wget http://nginx.org/download/nginx-1.6.2.tar.gz

wget https://github.com/openresty/headers-more-nginx-module/archive/v0.33.tar.gz

wget https://github.com/warmcat/libwebsockets/archive/v3.2.2.tar.gz

wget https://mosquitto.org/files/source/mosquitto-1.6.8.tar.gz

 sudo apt-get install cmake make zlib zlib-devel gcc-c++ libtool  openssl openssl-devel

sudo mkdir /opt/nginx
-- 解压nginx
 tar -xzvf nginx-1.13.6.tar.gz
cd nginx-1.13.6/
--将nginx的新曾模块解压到上一层目录安装目录/opt/nginx
sudo ./configure --prefix=/opt/nginx --with-http_stub_status_module --with-http_ssl_module --with-http_proxy_module  --add-module=../headers-more-nginx-module-0.33


sudo make

sudo make install

解压文件：
tar -xzvf v3.2.2.tar.gz

cd libwebsockets-3.2.2/

mkdir build

cmake ..

sudo make

sudo make install


参考文档
https://blog.csdn.net/houjixin/article/details/79789448

安装方案一
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
sudo apt-get update
sudo apt-get install mosquitto
安装完成查看版本
mosquitto -V

安装方案二

wget https://mosquitto.org/files/source/mosquitto-1.6.8.tar.gz
tar -xvzf mosquitto-1.6.8.tar.gz
cd mosquitto-1.6.8/
 make &&make install
参考
https://blog.csdn.net/russle/article/details/80469942
注意：make之前修改 config.mk 文件
WITH_WEBSOCKETS:=yes 改成yes

listener 8811
protocol websockets

sudo mosquitto -c /etc/mosquitto/mosquitto.conf

server {
    server_name  ****。**;
    location /mqtt/ {
        proxy_pass http://localhost:8811;
        proxy_redirect off;
        proxy_set_header Host localhost:8811;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header Sec-WebSocket-Protocol mqtt;
        more_clear_headers Sec-WebSocket-Protocol;

    }
  # certbot生成
    ssl on;
    listen 80;
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/I****。*/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/****。*/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}

/*******************************************************************************
 * Copyright (c) 2013 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Andrew Banks - initial API and implementation and initial documentation
 *******************************************************************************/


// Only expose a single object name in the global namespace.
// Everything must go through this module. Global Paho.MQTT module
// only has a single public function, client, which returns
// a Paho.MQTT client object given connection details.

/**
 * Send and receive messages using web browsers.
 * <p>
 * This programming interface lets a JavaScript client application use the MQTT V3.1 or
 * V3.1.1 protocol to connect to an MQTT-supporting messaging server.
 *
 * The function supported includes:
 * <ol>
 * <li>Connecting to and disconnecting from a server. The server is identified by its host name and port number.
 * <li>Specifying options that relate to the communications link with the server,
 * for example the frequency of keep-alive heartbeats, and whether SSL/TLS is required.
 * <li>Subscribing to and receiving messages from MQTT Topics.
 * <li>Publishing messages to MQTT Topics.
 * </ol>
 * <p>
 * The API consists of two main objects:
 * <dl>
 * <dt><b>{@link Paho.MQTT.Client}</b></dt>
 * <dd>This contains methods that provide the functionality of the API,
 * including provision of callbacks that notify the application when a message
 * arrives from or is delivered to the messaging server,
 * or when the status of its connection to the messaging server changes.</dd>
 * <dt><b>{@link Paho.MQTT.Message}</b></dt>
 * <dd>This encapsulates the payload of the message along with various attributes
 * associated with its delivery, in particular the destination to which it has
 * been (or is about to be) sent.</dd>
 * </dl>
 * <p>
 * The programming interface validates parameters passed to it, and will throw
 * an Error containing an error message intended for developer use, if it detects
 * an error with any parameter.
 * <p>
 * Example:
 *
 * <code><pre>
 client = new Paho.MQTT.Client(location.hostname, Number(location.port), "clientId");
 client.onConnectionLost = onConnectionLost;
 client.onMessageArrived = onMessageArrived;
 client.connect({onSuccess:onConnect});
 function onConnect() {
  // Once a connection has been made, make a subscription and send a message.
  console.log("onConnect");
  client.subscribe("/World");
  message = new Paho.MQTT.Message("Hello");
  message.destinationName = "/World";
  client.send(message);
};
 function onConnectionLost(responseObject) {
  if (responseObject.errorCode !== 0)
  console.log("onConnectionLost:"+responseObject.errorMessage);
};
 function onMessageArrived(message) {
  console.log("onMessageArrived:"+message.payloadString);
  client.disconnect();
};
 * </pre></code>
 * @namespace Paho.MQTT
 */

