// This is free and unencumbered software released into the public domain.
// See LICENSE.md for more information.

/**
 * @fileoverview Global |this| required for resolving indexes in node.
 * @suppress {globalThis}
 */
 (function(global) {
    'use strict';
  
    // If we're in node require encoding-indexes and attach it to the global.
    if (typeof module !== "undefined" && module.exports &&
      !global["encoding-indexes"]) {
      global["encoding-indexes"] =
        require("./encoding-indexes.js")["encoding-indexes"];
    }
  
    //
    // Utilities
    //
  
    /**
     * @param {number} a The number to test.
     * @param {number} min The minimum value in the range, inclusive.
     * @param {number} max The maximum value in the range, inclusive.
     * @return {boolean} True if a >= min and a <= max.
     */
    function inRange(a, min, max) {
      return min <= a && a <= max;
    }
  
    /**
     * @param {!Array.<*>} array The array to check.
     * @param {*} item The item to look for in the array.
     * @return {boolean} True if the item appears in the array.
     */
    function includes(array, item) {
      return array.indexOf(item) !== -1;
    }
  
    var floor = Math.floor;
  
    /**
     * @param {*} o
     * @return {Object}
     */
    function ToDictionary(o) {
      if (o === undefined) return {};
      if (o === Object(o)) return o;
      throw TypeError('Could not convert argument to dictionary');
    }
  
    /**
     * @param {string} string Input string of UTF-16 code units.
     * @return {!Array.<number>} Code points.
     */
    function stringToCodePoints(string) {
      // https://heycam.github.io/webidl/#dfn-obtain-unicode
  
      // 1. Let S be the DOMString value.
      var s = String(string);
  
      // 2. Let n be the length of S.
      var n = s.length;
  
      // 3. Initialize i to 0.
      var i = 0;
  
      // 4. Initialize U to be an empty sequence of Unicode characters.
      var u = [];
  
      // 5. While i < n:
      while (i < n) {
  
        // 1. Let c be the code unit in S at index i.
        var c = s.charCodeAt(i);
  
        // 2. Depending on the value of c:
  
        // c < 0xD800 or c > 0xDFFF
        if (c < 0xD800 || c > 0xDFFF) {
          // Append to U the Unicode character with code point c.
          u.push(c);
        }
  
        // 0xDC00 ≤ c ≤ 0xDFFF
        else if (0xDC00 <= c && c <= 0xDFFF) {
          // Append to U a U+FFFD REPLACEMENT CHARACTER.
          u.push(0xFFFD);
        }
  
        // 0xD800 ≤ c ≤ 0xDBFF
        else if (0xD800 <= c && c <= 0xDBFF) {
          // 1. If i = n−1, then append to U a U+FFFD REPLACEMENT
          // CHARACTER.
          if (i === n - 1) {
            u.push(0xFFFD);
          }
          // 2. Otherwise, i < n−1:
          else {
            // 1. Let d be the code unit in S at index i+1.
            var d = s.charCodeAt(i + 1);
  
            // 2. If 0xDC00 ≤ d ≤ 0xDFFF, then:
            if (0xDC00 <= d && d <= 0xDFFF) {
              // 1. Let a be c & 0x3FF.
              var a = c & 0x3FF;
  
              // 2. Let b be d & 0x3FF.
              var b = d & 0x3FF;
  
              // 3. Append to U the Unicode character with code point
              // 2^16+2^10*a+b.
              u.push(0x10000 + (a << 10) + b);
  
              // 4. Set i to i+1.
              i += 1;
            }
  
            // 3. Otherwise, d < 0xDC00 or d > 0xDFFF. Append to U a
            // U+FFFD REPLACEMENT CHARACTER.
            else  {
              u.push(0xFFFD);
            }
          }
        }
  
        // 3. Set i to i+1.
        i += 1;
      }
  
      // 6. Return U.
      return u;
    }
  
    /**
     * @param {!Array.<number>} code_points Array of code points.
     * @return {string} string String of UTF-16 code units.
     */
    function codePointsToString(code_points) {
      var s = '';
      for (var i = 0; i < code_points.length; ++i) {
        var cp = code_points[i];
        if (cp <= 0xFFFF) {
          s += String.fromCharCode(cp);
        } else {
          cp -= 0x10000;
          s += String.fromCharCode((cp >> 10) + 0xD800,
                                   (cp & 0x3FF) + 0xDC00);
        }
      }
      return s;
    }
  
  
    //
    // Implementation of Encoding specification
    // https://encoding.spec.whatwg.org/
    //
  
    //
    // 4. Terminology
    //
  
    /**
     * An ASCII byte is a byte in the range 0x00 to 0x7F, inclusive.
     * @param {number} a The number to test.
     * @return {boolean} True if a is in the range 0x00 to 0x7F, inclusive.
     */
    function isASCIIByte(a) {
      return 0x00 <= a && a <= 0x7F;
    }
  
    /**
     * An ASCII code point is a code point in the range U+0000 to
     * U+007F, inclusive.
     */
    var isASCIICodePoint = isASCIIByte;
  
  
    /**
     * End-of-stream is a special token that signifies no more tokens
     * are in the stream.
     * @const
     */ var end_of_stream = -1;
  
    /**
     * A stream represents an ordered sequence of tokens.
     *
     * @constructor
     * @param {!(Array.<number>|Uint8Array)} tokens Array of tokens that provide
     * the stream.
     */
    function Stream(tokens) {
      /** @type {!Array.<number>} */
      this.tokens = [].slice.call(tokens);
      // Reversed as push/pop is more efficient than shift/unshift.
      this.tokens.reverse();
    }
  
    Stream.prototype = {
      /**
       * @return {boolean} True if end-of-stream has been hit.
       */
      endOfStream: function() {
        return !this.tokens.length;
      },
  
      /**
       * When a token is read from a stream, the first token in the
       * stream must be returned and subsequently removed, and
       * end-of-stream must be returned otherwise.
       *
       * @return {number} Get the next token from the stream, or
       * end_of_stream.
       */
       read: function() {
        if (!this.tokens.length)
          return end_of_stream;
         return this.tokens.pop();
       },
  
      /**
       * When one or more tokens are prepended to a stream, those tokens
       * must be inserted, in given order, before the first token in the
       * stream.
       *
       * @param {(number|!Array.<number>)} token The token(s) to prepend to the
       * stream.
       */
      prepend: function(token) {
        if (Array.isArray(token)) {
          var tokens = /**@type {!Array.<number>}*/(token);
          while (tokens.length)
            this.tokens.push(tokens.pop());
        } else {
          this.tokens.push(token);
        }
      },
  
      /**
       * When one or more tokens are pushed to a stream, those tokens
       * must be inserted, in given order, after the last token in the
       * stream.
       *
       * @param {(number|!Array.<number>)} token The tokens(s) to push to the
       * stream.
       */
      push: function(token) {
        if (Array.isArray(token)) {
          var tokens = /**@type {!Array.<number>}*/(token);
          while (tokens.length)
            this.tokens.unshift(tokens.shift());
        } else {
          this.tokens.unshift(token);
        }
      }
    };
  
    //
    // 5. Encodings
    //
  
    // 5.1 Encoders and decoders
  
    /** @const */
    var finished = -1;
  
    /**
     * @param {boolean} fatal If true, decoding errors raise an exception.
     * @param {number=} opt_code_point Override the standard fallback code point.
     * @return {number} The code point to insert on a decoding error.
     */
    function decoderError(fatal, opt_code_point) {
      if (fatal)
        throw TypeError('Decoder error');
      return opt_code_point || 0xFFFD;
    }
  
    /**
     * @param {number} code_point The code point that could not be encoded.
     * @return {number} Always throws, no value is actually returned.
     */
    function encoderError(code_point) {
      throw TypeError('The code point ' + code_point + ' could not be encoded.');
    }
  
    /** @interface */
    function Decoder() {}
    Decoder.prototype = {
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point, or |finished|.
       */
      handler: function(stream, bite) {}
    };
  
    /** @interface */
    function Encoder() {}
    Encoder.prototype = {
      /**
       * @param {Stream} stream The stream of code points being encoded.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit, or |finished|.
       */
      handler: function(stream, code_point) {}
    };
  
    // 5.2 Names and labels
  
    // TODO: Define @typedef for Encoding: {name:string,labels:Array.<string>}
    // https://github.com/google/closure-compiler/issues/247
  
    /**
     * @param {string} label The encoding label.
     * @return {?{name:string,labels:Array.<string>}}
     */
    function getEncoding(label) {
      // 1. Remove any leading and trailing ASCII whitespace from label.
      label = String(label).trim().toLowerCase();
  
      // 2. If label is an ASCII case-insensitive match for any of the
      // labels listed in the table below, return the corresponding
      // encoding, and failure otherwise.
      if (Object.prototype.hasOwnProperty.call(label_to_encoding, label)) {
        return label_to_encoding[label];
      }
      return null;
    }
  
