code:
'use strict';

const zlib = require('zlib');

const bufferUtil = require('./buffer-util');
const Limiter = require('./limiter');
const { kStatusCode } = require('./constants');

const FastBuffer = Buffer[Symbol.species];
const TRAILER = Buffer.from([0x00, 0x00, 0xff, 0xff]);
const kPerMessageDeflate = Symbol('permessage-deflate');
const kTotalLength = Symbol('total-length');
const kCallback = Symbol('callback');
const kBuffers = Symbol('buffers');
const kError = Symbol('error');

//
// We limit zlib concurrency, which prevents severe memory fragmentation
// as documented in https://github.com/nodejs/node/issues/8871#issuecomment-250915913
// and https://github.com/websockets/ws/issues/1202
//
// Intentionally global; it's the global thread pool that's an issue.
//
let zlibLimiter;

/**
 * permessage-deflate implementation.
 */
class PerMessageDeflate {
  /**
   * Creates a PerMessageDeflate instance.
   *
   * @param {Object} [options] Configuration options
   * @param {(Boolean|Number)} [options.clientMaxWindowBits] Advertise support
   *     for, or request, a custom client window size
   * @param {Boolean} [options.clientNoContextTakeover=false] Advertise/
   *     acknowledge disabling of client context takeover
   * @param {Number} [options.concurrencyLimit=10] The number of concurrent
   *     calls to zlib
   * @param {(Boolean|Number)} [options.serverMaxWindowBits] Request/confirm the
   *     use of a custom server window size
   * @param {Boolean} [options.serverNoContextTakeover=false] Request/accept
   *     disabling of server context takeover
   * @param {Number} [options.threshold=1024] Size (in bytes) below which
   *     messages should not be compressed if context takeover is disabled
   * @param {Object} [options.zlibDeflateOptions] Options to pass to zlib on
   *     deflate
   * @param {Object} [options.zlibInflateOptions] Options to pass to zlib on
   *     inflate
   * @param {Boolean} [isServer=false] Create the instance in either server or
   *     client mode
   * @param {Number} [maxPayload=0] The maximum allowed message length
   */
  constructor(options, isServer, maxPayload) {
    this._maxPayload = maxPayload | 0;
    this._options = options || {};
    this._threshold =
      this._options.threshold !== undefined ? this._options.threshold : 1024;
    this._isServer = !!isServer;
    this._deflate = null;
    this._inflate = null;

    this.params = null;

    if (!zlibLimiter) {
      const concurrency =
        this._options.concurrencyLimit !== undefined
          ? this._options.concurrencyLimit
          : 10;
      zlibLimiter = new Limiter(concurrency);
    }
  }

  /**
   * @type {String}
   */
  static get extensionName() {
    return 'permessage-deflate';
  }

  /**
   * Create an extension negotiation offer.
   *
   * @return {Object} Extension parameters
   * @public
   */
  offer() {
    const params = {};

    if (this._options.serverNoContextTakeover) {
      params.server_no_context_takeover = true;
    }
    if (this._options.clientNoContextTakeover) {
      params.client_no_context_takeover = true;
    }
    if (this._options.serverMaxWindowBits) {
      params.server_max_window_bits = this._options.serverMaxWindowBits;
    }
    if (this._options.clientMaxWindowBits) {
      params.client_max_window_bits = this._options.clientMaxWindowBits;
    } else if (this._options.clientMaxWindowBits == null) {
      params.client_max_window_bits = true;
    }

    return params;
  }

  /**
   * Accept an extension negotiation offer/response.
   *
   * @param {Array} configurations The extension negotiation offers/reponse
   * @return {Object} Accepted configuration
   * @public
   */
  accept(configurations) {
    configurations = this.normalizeParams(configurations);

    this.params = this._isServer
      ? this.acceptAsServer(configurations)
      : this.acceptAsClient(configurations);

    return this.params;
  }

  /**
   * Releases all resources used by the extension.
   *
   * @public
   */
  cleanup() {
    if (this._inflate) {
      this._inflate.close();
      this._inflate = null;
    }

    if (this._deflate) {
      const callback = this._deflate[kCallback];

      this._deflate.close();
      this._deflate = null;

      if (callback) {
        callback(
          new Error(
            'The deflate stream was closed while data was being processed'
          )
        );
      }
    }
  }

  /**
   *  Accept an extension negotiation offer.
   *
   * @param {Array} offers The extension negotiation offers
   * @return {Object} Accepted configuration
   * @private
   */
  acceptAsServer(offers) {
    const opts = this._options;
    const accepted = offers.find((params) => {
      if (
        (opts.serverNoContextTakeover === false &&
          params.server_no_context_takeover) ||
        (params.server_max_window_bits &&
          (opts.serverMaxWindowBits === false ||
            (typeof opts.serverMaxWindowBits === 'number' &&
              opts.serverMaxWindowBits > params.server_max_window_bits))) ||
        (typeof opts.clientMaxWindowBits === 'number' &&
          !params.client_max_window_bits)
      ) {
        return false;
      }

      return true;
    });

    if (!accepted) {
      throw new Error('None of the extension offers can be accepted');
    }

    if (opts.serverNoContextTakeover) {
      accepted.server_no_context_takeover = true;
    }
    if (opts.clientNoContextTakeover) {
      accepted.client_no_context_takeover = true;
    }
    if (typeof opts.serverMaxWindowBits === 'number') {
      accepted.server_max_window_bits = opts.serverMaxWindowBits;
    }
    if (typeof opts.clientMaxWindowBits === 'number') {
      accepted.client_max_window_bits = opts.clientMaxWindowBits;
    } else if (
      accepted.client_max_window_bits === true ||
      opts.clientMaxWindowBits === false
    ) {
      delete accepted.client_max_window_bits;
    }

    return accepted;
  }

  /**
   * Accept the extension negotiation response.
   *
   * @param {Array} response The extension negotiation response
   * @return {Object} Accepted configuration
   * @private
   */
  acceptAsClient(response) {
    const params = response[0];

    if (
      this._options.clientNoContextTakeover === false &&
      params.client_no_context_takeover
    ) {
      throw new Error('Unexpected parameter "client_no_context_takeover"');
    }

    if (!params.client_max_window_bits) {
      if (typeof this._options.clientMaxWindowBits === 'number') {
        params.client_max_window_bits = this._options.clientMaxWindowBits;
      }
    } else if (
      this._options.clientMaxWindowBits === false ||
      (typeof this._options.clientMaxWindowBits === 'number' &&
        params.client_max_window_bits > this._options.clientMaxWindowBits)
    ) {
      throw new Error(
        'Unexpected or invalid parameter "client_max_window_bits"'
      );
    }

