buffer/index.js

Node.js Buffer API, for the browser

/*!
 * The buffer module from node.js, for the browser.
 *
 * @author   Feross Aboukhadijeh <http://feross.org>
 * @license  MIT
 */

var base64 = require('base64-js')
var ieee754 = require('ieee754')
var isArray = require('is-array')

exports.Buffer = Buffer
exports.SlowBuffer = Buffer
exports.INSPECT_MAX_BYTES = 50
Buffer.poolSize = 8192 // not used by this implementation

var kMaxLength = 0x3fffffff

/**
 * If `Buffer.TYPED_ARRAY_SUPPORT`:
 *   === true    Use Uint8Array implementation (fastest)
 *   === false   Use Object implementation (most compatible, even IE6)
 *
 * Browsers that support typed arrays are IE 10+, Firefox 4+, Chrome 7+, Safari 5.1+,
 * Opera 11.6+, iOS 4.2+.
 *
 * Note:
 *
 * - Implementation must support adding new properties to `Uint8Array` instances.
 *   Firefox 4-29 lacked support, fixed in Firefox 30+.
 *   See: https://bugzilla.mozilla.org/show_bug.cgi?id=695438.
 *
 *  - Chrome 9-10 is missing the `TypedArray.prototype.subarray` function.
 *
 *  - IE10 has a broken `TypedArray.prototype.subarray` function which returns arrays of
 *    incorrect length in some situations.
 *
 * We detect these buggy browsers and set `Buffer.TYPED_ARRAY_SUPPORT` to `false` so they will
 * get the Object implementation, which is slower but will work correctly.
 */
Buffer.TYPED_ARRAY_SUPPORT = (function () {
  try {
    var buf = new ArrayBuffer(0)
    var arr = new Uint8Array(buf)
    arr.foo = function () { return 42 }
    return 42 === arr.foo() && // typed array instances can be augmented
        typeof arr.subarray === 'function' && // chrome 9-10 lack `subarray`
        new Uint8Array(1).subarray(1, 1).byteLength === 0 // ie10 has broken `subarray`
  } catch (e) {
    return false
  }
})()

/**
 * Class: Buffer
 * =============
 *
 * The Buffer constructor returns instances of `Uint8Array` that are augmented
 * with function properties for all the node `Buffer` API functions. We use
 * `Uint8Array` so that square bracket notation works as expected -- it returns
 * a single octet.
 *
 * By augmenting the instances, we can avoid modifying the `Uint8Array`
 * prototype.
 */
function Buffer (subject, encoding, noZero) {
  if (!(this instanceof Buffer))
    return new Buffer(subject, encoding, noZero)

  var type = typeof subject

  // Find the length
  var length
  if (type === 'number')
    length = subject > 0 ? subject >>> 0 : 0
  else if (type === 'string') {
    if (encoding === 'base64')
      subject = base64clean(subject)
    length = Buffer.byteLength(subject, encoding)
  } else if (type === 'object' && subject !== null) { // assume object is array-like
    if (subject.type === 'Buffer' && isArray(subject.data))
      subject = subject.data
    length = +subject.length > 0 ? Math.floor(+subject.length) : 0
  } else
    throw new TypeError('must start with number, buffer, array or string')

  if (this.length > kMaxLength)
    throw new RangeError('Attempt to allocate Buffer larger than maximum ' +
      'size: 0x' + kMaxLength.toString(16) + ' bytes')

  var buf
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    // Preferred: Return an augmented `Uint8Array` instance for best performance
    buf = Buffer._augment(new Uint8Array(length))
  } else {
    // Fallback: Return THIS instance of Buffer (created by `new`)
    buf = this
    buf.length = length
    buf._isBuffer = true
  }

  var i
  if (Buffer.TYPED_ARRAY_SUPPORT && typeof subject.byteLength === 'number') {
    // Speed optimization -- use set if we're copying from a typed array
    buf._set(subject)
  } else if (isArrayish(subject)) {
    // Treat array-ish objects as a byte array
    if (Buffer.isBuffer(subject)) {
      for (i = 0; i < length; i++)
        buf[i] = subject.readUInt8(i)
    } else {
      for (i = 0; i < length; i++)
        buf[i] = ((subject[i] % 256) + 256) % 256
    }
  } else if (type === 'string') {
    buf.write(subject, 0, encoding)
  } else if (type === 'number' && !Buffer.TYPED_ARRAY_SUPPORT && !noZero) {
    for (i = 0; i < length; i++) {
      buf[i] = 0
    }
  }