    /**
     * Encodings table: https://encoding.spec.whatwg.org/encodings.json
     * @const
     * @type {!Array.<{
     *          heading: string,
     *          encodings: Array.<{name:string,labels:Array.<string>}>
     *        }>}
     */
    var encodings = [
      {
        "encodings": [
          {
            "labels": [
              "unicode-1-1-utf-8",
              "utf-8",
              "utf8"
            ],
            "name": "UTF-8"
          }
        ],
        "heading": "The Encoding"
      },
      {
        "encodings": [
          {
            "labels": [
              "866",
              "cp866",
              "csibm866",
              "ibm866"
            ],
            "name": "IBM866"
          },
          {
            "labels": [
              "csisolatin2",
              "iso-8859-2",
              "iso-ir-101",
              "iso8859-2",
              "iso88592",
              "iso_8859-2",
              "iso_8859-2:1987",
              "l2",
              "latin2"
            ],
            "name": "ISO-8859-2"
          },
          {
            "labels": [
              "csisolatin3",
              "iso-8859-3",
              "iso-ir-109",
              "iso8859-3",
              "iso88593",
              "iso_8859-3",
              "iso_8859-3:1988",
              "l3",
              "latin3"
            ],
            "name": "ISO-8859-3"
          },
          {
            "labels": [
              "csisolatin4",
              "iso-8859-4",
              "iso-ir-110",
              "iso8859-4",
              "iso88594",
              "iso_8859-4",
              "iso_8859-4:1988",
              "l4",
              "latin4"
            ],
            "name": "ISO-8859-4"
          },
          {
            "labels": [
              "csisolatincyrillic",
              "cyrillic",
              "iso-8859-5",
              "iso-ir-144",
              "iso8859-5",
              "iso88595",
              "iso_8859-5",
              "iso_8859-5:1988"
            ],
            "name": "ISO-8859-5"
          },
          {
            "labels": [
              "arabic",
              "asmo-708",
              "csiso88596e",
              "csiso88596i",
              "csisolatinarabic",
              "ecma-114",
              "iso-8859-6",
              "iso-8859-6-e",
              "iso-8859-6-i",
              "iso-ir-127",
              "iso8859-6",
              "iso88596",
              "iso_8859-6",
              "iso_8859-6:1987"
            ],
            "name": "ISO-8859-6"
          },
          {
            "labels": [
              "csisolatingreek",
              "ecma-118",
              "elot_928",
              "greek",
              "greek8",
              "iso-8859-7",
              "iso-ir-126",
              "iso8859-7",
              "iso88597",
              "iso_8859-7",
              "iso_8859-7:1987",
              "sun_eu_greek"
            ],
            "name": "ISO-8859-7"
          },
          {
            "labels": [
              "csiso88598e",
              "csisolatinhebrew",
              "hebrew",
              "iso-8859-8",
              "iso-8859-8-e",
              "iso-ir-138",
              "iso8859-8",
              "iso88598",
              "iso_8859-8",
              "iso_8859-8:1988",
              "visual"
            ],
            "name": "ISO-8859-8"
          },
          {
            "labels": [
              "csiso88598i",
              "iso-8859-8-i",
              "logical"
            ],
            "name": "ISO-8859-8-I"
          },
          {
            "labels": [
              "csisolatin6",
              "iso-8859-10",
              "iso-ir-157",
              "iso8859-10",
              "iso885910",
              "l6",
              "latin6"
            ],
            "name": "ISO-8859-10"
          },
          {
            "labels": [
              "iso-8859-13",
              "iso8859-13",
              "iso885913"
            ],
            "name": "ISO-8859-13"
          },
          {
            "labels": [
              "iso-8859-14",
              "iso8859-14",
              "iso885914"
            ],
            "name": "ISO-8859-14"
          },
          {
            "labels": [
              "csisolatin9",
              "iso-8859-15",
              "iso8859-15",
              "iso885915",
              "iso_8859-15",
              "l9"
            ],
            "name": "ISO-8859-15"
          },
          {
            "labels": [
              "iso-8859-16"
            ],
            "name": "ISO-8859-16"
          },
          {
            "labels": [
              "cskoi8r",
              "koi",
              "koi8",
              "koi8-r",
              "koi8_r"
            ],
            "name": "KOI8-R"
          },
          {
            "labels": [
              "koi8-ru",
              "koi8-u"
            ],
            "name": "KOI8-U"
          },
          {
            "labels": [
              "csmacintosh",
              "mac",
              "macintosh",
              "x-mac-roman"
            ],
            "name": "macintosh"
          },
          {
            "labels": [
              "dos-874",
              "iso-8859-11",
              "iso8859-11",
              "iso885911",
              "tis-620",
              "windows-874"
            ],
            "name": "windows-874"
          },
          {
            "labels": [
              "cp1250",
              "windows-1250",
              "x-cp1250"
            ],
            "name": "windows-1250"
          },
          {
            "labels": [
              "cp1251",
              "windows-1251",
              "x-cp1251"
            ],
            "name": "windows-1251"
          },
          {
            "labels": [
              "ansi_x3.4-1968",
              "ascii",
              "cp1252",
              "cp819",
              "csisolatin1",
              "ibm819",
              "iso-8859-1",
              "iso-ir-100",
              "iso8859-1",
              "iso88591",
              "iso_8859-1",
              "iso_8859-1:1987",
              "l1",
              "latin1",
              "us-ascii",
              "windows-1252",
              "x-cp1252"
            ],
            "name": "windows-1252"
          },
          {
            "labels": [
              "cp1253",
              "windows-1253",
              "x-cp1253"
            ],
            "name": "windows-1253"
          },
          {
            "labels": [
              "cp1254",
              "csisolatin5",
              "iso-8859-9",
              "iso-ir-148",
              "iso8859-9",
              "iso88599",
              "iso_8859-9",
              "iso_8859-9:1989",
              "l5",
              "latin5",
              "windows-1254",
              "x-cp1254"
            ],
            "name": "windows-1254"
          },
          {
            "labels": [
              "cp1255",
              "windows-1255",
              "x-cp1255"
            ],
            "name": "windows-1255"
          },
          {
            "labels": [
              "cp1256",
              "windows-1256",
              "x-cp1256"
            ],
            "name": "windows-1256"
          },
          {
            "labels": [
              "cp1257",
              "windows-1257",
              "x-cp1257"
            ],
            "name": "windows-1257"
          },
          {
            "labels": [
              "cp1258",
              "windows-1258",
              "x-cp1258"
            ],
            "name": "windows-1258"
          },
          {
            "labels": [
              "x-mac-cyrillic",
              "x-mac-ukrainian"
            ],
            "name": "x-mac-cyrillic"
          }
        ],
        "heading": "Legacy single-byte encodings"
      },
      {
        "encodings": [
          {
            "labels": [
              "chinese",
              "csgb2312",
              "csiso58gb231280",
              "gb2312",
              "gb_2312",
              "gb_2312-80",
              "gbk",
              "iso-ir-58",
              "x-gbk"
            ],
            "name": "GBK"
          },
          {
            "labels": [
              "gb18030"
            ],
            "name": "gb18030"
          }
        ],
        "heading": "Legacy multi-byte Chinese (simplified) encodings"
      },
      {
        "encodings": [
          {
            "labels": [
              "big5",
              "big5-hkscs",
              "cn-big5",
              "csbig5",
              "x-x-big5"
            ],
            "name": "Big5"
          }
        ],
        "heading": "Legacy multi-byte Chinese (traditional) encodings"
      },
      {
        "encodings": [
          {
            "labels": [
              "cseucpkdfmtjapanese",
              "euc-jp",
              "x-euc-jp"
            ],
            "name": "EUC-JP"
          },
          {
            "labels": [
              "csiso2022jp",
              "iso-2022-jp"
            ],
            "name": "ISO-2022-JP"
          },
          {
            "labels": [
              "csshiftjis",
              "ms932",
              "ms_kanji",
              "shift-jis",
              "shift_jis",
              "sjis",
              "windows-31j",
              "x-sjis"
            ],
            "name": "Shift_JIS"
          }
        ],
        "heading": "Legacy multi-byte Japanese encodings"
      },
      {
        "encodings": [
          {
            "labels": [
              "cseuckr",
              "csksc56011987",
              "euc-kr",
              "iso-ir-149",
              "korean",
              "ks_c_5601-1987",
              "ks_c_5601-1989",
              "ksc5601",
              "ksc_5601",
              "windows-949"
            ],
            "name": "EUC-KR"
          }
        ],
        "heading": "Legacy multi-byte Korean encodings"
      },
      {
        "encodings": [
          {
            "labels": [
              "csiso2022kr",
              "hz-gb-2312",
              "iso-2022-cn",
              "iso-2022-cn-ext",
              "iso-2022-kr"
            ],
            "name": "replacement"
          },
          {
            "labels": [
              "utf-16be"
            ],
            "name": "UTF-16BE"
          },
          {
            "labels": [
              "utf-16",
              "utf-16le"
            ],
            "name": "UTF-16LE"
          },
          {
            "labels": [
              "x-user-defined"
            ],
            "name": "x-user-defined"
          }
        ],
        "heading": "Legacy miscellaneous encodings"
      }
    ];
  
    // Label to encoding registry.
    /** @type {Object.<string,{name:string,labels:Array.<string>}>} */
    var label_to_encoding = {};
    encodings.forEach(function(category) {
      category.encodings.forEach(function(encoding) {
        encoding.labels.forEach(function(label) {
          label_to_encoding[label] = encoding;
        });
      });
    });
  
    // Registry of of encoder/decoder factories, by encoding name.
    /** @type {Object.<string, function({fatal:boolean}): Encoder>} */
    var encoders = {};
    /** @type {Object.<string, function({fatal:boolean}): Decoder>} */
    var decoders = {};
  
    //
    // 6. Indexes
    //
  
    /**
     * @param {number} pointer The |pointer| to search for.
     * @param {(!Array.<?number>|undefined)} index The |index| to search within.
     * @return {?number} The code point corresponding to |pointer| in |index|,
     *     or null if |code point| is not in |index|.
     */
    function indexCodePointFor(pointer, index) {
      if (!index) return null;
      return index[pointer] || null;
    }
  
    /**
     * @param {number} code_point The |code point| to search for.
     * @param {!Array.<?number>} index The |index| to search within.
     * @return {?number} The first pointer corresponding to |code point| in
     *     |index|, or null if |code point| is not in |index|.
     */
    function indexPointerFor(code_point, index) {
      var pointer = index.indexOf(code_point);
      return pointer === -1 ? null : pointer;
    }
  
    /**
     * @param {string} name Name of the index.
     * @return {(!Array.<number>|!Array.<Array.<number>>)}
     *  */
    function index(name) {
      if (!('encoding-indexes' in global)) {
        throw Error("Indexes missing." +
                    " Did you forget to include encoding-indexes.js first?");
      }
      return global['encoding-indexes'][name];
    }
  
    /**
     * @param {number} pointer The |pointer| to search for in the gb18030 index.
     * @return {?number} The code point corresponding to |pointer| in |index|,
     *     or null if |code point| is not in the gb18030 index.
     */
    function indexGB18030RangesCodePointFor(pointer) {
      // 1. If pointer is greater than 39419 and less than 189000, or
      // pointer is greater than 1237575, return null.
      if ((pointer > 39419 && pointer < 189000) || (pointer > 1237575))
        return null;
  
      // 2. If pointer is 7457, return code point U+E7C7.
      if (pointer === 7457) return 0xE7C7;
  
      // 3. Let offset be the last pointer in index gb18030 ranges that
      // is equal to or less than pointer and let code point offset be
      // its corresponding code point.
      var offset = 0;
      var code_point_offset = 0;
      var idx = index('gb18030-ranges');
      var i;
      for (i = 0; i < idx.length; ++i) {
        /** @type {!Array.<number>} */
        var entry = idx[i];
        if (entry[0] <= pointer) {
          offset = entry[0];
          code_point_offset = entry[1];
        } else {
          break;
        }
      }
  
      // 4. Return a code point whose value is code point offset +
      // pointer − offset.
      return code_point_offset + pointer - offset;
    }
  
    /**
     * @param {number} code_point The |code point| to locate in the gb18030 index.
     * @return {number} The first pointer corresponding to |code point| in the
     *     gb18030 index.
     */
    function indexGB18030RangesPointerFor(code_point) {
      // 1. If code point is U+E7C7, return pointer 7457.
      if (code_point === 0xE7C7) return 7457;
  
      // 2. Let offset be the last code point in index gb18030 ranges
      // that is equal to or less than code point and let pointer offset
      // be its corresponding pointer.
      var offset = 0;
      var pointer_offset = 0;
      var idx = index('gb18030-ranges');
      var i;
      for (i = 0; i < idx.length; ++i) {
        /** @type {!Array.<number>} */
        var entry = idx[i];
        if (entry[1] <= code_point) {
          offset = entry[1];
          pointer_offset = entry[0];
        } else {
          break;
        }
      }
  
      // 3. Return a pointer whose value is pointer offset + code point
      // − offset.
      return pointer_offset + code_point - offset;
    }
  
    /**
     * @param {number} code_point The |code_point| to search for in the Shift_JIS
     *     index.
     * @return {?number} The code point corresponding to |pointer| in |index|,
     *     or null if |code point| is not in the Shift_JIS index.
     */
    function indexShiftJISPointerFor(code_point) {
      // 1. Let index be index jis0208 excluding all entries whose
      // pointer is in the range 8272 to 8835, inclusive.
      shift_jis_index = shift_jis_index ||
        index('jis0208').map(function(code_point, pointer) {
          return inRange(pointer, 8272, 8835) ? null : code_point;
        });
      var index_ = shift_jis_index;
  
      // 2. Return the index pointer for code point in index.
      return index_.indexOf(code_point);
    }
    var shift_jis_index;
  
    /**
     * @param {number} code_point The |code_point| to search for in the big5
     *     index.
     * @return {?number} The code point corresponding to |pointer| in |index|,
     *     or null if |code point| is not in the big5 index.
     */
    function indexBig5PointerFor(code_point) {
      // 1. Let index be index Big5 excluding all entries whose pointer
      big5_index_no_hkscs = big5_index_no_hkscs ||
        index('big5').map(function(code_point, pointer) {
          return (pointer < (0xA1 - 0x81) * 157) ? null : code_point;
        });
      var index_ = big5_index_no_hkscs;
  
      // 2. If code point is U+2550, U+255E, U+2561, U+256A, U+5341, or
      // U+5345, return the last pointer corresponding to code point in
      // index.
      if (code_point === 0x2550 || code_point === 0x255E ||
          code_point === 0x2561 || code_point === 0x256A ||
          code_point === 0x5341 || code_point === 0x5345) {
        return index_.lastIndexOf(code_point);
      }
  
      // 3. Return the index pointer for code point in index.
      return indexPointerFor(code_point, index_);
    }
    var big5_index_no_hkscs;
  
    //
    // 8. API
    //
  
    /** @const */ var DEFAULT_ENCODING = 'utf-8';
  
    // 8.1 Interface TextDecoder
  
    /**
     * @constructor
     * @param {string=} label The label of the encoding;
     *     defaults to 'utf-8'.
     * @param {Object=} options
     */
    function TextDecoder(label, options) {
      // Web IDL conventions
      if (!(this instanceof TextDecoder))
        throw TypeError('Called as a function. Did you forget \'new\'?');
      label = label !== undefined ? String(label) : DEFAULT_ENCODING;
      options = ToDictionary(options);
  
      // A TextDecoder object has an associated encoding, decoder,
      // stream, ignore BOM flag (initially unset), BOM seen flag
      // (initially unset), error mode (initially replacement), and do
      // not flush flag (initially unset).
  