    return params;
  }

  /**
   * Normalize parameters.
   *
   * @param {Array} configurations The extension negotiation offers/reponse
   * @return {Array} The offers/response with normalized parameters
   * @private
   */
  normalizeParams(configurations) {
    configurations.forEach((params) => {
      Object.keys(params).forEach((key) => {
        let value = params[key];

        if (value.length > 1) {
          throw new Error(`Parameter "${key}" must have only a single value`);
        }

        value = value[0];

        if (key === 'client_max_window_bits') {
          if (value !== true) {
            const num = +value;
            if (!Number.isInteger(num) || num < 8 || num > 15) {
              throw new TypeError(
                `Invalid value for parameter "${key}": ${value}`
              );
            }
            value = num;
          } else if (!this._isServer) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
        } else if (key === 'server_max_window_bits') {
          const num = +value;
          if (!Number.isInteger(num) || num < 8 || num > 15) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
          value = num;
        } else if (
          key === 'client_no_context_takeover' ||
          key === 'server_no_context_takeover'
        ) {
          if (value !== true) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
        } else {
          throw new Error(`Unknown parameter "${key}"`);
        }

        params[key] = value;
      });
    });

    return configurations;
  }

  /**
   * Decompress data. Concurrency limited.
   *
   * @param {Buffer} data Compressed data
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @public
   */
  decompress(data, fin, callback) {
    zlibLimiter.add((done) => {
      this._decompress(data, fin, (err, result) => {
        done();
        callback(err, result);
      });
    });
  }

  /**
   * Compress data. Concurrency limited.
   *
   * @param {(Buffer|String)} data Data to compress
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @public
   */
  compress(data, fin, callback) {
    zlibLimiter.add((done) => {
      this._compress(data, fin, (err, result) => {
        done();
        callback(err, result);
      });
    });
  }

  /**
   * Decompress data.
   *
   * @param {Buffer} data Compressed data
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @private
   */
  _decompress(data, fin, callback) {
    const endpoint = this._isServer ? 'client' : 'server';

    if (!this._inflate) {
      const key = `${endpoint}_max_window_bits`;
      const windowBits =
        typeof this.params[key] !== 'number'
          ? zlib.Z_DEFAULT_WINDOWBITS
          : this.params[key];

      this._inflate = zlib.createInflateRaw({
        ...this._options.zlibInflateOptions,
        windowBits
      });
      this._inflate[kPerMessageDeflate] = this;
      this._inflate[kTotalLength] = 0;
      this._inflate[kBuffers] = [];
      this._inflate.on('error', inflateOnError);
      this._inflate.on('data', inflateOnData);
    }

    this._inflate[kCallback] = callback;

    this._inflate.write(data);
    if (fin) this._inflate.write(TRAILER);

    this._inflate.flush(() => {
      const err = this._inflate[kError];

      if (err) {
        this._inflate.close();
        this._inflate = null;
        callback(err);
        return;
      }

      const data = bufferUtil.concat(
        this._inflate[kBuffers],
        this._inflate[kTotalLength]
      );

      if (this._inflate._readableState.endEmitted) {
        this._inflate.close();
        this._inflate = null;
      } else {
        this._inflate[kTotalLength] = 0;
        this._inflate[kBuffers] = [];

        if (fin && this.params[`${endpoint}_no_context_takeover`]) {
          this._inflate.reset();
        }
      }

      callback(null, data);
    });
  }

  /**
   * Compress data.
   *
   * @param {(Buffer|String)} data Data to compress
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @private
   */
  _compress(data, fin, callback) {
    const endpoint = this._isServer ? 'server' : 'client';

    if (!this._deflate) {
      const key = `${endpoint}_max_window_bits`;
      const windowBits =
        typeof this.params[key] !== 'number'
          ? zlib.Z_DEFAULT_WINDOWBITS
          : this.params[key];

      this._deflate = zlib.createDeflateRaw({
        ...this._options.zlibDeflateOptions,
        windowBits
      });

      this._deflate[kTotalLength] = 0;
      this._deflate[kBuffers] = [];

      this._deflate.on('data', deflateOnData);
    }

    this._deflate[kCallback] = callback;

    this._deflate.write(data);
    this._deflate.flush(zlib.Z_SYNC_FLUSH, () => {
      if (!this._deflate) {
        //
        // The deflate stream was closed while data was being processed.
        //
        return;
      }

      let data = bufferUtil.concat(
        this._deflate[kBuffers],
        this._deflate[kTotalLength]
      );

      if (fin) {
        data = new FastBuffer(data.buffer, data.byteOffset, data.length - 4);
      }

      //
      // Ensure that the callback will not be called again in
      // `PerMessageDeflate#cleanup()`.
      //
      this._deflate[kCallback] = null;

      this._deflate[kTotalLength] = 0;
      this._deflate[kBuffers] = [];

      if (fin && this.params[`${endpoint}_no_context_takeover`]) {
        this._deflate.reset();
      }

      callback(null, data);
    });
  }
}

module.exports = PerMessageDeflate;

/**
 * The listener of the `zlib.DeflateRaw` stream `'data'` event.
 *
 * @param {Buffer} chunk A chunk of data
 * @private
 */
function deflateOnData(chunk) {
  this[kBuffers].push(chunk);
  this[kTotalLength] += chunk.length;
}

/**
 * The listener of the `zlib.InflateRaw` stream `'data'` event.
 *
 * @param {Buffer} chunk A chunk of data
 * @private
 */
function inflateOnData(chunk) {
  this[kTotalLength] += chunk.length;

  if (
    this[kPerMessageDeflate]._maxPayload < 1 ||
    this[kTotalLength] <= this[kPerMessageDeflate]._maxPayload
  ) {
    this[kBuffers].push(chunk);
    return;
  }

  this[kError] = new RangeError('Max payload size exceeded');
  this[kError].code = 'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH';
  this[kError][kStatusCode] = 1009;
  this.removeListener('data', inflateOnData);
  this.reset();
}