/* jshint shadow:true */
(function ExportLibrary(root, factory) {
  if (typeof exports === 'object' && typeof module === 'object') {
    module.exports = factory();
  } else if (typeof define === 'function' && define.amd) {
    define(factory);
  } else if (typeof exports === 'object') {
    exports = factory();
  } else {
    if (typeof root.Paho === 'undefined') {
      root.Paho = {};
    }
    root.Paho.MQTT = factory();
  }
})(global, function LibraryFactory() {


  var PahoMQTT = (function(wx) {

    // Private variables below, these are only visible inside the function closure
    // which is used to define the module.

    var version = "@VERSION@";
    var buildLevel = "@BUILDLEVEL@";

    /**
     * Unique message type identifiers, with associated
     * associated integer values.
     * @private
     */
    var MESSAGE_TYPE = {
      CONNECT: 1,
      CONNACK: 2,
      PUBLISH: 3,
      PUBACK: 4,
      PUBREC: 5,
      PUBREL: 6,
      PUBCOMP: 7,
      SUBSCRIBE: 8,
      SUBACK: 9,
      UNSUBSCRIBE: 10,
      UNSUBACK: 11,
      PINGREQ: 12,
      PINGRESP: 13,
      DISCONNECT: 14
    };

    // Collection of utility methods used to simplify module code
    // and promote the DRY pattern.

    /**
     * Validate an object's parameter names to ensure they
     * match a list of expected variables name for this option
     * type. Used to ensure option object passed into the API don't
     * contain erroneous parameters.
     * @param {Object} obj - User options object
     * @param {Object} keys - valid keys and types that may exist in obj.
     * @throws {Error} Invalid option parameter found.
     * @private
     */
    var validate = function(obj, keys) {
      for (var key in obj) {
        if (obj.hasOwnProperty(key)) {
          if (keys.hasOwnProperty(key)) {
            if (typeof obj[key] !== keys[key])
              throw new Error(format(ERROR.INVALID_TYPE, [typeof obj[key], key]));
          } else {
            var errorStr = "Unknown property, " + key + ". Valid properties are:";
            for (var validKey in keys)
              if (keys.hasOwnProperty(validKey))
                errorStr = errorStr + " " + validKey;
            throw new Error(errorStr);
          }
        }
      }
    };

    /**
     * Return a new function which runs the user function bound
     * to a fixed scope.
     * @param {function} User function
     * @param {object} Function scope
     * @return {function} User function bound to another scope
     * @private
     */
    var scope = function(f, scope) {
      return function() {
        return f.apply(scope, arguments);
      };
    };