      /** @private */
      this._encoding = null;
      /** @private @type {?Decoder} */
      this._decoder = null;
      /** @private @type {boolean} */
      this._ignoreBOM = false;
      /** @private @type {boolean} */
      this._BOMseen = false;
      /** @private @type {string} */
      this._error_mode = 'replacement';
      /** @private @type {boolean} */
      this._do_not_flush = false;
  
  
      // 1. Let encoding be the result of getting an encoding from
      // label.
      var encoding = getEncoding(label);
  
      // 2. If encoding is failure or replacement, throw a RangeError.
      if (encoding === null || encoding.name === 'replacement')
        throw RangeError('Unknown encoding: ' + label);
      if (!decoders[encoding.name]) {
        throw Error('Decoder not present.' +
                    ' Did you forget to include encoding-indexes.js first?');
      }
  
      // 3. Let dec be a new TextDecoder object.
      var dec = this;
  
      // 4. Set dec's encoding to encoding.
      dec._encoding = encoding;
  
      // 5. If options's fatal member is true, set dec's error mode to
      // fatal.
      if (Boolean(options['fatal']))
        dec._error_mode = 'fatal';
  
      // 6. If options's ignoreBOM member is true, set dec's ignore BOM
      // flag.
      if (Boolean(options['ignoreBOM']))
        dec._ignoreBOM = true;
  
      // For pre-ES5 runtimes:
      if (!Object.defineProperty) {
        this.encoding = dec._encoding.name.toLowerCase();
        this.fatal = dec._error_mode === 'fatal';
        this.ignoreBOM = dec._ignoreBOM;
      }
  
      // 7. Return dec.
      return dec;
    }
  
    if (Object.defineProperty) {
      // The encoding attribute's getter must return encoding's name.
      Object.defineProperty(TextDecoder.prototype, 'encoding', {
        /** @this {TextDecoder} */
        get: function() { return this._encoding.name.toLowerCase(); }
      });
  
      // The fatal attribute's getter must return true if error mode
      // is fatal, and false otherwise.
      Object.defineProperty(TextDecoder.prototype, 'fatal', {
        /** @this {TextDecoder} */
        get: function() { return this._error_mode === 'fatal'; }
      });
  
      // The ignoreBOM attribute's getter must return true if ignore
      // BOM flag is set, and false otherwise.
      Object.defineProperty(TextDecoder.prototype, 'ignoreBOM', {
        /** @this {TextDecoder} */
        get: function() { return this._ignoreBOM; }
      });
    }
  
    /**
     * @param {BufferSource=} input The buffer of bytes to decode.
     * @param {Object=} options
     * @return {string} The decoded string.
     */
    TextDecoder.prototype.decode = function decode(input, options) {
      var bytes;
      if (typeof input === 'object' && input instanceof ArrayBuffer) {
        bytes = new Uint8Array(input);
      } else if (typeof input === 'object' && 'buffer' in input &&
                 input.buffer instanceof ArrayBuffer) {
        bytes = new Uint8Array(input.buffer,
                               input.byteOffset,
                               input.byteLength);
      } else {
        bytes = new Uint8Array(0);
      }
  
      options = ToDictionary(options);
  
      // 1. If the do not flush flag is unset, set decoder to a new
      // encoding's decoder, set stream to a new stream, and unset the
      // BOM seen flag.
      if (!this._do_not_flush) {
        this._decoder = decoders[this._encoding.name]({
          fatal: this._error_mode === 'fatal'});
        this._BOMseen = false;
      }
  
      // 2. If options's stream is true, set the do not flush flag, and
      // unset the do not flush flag otherwise.
      this._do_not_flush = Boolean(options['stream']);
  
      // 3. If input is given, push a copy of input to stream.
      // TODO: Align with spec algorithm - maintain stream on instance.
      var input_stream = new Stream(bytes);
  
      // 4. Let output be a new stream.
      var output = [];
  
      /** @type {?(number|!Array.<number>)} */
      var result;
  
      // 5. While true:
      while (true) {
        // 1. Let token be the result of reading from stream.
        var token = input_stream.read();
  
        // 2. If token is end-of-stream and the do not flush flag is
        // set, return output, serialized.
        // TODO: Align with spec algorithm.
        if (token === end_of_stream)
          break;
  
        // 3. Otherwise, run these subsubsteps:
  
        // 1. Let result be the result of processing token for decoder,
        // stream, output, and error mode.
        result = this._decoder.handler(input_stream, token);
  
        // 2. If result is finished, return output, serialized.
        if (result === finished)
          break;
  
        if (result !== null) {
          if (Array.isArray(result))
            output.push.apply(output, /**@type {!Array.<number>}*/(result));
          else
            output.push(result);
        }
  
        // 3. Otherwise, if result is error, throw a TypeError.
        // (Thrown in handler)
  
        // 4. Otherwise, do nothing.
      }
      // TODO: Align with spec algorithm.
      if (!this._do_not_flush) {
        do {
          result = this._decoder.handler(input_stream, input_stream.read());
          if (result === finished)
            break;
          if (result === null)
            continue;
          if (Array.isArray(result))
            output.push.apply(output, /**@type {!Array.<number>}*/(result));
          else
            output.push(result);
        } while (!input_stream.endOfStream());
        this._decoder = null;
      }
  
      // A TextDecoder object also has an associated serialize stream
      // algorithm...
      /**
       * @param {!Array.<number>} stream
       * @return {string}
       * @this {TextDecoder}
       */
      function serializeStream(stream) {
        // 1. Let token be the result of reading from stream.
        // (Done in-place on array, rather than as a stream)
  
        // 2. If encoding is UTF-8, UTF-16BE, or UTF-16LE, and ignore
        // BOM flag and BOM seen flag are unset, run these subsubsteps:
        if (includes(['UTF-8', 'UTF-16LE', 'UTF-16BE'], this._encoding.name) &&
            !this._ignoreBOM && !this._BOMseen) {
          if (stream.length > 0 && stream[0] === 0xFEFF) {
            // 1. If token is U+FEFF, set BOM seen flag.
            this._BOMseen = true;
            stream.shift();
          } else if (stream.length > 0) {
            // 2. Otherwise, if token is not end-of-stream, set BOM seen
            // flag and append token to stream.
            this._BOMseen = true;
          } else {
            // 3. Otherwise, if token is not end-of-stream, append token
            // to output.
            // (no-op)
          }
        }
        // 4. Otherwise, return output.
        return codePointsToString(stream);
      }
  
      return serializeStream.call(this, output);
    };
  
    // 8.2 Interface TextEncoder
  
    /**
     * @constructor
     * @param {string=} label The label of the encoding. NONSTANDARD.
     * @param {Object=} options NONSTANDARD.
     */
    function TextEncoder(label, options) {
      // Web IDL conventions
      if (!(this instanceof TextEncoder))
        throw TypeError('Called as a function. Did you forget \'new\'?');
      options = ToDictionary(options);
  
      // A TextEncoder object has an associated encoding and encoder.
  
      /** @private */
      this._encoding = null;
      /** @private @type {?Encoder} */
      this._encoder = null;
  
      // Non-standard
      /** @private @type {boolean} */
      this._do_not_flush = false;
      /** @private @type {string} */
      this._fatal = Boolean(options['fatal']) ? 'fatal' : 'replacement';
  
      // 1. Let enc be a new TextEncoder object.
      var enc = this;
  
      // 2. Set enc's encoding to UTF-8's encoder.
      if (Boolean(options['NONSTANDARD_allowLegacyEncoding'])) {
        // NONSTANDARD behavior.
        label = label !== undefined ? String(label) : DEFAULT_ENCODING;
        var encoding = getEncoding(label);
        if (encoding === null || encoding.name === 'replacement')
          throw RangeError('Unknown encoding: ' + label);
        if (!encoders[encoding.name]) {
          throw Error('Encoder not present.' +
                      ' Did you forget to include encoding-indexes.js first?');
        }
        enc._encoding = encoding;
      } else {
        // Standard behavior.
        enc._encoding = getEncoding('utf-8');
  
        if (label !== undefined && 'console' in global) {
          console.warn('TextEncoder constructor called with encoding label, '
                       + 'which is ignored.');
        }
      }
  
      // For pre-ES5 runtimes:
      if (!Object.defineProperty)
        this.encoding = enc._encoding.name.toLowerCase();
  
      // 3. Return enc.
      return enc;
    }
  
    if (Object.defineProperty) {
      // The encoding attribute's getter must return encoding's name.
      Object.defineProperty(TextEncoder.prototype, 'encoding', {
        /** @this {TextEncoder} */
        get: function() { return this._encoding.name.toLowerCase(); }
      });
    }
  
    /**
     * @param {string=} opt_string The string to encode.
     * @param {Object=} options
     * @return {!Uint8Array} Encoded bytes, as a Uint8Array.
     */
    TextEncoder.prototype.encode = function encode(opt_string, options) {
      opt_string = opt_string === undefined ? '' : String(opt_string);
      options = ToDictionary(options);
  
      // NOTE: This option is nonstandard. None of the encodings
      // permitted for encoding (i.e. UTF-8, UTF-16) are stateful when
      // the input is a USVString so streaming is not necessary.
      if (!this._do_not_flush)
        this._encoder = encoders[this._encoding.name]({
          fatal: this._fatal === 'fatal'});
      this._do_not_flush = Boolean(options['stream']);
  
      // 1. Convert input to a stream.
      var input = new Stream(stringToCodePoints(opt_string));
  
      // 2. Let output be a new stream
      var output = [];
  