  return buf
}

Buffer.isBuffer = function (b) {
  return !!(b != null && b._isBuffer)
}

Buffer.compare = function (a, b) {
  if (!Buffer.isBuffer(a) || !Buffer.isBuffer(b))
    throw new TypeError('Arguments must be Buffers')

  var x = a.length
  var y = b.length
  for (var i = 0, len = Math.min(x, y); i < len && a[i] === b[i]; i++) {}
  if (i !== len) {
    x = a[i]
    y = b[i]
  }
  if (x < y) return -1
  if (y < x) return 1
  return 0
}

Buffer.isEncoding = function (encoding) {
  switch (String(encoding).toLowerCase()) {
    case 'hex':
    case 'utf8':
    case 'utf-8':
    case 'ascii':
    case 'binary':
    case 'base64':
    case 'raw':
    case 'ucs2':
    case 'ucs-2':
    case 'utf16le':
    case 'utf-16le':
      return true
    default:
      return false
  }
}

Buffer.concat = function (list, totalLength) {
  if (!isArray(list)) throw new TypeError('Usage: Buffer.concat(list[, length])')

  if (list.length === 0) {
    return new Buffer(0)
  } else if (list.length === 1) {
    return list[0]
  }

  var i
  if (totalLength === undefined) {
    totalLength = 0
    for (i = 0; i < list.length; i++) {
      totalLength += list[i].length
    }
  }

  var buf = new Buffer(totalLength)
  var pos = 0
  for (i = 0; i < list.length; i++) {
    var item = list[i]
    item.copy(buf, pos)
    pos += item.length
  }
  return buf
}

Buffer.byteLength = function (str, encoding) {
  var ret
  str = str + ''
  switch (encoding || 'utf8') {
    case 'ascii':
    case 'binary':
    case 'raw':
      ret = str.length
      break
    case 'ucs2':
    case 'ucs-2':
    case 'utf16le':
    case 'utf-16le':
      ret = str.length * 2
      break
    case 'hex':
      ret = str.length >>> 1
      break
    case 'utf8':
    case 'utf-8':
      ret = utf8ToBytes(str).length
      break
    case 'base64':
      ret = base64ToBytes(str).length
      break
    default:
      ret = str.length
  }
  return ret
}

// pre-set for values that may exist in the future
Buffer.prototype.length = undefined
Buffer.prototype.parent = undefined

// toString(encoding, start=0, end=buffer.length)
Buffer.prototype.toString = function (encoding, start, end) {
  var loweredCase = false

  start = start >>> 0
  end = end === undefined || end === Infinity ? this.length : end >>> 0

  if (!encoding) encoding = 'utf8'
  if (start < 0) start = 0
  if (end > this.length) end = this.length
  if (end <= start) return ''

  while (true) {
    switch (encoding) {
      case 'hex':
        return hexSlice(this, start, end)

      case 'utf8':
      case 'utf-8':
        return utf8Slice(this, start, end)

      case 'ascii':
        return asciiSlice(this, start, end)

      case 'binary':
        return binarySlice(this, start, end)

      case 'base64':
        return base64Slice(this, start, end)

      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return utf16leSlice(this, start, end)

      default:
        if (loweredCase)
          throw new TypeError('Unknown encoding: ' + encoding)
        encoding = (encoding + '').toLowerCase()
        loweredCase = true
    }
  }
}

Buffer.prototype.equals = function (b) {
  if(!Buffer.isBuffer(b)) throw new TypeError('Argument must be a Buffer')
  return Buffer.compare(this, b) === 0
}

Buffer.prototype.inspect = function () {
  var str = ''
  var max = exports.INSPECT_MAX_BYTES
  if (this.length > 0) {
    str = this.toString('hex', 0, max).match(/.{2}/g).join(' ')
    if (this.length > max)
      str += ' ... '
  }
  return '<Buffer ' + str + '>'
}

Buffer.prototype.compare = function (b) {
  if (!Buffer.isBuffer(b)) throw new TypeError('Argument must be a Buffer')
  return Buffer.compare(this, b)
}