/**
 * The listener of the `zlib.InflateRaw` stream `'error'` event.
 *
 * @param {Error} err The emitted error
 * @private
 */
function inflateOnError(err) {
  //
  // There is no need to call `Zlib#close()` as the handle is automatically
  // closed when an error is emitted.
  //
  this[kPerMessageDeflate]._inflate = null;
  err[kStatusCode] = 1007;
  this[kCallback](err);
}


code:
'use strict';

const { Writable } = require('stream');

const PerMessageDeflate = require('./permessage-deflate');
const {
  BINARY_TYPES,
  EMPTY_BUFFER,
  kStatusCode,
  kWebSocket
} = require('./constants');
const { concat, toArrayBuffer, unmask } = require('./buffer-util');
const { isValidStatusCode, isValidUTF8 } = require('./validation');

const FastBuffer = Buffer[Symbol.species];

const GET_INFO = 0;
const GET_PAYLOAD_LENGTH_16 = 1;
const GET_PAYLOAD_LENGTH_64 = 2;
const GET_MASK = 3;
const GET_DATA = 4;
const INFLATING = 5;
const DEFER_EVENT = 6;

/**
 * HyBi Receiver implementation.
 *
 * @extends Writable
 */
class Receiver extends Writable {
  /**
   * Creates a Receiver instance.
   *
   * @param {Object} [options] Options object
   * @param {Boolean} [options.allowSynchronousEvents=true] Specifies whether
   *     any of the `'message'`, `'ping'`, and `'pong'` events can be emitted
   *     multiple times in the same tick
   * @param {String} [options.binaryType=nodebuffer] The type for binary data
   * @param {Object} [options.extensions] An object containing the negotiated
   *     extensions
   * @param {Boolean} [options.isServer=false] Specifies whether to operate in
   *     client or server mode
   * @param {Number} [options.maxPayload=0] The maximum allowed message length
   * @param {Boolean} [options.skipUTF8Validation=false] Specifies whether or
   *     not to skip UTF-8 validation for text and close messages
   */
  constructor(options = {}) {
    super();

    this._allowSynchronousEvents =
      options.allowSynchronousEvents !== undefined
        ? options.allowSynchronousEvents
        : true;
    this._binaryType = options.binaryType || BINARY_TYPES[0];
    this._extensions = options.extensions || {};
    this._isServer = !!options.isServer;
    this._maxPayload = options.maxPayload | 0;
    this._skipUTF8Validation = !!options.skipUTF8Validation;
    this[kWebSocket] = undefined;

    this._bufferedBytes = 0;
    this._buffers = [];

    this._compressed = false;
    this._payloadLength = 0;
    this._mask = undefined;
    this._fragmented = 0;
    this._masked = false;
    this._fin = false;
    this._opcode = 0;

    this._totalPayloadLength = 0;
    this._messageLength = 0;
    this._fragments = [];

    this._errored = false;
    this._loop = false;
    this._state = GET_INFO;
  }

  /**
   * Implements `Writable.prototype._write()`.
   *
   * @param {Buffer} chunk The chunk of data to write
   * @param {String} encoding The character encoding of `chunk`
   * @param {Function} cb Callback
   * @private
   */
  _write(chunk, encoding, cb) {
    if (this._opcode === 0x08 && this._state == GET_INFO) return cb();

    this._bufferedBytes += chunk.length;
    this._buffers.push(chunk);
    this.startLoop(cb);
  }

  /**
   * Consumes `n` bytes from the buffered data.
   *
   * @param {Number} n The number of bytes to consume
   * @return {Buffer} The consumed bytes
   * @private
   */
  consume(n) {
    this._bufferedBytes -= n;

    if (n === this._buffers[0].length) return this._buffers.shift();

    if (n < this._buffers[0].length) {
      const buf = this._buffers[0];
      this._buffers[0] = new FastBuffer(
        buf.buffer,
        buf.byteOffset + n,
        buf.length - n
      );

      return new FastBuffer(buf.buffer, buf.byteOffset, n);
    }

    const dst = Buffer.allocUnsafe(n);

    do {
      const buf = this._buffers[0];
      const offset = dst.length - n;

      if (n >= buf.length) {
        dst.set(this._buffers.shift(), offset);
      } else {
        dst.set(new Uint8Array(buf.buffer, buf.byteOffset, n), offset);
        this._buffers[0] = new FastBuffer(
          buf.buffer,
          buf.byteOffset + n,
          buf.length - n
        );
      }

      n -= buf.length;
    } while (n > 0);

    return dst;
  }

  /**
   * Starts the parsing loop.
   *
   * @param {Function} cb Callback
   * @private
   */
  startLoop(cb) {
    this._loop = true;

    do {
      switch (this._state) {
        case GET_INFO:
          this.getInfo(cb);
          break;
        case GET_PAYLOAD_LENGTH_16:
          this.getPayloadLength16(cb);
          break;
        case GET_PAYLOAD_LENGTH_64:
          this.getPayloadLength64(cb);
          break;
        case GET_MASK:
          this.getMask();
          break;
        case GET_DATA:
          this.getData(cb);
          break;
        case INFLATING:
        case DEFER_EVENT:
          this._loop = false;
          return;
      }
    } while (this._loop);

    if (!this._errored) cb();
  }

  /**
   * Reads the first two bytes of a frame.
   *
   * @param {Function} cb Callback
   * @private
   */
  getInfo(cb) {
    if (this._bufferedBytes < 2) {
      this._loop = false;
      return;
    }

    const buf = this.consume(2);

    if ((buf[0] & 0x30) !== 0x00) {
      const error = this.createError(
        RangeError,
        'RSV2 and RSV3 must be clear',
        true,
        1002,
        'WS_ERR_UNEXPECTED_RSV_2_3'
      );

      cb(error);
      return;
    }

    const compressed = (buf[0] & 0x40) === 0x40;

    if (compressed && !this._extensions[PerMessageDeflate.extensionName]) {
      const error = this.createError(
        RangeError,
        'RSV1 must be clear',
        true,
        1002,
        'WS_ERR_UNEXPECTED_RSV_1'
      );

      cb(error);
      return;
    }

    this._fin = (buf[0] & 0x80) === 0x80;
    this._opcode = buf[0] & 0x0f;
    this._payloadLength = buf[1] & 0x7f;

    if (this._opcode === 0x00) {
      if (compressed) {
        const error = this.createError(
          RangeError,
          'RSV1 must be clear',
          true,
          1002,
          'WS_ERR_UNEXPECTED_RSV_1'
        );

        cb(error);
        return;
      }

      if (!this._fragmented) {
        const error = this.createError(
          RangeError,
          'invalid opcode 0',
          true,
          1002,
          'WS_ERR_INVALID_OPCODE'
        );

        cb(error);
        return;
      }

      this._opcode = this._fragmented;
    } else if (this._opcode === 0x01 || this._opcode === 0x02) {
      if (this._fragmented) {
        const error = this.createError(
          RangeError,
          `invalid opcode ${this._opcode}`,
          true,
          1002,
          'WS_ERR_INVALID_OPCODE'
        );