      /** @type {?(number|!Array.<number>)} */
      var result;
      // 3. While true, run these substeps:
      while (true) {
        // 1. Let token be the result of reading from input.
        var token = input.read();
        if (token === end_of_stream)
          break;
        // 2. Let result be the result of processing token for encoder,
        // input, output.
        result = this._encoder.handler(input, token);
        if (result === finished)
          break;
        if (Array.isArray(result))
          output.push.apply(output, /**@type {!Array.<number>}*/(result));
        else
          output.push(result);
      }
      // TODO: Align with spec algorithm.
      if (!this._do_not_flush) {
        while (true) {
          result = this._encoder.handler(input, input.read());
          if (result === finished)
            break;
          if (Array.isArray(result))
            output.push.apply(output, /**@type {!Array.<number>}*/(result));
          else
            output.push(result);
        }
        this._encoder = null;
      }
      // 3. If result is finished, convert output into a byte sequence,
      // and then return a Uint8Array object wrapping an ArrayBuffer
      // containing output.
      return new Uint8Array(output);
    };
  
  
    //
    // 9. The encoding
    //
  
    // 9.1 utf-8
  
    // 9.1.1 utf-8 decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function UTF8Decoder(options) {
      var fatal = options.fatal;
  
      // utf-8's decoder's has an associated utf-8 code point, utf-8
      // bytes seen, and utf-8 bytes needed (all initially 0), a utf-8
      // lower boundary (initially 0x80), and a utf-8 upper boundary
      // (initially 0xBF).
      var /** @type {number} */ utf8_code_point = 0,
          /** @type {number} */ utf8_bytes_seen = 0,
          /** @type {number} */ utf8_bytes_needed = 0,
          /** @type {number} */ utf8_lower_boundary = 0x80,
          /** @type {number} */ utf8_upper_boundary = 0xBF;
  
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and utf-8 bytes needed is not 0,
        // set utf-8 bytes needed to 0 and return error.
        if (bite === end_of_stream && utf8_bytes_needed !== 0) {
          utf8_bytes_needed = 0;
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream, return finished.
        if (bite === end_of_stream)
          return finished;
  
        // 3. If utf-8 bytes needed is 0, based on byte:
        if (utf8_bytes_needed === 0) {
  
          // 0x00 to 0x7F
          if (inRange(bite, 0x00, 0x7F)) {
            // Return a code point whose value is byte.
            return bite;
          }
  
          // 0xC2 to 0xDF
          else if (inRange(bite, 0xC2, 0xDF)) {
            // 1. Set utf-8 bytes needed to 1.
            utf8_bytes_needed = 1;
  
            // 2. Set UTF-8 code point to byte & 0x1F.
            utf8_code_point = bite & 0x1F;
          }
  
          // 0xE0 to 0xEF
          else if (inRange(bite, 0xE0, 0xEF)) {
            // 1. If byte is 0xE0, set utf-8 lower boundary to 0xA0.
            if (bite === 0xE0)
              utf8_lower_boundary = 0xA0;
            // 2. If byte is 0xED, set utf-8 upper boundary to 0x9F.
            if (bite === 0xED)
              utf8_upper_boundary = 0x9F;
            // 3. Set utf-8 bytes needed to 2.
            utf8_bytes_needed = 2;
            // 4. Set UTF-8 code point to byte & 0xF.
            utf8_code_point = bite & 0xF;
          }
  
          // 0xF0 to 0xF4
          else if (inRange(bite, 0xF0, 0xF4)) {
            // 1. If byte is 0xF0, set utf-8 lower boundary to 0x90.
            if (bite === 0xF0)
              utf8_lower_boundary = 0x90;
            // 2. If byte is 0xF4, set utf-8 upper boundary to 0x8F.
            if (bite === 0xF4)
              utf8_upper_boundary = 0x8F;
            // 3. Set utf-8 bytes needed to 3.
            utf8_bytes_needed = 3;
            // 4. Set UTF-8 code point to byte & 0x7.
            utf8_code_point = bite & 0x7;
          }
  
          // Otherwise
          else {
            // Return error.
            return decoderError(fatal);
          }
  
          // Return continue.
          return null;
        }
  
        // 4. If byte is not in the range utf-8 lower boundary to utf-8
        // upper boundary, inclusive, run these substeps:
        if (!inRange(bite, utf8_lower_boundary, utf8_upper_boundary)) {
  
          // 1. Set utf-8 code point, utf-8 bytes needed, and utf-8
          // bytes seen to 0, set utf-8 lower boundary to 0x80, and set
          // utf-8 upper boundary to 0xBF.
          utf8_code_point = utf8_bytes_needed = utf8_bytes_seen = 0;
          utf8_lower_boundary = 0x80;
          utf8_upper_boundary = 0xBF;
  
          // 2. Prepend byte to stream.
          stream.prepend(bite);
  
          // 3. Return error.
          return decoderError(fatal);
        }
  
        // 5. Set utf-8 lower boundary to 0x80 and utf-8 upper boundary
        // to 0xBF.
        utf8_lower_boundary = 0x80;
        utf8_upper_boundary = 0xBF;
  
        // 6. Set UTF-8 code point to (UTF-8 code point << 6) | (byte &
        // 0x3F)
        utf8_code_point = (utf8_code_point << 6) | (bite & 0x3F);
  
        // 7. Increase utf-8 bytes seen by one.
        utf8_bytes_seen += 1;
  
        // 8. If utf-8 bytes seen is not equal to utf-8 bytes needed,
        // continue.
        if (utf8_bytes_seen !== utf8_bytes_needed)
          return null;
  
        // 9. Let code point be utf-8 code point.
        var code_point = utf8_code_point;
  
        // 10. Set utf-8 code point, utf-8 bytes needed, and utf-8 bytes
        // seen to 0.
        utf8_code_point = utf8_bytes_needed = utf8_bytes_seen = 0;
  
        // 11. Return a code point whose value is code point.
        return code_point;
      };
    }
  
    // 9.1.2 utf-8 encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function UTF8Encoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. Set count and offset based on the range code point is in:
        var count, offset;
        // U+0080 to U+07FF, inclusive:
        if (inRange(code_point, 0x0080, 0x07FF)) {
          // 1 and 0xC0
          count = 1;
          offset = 0xC0;
        }
        // U+0800 to U+FFFF, inclusive:
        else if (inRange(code_point, 0x0800, 0xFFFF)) {
          // 2 and 0xE0
          count = 2;
          offset = 0xE0;
        }
        // U+10000 to U+10FFFF, inclusive:
        else if (inRange(code_point, 0x10000, 0x10FFFF)) {
          // 3 and 0xF0
          count = 3;
          offset = 0xF0;
        }
  
        // 4. Let bytes be a byte sequence whose first byte is (code
        // point >> (6 × count)) + offset.
        var bytes = [(code_point >> (6 * count)) + offset];
  
        // 5. Run these substeps while count is greater than 0:
        while (count > 0) {
  
          // 1. Set temp to code point >> (6 × (count − 1)).
          var temp = code_point >> (6 * (count - 1));
  
          // 2. Append to bytes 0x80 | (temp & 0x3F).
          bytes.push(0x80 | (temp & 0x3F));
  
          // 3. Decrease count by one.
          count -= 1;
        }
  
        // 6. Return bytes bytes, in order.
        return bytes;
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['UTF-8'] = function(options) {
      return new UTF8Encoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['UTF-8'] = function(options) {
      return new UTF8Decoder(options);
    };
  
    //
    // 10. Legacy single-byte encodings
    //
  
    // 10.1 single-byte decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {!Array.<number>} index The encoding index.
     * @param {{fatal: boolean}} options
     */
    function SingleByteDecoder(index, options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream, return finished.
        if (bite === end_of_stream)
          return finished;
  
        // 2. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 3. Let code point be the index code point for byte − 0x80 in
        // index single-byte.
        var code_point = index[bite - 0x80];
  
        // 4. If code point is null, return error.
        if (code_point === null)
          return decoderError(fatal);
  
        // 5. Return a code point whose value is code point.
        return code_point;
      };
    }
  
    // 10.2 single-byte encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {!Array.<?number>} index The encoding index.
     * @param {{fatal: boolean}} options
     */
    function SingleByteEncoder(index, options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. Let pointer be the index pointer for code point in index
        // single-byte.
        var pointer = indexPointerFor(code_point, index);
  
        // 4. If pointer is null, return error with code point.
        if (pointer === null)
          encoderError(code_point);
  
        // 5. Return a byte whose value is pointer + 0x80.
        return pointer + 0x80;
      };
    }
  
    (function() {
      if (!('encoding-indexes' in global))
        return;
      encodings.forEach(function(category) {
        if (category.heading !== 'Legacy single-byte encodings')
          return;
        category.encodings.forEach(function(encoding) {
          var name = encoding.name;
          var idx = index(name.toLowerCase());
          /** @param {{fatal: boolean}} options */
          decoders[name] = function(options) {
            return new SingleByteDecoder(idx, options);
          };
          /** @param {{fatal: boolean}} options */
          encoders[name] = function(options) {
            return new SingleByteEncoder(idx, options);
          };
        });
      });
    }());
  
    //
    // 11. Legacy multi-byte Chinese (simplified) encodings
    //
  
    // 11.1 gbk
  
    // 11.1.1 gbk decoder
    // gbk's decoder is gb18030's decoder.
    /** @param {{fatal: boolean}} options */
    decoders['GBK'] = function(options) {
      return new GB18030Decoder(options);
    };
  
    // 11.1.2 gbk encoder
    // gbk's encoder is gb18030's encoder with its gbk flag set.
    /** @param {{fatal: boolean}} options */
    encoders['GBK'] = function(options) {
      return new GB18030Encoder(options, true);
    };
  
    // 11.2 gb18030
  
    // 11.2.1 gb18030 decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function GB18030Decoder(options) {
      var fatal = options.fatal;
      // gb18030's decoder has an associated gb18030 first, gb18030
      // second, and gb18030 third (all initially 0x00).
      var /** @type {number} */ gb18030_first = 0x00,
          /** @type {number} */ gb18030_second = 0x00,
          /** @type {number} */ gb18030_third = 0x00;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and gb18030 first, gb18030
        // second, and gb18030 third are 0x00, return finished.
        if (bite === end_of_stream && gb18030_first === 0x00 &&
            gb18030_second === 0x00 && gb18030_third === 0x00) {
          return finished;
        }
        // 2. If byte is end-of-stream, and gb18030 first, gb18030
        // second, or gb18030 third is not 0x00, set gb18030 first,
        // gb18030 second, and gb18030 third to 0x00, and return error.
        if (bite === end_of_stream &&
            (gb18030_first !== 0x00 || gb18030_second !== 0x00 ||
             gb18030_third !== 0x00)) {
          gb18030_first = 0x00;
          gb18030_second = 0x00;
          gb18030_third = 0x00;
          decoderError(fatal);
        }
        var code_point;
        // 3. If gb18030 third is not 0x00, run these substeps:
        if (gb18030_third !== 0x00) {
          // 1. Let code point be null.
          code_point = null;
          // 2. If byte is in the range 0x30 to 0x39, inclusive, set
          // code point to the index gb18030 ranges code point for
          // (((gb18030 first − 0x81) × 10 + gb18030 second − 0x30) ×
          // 126 + gb18030 third − 0x81) × 10 + byte − 0x30.
          if (inRange(bite, 0x30, 0x39)) {
            code_point = indexGB18030RangesCodePointFor(
                (((gb18030_first - 0x81) * 10 + gb18030_second - 0x30) * 126 +
                 gb18030_third - 0x81) * 10 + bite - 0x30);
          }
  
          // 3. Let buffer be a byte sequence consisting of gb18030
          // second, gb18030 third, and byte, in order.
          var buffer = [gb18030_second, gb18030_third, bite];
  