// `get` will be removed in Node 0.13+
Buffer.prototype.get = function (offset) {
  console.log('.get() is deprecated. Access using array indexes instead.')
  return this.readUInt8(offset)
}

// `set` will be removed in Node 0.13+
Buffer.prototype.set = function (v, offset) {
  console.log('.set() is deprecated. Access using array indexes instead.')
  return this.writeUInt8(v, offset)
}

function hexWrite (buf, string, offset, length) {
  offset = Number(offset) || 0
  var remaining = buf.length - offset
  if (!length) {
    length = remaining
  } else {
    length = Number(length)
    if (length > remaining) {
      length = remaining
    }
  }

  // must be an even number of digits
  var strLen = string.length
  if (strLen % 2 !== 0) throw new Error('Invalid hex string')

  if (length > strLen / 2) {
    length = strLen / 2
  }
  for (var i = 0; i < length; i++) {
    var byte = parseInt(string.substr(i * 2, 2), 16)
    if (isNaN(byte)) throw new Error('Invalid hex string')
    buf[offset + i] = byte
  }
  return i
}

function utf8Write (buf, string, offset, length) {
  var charsWritten = blitBuffer(utf8ToBytes(string), buf, offset, length)
  return charsWritten
}

function asciiWrite (buf, string, offset, length) {
  var charsWritten = blitBuffer(asciiToBytes(string), buf, offset, length)
  return charsWritten
}

function binaryWrite (buf, string, offset, length) {
  return asciiWrite(buf, string, offset, length)
}

function base64Write (buf, string, offset, length) {
  var charsWritten = blitBuffer(base64ToBytes(string), buf, offset, length)
  return charsWritten
}

function utf16leWrite (buf, string, offset, length) {
  var charsWritten = blitBuffer(utf16leToBytes(string), buf, offset, length, 2)
  return charsWritten
}

Buffer.prototype.write = function (string, offset, length, encoding) {
  // Support both (string, offset, length, encoding)
  // and the legacy (string, encoding, offset, length)
  if (isFinite(offset)) {
    if (!isFinite(length)) {
      encoding = length
      length = undefined
    }
  } else {  // legacy
    var swap = encoding
    encoding = offset
    offset = length
    length = swap
  }

  offset = Number(offset) || 0
  var remaining = this.length - offset
  if (!length) {
    length = remaining
  } else {
    length = Number(length)
    if (length > remaining) {
      length = remaining
    }
  }
  encoding = String(encoding || 'utf8').toLowerCase()

  var ret
  switch (encoding) {
    case 'hex':
      ret = hexWrite(this, string, offset, length)
      break
    case 'utf8':
    case 'utf-8':
      ret = utf8Write(this, string, offset, length)
      break
    case 'ascii':
      ret = asciiWrite(this, string, offset, length)
      break
    case 'binary':
      ret = binaryWrite(this, string, offset, length)
      break
    case 'base64':
      ret = base64Write(this, string, offset, length)
      break
    case 'ucs2':
    case 'ucs-2':
    case 'utf16le':
    case 'utf-16le':
      ret = utf16leWrite(this, string, offset, length)
      break
    default:
      throw new TypeError('Unknown encoding: ' + encoding)
  }
  return ret
}

Buffer.prototype.toJSON = function () {
  return {
    type: 'Buffer',
    data: Array.prototype.slice.call(this._arr || this, 0)
  }
}

function base64Slice (buf, start, end) {
  if (start === 0 && end === buf.length) {
    return base64.fromByteArray(buf)
  } else {
    return base64.fromByteArray(buf.slice(start, end))
  }
}

function utf8Slice (buf, start, end) {
  var res = ''
  var tmp = ''
  end = Math.min(buf.length, end)

  for (var i = start; i < end; i++) {
    if (buf[i] <= 0x7F) {
      res += decodeUtf8Char(tmp) + String.fromCharCode(buf[i])
      tmp = ''
    } else {
      tmp += '%' + buf[i].toString(16)
    }
  }

  return res + decodeUtf8Char(tmp)
}

function asciiSlice (buf, start, end) {
  var ret = ''
  end = Math.min(buf.length, end)