        cb(error);
        return;
      }

      this._compressed = compressed;
    } else if (this._opcode > 0x07 && this._opcode < 0x0b) {
      if (!this._fin) {
        const error = this.createError(
          RangeError,
          'FIN must be set',
          true,
          1002,
          'WS_ERR_EXPECTED_FIN'
        );

        cb(error);
        return;
      }

      if (compressed) {
        const error = this.createError(
          RangeError,
          'RSV1 must be clear',
          true,
          1002,
          'WS_ERR_UNEXPECTED_RSV_1'
        );

        cb(error);
        return;
      }

      if (
        this._payloadLength > 0x7d ||
        (this._opcode === 0x08 && this._payloadLength === 1)
      ) {
        const error = this.createError(
          RangeError,
          `invalid payload length ${this._payloadLength}`,
          true,
          1002,
          'WS_ERR_INVALID_CONTROL_PAYLOAD_LENGTH'
        );

        cb(error);
        return;
      }
    } else {
      const error = this.createError(
        RangeError,
        `invalid opcode ${this._opcode}`,
        true,
        1002,
        'WS_ERR_INVALID_OPCODE'
      );

      cb(error);
      return;
    }

    if (!this._fin && !this._fragmented) this._fragmented = this._opcode;
    this._masked = (buf[1] & 0x80) === 0x80;

    if (this._isServer) {
      if (!this._masked) {
        const error = this.createError(
          RangeError,
          'MASK must be set',
          true,
          1002,
          'WS_ERR_EXPECTED_MASK'
        );

        cb(error);
        return;
      }
    } else if (this._masked) {
      const error = this.createError(
        RangeError,
        'MASK must be clear',
        true,
        1002,
        'WS_ERR_UNEXPECTED_MASK'
      );

      cb(error);
      return;
    }

    if (this._payloadLength === 126) this._state = GET_PAYLOAD_LENGTH_16;
    else if (this._payloadLength === 127) this._state = GET_PAYLOAD_LENGTH_64;
    else this.haveLength(cb);
  }

  /**
   * Gets extended payload length (7+16).
   *
   * @param {Function} cb Callback
   * @private
   */
  getPayloadLength16(cb) {
    if (this._bufferedBytes < 2) {
      this._loop = false;
      return;
    }

    this._payloadLength = this.consume(2).readUInt16BE(0);
    this.haveLength(cb);
  }

  /**
   * Gets extended payload length (7+64).
   *
   * @param {Function} cb Callback
   * @private
   */
  getPayloadLength64(cb) {
    if (this._bufferedBytes < 8) {
      this._loop = false;
      return;
    }

    const buf = this.consume(8);
    const num = buf.readUInt32BE(0);

    //
    // The maximum safe integer in JavaScript is 2^53 - 1. An error is returned
    // if payload length is greater than this number.
    //
    if (num > Math.pow(2, 53 - 32) - 1) {
      const error = this.createError(
        RangeError,
        'Unsupported WebSocket frame: payload length > 2^53 - 1',
        false,
        1009,
        'WS_ERR_UNSUPPORTED_DATA_PAYLOAD_LENGTH'
      );

      cb(error);
      return;
    }

    this._payloadLength = num * Math.pow(2, 32) + buf.readUInt32BE(4);
    this.haveLength(cb);
  }

  /**
   * Payload length has been read.
   *
   * @param {Function} cb Callback
   * @private
   */
  haveLength(cb) {
    if (this._payloadLength && this._opcode < 0x08) {
      this._totalPayloadLength += this._payloadLength;
      if (this._totalPayloadLength > this._maxPayload && this._maxPayload > 0) {
        const error = this.createError(
          RangeError,
          'Max payload size exceeded',
          false,
          1009,
          'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH'
        );

        cb(error);
        return;
      }
    }

    if (this._masked) this._state = GET_MASK;
    else this._state = GET_DATA;
  }

  /**
   * Reads mask bytes.
   *
   * @private
   */
  getMask() {
    if (this._bufferedBytes < 4) {
      this._loop = false;
      return;
    }

    this._mask = this.consume(4);
    this._state = GET_DATA;
  }

  /**
   * Reads data bytes.
   *
   * @param {Function} cb Callback
   * @private
   */
  getData(cb) {
    let data = EMPTY_BUFFER;

    if (this._payloadLength) {
      if (this._bufferedBytes < this._payloadLength) {
        this._loop = false;
        return;
      }

      data = this.consume(this._payloadLength);

      if (
        this._masked &&
        (this._mask[0] | this._mask[1] | this._mask[2] | this._mask[3]) !== 0
      ) {
        unmask(data, this._mask);
      }
    }

    if (this._opcode > 0x07) {
      this.controlMessage(data, cb);
      return;
    }

    if (this._compressed) {
      this._state = INFLATING;
      this.decompress(data, cb);
      return;
    }

    if (data.length) {
      //
      // This message is not compressed so its length is the sum of the payload
      // length of all fragments.
      //
      this._messageLength = this._totalPayloadLength;
      this._fragments.push(data);
    }

    this.dataMessage(cb);
  }

  /**
   * Decompresses data.
   *
   * @param {Buffer} data Compressed data
   * @param {Function} cb Callback
   * @private
   */
  decompress(data, cb) {
    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];

    perMessageDeflate.decompress(data, this._fin, (err, buf) => {
      if (err) return cb(err);

      if (buf.length) {
        this._messageLength += buf.length;
        if (this._messageLength > this._maxPayload && this._maxPayload > 0) {
          const error = this.createError(
            RangeError,
            'Max payload size exceeded',
            false,
            1009,
            'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH'
          );

          cb(error);
          return;
        }

        this._fragments.push(buf);
      }

      this.dataMessage(cb);
      if (this._state === GET_INFO) this.startLoop(cb);
    });
  }