          // 4. Set gb18030 first, gb18030 second, and gb18030 third to
          // 0x00.
          gb18030_first = 0x00;
          gb18030_second = 0x00;
          gb18030_third = 0x00;
  
          // 5. If code point is null, prepend buffer to stream and
          // return error.
          if (code_point === null) {
            stream.prepend(buffer);
            return decoderError(fatal);
          }
  
          // 6. Return a code point whose value is code point.
          return code_point;
        }
  
        // 4. If gb18030 second is not 0x00, run these substeps:
        if (gb18030_second !== 0x00) {
  
          // 1. If byte is in the range 0x81 to 0xFE, inclusive, set
          // gb18030 third to byte and return continue.
          if (inRange(bite, 0x81, 0xFE)) {
            gb18030_third = bite;
            return null;
          }
  
          // 2. Prepend gb18030 second followed by byte to stream, set
          // gb18030 first and gb18030 second to 0x00, and return error.
          stream.prepend([gb18030_second, bite]);
          gb18030_first = 0x00;
          gb18030_second = 0x00;
          return decoderError(fatal);
        }
  
        // 5. If gb18030 first is not 0x00, run these substeps:
        if (gb18030_first !== 0x00) {
  
          // 1. If byte is in the range 0x30 to 0x39, inclusive, set
          // gb18030 second to byte and return continue.
          if (inRange(bite, 0x30, 0x39)) {
            gb18030_second = bite;
            return null;
          }
  
          // 2. Let lead be gb18030 first, let pointer be null, and set
          // gb18030 first to 0x00.
          var lead = gb18030_first;
          var pointer = null;
          gb18030_first = 0x00;
  
          // 3. Let offset be 0x40 if byte is less than 0x7F and 0x41
          // otherwise.
          var offset = bite < 0x7F ? 0x40 : 0x41;
  
          // 4. If byte is in the range 0x40 to 0x7E, inclusive, or 0x80
          // to 0xFE, inclusive, set pointer to (lead − 0x81) × 190 +
          // (byte − offset).
          if (inRange(bite, 0x40, 0x7E) || inRange(bite, 0x80, 0xFE))
            pointer = (lead - 0x81) * 190 + (bite - offset);
  
          // 5. Let code point be null if pointer is null and the index
          // code point for pointer in index gb18030 otherwise.
          code_point = pointer === null ? null :
              indexCodePointFor(pointer, index('gb18030'));
  
          // 6. If code point is null and byte is an ASCII byte, prepend
          // byte to stream.
          if (code_point === null && isASCIIByte(bite))
            stream.prepend(bite);
  
          // 7. If code point is null, return error.
          if (code_point === null)
            return decoderError(fatal);
  
          // 8. Return a code point whose value is code point.
          return code_point;
        }
  
        // 6. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 7. If byte is 0x80, return code point U+20AC.
        if (bite === 0x80)
          return 0x20AC;
  
        // 8. If byte is in the range 0x81 to 0xFE, inclusive, set
        // gb18030 first to byte and return continue.
        if (inRange(bite, 0x81, 0xFE)) {
          gb18030_first = bite;
          return null;
        }
  
        // 9. Return error.
        return decoderError(fatal);
      };
    }
  
    // 11.2.2 gb18030 encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     * @param {boolean=} gbk_flag
     */
    function GB18030Encoder(options, gbk_flag) {
      var fatal = options.fatal;
      // gb18030's decoder has an associated gbk flag (initially unset).
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. If code point is U+E5E5, return error with code point.
        if (code_point === 0xE5E5)
          return encoderError(code_point);
  
        // 4. If the gbk flag is set and code point is U+20AC, return
        // byte 0x80.
        if (gbk_flag && code_point === 0x20AC)
          return 0x80;
  
        // 5. Let pointer be the index pointer for code point in index
        // gb18030.
        var pointer = indexPointerFor(code_point, index('gb18030'));
  
        // 6. If pointer is not null, run these substeps:
        if (pointer !== null) {
  
          // 1. Let lead be floor(pointer / 190) + 0x81.
          var lead = floor(pointer / 190) + 0x81;
  
          // 2. Let trail be pointer % 190.
          var trail = pointer % 190;
  
          // 3. Let offset be 0x40 if trail is less than 0x3F and 0x41 otherwise.
          var offset = trail < 0x3F ? 0x40 : 0x41;
  
          // 4. Return two bytes whose values are lead and trail + offset.
          return [lead, trail + offset];
        }
  
        // 7. If gbk flag is set, return error with code point.
        if (gbk_flag)
          return encoderError(code_point);
  
        // 8. Set pointer to the index gb18030 ranges pointer for code
        // point.
        pointer = indexGB18030RangesPointerFor(code_point);
  
        // 9. Let byte1 be floor(pointer / 10 / 126 / 10).
        var byte1 = floor(pointer / 10 / 126 / 10);
  
        // 10. Set pointer to pointer − byte1 × 10 × 126 × 10.
        pointer = pointer - byte1 * 10 * 126 * 10;
  
        // 11. Let byte2 be floor(pointer / 10 / 126).
        var byte2 = floor(pointer / 10 / 126);
  
        // 12. Set pointer to pointer − byte2 × 10 × 126.
        pointer = pointer - byte2 * 10 * 126;
  
        // 13. Let byte3 be floor(pointer / 10).
        var byte3 = floor(pointer / 10);
  
        // 14. Let byte4 be pointer − byte3 × 10.
        var byte4 = pointer - byte3 * 10;
  
        // 15. Return four bytes whose values are byte1 + 0x81, byte2 +
        // 0x30, byte3 + 0x81, byte4 + 0x30.
        return [byte1 + 0x81,
                byte2 + 0x30,
                byte3 + 0x81,
                byte4 + 0x30];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['gb18030'] = function(options) {
      return new GB18030Encoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['gb18030'] = function(options) {
      return new GB18030Decoder(options);
    };
  
  
    //
    // 12. Legacy multi-byte Chinese (traditional) encodings
    //
  
    // 12.1 Big5
  
    // 12.1.1 Big5 decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function Big5Decoder(options) {
      var fatal = options.fatal;
      // Big5's decoder has an associated Big5 lead (initially 0x00).
      var /** @type {number} */ Big5_lead = 0x00;
  
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and Big5 lead is not 0x00, set
        // Big5 lead to 0x00 and return error.
        if (bite === end_of_stream && Big5_lead !== 0x00) {
          Big5_lead = 0x00;
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream and Big5 lead is 0x00, return
        // finished.
        if (bite === end_of_stream && Big5_lead === 0x00)
          return finished;
  
        // 3. If Big5 lead is not 0x00, let lead be Big5 lead, let
        // pointer be null, set Big5 lead to 0x00, and then run these
        // substeps:
        if (Big5_lead !== 0x00) {
          var lead = Big5_lead;
          var pointer = null;
          Big5_lead = 0x00;
  
          // 1. Let offset be 0x40 if byte is less than 0x7F and 0x62
          // otherwise.
          var offset = bite < 0x7F ? 0x40 : 0x62;
  
          // 2. If byte is in the range 0x40 to 0x7E, inclusive, or 0xA1
          // to 0xFE, inclusive, set pointer to (lead − 0x81) × 157 +
          // (byte − offset).
          if (inRange(bite, 0x40, 0x7E) || inRange(bite, 0xA1, 0xFE))
            pointer = (lead - 0x81) * 157 + (bite - offset);
  
          // 3. If there is a row in the table below whose first column
          // is pointer, return the two code points listed in its second
          // column
          // Pointer | Code points
          // --------+--------------
          // 1133    | U+00CA U+0304
          // 1135    | U+00CA U+030C
          // 1164    | U+00EA U+0304
          // 1166    | U+00EA U+030C
          switch (pointer) {
            case 1133: return [0x00CA, 0x0304];
            case 1135: return [0x00CA, 0x030C];
            case 1164: return [0x00EA, 0x0304];
            case 1166: return [0x00EA, 0x030C];
          }
  
          // 4. Let code point be null if pointer is null and the index
          // code point for pointer in index Big5 otherwise.
          var code_point = (pointer === null) ? null :
              indexCodePointFor(pointer, index('big5'));
  
          // 5. If code point is null and byte is an ASCII byte, prepend
          // byte to stream.
          if (code_point === null && isASCIIByte(bite))
            stream.prepend(bite);
  
          // 6. If code point is null, return error.
          if (code_point === null)
            return decoderError(fatal);
  
          // 7. Return a code point whose value is code point.
          return code_point;
        }
  
        // 4. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 5. If byte is in the range 0x81 to 0xFE, inclusive, set Big5
        // lead to byte and return continue.
        if (inRange(bite, 0x81, 0xFE)) {
          Big5_lead = bite;
          return null;
        }
  
        // 6. Return error.
        return decoderError(fatal);
      };
    }
  
    // 12.1.2 Big5 encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function Big5Encoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. Let pointer be the index Big5 pointer for code point.
        var pointer = indexBig5PointerFor(code_point);
  
        // 4. If pointer is null, return error with code point.
        if (pointer === null)
          return encoderError(code_point);
  
        // 5. Let lead be floor(pointer / 157) + 0x81.
        var lead = floor(pointer / 157) + 0x81;
  
        // 6. If lead is less than 0xA1, return error with code point.
        if (lead < 0xA1)
          return encoderError(code_point);
  
        // 7. Let trail be pointer % 157.
        var trail = pointer % 157;
  
        // 8. Let offset be 0x40 if trail is less than 0x3F and 0x62
        // otherwise.
        var offset = trail < 0x3F ? 0x40 : 0x62;
  
        // Return two bytes whose values are lead and trail + offset.
        return [lead, trail + offset];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['Big5'] = function(options) {
      return new Big5Encoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['Big5'] = function(options) {
      return new Big5Decoder(options);
    };
  
  
    //
    // 13. Legacy multi-byte Japanese encodings
    //
  
    // 13.1 euc-jp
  
    // 13.1.1 euc-jp decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function EUCJPDecoder(options) {
      var fatal = options.fatal;
  
      // euc-jp's decoder has an associated euc-jp jis0212 flag
      // (initially unset) and euc-jp lead (initially 0x00).
      var /** @type {boolean} */ eucjp_jis0212_flag = false,
          /** @type {number} */ eucjp_lead = 0x00;
  
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and euc-jp lead is not 0x00, set
        // euc-jp lead to 0x00, and return error.
        if (bite === end_of_stream && eucjp_lead !== 0x00) {
          eucjp_lead = 0x00;
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream and euc-jp lead is 0x00, return
        // finished.
        if (bite === end_of_stream && eucjp_lead === 0x00)
          return finished;
  
        // 3. If euc-jp lead is 0x8E and byte is in the range 0xA1 to
        // 0xDF, inclusive, set euc-jp lead to 0x00 and return a code
        // point whose value is 0xFF61 − 0xA1 + byte.
        if (eucjp_lead === 0x8E && inRange(bite, 0xA1, 0xDF)) {
          eucjp_lead = 0x00;
          return 0xFF61 - 0xA1 + bite;
        }
  
        // 4. If euc-jp lead is 0x8F and byte is in the range 0xA1 to
        // 0xFE, inclusive, set the euc-jp jis0212 flag, set euc-jp lead
        // to byte, and return continue.
        if (eucjp_lead === 0x8F && inRange(bite, 0xA1, 0xFE)) {
          eucjp_jis0212_flag = true;
          eucjp_lead = bite;
          return null;
        }
  