  for (var i = start; i < end; i++) {
    ret += String.fromCharCode(buf[i])
  }
  return ret
}

function binarySlice (buf, start, end) {
  return asciiSlice(buf, start, end)
}

function hexSlice (buf, start, end) {
  var len = buf.length

  if (!start || start < 0) start = 0
  if (!end || end < 0 || end > len) end = len

  var out = ''
  for (var i = start; i < end; i++) {
    out += toHex(buf[i])
  }
  return out
}

function utf16leSlice (buf, start, end) {
  var bytes = buf.slice(start, end)
  var res = ''
  for (var i = 0; i < bytes.length; i += 2) {
    res += String.fromCharCode(bytes[i] + bytes[i + 1] * 256)
  }
  return res
}

Buffer.prototype.slice = function (start, end) {
  var len = this.length
  start = ~~start
  end = end === undefined ? len : ~~end

  if (start < 0) {
    start += len;
    if (start < 0)
      start = 0
  } else if (start > len) {
    start = len
  }

  if (end < 0) {
    end += len
    if (end < 0)
      end = 0
  } else if (end > len) {
    end = len
  }

  if (end < start)
    end = start

  if (Buffer.TYPED_ARRAY_SUPPORT) {
    return Buffer._augment(this.subarray(start, end))
  } else {
    var sliceLen = end - start
    var newBuf = new Buffer(sliceLen, undefined, true)
    for (var i = 0; i < sliceLen; i++) {
      newBuf[i] = this[i + start]
    }
    return newBuf
  }
}

/*
 * Need to make sure that buffer isn't trying to write out of bounds.
 */
function checkOffset (offset, ext, length) {
  if ((offset % 1) !== 0 || offset < 0)
    throw new RangeError('offset is not uint')
  if (offset + ext > length)
    throw new RangeError('Trying to access beyond buffer length')
}

Buffer.prototype.readUInt8 = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 1, this.length)
  return this[offset]
}

Buffer.prototype.readUInt16LE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 2, this.length)
  return this[offset] | (this[offset + 1] << 8)
}

Buffer.prototype.readUInt16BE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 2, this.length)
  return (this[offset] << 8) | this[offset + 1]
}

Buffer.prototype.readUInt32LE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)

  return ((this[offset]) |
      (this[offset + 1] << 8) |
      (this[offset + 2] << 16)) +
      (this[offset + 3] * 0x1000000)
}

Buffer.prototype.readUInt32BE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)

  return (this[offset] * 0x1000000) +
      ((this[offset + 1] << 16) |
      (this[offset + 2] << 8) |
      this[offset + 3])
}

Buffer.prototype.readInt8 = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 1, this.length)
  if (!(this[offset] & 0x80))
    return (this[offset])
  return ((0xff - this[offset] + 1) * -1)
}

Buffer.prototype.readInt16LE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 2, this.length)
  var val = this[offset] | (this[offset + 1] << 8)
  return (val & 0x8000) ? val | 0xFFFF0000 : val
}

Buffer.prototype.readInt16BE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 2, this.length)
  var val = this[offset + 1] | (this[offset] << 8)
  return (val & 0x8000) ? val | 0xFFFF0000 : val
}

Buffer.prototype.readInt32LE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)

  return (this[offset]) |
      (this[offset + 1] << 8) |
      (this[offset + 2] << 16) |
      (this[offset + 3] << 24)
}

Buffer.prototype.readInt32BE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)

  return (this[offset] << 24) |
      (this[offset + 1] << 16) |
      (this[offset + 2] << 8) |
      (this[offset + 3])
}

Buffer.prototype.readFloatLE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)
  return ieee754.read(this, offset, true, 23, 4)
}

Buffer.prototype.readFloatBE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 4, this.length)
  return ieee754.read(this, offset, false, 23, 4)
}

Buffer.prototype.readDoubleLE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 8, this.length)
  return ieee754.read(this, offset, true, 52, 8)
}

Buffer.prototype.readDoubleBE = function (offset, noAssert) {
  if (!noAssert)
    checkOffset(offset, 8, this.length)
  return ieee754.read(this, offset, false, 52, 8)
}

function checkInt (buf, value, offset, ext, max, min) {
  if (!Buffer.isBuffer(buf)) throw new TypeError('buffer must be a Buffer instance')
  if (value > max || value < min) throw new TypeError('value is out of bounds')
  if (offset + ext > buf.length) throw new TypeError('index out of range')
}