    /**
     * Unique message type identifiers, with associated
     * associated integer values.
     * @private
     */
    var ERROR = {
      OK: { code: 0, text: "AMQJSC0000I OK." },
      CONNECT_TIMEOUT: { code: 1, text: "AMQJSC0001E Connect timed out." },
      SUBSCRIBE_TIMEOUT: { code: 2, text: "AMQJS0002E Subscribe timed out." },
      UNSUBSCRIBE_TIMEOUT: { code: 3, text: "AMQJS0003E Unsubscribe timed out." },
      PING_TIMEOUT: { code: 4, text: "AMQJS0004E Ping timed out." },
      INTERNAL_ERROR: { code: 5, text: "AMQJS0005E Internal error. Error Message: {0}, Stack trace: {1}" },
      CONNACK_RETURNCODE: { code: 6, text: "AMQJS0006E Bad Connack return code:{0} {1}." },
      SOCKET_ERROR: { code: 7, text: "AMQJS0007E Socket error:{0}." },
      SOCKET_CLOSE: { code: 8, text: "AMQJS0008I Socket closed." },
      MALFORMED_UTF: { code: 9, text: "AMQJS0009E Malformed UTF data:{0} {1} {2}." },
      UNSUPPORTED: { code: 10, text: "AMQJS0010E {0} is not supported by this browser." },
      INVALID_STATE: { code: 11, text: "AMQJS0011E Invalid state {0}." },
      INVALID_TYPE: { code: 12, text: "AMQJS0012E Invalid type {0} for {1}." },
      INVALID_ARGUMENT: { code: 13, text: "AMQJS0013E Invalid argument {0} for {1}." },
      UNSUPPORTED_OPERATION: { code: 14, text: "AMQJS0014E Unsupported operation." },
      INVALID_STORED_DATA: { code: 15, text: "AMQJS0015E Invalid data in local storage key={0} value={1}." },
      INVALID_MQTT_MESSAGE_TYPE: { code: 16, text: "AMQJS0016E Invalid MQTT message type {0}." },
      MALFORMED_UNICODE: { code: 17, text: "AMQJS0017E Malformed Unicode string:{0} {1}." },
      BUFFER_FULL: { code: 18, text: "AMQJS0018E Message buffer is full, maximum buffer size: {0}." },
    };

    /** CONNACK RC Meaning. */
    var CONNACK_RC = {
      0: "Connection Accepted",
      1: "Connection Refused: unacceptable protocol version",
      2: "Connection Refused: identifier rejected",
      3: "Connection Refused: server unavailable",
      4: "Connection Refused: bad user name or password",
      5: "Connection Refused: not authorized"
    };

    /**
     * Format an error message text.
     * @private
     * @param {error} ERROR.KEY value above.
     * @param {substitutions} [array] substituted into the text.
     * @return the text with the substitutions made.
     */
    var format = function(error, substitutions) {
      var text = error.text;
      if (substitutions) {
        var field, start;
        for (var i = 0; i < substitutions.length; i++) {
          field = "{" + i + "}";
          start = text.indexOf(field);
          if (start > 0) {
            var part1 = text.substring(0, start);
            var part2 = text.substring(start + field.length);
            text = part1 + substitutions[i] + part2;
          }
        }
      }
      return text;
    };

    //MQTT protocol and version          6    M    Q    I    s    d    p    3
    var MqttProtoIdentifierv3 = [0x00, 0x06, 0x4d, 0x51, 0x49, 0x73, 0x64, 0x70, 0x03];
    //MQTT proto/version for 311         4    M    Q    T    T    4
    var MqttProtoIdentifierv4 = [0x00, 0x04, 0x4d, 0x51, 0x54, 0x54, 0x04];

    /**
     * Construct an MQTT wire protocol message.
     * @param type MQTT packet type.
     * @param options optional wire message attributes.
     *
     * Optional properties
     *
     * messageIdentifier: message ID in the range [0..65535]
     * payloadMessage:  Application Message - PUBLISH only
     * connectStrings:  array of 0 or more Strings to be put into the CONNECT payload
     * topics:      array of strings (SUBSCRIBE, UNSUBSCRIBE)
     * requestQoS:    array of QoS values [0..2]
     *
     * "Flag" properties
     * cleanSession:  true if present / false if absent (CONNECT)
     * willMessage:   true if present / false if absent (CONNECT)
     * isRetained:    true if present / false if absent (CONNECT)
     * userName:    true if present / false if absent (CONNECT)
     * password:    true if present / false if absent (CONNECT)
     * keepAliveInterval: integer [0..65535]  (CONNECT)
     *
     * @private
     * @ignore
     */
    var WireMessage = function(type, options) {
      this.type = type;
      for (var name in options) {
        if (options.hasOwnProperty(name)) {
          this[name] = options[name];
        }
      }
    };

    WireMessage.prototype.encode = function() {
      // Compute the first byte of the fixed header
      var first = ((this.type & 0x0f) << 4);