        // 5. If euc-jp lead is not 0x00, let lead be euc-jp lead, set
        // euc-jp lead to 0x00, and run these substeps:
        if (eucjp_lead !== 0x00) {
          var lead = eucjp_lead;
          eucjp_lead = 0x00;
  
          // 1. Let code point be null.
          var code_point = null;
  
          // 2. If lead and byte are both in the range 0xA1 to 0xFE,
          // inclusive, set code point to the index code point for (lead
          // − 0xA1) × 94 + byte − 0xA1 in index jis0208 if the euc-jp
          // jis0212 flag is unset and in index jis0212 otherwise.
          if (inRange(lead, 0xA1, 0xFE) && inRange(bite, 0xA1, 0xFE)) {
            code_point = indexCodePointFor(
              (lead - 0xA1) * 94 + (bite - 0xA1),
              index(!eucjp_jis0212_flag ? 'jis0208' : 'jis0212'));
          }
  
          // 3. Unset the euc-jp jis0212 flag.
          eucjp_jis0212_flag = false;
  
          // 4. If byte is not in the range 0xA1 to 0xFE, inclusive,
          // prepend byte to stream.
          if (!inRange(bite, 0xA1, 0xFE))
            stream.prepend(bite);
  
          // 5. If code point is null, return error.
          if (code_point === null)
            return decoderError(fatal);
  
          // 6. Return a code point whose value is code point.
          return code_point;
        }
  
        // 6. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 7. If byte is 0x8E, 0x8F, or in the range 0xA1 to 0xFE,
        // inclusive, set euc-jp lead to byte and return continue.
        if (bite === 0x8E || bite === 0x8F || inRange(bite, 0xA1, 0xFE)) {
          eucjp_lead = bite;
          return null;
        }
  
        // 8. Return error.
        return decoderError(fatal);
      };
    }
  
    // 13.1.2 euc-jp encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function EUCJPEncoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. If code point is U+00A5, return byte 0x5C.
        if (code_point === 0x00A5)
          return 0x5C;
  
        // 4. If code point is U+203E, return byte 0x7E.
        if (code_point === 0x203E)
          return 0x7E;
  
        // 5. If code point is in the range U+FF61 to U+FF9F, inclusive,
        // return two bytes whose values are 0x8E and code point −
        // 0xFF61 + 0xA1.
        if (inRange(code_point, 0xFF61, 0xFF9F))
          return [0x8E, code_point - 0xFF61 + 0xA1];
  
        // 6. If code point is U+2212, set it to U+FF0D.
        if (code_point === 0x2212)
          code_point = 0xFF0D;
  
        // 7. Let pointer be the index pointer for code point in index
        // jis0208.
        var pointer = indexPointerFor(code_point, index('jis0208'));
  
        // 8. If pointer is null, return error with code point.
        if (pointer === null)
          return encoderError(code_point);
  
        // 9. Let lead be floor(pointer / 94) + 0xA1.
        var lead = floor(pointer / 94) + 0xA1;
  
        // 10. Let trail be pointer % 94 + 0xA1.
        var trail = pointer % 94 + 0xA1;
  
        // 11. Return two bytes whose values are lead and trail.
        return [lead, trail];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['EUC-JP'] = function(options) {
      return new EUCJPEncoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['EUC-JP'] = function(options) {
      return new EUCJPDecoder(options);
    };
  
    // 13.2 iso-2022-jp
  
    // 13.2.1 iso-2022-jp decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function ISO2022JPDecoder(options) {
      var fatal = options.fatal;
      /** @enum */
      var states = {
        ASCII: 0,
        Roman: 1,
        Katakana: 2,
        LeadByte: 3,
        TrailByte: 4,
        EscapeStart: 5,
        Escape: 6
      };
      // iso-2022-jp's decoder has an associated iso-2022-jp decoder
      // state (initially ASCII), iso-2022-jp decoder output state
      // (initially ASCII), iso-2022-jp lead (initially 0x00), and
      // iso-2022-jp output flag (initially unset).
      var /** @type {number} */ iso2022jp_decoder_state = states.ASCII,
          /** @type {number} */ iso2022jp_decoder_output_state = states.ASCII,
          /** @type {number} */ iso2022jp_lead = 0x00,
          /** @type {boolean} */ iso2022jp_output_flag = false;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // switching on iso-2022-jp decoder state:
        switch (iso2022jp_decoder_state) {
        default:
        case states.ASCII:
          // ASCII
          // Based on byte:
  
          // 0x1B
          if (bite === 0x1B) {
            // Set iso-2022-jp decoder state to escape start and return
            // continue.
            iso2022jp_decoder_state = states.EscapeStart;
            return null;
          }
  
          // 0x00 to 0x7F, excluding 0x0E, 0x0F, and 0x1B
          if (inRange(bite, 0x00, 0x7F) && bite !== 0x0E
              && bite !== 0x0F && bite !== 0x1B) {
            // Unset the iso-2022-jp output flag and return a code point
            // whose value is byte.
            iso2022jp_output_flag = false;
            return bite;
          }
  
          // end-of-stream
          if (bite === end_of_stream) {
            // Return finished.
            return finished;
          }
  
          // Otherwise
          // Unset the iso-2022-jp output flag and return error.
          iso2022jp_output_flag = false;
          return decoderError(fatal);
  
        case states.Roman:
          // Roman
          // Based on byte:
  
          // 0x1B
          if (bite === 0x1B) {
            // Set iso-2022-jp decoder state to escape start and return
            // continue.
            iso2022jp_decoder_state = states.EscapeStart;
            return null;
          }
  
          // 0x5C
          if (bite === 0x5C) {
            // Unset the iso-2022-jp output flag and return code point
            // U+00A5.
            iso2022jp_output_flag = false;
            return 0x00A5;
          }
  
          // 0x7E
          if (bite === 0x7E) {
            // Unset the iso-2022-jp output flag and return code point
            // U+203E.
            iso2022jp_output_flag = false;
            return 0x203E;
          }
  
          // 0x00 to 0x7F, excluding 0x0E, 0x0F, 0x1B, 0x5C, and 0x7E
          if (inRange(bite, 0x00, 0x7F) && bite !== 0x0E && bite !== 0x0F
              && bite !== 0x1B && bite !== 0x5C && bite !== 0x7E) {
            // Unset the iso-2022-jp output flag and return a code point
            // whose value is byte.
            iso2022jp_output_flag = false;
            return bite;
          }
  
          // end-of-stream
          if (bite === end_of_stream) {
            // Return finished.
            return finished;
          }
  
          // Otherwise
          // Unset the iso-2022-jp output flag and return error.
          iso2022jp_output_flag = false;
          return decoderError(fatal);
  
        case states.Katakana:
          // Katakana
          // Based on byte:
  
          // 0x1B
          if (bite === 0x1B) {
            // Set iso-2022-jp decoder state to escape start and return
            // continue.
            iso2022jp_decoder_state = states.EscapeStart;
            return null;
          }
  
          // 0x21 to 0x5F
          if (inRange(bite, 0x21, 0x5F)) {
            // Unset the iso-2022-jp output flag and return a code point
            // whose value is 0xFF61 − 0x21 + byte.
            iso2022jp_output_flag = false;
            return 0xFF61 - 0x21 + bite;
          }
  
          // end-of-stream
          if (bite === end_of_stream) {
            // Return finished.
            return finished;
          }
  
          // Otherwise
          // Unset the iso-2022-jp output flag and return error.
          iso2022jp_output_flag = false;
          return decoderError(fatal);
  
        case states.LeadByte:
          // Lead byte
          // Based on byte:
  
          // 0x1B
          if (bite === 0x1B) {
            // Set iso-2022-jp decoder state to escape start and return
            // continue.
            iso2022jp_decoder_state = states.EscapeStart;
            return null;
          }
  
          // 0x21 to 0x7E
          if (inRange(bite, 0x21, 0x7E)) {
            // Unset the iso-2022-jp output flag, set iso-2022-jp lead
            // to byte, iso-2022-jp decoder state to trail byte, and
            // return continue.
            iso2022jp_output_flag = false;
            iso2022jp_lead = bite;
            iso2022jp_decoder_state = states.TrailByte;
            return null;
          }
  
          // end-of-stream
          if (bite === end_of_stream) {
            // Return finished.
            return finished;
          }
  
          // Otherwise
          // Unset the iso-2022-jp output flag and return error.
          iso2022jp_output_flag = false;
          return decoderError(fatal);
  
        case states.TrailByte:
          // Trail byte
          // Based on byte:
  
          // 0x1B
          if (bite === 0x1B) {
            // Set iso-2022-jp decoder state to escape start and return
            // continue.
            iso2022jp_decoder_state = states.EscapeStart;
            return decoderError(fatal);
          }
  
          // 0x21 to 0x7E
          if (inRange(bite, 0x21, 0x7E)) {
            // 1. Set the iso-2022-jp decoder state to lead byte.
            iso2022jp_decoder_state = states.LeadByte;
  
            // 2. Let pointer be (iso-2022-jp lead − 0x21) × 94 + byte − 0x21.
            var pointer = (iso2022jp_lead - 0x21) * 94 + bite - 0x21;
  
            // 3. Let code point be the index code point for pointer in
            // index jis0208.
            var code_point = indexCodePointFor(pointer, index('jis0208'));
  
            // 4. If code point is null, return error.
            if (code_point === null)
              return decoderError(fatal);
  
            // 5. Return a code point whose value is code point.
            return code_point;
          }
  
          // end-of-stream
          if (bite === end_of_stream) {
            // Set the iso-2022-jp decoder state to lead byte, prepend
            // byte to stream, and return error.
            iso2022jp_decoder_state = states.LeadByte;
            stream.prepend(bite);
            return decoderError(fatal);
          }
  
          // Otherwise
          // Set iso-2022-jp decoder state to lead byte and return
          // error.
          iso2022jp_decoder_state = states.LeadByte;
          return decoderError(fatal);
  
        case states.EscapeStart:
          // Escape start
  
          // 1. If byte is either 0x24 or 0x28, set iso-2022-jp lead to
          // byte, iso-2022-jp decoder state to escape, and return
          // continue.
          if (bite === 0x24 || bite === 0x28) {
            iso2022jp_lead = bite;
            iso2022jp_decoder_state = states.Escape;
            return null;
          }
  
          // 2. Prepend byte to stream.
          stream.prepend(bite);
  
          // 3. Unset the iso-2022-jp output flag, set iso-2022-jp
          // decoder state to iso-2022-jp decoder output state, and
          // return error.
          iso2022jp_output_flag = false;
          iso2022jp_decoder_state = iso2022jp_decoder_output_state;
          return decoderError(fatal);
  
        case states.Escape:
          // Escape
  
          // 1. Let lead be iso-2022-jp lead and set iso-2022-jp lead to
          // 0x00.
          var lead = iso2022jp_lead;
          iso2022jp_lead = 0x00;
  
          // 2. Let state be null.
          var state = null;
  
          // 3. If lead is 0x28 and byte is 0x42, set state to ASCII.
          if (lead === 0x28 && bite === 0x42)
            state = states.ASCII;
  
          // 4. If lead is 0x28 and byte is 0x4A, set state to Roman.
          if (lead === 0x28 && bite === 0x4A)
            state = states.Roman;
  
          // 5. If lead is 0x28 and byte is 0x49, set state to Katakana.
          if (lead === 0x28 && bite === 0x49)
            state = states.Katakana;
  
          // 6. If lead is 0x24 and byte is either 0x40 or 0x42, set
          // state to lead byte.
          if (lead === 0x24 && (bite === 0x40 || bite === 0x42))
            state = states.LeadByte;
  