  /**
   * Handles a data message.
   *
   * @param {Function} cb Callback
   * @private
   */
  dataMessage(cb) {
    if (!this._fin) {
      this._state = GET_INFO;
      return;
    }

    const messageLength = this._messageLength;
    const fragments = this._fragments;

    this._totalPayloadLength = 0;
    this._messageLength = 0;
    this._fragmented = 0;
    this._fragments = [];

    if (this._opcode === 2) {
      let data;

      if (this._binaryType === 'nodebuffer') {
        data = concat(fragments, messageLength);
      } else if (this._binaryType === 'arraybuffer') {
        data = toArrayBuffer(concat(fragments, messageLength));
      } else if (this._binaryType === 'blob') {
        data = new Blob(fragments);
      } else {
        data = fragments;
      }

      if (this._allowSynchronousEvents) {
        this.emit('message', data, true);
        this._state = GET_INFO;
      } else {
        this._state = DEFER_EVENT;
        setImmediate(() => {
          this.emit('message', data, true);
          this._state = GET_INFO;
          this.startLoop(cb);
        });
      }
    } else {
      const buf = concat(fragments, messageLength);

      if (!this._skipUTF8Validation && !isValidUTF8(buf)) {
        const error = this.createError(
          Error,
          'invalid UTF-8 sequence',
          true,
          1007,
          'WS_ERR_INVALID_UTF8'
        );

        cb(error);
        return;
      }

      if (this._state === INFLATING || this._allowSynchronousEvents) {
        this.emit('message', buf, false);
        this._state = GET_INFO;
      } else {
        this._state = DEFER_EVENT;
        setImmediate(() => {
          this.emit('message', buf, false);
          this._state = GET_INFO;
          this.startLoop(cb);
        });
      }
    }
  }

  /**
   * Handles a control message.
   *
   * @param {Buffer} data Data to handle
   * @return {(Error|RangeError|undefined)} A possible error
   * @private
   */
  controlMessage(data, cb) {
    if (this._opcode === 0x08) {
      if (data.length === 0) {
        this._loop = false;
        this.emit('conclude', 1005, EMPTY_BUFFER);
        this.end();
      } else {
        const code = data.readUInt16BE(0);

        if (!isValidStatusCode(code)) {
          const error = this.createError(
            RangeError,
            `invalid status code ${code}`,
            true,
            1002,
            'WS_ERR_INVALID_CLOSE_CODE'
          );

          cb(error);
          return;
        }

        const buf = new FastBuffer(
          data.buffer,
          data.byteOffset + 2,
          data.length - 2
        );

        if (!this._skipUTF8Validation && !isValidUTF8(buf)) {
          const error = this.createError(
            Error,
            'invalid UTF-8 sequence',
            true,
            1007,
            'WS_ERR_INVALID_UTF8'
          );

          cb(error);
          return;
        }

        this._loop = false;
        this.emit('conclude', code, buf);
        this.end();
      }

      this._state = GET_INFO;
      return;
    }

    if (this._allowSynchronousEvents) {
      this.emit(this._opcode === 0x09 ? 'ping' : 'pong', data);
      this._state = GET_INFO;
    } else {
      this._state = DEFER_EVENT;
      setImmediate(() => {
        this.emit(this._opcode === 0x09 ? 'ping' : 'pong', data);
        this._state = GET_INFO;
        this.startLoop(cb);
      });
    }
  }

  /**
   * Builds an error object.
   *
   * @param {function(new:Error|RangeError)} ErrorCtor The error constructor
   * @param {String} message The error message
   * @param {Boolean} prefix Specifies whether or not to add a default prefix to
   *     `message`
   * @param {Number} statusCode The status code
   * @param {String} errorCode The exposed error code
   * @return {(Error|RangeError)} The error
   * @private
   */
  createError(ErrorCtor, message, prefix, statusCode, errorCode) {
    this._loop = false;
    this._errored = true;

    const err = new ErrorCtor(
      prefix ? `Invalid WebSocket frame: ${message}` : message
    );

    Error.captureStackTrace(err, this.createError);
    err.code = errorCode;
    err[kStatusCode] = statusCode;
    return err;
  }
}

module.exports = Receiver;

license: mit


code:
/* eslint no-unused-vars: ["error", { "varsIgnorePattern": "^Duplex" }] */

'use strict';

const { Duplex } = require('stream');
const { randomFillSync } = require('crypto');

const PerMessageDeflate = require('./permessage-deflate');
const { EMPTY_BUFFER, kWebSocket, NOOP } = require('./constants');
const { isBlob, isValidStatusCode } = require('./validation');
const { mask: applyMask, toBuffer } = require('./buffer-util');

const kByteLength = Symbol('kByteLength');
const maskBuffer = Buffer.alloc(4);
const RANDOM_POOL_SIZE = 8 * 1024;
let randomPool;
let randomPoolPointer = RANDOM_POOL_SIZE;

const DEFAULT = 0;
const DEFLATING = 1;
const GET_BLOB_DATA = 2;

/**
 * HyBi Sender implementation.
 */
class Sender {
  /**
   * Creates a Sender instance.
   *
   * @param {Duplex} socket The connection socket
   * @param {Object} [extensions] An object containing the negotiated extensions
   * @param {Function} [generateMask] The function used to generate the masking
   *     key
   */
  constructor(socket, extensions, generateMask) {
    this._extensions = extensions || {};

    if (generateMask) {
      this._generateMask = generateMask;
      this._maskBuffer = Buffer.alloc(4);
    }

    this._socket = socket;

    this._firstFragment = true;
    this._compress = false;

    this._bufferedBytes = 0;
    this._queue = [];
    this._state = DEFAULT;
    this.onerror = NOOP;
    this[kWebSocket] = undefined;
  }

  /**
   * Frames a piece of data according to the HyBi WebSocket protocol.
   *
   * @param {(Buffer|String)} data The data to frame
   * @param {Object} options Options object
   * @param {Boolean} [options.fin=false] Specifies whether or not to set the
   *     FIN bit
   * @param {Function} [options.generateMask] The function used to generate the
   *     masking key
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Buffer} [options.maskBuffer] The buffer used to store the masking
   *     key
   * @param {Number} options.opcode The opcode
   * @param {Boolean} [options.readOnly=false] Specifies whether `data` can be
   *     modified
   * @param {Boolean} [options.rsv1=false] Specifies whether or not to set the
   *     RSV1 bit
   * @return {(Buffer|String)[]} The framed data
   * @public
   */
  static frame(data, options) {
    let mask;
    let merge = false;
    let offset = 2;
    let skipMasking = false;

    if (options.mask) {
      mask = options.maskBuffer || maskBuffer;

      if (options.generateMask) {
        options.generateMask(mask);
      } else {
        if (randomPoolPointer === RANDOM_POOL_SIZE) {
          /* istanbul ignore else  */
          if (randomPool === undefined) {
            //
            // This is lazily initialized because server-sent frames must not
            // be masked so it may never be used.
            //
            randomPool = Buffer.alloc(RANDOM_POOL_SIZE);
          }

          randomFillSync(randomPool, 0, RANDOM_POOL_SIZE);
          randomPoolPointer = 0;
        }

        mask[0] = randomPool[randomPoolPointer++];
        mask[1] = randomPool[randomPoolPointer++];
        mask[2] = randomPool[randomPoolPointer++];
        mask[3] = randomPool[randomPoolPointer++];
      }