      /*
       * Now calculate the length of the variable header + payload by adding up the lengths
       * of all the component parts
       */

      var remLength = 0;
      var topicStrLength = [];
      var destinationNameLength = 0;
      var willMessagePayloadBytes;

      // if the message contains a messageIdentifier then we need two bytes for that
      if (this.messageIdentifier !== undefined)
        remLength += 2;

      switch (this.type) {
        // If this a Connect then we need to include 12 bytes for its header
        case MESSAGE_TYPE.CONNECT:
          switch (this.mqttVersion) {
            case 3:
              remLength += MqttProtoIdentifierv3.length + 3;
              break;
            case 4:
              remLength += MqttProtoIdentifierv4.length + 3;
              break;
          }

          remLength += UTF8Length(this.clientId) + 2;
          if (this.willMessage !== undefined) {
            remLength += UTF8Length(this.willMessage.destinationName) + 2;
            // Will message is always a string, sent as UTF-8 characters with a preceding length.
            willMessagePayloadBytes = this.willMessage.payloadBytes;
            if (!(willMessagePayloadBytes instanceof Uint8Array))
              willMessagePayloadBytes = new Uint8Array(payloadBytes);
            remLength += willMessagePayloadBytes.byteLength + 2;
          }
          if (this.userName !== undefined)
            remLength += UTF8Length(this.userName) + 2;
          if (this.password !== undefined)
            remLength += UTF8Length(this.password) + 2;
          break;

        // Subscribe, Unsubscribe can both contain topic strings
        case MESSAGE_TYPE.SUBSCRIBE:
          first |= 0x02; // Qos = 1;
          for (var i = 0; i < this.topics.length; i++) {
            topicStrLength[i] = UTF8Length(this.topics[i]);
            remLength += topicStrLength[i] + 2;
          }
          remLength += this.requestedQos.length; // 1 byte for each topic's Qos
          // QoS on Subscribe only
          break;

        case MESSAGE_TYPE.UNSUBSCRIBE:
          first |= 0x02; // Qos = 1;
          for (var i = 0; i < this.topics.length; i++) {
            topicStrLength[i] = UTF8Length(this.topics[i]);
            remLength += topicStrLength[i] + 2;
          }
          break;

        case MESSAGE_TYPE.PUBREL:
          first |= 0x02; // Qos = 1;
          break;

        case MESSAGE_TYPE.PUBLISH:
          if (this.payloadMessage.duplicate) first |= 0x08;
          first = first |= (this.payloadMessage.qos << 1);
          if (this.payloadMessage.retained) first |= 0x01;
          destinationNameLength = UTF8Length(this.payloadMessage.destinationName);
          remLength += destinationNameLength + 2;
          var payloadBytes = this.payloadMessage.payloadBytes;
          remLength += payloadBytes.byteLength;
          if (payloadBytes instanceof ArrayBuffer)
            payloadBytes = new Uint8Array(payloadBytes);
          else if (!(payloadBytes instanceof Uint8Array))
            payloadBytes = new Uint8Array(payloadBytes.buffer);
          break;

        case MESSAGE_TYPE.DISCONNECT:
          break;

        default:
          break;
      }

      // Now we can allocate a buffer for the message

      var mbi = encodeMBI(remLength); // Convert the length to MQTT MBI format
      var pos = mbi.length + 1; // Offset of start of variable header
      var buffer = new ArrayBuffer(remLength + pos);
      var byteStream = new Uint8Array(buffer); // view it as a sequence of bytes

      //Write the fixed header into the buffer
      byteStream[0] = first;
      byteStream.set(mbi, 1);