          // 7. If state is non-null, run these substeps:
          if (state !== null) {
            // 1. Set iso-2022-jp decoder state and iso-2022-jp decoder
            // output state to states.
            iso2022jp_decoder_state = iso2022jp_decoder_state = state;
  
            // 2. Let output flag be the iso-2022-jp output flag.
            var output_flag = iso2022jp_output_flag;
  
            // 3. Set the iso-2022-jp output flag.
            iso2022jp_output_flag = true;
  
            // 4. Return continue, if output flag is unset, and error
            // otherwise.
            return !output_flag ? null : decoderError(fatal);
          }
  
          // 8. Prepend lead and byte to stream.
          stream.prepend([lead, bite]);
  
          // 9. Unset the iso-2022-jp output flag, set iso-2022-jp
          // decoder state to iso-2022-jp decoder output state and
          // return error.
          iso2022jp_output_flag = false;
          iso2022jp_decoder_state = iso2022jp_decoder_output_state;
          return decoderError(fatal);
        }
      };
    }
  
    // 13.2.2 iso-2022-jp encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function ISO2022JPEncoder(options) {
      var fatal = options.fatal;
      // iso-2022-jp's encoder has an associated iso-2022-jp encoder
      // state which is one of ASCII, Roman, and jis0208 (initially
      // ASCII).
      /** @enum */
      var states = {
        ASCII: 0,
        Roman: 1,
        jis0208: 2
      };
      var /** @type {number} */ iso2022jp_state = states.ASCII;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream and iso-2022-jp encoder
        // state is not ASCII, prepend code point to stream, set
        // iso-2022-jp encoder state to ASCII, and return three bytes
        // 0x1B 0x28 0x42.
        if (code_point === end_of_stream &&
            iso2022jp_state !== states.ASCII) {
          stream.prepend(code_point);
          iso2022jp_state = states.ASCII;
          return [0x1B, 0x28, 0x42];
        }
  
        // 2. If code point is end-of-stream and iso-2022-jp encoder
        // state is ASCII, return finished.
        if (code_point === end_of_stream && iso2022jp_state === states.ASCII)
          return finished;
  
        // 3. If ISO-2022-JP encoder state is ASCII or Roman, and code
        // point is U+000E, U+000F, or U+001B, return error with U+FFFD.
        if ((iso2022jp_state === states.ASCII ||
             iso2022jp_state === states.Roman) &&
            (code_point === 0x000E || code_point === 0x000F ||
             code_point === 0x001B)) {
          return encoderError(0xFFFD);
        }
  
        // 4. If iso-2022-jp encoder state is ASCII and code point is an
        // ASCII code point, return a byte whose value is code point.
        if (iso2022jp_state === states.ASCII &&
            isASCIICodePoint(code_point))
          return code_point;
  
        // 5. If iso-2022-jp encoder state is Roman and code point is an
        // ASCII code point, excluding U+005C and U+007E, or is U+00A5
        // or U+203E, run these substeps:
        if (iso2022jp_state === states.Roman &&
            ((isASCIICodePoint(code_point) &&
             code_point !== 0x005C && code_point !== 0x007E) ||
            (code_point == 0x00A5 || code_point == 0x203E))) {
  
          // 1. If code point is an ASCII code point, return a byte
          // whose value is code point.
          if (isASCIICodePoint(code_point))
            return code_point;
  
          // 2. If code point is U+00A5, return byte 0x5C.
          if (code_point === 0x00A5)
            return 0x5C;
  
          // 3. If code point is U+203E, return byte 0x7E.
          if (code_point === 0x203E)
            return 0x7E;
        }
  
        // 6. If code point is an ASCII code point, and iso-2022-jp
        // encoder state is not ASCII, prepend code point to stream, set
        // iso-2022-jp encoder state to ASCII, and return three bytes
        // 0x1B 0x28 0x42.
        if (isASCIICodePoint(code_point) &&
            iso2022jp_state !== states.ASCII) {
          stream.prepend(code_point);
          iso2022jp_state = states.ASCII;
          return [0x1B, 0x28, 0x42];
        }
  
        // 7. If code point is either U+00A5 or U+203E, and iso-2022-jp
        // encoder state is not Roman, prepend code point to stream, set
        // iso-2022-jp encoder state to Roman, and return three bytes
        // 0x1B 0x28 0x4A.
        if ((code_point === 0x00A5 || code_point === 0x203E) &&
            iso2022jp_state !== states.Roman) {
          stream.prepend(code_point);
          iso2022jp_state = states.Roman;
          return [0x1B, 0x28, 0x4A];
        }
  
        // 8. If code point is U+2212, set it to U+FF0D.
        if (code_point === 0x2212)
          code_point = 0xFF0D;
  
        // 9. Let pointer be the index pointer for code point in index
        // jis0208.
        var pointer = indexPointerFor(code_point, index('jis0208'));
  
        // 10. If pointer is null, return error with code point.
        if (pointer === null)
          return encoderError(code_point);
  
        // 11. If iso-2022-jp encoder state is not jis0208, prepend code
        // point to stream, set iso-2022-jp encoder state to jis0208,
        // and return three bytes 0x1B 0x24 0x42.
        if (iso2022jp_state !== states.jis0208) {
          stream.prepend(code_point);
          iso2022jp_state = states.jis0208;
          return [0x1B, 0x24, 0x42];
        }
  
        // 12. Let lead be floor(pointer / 94) + 0x21.
        var lead = floor(pointer / 94) + 0x21;
  
        // 13. Let trail be pointer % 94 + 0x21.
        var trail = pointer % 94 + 0x21;
  
        // 14. Return two bytes whose values are lead and trail.
        return [lead, trail];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['ISO-2022-JP'] = function(options) {
      return new ISO2022JPEncoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['ISO-2022-JP'] = function(options) {
      return new ISO2022JPDecoder(options);
    };
  
    // 13.3 Shift_JIS
  
    // 13.3.1 Shift_JIS decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function ShiftJISDecoder(options) {
      var fatal = options.fatal;
      // Shift_JIS's decoder has an associated Shift_JIS lead (initially
      // 0x00).
      var /** @type {number} */ Shift_JIS_lead = 0x00;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and Shift_JIS lead is not 0x00,
        // set Shift_JIS lead to 0x00 and return error.
        if (bite === end_of_stream && Shift_JIS_lead !== 0x00) {
          Shift_JIS_lead = 0x00;
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream and Shift_JIS lead is 0x00,
        // return finished.
        if (bite === end_of_stream && Shift_JIS_lead === 0x00)
          return finished;
  
        // 3. If Shift_JIS lead is not 0x00, let lead be Shift_JIS lead,
        // let pointer be null, set Shift_JIS lead to 0x00, and then run
        // these substeps:
        if (Shift_JIS_lead !== 0x00) {
          var lead = Shift_JIS_lead;
          var pointer = null;
          Shift_JIS_lead = 0x00;
  
          // 1. Let offset be 0x40, if byte is less than 0x7F, and 0x41
          // otherwise.
          var offset = (bite < 0x7F) ? 0x40 : 0x41;
  
          // 2. Let lead offset be 0x81, if lead is less than 0xA0, and
          // 0xC1 otherwise.
          var lead_offset = (lead < 0xA0) ? 0x81 : 0xC1;
  
          // 3. If byte is in the range 0x40 to 0x7E, inclusive, or 0x80
          // to 0xFC, inclusive, set pointer to (lead − lead offset) ×
          // 188 + byte − offset.
          if (inRange(bite, 0x40, 0x7E) || inRange(bite, 0x80, 0xFC))
            pointer = (lead - lead_offset) * 188 + bite - offset;
  
          // 4. If pointer is in the range 8836 to 10715, inclusive,
          // return a code point whose value is 0xE000 − 8836 + pointer.
          if (inRange(pointer, 8836, 10715))
            return 0xE000 - 8836 + pointer;
  
          // 5. Let code point be null, if pointer is null, and the
          // index code point for pointer in index jis0208 otherwise.
          var code_point = (pointer === null) ? null :
                indexCodePointFor(pointer, index('jis0208'));
  
          // 6. If code point is null and byte is an ASCII byte, prepend
          // byte to stream.
          if (code_point === null && isASCIIByte(bite))
            stream.prepend(bite);
  
          // 7. If code point is null, return error.
          if (code_point === null)
            return decoderError(fatal);
  
          // 8. Return a code point whose value is code point.
          return code_point;
        }
  
        // 4. If byte is an ASCII byte or 0x80, return a code point
        // whose value is byte.
        if (isASCIIByte(bite) || bite === 0x80)
          return bite;
  
        // 5. If byte is in the range 0xA1 to 0xDF, inclusive, return a
        // code point whose value is 0xFF61 − 0xA1 + byte.
        if (inRange(bite, 0xA1, 0xDF))
          return 0xFF61 - 0xA1 + bite;
  
        // 6. If byte is in the range 0x81 to 0x9F, inclusive, or 0xE0
        // to 0xFC, inclusive, set Shift_JIS lead to byte and return
        // continue.
        if (inRange(bite, 0x81, 0x9F) || inRange(bite, 0xE0, 0xFC)) {
          Shift_JIS_lead = bite;
          return null;
        }
  
        // 7. Return error.
        return decoderError(fatal);
      };
    }
  
    // 13.3.2 Shift_JIS encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function ShiftJISEncoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point or U+0080, return a
        // byte whose value is code point.
        if (isASCIICodePoint(code_point) || code_point === 0x0080)
          return code_point;
  
        // 3. If code point is U+00A5, return byte 0x5C.
        if (code_point === 0x00A5)
          return 0x5C;
  
        // 4. If code point is U+203E, return byte 0x7E.
        if (code_point === 0x203E)
          return 0x7E;
  
        // 5. If code point is in the range U+FF61 to U+FF9F, inclusive,
        // return a byte whose value is code point − 0xFF61 + 0xA1.
        if (inRange(code_point, 0xFF61, 0xFF9F))
          return code_point - 0xFF61 + 0xA1;
  
        // 6. If code point is U+2212, set it to U+FF0D.
        if (code_point === 0x2212)
          code_point = 0xFF0D;
  
        // 7. Let pointer be the index Shift_JIS pointer for code point.
        var pointer = indexShiftJISPointerFor(code_point);
  
        // 8. If pointer is null, return error with code point.
        if (pointer === null)
          return encoderError(code_point);
  
        // 9. Let lead be floor(pointer / 188).
        var lead = floor(pointer / 188);
  
        // 10. Let lead offset be 0x81, if lead is less than 0x1F, and
        // 0xC1 otherwise.
        var lead_offset = (lead < 0x1F) ? 0x81 : 0xC1;
  
        // 11. Let trail be pointer % 188.
        var trail = pointer % 188;
  
        // 12. Let offset be 0x40, if trail is less than 0x3F, and 0x41
        // otherwise.
        var offset = (trail < 0x3F) ? 0x40 : 0x41;
  
        // 13. Return two bytes whose values are lead + lead offset and
        // trail + offset.
        return [lead + lead_offset, trail + offset];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['Shift_JIS'] = function(options) {
      return new ShiftJISEncoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['Shift_JIS'] = function(options) {
      return new ShiftJISDecoder(options);
    };
  
    //
    // 14. Legacy multi-byte Korean encodings
    //
  
    // 14.1 euc-kr
  
    // 14.1.1 euc-kr decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function EUCKRDecoder(options) {
      var fatal = options.fatal;
  