      skipMasking = (mask[0] | mask[1] | mask[2] | mask[3]) === 0;
      offset = 6;
    }

    let dataLength;

    if (typeof data === 'string') {
      if (
        (!options.mask || skipMasking) &&
        options[kByteLength] !== undefined
      ) {
        dataLength = options[kByteLength];
      } else {
        data = Buffer.from(data);
        dataLength = data.length;
      }
    } else {
      dataLength = data.length;
      merge = options.mask && options.readOnly && !skipMasking;
    }

    let payloadLength = dataLength;

    if (dataLength >= 65536) {
      offset += 8;
      payloadLength = 127;
    } else if (dataLength > 125) {
      offset += 2;
      payloadLength = 126;
    }

    const target = Buffer.allocUnsafe(merge ? dataLength + offset : offset);

    target[0] = options.fin ? options.opcode | 0x80 : options.opcode;
    if (options.rsv1) target[0] |= 0x40;

    target[1] = payloadLength;

    if (payloadLength === 126) {
      target.writeUInt16BE(dataLength, 2);
    } else if (payloadLength === 127) {
      target[2] = target[3] = 0;
      target.writeUIntBE(dataLength, 4, 6);
    }

    if (!options.mask) return [target, data];

    target[1] |= 0x80;
    target[offset - 4] = mask[0];
    target[offset - 3] = mask[1];
    target[offset - 2] = mask[2];
    target[offset - 1] = mask[3];

    if (skipMasking) return [target, data];

    if (merge) {
      applyMask(data, mask, target, offset, dataLength);
      return [target];
    }

    applyMask(data, mask, data, 0, dataLength);
    return [target, data];
  }

  /**
   * Sends a close message to the other peer.
   *
   * @param {Number} [code] The status code component of the body
   * @param {(String|Buffer)} [data] The message component of the body
   * @param {Boolean} [mask=false] Specifies whether or not to mask the message
   * @param {Function} [cb] Callback
   * @public
   */
  close(code, data, mask, cb) {
    let buf;

    if (code === undefined) {
      buf = EMPTY_BUFFER;
    } else if (typeof code !== 'number' || !isValidStatusCode(code)) {
      throw new TypeError('First argument must be a valid error code number');
    } else if (data === undefined || !data.length) {
      buf = Buffer.allocUnsafe(2);
      buf.writeUInt16BE(code, 0);
    } else {
      const length = Buffer.byteLength(data);

      if (length > 123) {
        throw new RangeError('The message must not be greater than 123 bytes');
      }

      buf = Buffer.allocUnsafe(2 + length);
      buf.writeUInt16BE(code, 0);

      if (typeof data === 'string') {
        buf.write(data, 2);
      } else {
        buf.set(data, 2);
      }
    }

    const options = {
      [kByteLength]: buf.length,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x08,
      readOnly: false,
      rsv1: false
    };

    if (this._state !== DEFAULT) {
      this.enqueue([this.dispatch, buf, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(buf, options), cb);
    }
  }

  /**
   * Sends a ping message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Boolean} [mask=false] Specifies whether or not to mask `data`
   * @param {Function} [cb] Callback
   * @public
   */
  ping(data, mask, cb) {
    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else if (isBlob(data)) {
      byteLength = data.size;
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (byteLength > 125) {
      throw new RangeError('The data size must not be greater than 125 bytes');
    }

    const options = {
      [kByteLength]: byteLength,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x09,
      readOnly,
      rsv1: false
    };

    if (isBlob(data)) {
      if (this._state !== DEFAULT) {
        this.enqueue([this.getBlobData, data, false, options, cb]);
      } else {
        this.getBlobData(data, false, options, cb);
      }
    } else if (this._state !== DEFAULT) {
      this.enqueue([this.dispatch, data, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(data, options), cb);
    }
  }

  /**
   * Sends a pong message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Boolean} [mask=false] Specifies whether or not to mask `data`
   * @param {Function} [cb] Callback
   * @public
   */
  pong(data, mask, cb) {
    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else if (isBlob(data)) {
      byteLength = data.size;
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (byteLength > 125) {
      throw new RangeError('The data size must not be greater than 125 bytes');
    }

    const options = {
      [kByteLength]: byteLength,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x0a,
      readOnly,
      rsv1: false
    };

    if (isBlob(data)) {
      if (this._state !== DEFAULT) {
        this.enqueue([this.getBlobData, data, false, options, cb]);
      } else {
        this.getBlobData(data, false, options, cb);
      }
    } else if (this._state !== DEFAULT) {
      this.enqueue([this.dispatch, data, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(data, options), cb);
    }
  }

  /**
   * Sends a data message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Object} options Options object
   * @param {Boolean} [options.binary=false] Specifies whether `data` is binary
   *     or text
   * @param {Boolean} [options.compress=false] Specifies whether or not to
   *     compress `data`
   * @param {Boolean} [options.fin=false] Specifies whether the fragment is the
   *     last one
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Function} [cb] Callback
   * @public
   */
  send(data, options, cb) {
    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];
    let opcode = options.binary ? 2 : 1;
    let rsv1 = options.compress;

    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else if (isBlob(data)) {
      byteLength = data.size;
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (this._firstFragment) {
      this._firstFragment = false;
      if (
        rsv1 &&
        perMessageDeflate &&
        perMessageDeflate.params[
          perMessageDeflate._isServer
            ? 'server_no_context_takeover'
            : 'client_no_context_takeover'
        ]
      ) {
        rsv1 = byteLength >= perMessageDeflate._threshold;
      }
      this._compress = rsv1;
    } else {
      rsv1 = false;
      opcode = 0;
    }

    if (options.fin) this._firstFragment = true;

    const opts = {
      [kByteLength]: byteLength,
      fin: options.fin,
      generateMask: this._generateMask,
      mask: options.mask,
      maskBuffer: this._maskBuffer,
      opcode,
      readOnly,
      rsv1
    };

    if (isBlob(data)) {
      if (this._state !== DEFAULT) {
        this.enqueue([this.getBlobData, data, this._compress, opts, cb]);
      } else {
        this.getBlobData(data, this._compress, opts, cb);
      }
    } else if (this._state !== DEFAULT) {
      this.enqueue([this.dispatch, data, this._compress, opts, cb]);
    } else {
      this.dispatch(data, this._compress, opts, cb);
    }
  }

