
1640      var bytes = Buffer.isBuffer(val)
1641        ? val
1642        : Buffer.from(val, encoding)
1643      var len = bytes.length
1644      if (len === 0) {
1645        throw new TypeError('The value "' + val +
1646          '" is invalid for argument "value"')
1647      }
1648      for (i = 0; i < end - start; ++i) {
1649        this[i + start] = bytes[i % len]
1650      }
1651    }
1652  
1653    return this
1654  }
1655  
1656  // HELPER FUNCTIONS
1657  // ================
1658  
1659  var INVALID_BASE64_RE = /[^+/0-9A-Za-z-_]/g
1660  
1661  function base64clean (str) {
1662    // Node takes equal signs as end of the Base64 encoding
1663    str = str.split('=')[0]
1664    // Node strips out invalid characters like \n and \t from the string, base64-js does not
1665    str = str.trim().replace(INVALID_BASE64_RE, '')
1666    // Node converts strings with length < 2 to ''
1667    if (str.length < 2) return ''
1668    // Node allows for non-padded base64 strings (missing trailing ===), base64-js does not
1669    while (str.length % 4 !== 0) {
1670      str = str + '='
1671    }
1672    return str
1673  }
1674  
1675  function utf8ToBytes (string, units) {
1676    units = units || Infinity
1677    var codePoint
1678    var length = string.length
1679    var leadSurrogate = null
1680    var bytes = []
1681  
1682    for (var i = 0; i < length; ++i) {
1683      codePoint = string.charCodeAt(i)
1684  
1685      // is surrogate component
1686      if (codePoint > 0xD7FF && codePoint < 0xE000) {
1687        // last char was a lead
1688        if (!leadSurrogate) {
1689          // no lead yet
1690          if (codePoint > 0xDBFF) {
1691            // unexpected trail
1692            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
1693            continue
1694          } else if (i + 1 === length) {
1695            // unpaired lead
1696            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
1697            continue
1698          }
1699  
1700          // valid lead
1701          leadSurrogate = codePoint
1702  
1703          continue
1704        }
1705  
1706        // 2 leads in a row
1707        if (codePoint < 0xDC00) {
1708          if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
1709          leadSurrogate = codePoint
1710          continue
1711        }
1712  
1713        // valid surrogate pair
1714        codePoint = (leadSurrogate - 0xD800 << 10 | codePoint - 0xDC00) + 0x10000
1715      } else if (leadSurrogate) {
1716        // valid bmp char, but last char was a lead
1717        if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
1718      }
1719  
1720      leadSurrogate = null
1721  
1722      // encode utf8
1723      if (codePoint < 0x80) {
1724        if ((units -= 1) < 0) break
1725        bytes.push(codePoint)
1726      } else if (codePoint < 0x800) {
1727        if ((units -= 2) < 0) break
1728        bytes.push(
1729          codePoint >> 0x6 | 0xC0,
1730          codePoint & 0x3F | 0x80
1731        )
1732      } else if (codePoint < 0x10000) {
1733        if ((units -= 3) < 0) break
1734        bytes.push(
1735          codePoint >> 0xC | 0xE0,
1736          codePoint >> 0x6 & 0x3F | 0x80,
1737          codePoint & 0x3F | 0x80
1738        )
1739      } else if (codePoint < 0x110000) {
1740        if ((units -= 4) < 0) break
1741        bytes.push(
1742          codePoint >> 0x12 | 0xF0,
1743          codePoint >> 0xC & 0x3F | 0x80,
1744          codePoint >> 0x6 & 0x3F | 0x80,
1745          codePoint & 0x3F | 0x80
1746        )
1747      } else {
1748        throw new Error('Invalid code point')
1749      }
1750    }
1751  
1752    return bytes
1753  }
1754  
1755  function asciiToBytes (str) {
1756    var byteArray = []
1757    for (var i = 0; i < str.length; ++i) {
1758      // Node's code seems to be doing this and not & 0x7F..
1759      byteArray.push(str.charCodeAt(i) & 0xFF)
1760    }
1761    return byteArray
1762  }
1763  
1764  function utf16leToBytes (str, units) {
1765    var c, hi, lo
1766    var byteArray = []
1767    for (var i = 0; i < str.length; ++i) {
1768      if ((units -= 2) < 0) break
1769  
1770      c = str.charCodeAt(i)
1771      hi = c >> 8
1772      lo = c % 256
1773      byteArray.push(lo)
1774      byteArray.push(hi)
1775    }
1776  
1777    return byteArray
1778  }
1779  
1780  function base64ToBytes (str) {
1781    return base64.toByteArray(base64clean(str))
1782  }
1783  
1784  function blitBuffer (src, dst, offset, length) {
1785    for (var i = 0; i < length; ++i) {
1786      if ((i + offset >= dst.length) || (i >= src.length)) break
1787      dst[i + offset] = src[i]
1788    }
1789    return i
1790  }
1791  
1792  // ArrayBuffer or Uint8Array objects from other contexts (i.e. iframes) do not pass
1793  // the `instanceof` check but they should be treated as of that type.
1794  // See: https://github.com/feross/buffer/issues/166
1795  function isInstance (obj, type) {
1796    return obj instanceof type ||
1797      (obj != null && obj.constructor != null && obj.constructor.name != null &&
1798        obj.constructor.name === type.name)
1799  }
1800  function numberIsNaN (obj) {
1801    // For IE11 support
1802    return obj !== obj // eslint-disable-line no-self-compare
1803  }
1804  
1805  // Create lookup table for `toString('hex')`
1806  // See: https://github.com/feross/buffer/issues/219
1807  var hexSliceLookupTable = (function () {
1808    var alphabet = '0123456789abcdef'
1809    var table = new Array(256)
1810    for (var i = 0; i < 16; ++i) {
1811      var i16 = i * 16
1812      for (var j = 0; j < 16; ++j) {
1813        table[i16 + j] = alphabet[i] + alphabet[j]
1814      }
1815    }
1816    return table
1817  })()