Buffer.prototype.writeUInt8 = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 1, 0xff, 0)
  if (!Buffer.TYPED_ARRAY_SUPPORT) value = Math.floor(value)
  this[offset] = value
  return offset + 1
}

function objectWriteUInt16 (buf, value, offset, littleEndian) {
  if (value < 0) value = 0xffff + value + 1
  for (var i = 0, j = Math.min(buf.length - offset, 2); i < j; i++) {
    buf[offset + i] = (value & (0xff << (8 * (littleEndian ? i : 1 - i)))) >>>
      (littleEndian ? i : 1 - i) * 8
  }
}

Buffer.prototype.writeUInt16LE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 2, 0xffff, 0)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = value
    this[offset + 1] = (value >>> 8)
  } else objectWriteUInt16(this, value, offset, true)
  return offset + 2
}

Buffer.prototype.writeUInt16BE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 2, 0xffff, 0)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = (value >>> 8)
    this[offset + 1] = value
  } else objectWriteUInt16(this, value, offset, false)
  return offset + 2
}

function objectWriteUInt32 (buf, value, offset, littleEndian) {
  if (value < 0) value = 0xffffffff + value + 1
  for (var i = 0, j = Math.min(buf.length - offset, 4); i < j; i++) {
    buf[offset + i] = (value >>> (littleEndian ? i : 3 - i) * 8) & 0xff
  }
}

Buffer.prototype.writeUInt32LE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 4, 0xffffffff, 0)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset + 3] = (value >>> 24)
    this[offset + 2] = (value >>> 16)
    this[offset + 1] = (value >>> 8)
    this[offset] = value
  } else objectWriteUInt32(this, value, offset, true)
  return offset + 4
}

Buffer.prototype.writeUInt32BE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 4, 0xffffffff, 0)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = (value >>> 24)
    this[offset + 1] = (value >>> 16)
    this[offset + 2] = (value >>> 8)
    this[offset + 3] = value
  } else objectWriteUInt32(this, value, offset, false)
  return offset + 4
}

Buffer.prototype.writeInt8 = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 1, 0x7f, -0x80)
  if (!Buffer.TYPED_ARRAY_SUPPORT) value = Math.floor(value)
  if (value < 0) value = 0xff + value + 1
  this[offset] = value
  return offset + 1
}

Buffer.prototype.writeInt16LE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 2, 0x7fff, -0x8000)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = value
    this[offset + 1] = (value >>> 8)
  } else objectWriteUInt16(this, value, offset, true)
  return offset + 2
}

Buffer.prototype.writeInt16BE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 2, 0x7fff, -0x8000)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = (value >>> 8)
    this[offset + 1] = value
  } else objectWriteUInt16(this, value, offset, false)
  return offset + 2
}

Buffer.prototype.writeInt32LE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = value
    this[offset + 1] = (value >>> 8)
    this[offset + 2] = (value >>> 16)
    this[offset + 3] = (value >>> 24)
  } else objectWriteUInt32(this, value, offset, true)
  return offset + 4
}

Buffer.prototype.writeInt32BE = function (value, offset, noAssert) {
  value = +value
  offset = offset >>> 0
  if (!noAssert)
    checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000)
  if (value < 0) value = 0xffffffff + value + 1
  if (Buffer.TYPED_ARRAY_SUPPORT) {
    this[offset] = (value >>> 24)
    this[offset + 1] = (value >>> 16)
    this[offset + 2] = (value >>> 8)
    this[offset + 3] = value
  } else objectWriteUInt32(this, value, offset, false)
  return offset + 4
}

function checkIEEE754 (buf, value, offset, ext, max, min) {
  if (value > max || value < min) throw new TypeError('value is out of bounds')
  if (offset + ext > buf.length) throw new TypeError('index out of range')
}

function writeFloat (buf, value, offset, littleEndian, noAssert) {
  if (!noAssert)
    checkIEEE754(buf, value, offset, 4, 3.4028234663852886e+38, -3.4028234663852886e+38)
  ieee754.write(buf, value, offset, littleEndian, 23, 4)
  return offset + 4
}