  /**
   * Gets the contents of a blob as binary data.
   *
   * @param {Blob} blob The blob
   * @param {Boolean} [compress=false] Specifies whether or not to compress
   *     the data
   * @param {Object} options Options object
   * @param {Boolean} [options.fin=false] Specifies whether or not to set the
   *     FIN bit
   * @param {Function} [options.generateMask] The function used to generate the
   *     masking key
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Buffer} [options.maskBuffer] The buffer used to store the masking
   *     key
   * @param {Number} options.opcode The opcode
   * @param {Boolean} [options.readOnly=false] Specifies whether `data` can be
   *     modified
   * @param {Boolean} [options.rsv1=false] Specifies whether or not to set the
   *     RSV1 bit
   * @param {Function} [cb] Callback
   * @private
   */
  getBlobData(blob, compress, options, cb) {
    this._bufferedBytes += options[kByteLength];
    this._state = GET_BLOB_DATA;

    blob
      .arrayBuffer()
      .then((arrayBuffer) => {
        if (this._socket.destroyed) {
          const err = new Error(
            'The socket was closed while the blob was being read'
          );

          //
          // `callCallbacks` is called in the next tick to ensure that errors
          // that might be thrown in the callbacks behave like errors thrown
          // outside the promise chain.
          //
          process.nextTick(callCallbacks, this, err, cb);
          return;
        }

        this._bufferedBytes -= options[kByteLength];
        const data = toBuffer(arrayBuffer);

        if (!compress) {
          this._state = DEFAULT;
          this.sendFrame(Sender.frame(data, options), cb);
          this.dequeue();
        } else {
          this.dispatch(data, compress, options, cb);
        }
      })
      .catch((err) => {
        //
        // `onError` is called in the next tick for the same reason that
        // `callCallbacks` above is.
        //
        process.nextTick(onError, this, err, cb);
      });
  }

  /**
   * Dispatches a message.
   *
   * @param {(Buffer|String)} data The message to send
   * @param {Boolean} [compress=false] Specifies whether or not to compress
   *     `data`
   * @param {Object} options Options object
   * @param {Boolean} [options.fin=false] Specifies whether or not to set the
   *     FIN bit
   * @param {Function} [options.generateMask] The function used to generate the
   *     masking key
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Buffer} [options.maskBuffer] The buffer used to store the masking
   *     key
   * @param {Number} options.opcode The opcode
   * @param {Boolean} [options.readOnly=false] Specifies whether `data` can be
   *     modified
   * @param {Boolean} [options.rsv1=false] Specifies whether or not to set the
   *     RSV1 bit
   * @param {Function} [cb] Callback
   * @private
   */
  dispatch(data, compress, options, cb) {
    if (!compress) {
      this.sendFrame(Sender.frame(data, options), cb);
      return;
    }

    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];

    this._bufferedBytes += options[kByteLength];
    this._state = DEFLATING;
    perMessageDeflate.compress(data, options.fin, (_, buf) => {
      if (this._socket.destroyed) {
        const err = new Error(
          'The socket was closed while data was being compressed'
        );

        callCallbacks(this, err, cb);
        return;
      }

      this._bufferedBytes -= options[kByteLength];
      this._state = DEFAULT;
      options.readOnly = false;
      this.sendFrame(Sender.frame(buf, options), cb);
      this.dequeue();
    });
  }

  /**
   * Executes queued send operations.
   *
   * @private
   */
  dequeue() {
    while (this._state === DEFAULT && this._queue.length) {
      const params = this._queue.shift();

      this._bufferedBytes -= params[3][kByteLength];
      Reflect.apply(params[0], this, params.slice(1));
    }
  }

  /**
   * Enqueues a send operation.
   *
   * @param {Array} params Send operation parameters.
   * @private
   */
  enqueue(params) {
    this._bufferedBytes += params[3][kByteLength];
    this._queue.push(params);
  }

  /**
   * Sends a frame.
   *
   * @param {Buffer[]} list The frame to send
   * @param {Function} [cb] Callback
   * @private
   */
  sendFrame(list, cb) {
    if (list.length === 2) {
      this._socket.cork();
      this._socket.write(list[0]);
      this._socket.write(list[1], cb);
      this._socket.uncork();
    } else {
      this._socket.write(list[0], cb);
    }
  }
}

module.exports = Sender;

/**
 * Calls queued callbacks with an error.
 *
 * @param {Sender} sender The `Sender` instance
 * @param {Error} err The error to call the callbacks with
 * @param {Function} [cb] The first callback
 * @private
 */
function callCallbacks(sender, err, cb) {
  if (typeof cb === 'function') cb(err);

  for (let i = 0; i < sender._queue.length; i++) {
    const params = sender._queue[i];
    const callback = params[params.length - 1];

    if (typeof callback === 'function') callback(err);
  }
}

/**
 * Handles a `Sender` error.
 *
 * @param {Sender} sender The `Sender` instance
 * @param {Error} err The error
 * @param {Function} [cb] The first pending callback
 * @private
 */
function onError(sender, err, cb) {
  callCallbacks(sender, err, cb);
  sender.onerror(err);
}


code:
'use strict';

const { Duplex } = require('stream');

/**
 * Emits the `'close'` event on a stream.
 *
 * @param {Duplex} stream The stream.
 * @private
 */
function emitClose(stream) {
  stream.emit('close');
}

/**
 * The listener of the `'end'` event.
 *
 * @private
 */
function duplexOnEnd() {
  if (!this.destroyed && this._writableState.finished) {
    this.destroy();
  }
}

/**
 * The listener of the `'error'` event.
 *
 * @param {Error} err The error
 * @private
 */
function duplexOnError(err) {
  this.removeListener('error', duplexOnError);
  this.destroy();
  if (this.listenerCount('error') === 0) {
    // Do not suppress the throwing behavior.
    this.emit('error', err);
  }
}

/**
 * Wraps a `WebSocket` in a duplex stream.
 *
 * @param {WebSocket} ws The `WebSocket` to wrap
 * @param {Object} [options] The options for the `Duplex` constructor
 * @return {Duplex} The duplex stream
 * @public
 */
function createWebSocketStream(ws, options) {
  let terminateOnDestroy = true;

  const duplex = new Duplex({
    ...options,
    autoDestroy: false,
    emitClose: false,
    objectMode: false,
    writableObjectMode: false
  });

  ws.on('message', function message(msg, isBinary) {
    const data =
      !isBinary && duplex._readableState.objectMode ? msg.toString() : msg;

    if (!duplex.push(data)) ws.pause();
  });

  ws.once('error', function error(err) {
    if (duplex.destroyed) return;