      // If this is a PUBLISH then the variable header starts with a topic
      if (this.type == MESSAGE_TYPE.PUBLISH)
        pos = writeString(this.payloadMessage.destinationName, destinationNameLength, byteStream, pos);
      // If this is a CONNECT then the variable header contains the protocol name/version, flags and keepalive time

      else if (this.type == MESSAGE_TYPE.CONNECT) {
        switch (this.mqttVersion) {
          case 3:
            byteStream.set(MqttProtoIdentifierv3, pos);
            pos += MqttProtoIdentifierv3.length;
            break;
          case 4:
            byteStream.set(MqttProtoIdentifierv4, pos);
            pos += MqttProtoIdentifierv4.length;
            break;
        }
        var connectFlags = 0;
        if (this.cleanSession)
          connectFlags = 0x02;
        if (this.willMessage !== undefined) {
          connectFlags |= 0x04;
          connectFlags |= (this.willMessage.qos << 3);
          if (this.willMessage.retained) {
            connectFlags |= 0x20;
          }
        }
        if (this.userName !== undefined)
          connectFlags |= 0x80;
        if (this.password !== undefined)
          connectFlags |= 0x40;
        byteStream[pos++] = connectFlags;
        pos = writeUint16(this.keepAliveInterval, byteStream, pos);
      }

      // Output the messageIdentifier - if there is one
      if (this.messageIdentifier !== undefined)
        pos = writeUint16(this.messageIdentifier, byteStream, pos);

      switch (this.type) {
        case MESSAGE_TYPE.CONNECT:
          pos = writeString(this.clientId, UTF8Length(this.clientId), byteStream, pos);
          if (this.willMessage !== undefined) {
            pos = writeString(this.willMessage.destinationName, UTF8Length(this.willMessage.destinationName), byteStream, pos);
            pos = writeUint16(willMessagePayloadBytes.byteLength, byteStream, pos);
            byteStream.set(willMessagePayloadBytes, pos);
            pos += willMessagePayloadBytes.byteLength;

          }
          if (this.userName !== undefined)
            pos = writeString(this.userName, UTF8Length(this.userName), byteStream, pos);
          if (this.password !== undefined)
            pos = writeString(this.password, UTF8Length(this.password), byteStream, pos);
          break;

        case MESSAGE_TYPE.PUBLISH:
          // PUBLISH has a text or binary payload, if text do not add a 2 byte length field, just the UTF characters.
          byteStream.set(payloadBytes, pos);

          break;

        //          case MESSAGE_TYPE.PUBREC:
        //          case MESSAGE_TYPE.PUBREL:
        //          case MESSAGE_TYPE.PUBCOMP:
        //            break;

        case MESSAGE_TYPE.SUBSCRIBE:
          // SUBSCRIBE has a list of topic strings and request QoS
          for (var i = 0; i < this.topics.length; i++) {
            pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
            byteStream[pos++] = this.requestedQos[i];
          }
          break;

        case MESSAGE_TYPE.UNSUBSCRIBE:
          // UNSUBSCRIBE has a list of topic strings
          for (var i = 0; i < this.topics.length; i++)
            pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
          break;

        default:
        // Do nothing.
      }

      return buffer;
    };

    function decodeMessage(input, pos) {
      var startingPos = pos;
      var first = input[pos];
      var type = first >> 4;
      var messageInfo = first &= 0x0f;
      pos += 1;


      // Decode the remaining length (MBI format)

      var digit;
      var remLength = 0;
      var multiplier = 1;
      do {
        if (pos == input.length) {
          return [null, startingPos];
        }
        digit = input[pos++];
        remLength += ((digit & 0x7F) * multiplier);
        multiplier *= 128;
      } while ((digit & 0x80) !== 0);

      var endPos = pos + remLength;
      if (endPos > input.length) {
        return [null, startingPos];
      }

      var wireMessage = new WireMessage(type);
      switch (type) {
        case MESSAGE_TYPE.CONNACK:
          var connectAcknowledgeFlags = input[pos++];
          if (connectAcknowledgeFlags & 0x01)
            wireMessage.sessionPresent = true;
          wireMessage.returnCode = input[pos++];
          break;

        case MESSAGE_TYPE.PUBLISH:
          var qos = (messageInfo >> 1) & 0x03;

          var len = readUint16(input, pos);
          pos += 2;
          var topicName = parseUTF8(input, pos, len);
          pos += len;
          // If QoS 1 or 2 there will be a messageIdentifier
          if (qos > 0) {
            wireMessage.messageIdentifier = readUint16(input, pos);
            pos += 2;
          }