Buffer.prototype.writeFloatLE = function (value, offset, noAssert) {
  return writeFloat(this, value, offset, true, noAssert)
}

Buffer.prototype.writeFloatBE = function (value, offset, noAssert) {
  return writeFloat(this, value, offset, false, noAssert)
}

function writeDouble (buf, value, offset, littleEndian, noAssert) {
  if (!noAssert)
    checkIEEE754(buf, value, offset, 8, 1.7976931348623157E+308, -1.7976931348623157E+308)
  ieee754.write(buf, value, offset, littleEndian, 52, 8)
  return offset + 8
}

Buffer.prototype.writeDoubleLE = function (value, offset, noAssert) {
  return writeDouble(this, value, offset, true, noAssert)
}

Buffer.prototype.writeDoubleBE = function (value, offset, noAssert) {
  return writeDouble(this, value, offset, false, noAssert)
}

// copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
Buffer.prototype.copy = function (target, target_start, start, end) {
  var source = this

  if (!start) start = 0
  if (!end && end !== 0) end = this.length
  if (!target_start) target_start = 0

  // Copy 0 bytes; we're done
  if (end === start) return
  if (target.length === 0 || source.length === 0) return

  // Fatal error conditions
  if (end < start) throw new TypeError('sourceEnd < sourceStart')
  if (target_start < 0 || target_start >= target.length)
    throw new TypeError('targetStart out of bounds')
  if (start < 0 || start >= source.length) throw new TypeError('sourceStart out of bounds')
  if (end < 0 || end > source.length) throw new TypeError('sourceEnd out of bounds')

  // Are we oob?
  if (end > this.length)
    end = this.length
  if (target.length - target_start < end - start)
    end = target.length - target_start + start

  var len = end - start

  if (len < 1000 || !Buffer.TYPED_ARRAY_SUPPORT) {
    for (var i = 0; i < len; i++) {
      target[i + target_start] = this[i + start]
    }
  } else {
    target._set(this.subarray(start, start + len), target_start)
  }
}

// fill(value, start=0, end=buffer.length)
Buffer.prototype.fill = function (value, start, end) {
  if (!value) value = 0
  if (!start) start = 0
  if (!end) end = this.length

  if (end < start) throw new TypeError('end < start')

  // Fill 0 bytes; we're done
  if (end === start) return
  if (this.length === 0) return

  if (start < 0 || start >= this.length) throw new TypeError('start out of bounds')
  if (end < 0 || end > this.length) throw new TypeError('end out of bounds')

  var i
  if (typeof value === 'number') {
    for (i = start; i < end; i++) {
      this[i] = value
    }
  } else {
    var bytes = utf8ToBytes(value.toString())
    var len = bytes.length
    for (i = start; i < end; i++) {
      this[i] = bytes[i % len]
    }
  }

  return this
}

/**
 * Creates a new `ArrayBuffer` with the *copied* memory of the buffer instance.
 * Added in Node 0.12. Only available in browsers that support ArrayBuffer.
 */
Buffer.prototype.toArrayBuffer = function () {
  if (typeof Uint8Array !== 'undefined') {
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      return (new Buffer(this)).buffer
    } else {
      var buf = new Uint8Array(this.length)
      for (var i = 0, len = buf.length; i < len; i += 1) {
        buf[i] = this[i]
      }
      return buf.buffer
    }
  } else {
    throw new TypeError('Buffer.toArrayBuffer not supported in this browser')
  }
}

// HELPER FUNCTIONS
// ================

var BP = Buffer.prototype

/**
 * Augment a Uint8Array *instance* (not the Uint8Array class!) with Buffer methods
 */
Buffer._augment = function (arr) {
  arr.constructor = Buffer
  arr._isBuffer = true

  // save reference to original Uint8Array get/set methods before overwriting
  arr._get = arr.get
  arr._set = arr.set