      // euc-kr's decoder has an associated euc-kr lead (initially 0x00).
      var /** @type {number} */ euckr_lead = 0x00;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and euc-kr lead is not 0x00, set
        // euc-kr lead to 0x00 and return error.
        if (bite === end_of_stream && euckr_lead !== 0) {
          euckr_lead = 0x00;
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream and euc-kr lead is 0x00, return
        // finished.
        if (bite === end_of_stream && euckr_lead === 0)
          return finished;
  
        // 3. If euc-kr lead is not 0x00, let lead be euc-kr lead, let
        // pointer be null, set euc-kr lead to 0x00, and then run these
        // substeps:
        if (euckr_lead !== 0x00) {
          var lead = euckr_lead;
          var pointer = null;
          euckr_lead = 0x00;
  
          // 1. If byte is in the range 0x41 to 0xFE, inclusive, set
          // pointer to (lead − 0x81) × 190 + (byte − 0x41).
          if (inRange(bite, 0x41, 0xFE))
            pointer = (lead - 0x81) * 190 + (bite - 0x41);
  
          // 2. Let code point be null, if pointer is null, and the
          // index code point for pointer in index euc-kr otherwise.
          var code_point = (pointer === null)
                ? null : indexCodePointFor(pointer, index('euc-kr'));
  
          // 3. If code point is null and byte is an ASCII byte, prepend
          // byte to stream.
          if (pointer === null && isASCIIByte(bite))
            stream.prepend(bite);
  
          // 4. If code point is null, return error.
          if (code_point === null)
            return decoderError(fatal);
  
          // 5. Return a code point whose value is code point.
          return code_point;
        }
  
        // 4. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 5. If byte is in the range 0x81 to 0xFE, inclusive, set
        // euc-kr lead to byte and return continue.
        if (inRange(bite, 0x81, 0xFE)) {
          euckr_lead = bite;
          return null;
        }
  
        // 6. Return error.
        return decoderError(fatal);
      };
    }
  
    // 14.1.2 euc-kr encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function EUCKREncoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. Let pointer be the index pointer for code point in index
        // euc-kr.
        var pointer = indexPointerFor(code_point, index('euc-kr'));
  
        // 4. If pointer is null, return error with code point.
        if (pointer === null)
          return encoderError(code_point);
  
        // 5. Let lead be floor(pointer / 190) + 0x81.
        var lead = floor(pointer / 190) + 0x81;
  
        // 6. Let trail be pointer % 190 + 0x41.
        var trail = (pointer % 190) + 0x41;
  
        // 7. Return two bytes whose values are lead and trail.
        return [lead, trail];
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['EUC-KR'] = function(options) {
      return new EUCKREncoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['EUC-KR'] = function(options) {
      return new EUCKRDecoder(options);
    };
  
  
    //
    // 15. Legacy miscellaneous encodings
    //
  
    // 15.1 replacement
  
    // Not needed - API throws RangeError
  
    // 15.2 Common infrastructure for utf-16be and utf-16le
  
    /**
     * @param {number} code_unit
     * @param {boolean} utf16be
     * @return {!Array.<number>} bytes
     */
    function convertCodeUnitToBytes(code_unit, utf16be) {
      // 1. Let byte1 be code unit >> 8.
      var byte1 = code_unit >> 8;
  
      // 2. Let byte2 be code unit & 0x00FF.
      var byte2 = code_unit & 0x00FF;
  
      // 3. Then return the bytes in order:
          // utf-16be flag is set: byte1, then byte2.
      if (utf16be)
        return [byte1, byte2];
      // utf-16be flag is unset: byte2, then byte1.
      return [byte2, byte1];
    }
  
    // 15.2.1 shared utf-16 decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {boolean} utf16_be True if big-endian, false if little-endian.
     * @param {{fatal: boolean}} options
     */
    function UTF16Decoder(utf16_be, options) {
      var fatal = options.fatal;
      var /** @type {?number} */ utf16_lead_byte = null,
          /** @type {?number} */ utf16_lead_surrogate = null;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream and either utf-16 lead byte or
        // utf-16 lead surrogate is not null, set utf-16 lead byte and
        // utf-16 lead surrogate to null, and return error.
        if (bite === end_of_stream && (utf16_lead_byte !== null ||
                                  utf16_lead_surrogate !== null)) {
          return decoderError(fatal);
        }
  
        // 2. If byte is end-of-stream and utf-16 lead byte and utf-16
        // lead surrogate are null, return finished.
        if (bite === end_of_stream && utf16_lead_byte === null &&
            utf16_lead_surrogate === null) {
          return finished;
        }
  
        // 3. If utf-16 lead byte is null, set utf-16 lead byte to byte
        // and return continue.
        if (utf16_lead_byte === null) {
          utf16_lead_byte = bite;
          return null;
        }
  
        // 4. Let code unit be the result of:
        var code_unit;
        if (utf16_be) {
          // utf-16be decoder flag is set
          //   (utf-16 lead byte << 8) + byte.
          code_unit = (utf16_lead_byte << 8) + bite;
        } else {
          // utf-16be decoder flag is unset
          //   (byte << 8) + utf-16 lead byte.
          code_unit = (bite << 8) + utf16_lead_byte;
        }
        // Then set utf-16 lead byte to null.
        utf16_lead_byte = null;
  
        // 5. If utf-16 lead surrogate is not null, let lead surrogate
        // be utf-16 lead surrogate, set utf-16 lead surrogate to null,
        // and then run these substeps:
        if (utf16_lead_surrogate !== null) {
          var lead_surrogate = utf16_lead_surrogate;
          utf16_lead_surrogate = null;
  
          // 1. If code unit is in the range U+DC00 to U+DFFF,
          // inclusive, return a code point whose value is 0x10000 +
          // ((lead surrogate − 0xD800) << 10) + (code unit − 0xDC00).
          if (inRange(code_unit, 0xDC00, 0xDFFF)) {
            return 0x10000 + (lead_surrogate - 0xD800) * 0x400 +
                (code_unit - 0xDC00);
          }
  
          // 2. Prepend the sequence resulting of converting code unit
          // to bytes using utf-16be decoder flag to stream and return
          // error.
          stream.prepend(convertCodeUnitToBytes(code_unit, utf16_be));
          return decoderError(fatal);
        }
  
        // 6. If code unit is in the range U+D800 to U+DBFF, inclusive,
        // set utf-16 lead surrogate to code unit and return continue.
        if (inRange(code_unit, 0xD800, 0xDBFF)) {
          utf16_lead_surrogate = code_unit;
          return null;
        }
  
        // 7. If code unit is in the range U+DC00 to U+DFFF, inclusive,
        // return error.
        if (inRange(code_unit, 0xDC00, 0xDFFF))
          return decoderError(fatal);
  
        // 8. Return code point code unit.
        return code_unit;
      };
    }
  
    // 15.2.2 shared utf-16 encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {boolean} utf16_be True if big-endian, false if little-endian.
     * @param {{fatal: boolean}} options
     */
    function UTF16Encoder(utf16_be, options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1. If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is in the range U+0000 to U+FFFF, inclusive,
        // return the sequence resulting of converting code point to
        // bytes using utf-16be encoder flag.
        if (inRange(code_point, 0x0000, 0xFFFF))
          return convertCodeUnitToBytes(code_point, utf16_be);
  
        // 3. Let lead be ((code point − 0x10000) >> 10) + 0xD800,
        // converted to bytes using utf-16be encoder flag.
        var lead = convertCodeUnitToBytes(
          ((code_point - 0x10000) >> 10) + 0xD800, utf16_be);
  
        // 4. Let trail be ((code point − 0x10000) & 0x3FF) + 0xDC00,
        // converted to bytes using utf-16be encoder flag.
        var trail = convertCodeUnitToBytes(
          ((code_point - 0x10000) & 0x3FF) + 0xDC00, utf16_be);
  
        // 5. Return a byte sequence of lead followed by trail.
        return lead.concat(trail);
      };
    }
  
    // 15.3 utf-16be
    // 15.3.1 utf-16be decoder
    /** @param {{fatal: boolean}} options */
    encoders['UTF-16BE'] = function(options) {
      return new UTF16Encoder(true, options);
    };
    // 15.3.2 utf-16be encoder
    /** @param {{fatal: boolean}} options */
    decoders['UTF-16BE'] = function(options) {
      return new UTF16Decoder(true, options);
    };
  
    // 15.4 utf-16le
    // 15.4.1 utf-16le decoder
    /** @param {{fatal: boolean}} options */
    encoders['UTF-16LE'] = function(options) {
      return new UTF16Encoder(false, options);
    };
    // 15.4.2 utf-16le encoder
    /** @param {{fatal: boolean}} options */
    decoders['UTF-16LE'] = function(options) {
      return new UTF16Decoder(false, options);
    };
  
    // 15.5 x-user-defined
  
    // 15.5.1 x-user-defined decoder
    /**
     * @constructor
     * @implements {Decoder}
     * @param {{fatal: boolean}} options
     */
    function XUserDefinedDecoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream The stream of bytes being decoded.
       * @param {number} bite The next byte read from the stream.
       * @return {?(number|!Array.<number>)} The next code point(s)
       *     decoded, or null if not enough data exists in the input
       *     stream to decode a complete code point.
       */
      this.handler = function(stream, bite) {
        // 1. If byte is end-of-stream, return finished.
        if (bite === end_of_stream)
          return finished;
  
        // 2. If byte is an ASCII byte, return a code point whose value
        // is byte.
        if (isASCIIByte(bite))
          return bite;
  
        // 3. Return a code point whose value is 0xF780 + byte − 0x80.
        return 0xF780 + bite - 0x80;
      };
    }
  
    // 15.5.2 x-user-defined encoder
    /**
     * @constructor
     * @implements {Encoder}
     * @param {{fatal: boolean}} options
     */
    function XUserDefinedEncoder(options) {
      var fatal = options.fatal;
      /**
       * @param {Stream} stream Input stream.
       * @param {number} code_point Next code point read from the stream.
       * @return {(number|!Array.<number>)} Byte(s) to emit.
       */
      this.handler = function(stream, code_point) {
        // 1.If code point is end-of-stream, return finished.
        if (code_point === end_of_stream)
          return finished;
  
        // 2. If code point is an ASCII code point, return a byte whose
        // value is code point.
        if (isASCIICodePoint(code_point))
          return code_point;
  
        // 3. If code point is in the range U+F780 to U+F7FF, inclusive,
        // return a byte whose value is code point − 0xF780 + 0x80.
        if (inRange(code_point, 0xF780, 0xF7FF))
          return code_point - 0xF780 + 0x80;
  
        // 4. Return error with code point.
        return encoderError(code_point);
      };
    }
  
    /** @param {{fatal: boolean}} options */
    encoders['x-user-defined'] = function(options) {
      return new XUserDefinedEncoder(options);
    };
    /** @param {{fatal: boolean}} options */
    decoders['x-user-defined'] = function(options) {
      return new XUserDefinedDecoder(options);
    };
  
    if (!global['TextEncoder'])
      global['TextEncoder'] = TextEncoder;
    if (!global['TextDecoder'])
      global['TextDecoder'] = TextDecoder;
  
    if (typeof module !== "undefined" && module.exports) {
      module.exports = {
        TextEncoder: global['TextEncoder'],
        TextDecoder: global['TextDecoder'],
        EncodingIndexes: global["encoding-indexes"]
      };
    }
  
  // For strict environments where `this` inside the global scope
  // is `undefined`, take a pure object instead
  }(this || {}));