          var message = new Message(input.subarray(pos, endPos));
          if ((messageInfo & 0x01) == 0x01)
            message.retained = true;
          if ((messageInfo & 0x08) == 0x08)
            message.duplicate = true;
          message.qos = qos;
          message.destinationName = topicName;
          wireMessage.payloadMessage = message;
          break;

        case MESSAGE_TYPE.PUBACK:
        case MESSAGE_TYPE.PUBREC:
        case MESSAGE_TYPE.PUBREL:
        case MESSAGE_TYPE.PUBCOMP:
        case MESSAGE_TYPE.UNSUBACK:
          wireMessage.messageIdentifier = readUint16(input, pos);
          break;

        case MESSAGE_TYPE.SUBACK:
          wireMessage.messageIdentifier = readUint16(input, pos);
          pos += 2;
          wireMessage.returnCode = input.subarray(pos, endPos);
          break;

        default:
          break;
      }

      return [wireMessage, endPos];
    }

    function writeUint16(input, buffer, offset) {
      buffer[offset++] = input >> 8; //MSB
      buffer[offset++] = input % 256; //LSB
      return offset;
    }

    function writeString(input, utf8Length, buffer, offset) {
      offset = writeUint16(utf8Length, buffer, offset);
      stringToUTF8(input, buffer, offset);
      return offset + utf8Length;
    }

    function readUint16(buffer, offset) {
      return 256 * buffer[offset] + buffer[offset + 1];
    }

    /**
     * Encodes an MQTT Multi-Byte Integer
     * @private
     */
    function encodeMBI(number) {
      var output = new Array(1);
      var numBytes = 0;

      do {
        var digit = number % 128;
        number = number >> 7;
        if (number > 0) {
          digit |= 0x80;
        }
        output[numBytes++] = digit;
      } while ((number > 0) && (numBytes < 4));

      return output;
    }

    /**
     * Takes a String and calculates its length in bytes when encoded in UTF8.
     * @private
     */
    function UTF8Length(input) {
      var output = 0;
      for (var i = 0; i < input.length; i++) {
        var charCode = input.charCodeAt(i);
        if (charCode > 0x7FF) {
          // Surrogate pair means its a 4 byte character
          if (0xD800 <= charCode && charCode <= 0xDBFF) {
            i++;
            output++;
          }
          output += 3;
        } else if (charCode > 0x7F)
          output += 2;
        else
          output++;
      }
      return output;
    }

    /**
     * Takes a String and writes it into an array as UTF8 encoded bytes.
     * @private
     */
    function stringToUTF8(input, output, start) {
      var pos = start;
      for (var i = 0; i < input.length; i++) {
        var charCode = input.charCodeAt(i);

        // Check for a surrogate pair.
        if (0xD800 <= charCode && charCode <= 0xDBFF) {
          var lowCharCode = input.charCodeAt(++i);
          if (isNaN(lowCharCode)) {
            throw new Error(format(ERROR.MALFORMED_UNICODE, [charCode, lowCharCode]));
          }
          charCode = ((charCode - 0xD800) << 10) + (lowCharCode - 0xDC00) + 0x10000;

        }

        if (charCode <= 0x7F) {
          output[pos++] = charCode;
        } else if (charCode <= 0x7FF) {
          output[pos++] = charCode >> 6 & 0x1F | 0xC0;
          output[pos++] = charCode & 0x3F | 0x80;
        } else if (charCode <= 0xFFFF) {
          output[pos++] = charCode >> 12 & 0x0F | 0xE0;
          output[pos++] = charCode >> 6 & 0x3F | 0x80;
          output[pos++] = charCode & 0x3F | 0x80;
        } else {
          output[pos++] = charCode >> 18 & 0x07 | 0xF0;
          output[pos++] = charCode >> 12 & 0x3F | 0x80;
          output[pos++] = charCode >> 6 & 0x3F | 0x80;
          output[pos++] = charCode & 0x3F | 0x80;
        }
      }
      return output;
    }

    function parseUTF8(input, offset, length) {
      var output = "";
      var utf16;
      var pos = offset;

      while (pos < offset + length) {
        var byte1 = input[pos++];
        if (byte1 < 128)
          utf16 = byte1;
        else {
          var