  // deprecated, will be removed in node 0.13+
  arr.get = BP.get
  arr.set = BP.set

  arr.write = BP.write
  arr.toString = BP.toString
  arr.toLocaleString = BP.toString
  arr.toJSON = BP.toJSON
  arr.equals = BP.equals
  arr.compare = BP.compare
  arr.copy = BP.copy
  arr.slice = BP.slice
  arr.readUInt8 = BP.readUInt8
  arr.readUInt16LE = BP.readUInt16LE
  arr.readUInt16BE = BP.readUInt16BE
  arr.readUInt32LE = BP.readUInt32LE
  arr.readUInt32BE = BP.readUInt32BE
  arr.readInt8 = BP.readInt8
  arr.readInt16LE = BP.readInt16LE
  arr.readInt16BE = BP.readInt16BE
  arr.readInt32LE = BP.readInt32LE
  arr.readInt32BE = BP.readInt32BE
  arr.readFloatLE = BP.readFloatLE
  arr.readFloatBE = BP.readFloatBE
  arr.readDoubleLE = BP.readDoubleLE
  arr.readDoubleBE = BP.readDoubleBE
  arr.writeUInt8 = BP.writeUInt8
  arr.writeUInt16LE = BP.writeUInt16LE
  arr.writeUInt16BE = BP.writeUInt16BE
  arr.writeUInt32LE = BP.writeUInt32LE
  arr.writeUInt32BE = BP.writeUInt32BE
  arr.writeInt8 = BP.writeInt8
  arr.writeInt16LE = BP.writeInt16LE
  arr.writeInt16BE = BP.writeInt16BE
  arr.writeInt32LE = BP.writeInt32LE
  arr.writeInt32BE = BP.writeInt32BE
  arr.writeFloatLE = BP.writeFloatLE
  arr.writeFloatBE = BP.writeFloatBE
  arr.writeDoubleLE = BP.writeDoubleLE
  arr.writeDoubleBE = BP.writeDoubleBE
  arr.fill = BP.fill
  arr.inspect = BP.inspect
  arr.toArrayBuffer = BP.toArrayBuffer

  return arr
}

var INVALID_BASE64_RE = /[^+\/0-9A-z]/g

function base64clean (str) {
  // Node strips out invalid characters like \n and \t from the string, base64-js does not
  str = stringtrim(str).replace(INVALID_BASE64_RE, '')
  // Node allows for non-padded base64 strings (missing trailing ===), base64-js does not
  while (str.length % 4 !== 0) {
    str = str + '='
  }
  return str
}

function stringtrim (str) {
  if (str.trim) return str.trim()
  return str.replace(/^\s+|\s+$/g, '')
}

function isArrayish (subject) {
  return isArray(subject) || Buffer.isBuffer(subject) ||
      subject && typeof subject === 'object' &&
      typeof subject.length === 'number'
}

function toHex (n) {
  if (n < 16) return '0' + n.toString(16)
  return n.toString(16)
}

function utf8ToBytes (str) {
  var byteArray = []
  for (var i = 0; i < str.length; i++) {
    var b = str.charCodeAt(i)
    if (b <= 0x7F) {
      byteArray.push(b)
    } else {
      var start = i
      if (b >= 0xD800 && b <= 0xDFFF) i++
      var h = encodeURIComponent(str.slice(start, i+1)).substr(1).split('%')
      for (var j = 0; j < h.length; j++) {
        byteArray.push(parseInt(h[j], 16))
      }
    }
  }
  return byteArray
}

function asciiToBytes (str) {
  var byteArray = []
  for (var i = 0; i < str.length; i++) {
    // Node's code seems to be doing this and not & 0x7F..
    byteArray.push(str.charCodeAt(i) & 0xFF)
  }
  return byteArray
}

function utf16leToBytes (str) {
  var c, hi, lo
  var byteArray = []
  for (var i = 0; i < str.length; i++) {
    c = str.charCodeAt(i)
    hi = c >> 8
    lo = c % 256
    byteArray.push(lo)
    byteArray.push(hi)
  }

  return byteArray
}

function base64ToBytes (str) {
  return base64.toByteArray(str)
}

function blitBuffer (src, dst, offset, length, unitSize) {
  if (unitSize) length -= length % unitSize;
  for (var i = 0; i < length; i++) {
    if ((i + offset >= dst.length) || (i >= src.length))
      break
    dst[i + offset] = src[i]
  }
  return i
}

function decodeUtf8Char (str) {
  try {
    return decodeURIComponent(str)
  } catch (err) {
    return String.fromCharCode(0xFFFD) // UTF 8 invalid char
  }
}