    // Prevent `ws.terminate()` from being called by `duplex._destroy()`.
    //
    // - If the `'error'` event is emitted before the `'open'` event, then
    //   `ws.terminate()` is a noop as no socket is assigned.
    // - Otherwise, the error is re-emitted by the listener of the `'error'`
    //   event of the `Receiver` object. The listener already closes the
    //   connection by calling `ws.close()`. This allows a close frame to be
    //   sent to the other peer. If `ws.terminate()` is called right after this,
    //   then the close frame might not be sent.
    terminateOnDestroy = false;
    duplex.destroy(err);
  });

  ws.once('close', function close() {
    if (duplex.destroyed) return;

    duplex.push(null);
  });

  duplex._destroy = function (err, callback) {
    if (ws.readyState === ws.CLOSED) {
      callback(err);
      process.nextTick(emitClose, duplex);
      return;
    }

    let called = false;

    ws.once('error', function error(err) {
      called = true;
      callback(err);
    });

    ws.once('close', function close() {
      if (!called) callback(err);
      process.nextTick(emitClose, duplex);
    });

    if (terminateOnDestroy) ws.terminate();
  };

  duplex._final = function (callback) {
    if (ws.readyState === ws.CONNECTING) {
      ws.once('open', function open() {
        duplex._final(callback);
      });
      return;
    }

    // If the value of the `_socket` property is `null` it means that `ws` is a
    // client websocket and the handshake failed. In fact, when this happens, a
    // socket is never assigned to the websocket. Wait for the `'error'` event
    // that will be emitted by the websocket.
    if (ws._socket === null) return;

    if (ws._socket._writableState.finished) {
      callback();
      if (duplex._readableState.endEmitted) duplex.destroy();
    } else {
      ws._socket.once('finish', function finish() {
        // `duplex` is not destroyed here because the `'end'` event will be
        // emitted on `duplex` after this `'finish'` event. The EOF signaling
        // `null` chunk is, in fact, pushed when the websocket emits `'close'`.
        callback();
      });
      ws.close();
    }
  };

  duplex._read = function () {
    if (ws.isPaused) ws.resume();
  };

  duplex._write = function (chunk, encoding, callback) {
    if (ws.readyState === ws.CONNECTING) {
      ws.once('open', function open() {
        duplex._write(chunk, encoding, callback);
      });
      return;
    }

    ws.send(chunk, callback);
  };

  duplex.on('end', duplexOnEnd);
  duplex.on('error', duplexOnError);
  return duplex;
}

module.exports = createWebSocketStream;


code:
'use strict';

const { tokenChars } = require('./validation');

/**
 * Parses the `Sec-WebSocket-Protocol` header into a set of subprotocol names.
 *
 * @param {String} header The field value of the header
 * @return {Set} The subprotocol names
 * @public
 */
function parse(header) {
  const protocols = new Set();
  let start = -1;
  let end = -1;
  let i = 0;

  for (i; i < header.length; i++) {
    const code = header.charCodeAt(i);

    if (end === -1 && tokenChars[code] === 1) {
      if (start === -1) start = i;
    } else if (
      i !== 0 &&
      (code === 0x20 /* ' ' */ || code === 0x09) /* '\t' */
    ) {
      if (end === -1 && start !== -1) end = i;
    } else if (code === 0x2c /* ',' */) {
      if (start === -1) {
        throw new SyntaxError(`Unexpected character at index ${i}`);
      }

      if (end === -1) end = i;

      const protocol = header.slice(start, end);

      if (protocols.has(protocol)) {
        throw new SyntaxError(`The "${protocol}" subprotocol is duplicated`);
      }

      protocols.add(protocol);
      start = end = -1;
    } else {
      throw new SyntaxError(`Unexpected character at index ${i}`);
    }
  }

  if (start === -1 || end !== -1) {
    throw new SyntaxError('Unexpected end of input');
  }

  const protocol = header.slice(start, i);

  if (protocols.has(protocol)) {
    throw new SyntaxError(`The "${protocol}" subprotocol is duplicated`);
  }

  protocols.add(protocol);
  return protocols;
}

module.exports = { parse };


code:
/* eslint no-unused-vars: ["error", { "varsIgnorePattern": "^Duplex$", "caughtErrors": "none" }] */

'use strict';

const EventEmitter = require('events');
const http = require('http');
const { Duplex } = require('stream');
const { createHash } = require('crypto');

const extension = require('./extension');
const PerMessageDeflate = require('./permessage-deflate');
const subprotocol = require('./subprotocol');
const WebSocket = require('./websocket');
const { GUID, kWebSocket } = require('./constants');

const keyRegex = /^[+/0-9A-Za-z]{22}==$/;

const RUNNING = 0;
const CLOSING = 1;
const CLOSED = 2;

/**
 * Class representing a WebSocket server.
 *
 * @extends EventEmitter
 */
class WebSocketServer extends EventEmitter {
  /**
   * Create a `WebSocketServer` instance.
   *
   * @param {Object} options Configuration options
   * @param {Boolean} [options.allowSynchronousEvents=true] Specifies whether
   *     any of the `'message'`, `'ping'`, and `'pong'` events can be emitted
   *     multiple times in the same tick
   * @param {Boolean} [options.autoPong=true] Specifies whether or not to
   *     automatically send a pong in response to a ping
   * @param {Number} [options.backlog=511] The maximum length of the queue of
   *     pending connections
   * @param {Boolean} [options.clientTracking=true] Specifies whether or not to
   *     track clients
   * @param {Function} [options.handleProtocols] A hook to handle protocols
   * @param {String} [options.host] The hostname where to bind the server
   * @param {Number} [options.maxPayload=104857600] The maximum allowed message
   *     size
   * @param {Boolean} [options.noServer=false] Enable no server mode
   * @param {String} [options.path] Accept only connections matching this path
   * @param {(Boolean|Object)} [options.perMessageDeflate=false] Enable/disable
   *     permessage-deflate
   * @param {Number} [options.port] The port where to bind the server
   * @param {(http.Server|https.Server)} [options.server] A pre-created HTTP/S
   *     server to use
   * @param {Boolean} [options.skipUTF8Validation=false] Specifies whether or
   *     not to skip UTF-8 validation for text and close messages
   * @param {Function} [options.verifyClient] A hook to reject connections
   * @param {Function} [options.WebSocket=WebSocket] Specifies the `WebSocket`
   *     class to use. It must be the `WebSocket` class or class that extends it
   * @param {Function} [callback] A listener for the `listening` event
   */
  constructor(options, callback) {
    super();

    options = {
      allowSynchronousEvents: true,
      autoPong: true,
      maxPayload: 100 * 1024 * 1024,
      skipUTF8Validation: false,
      perMessageDeflate: false,
      handleProtocols: null,
      clientTracking: true,
      verifyClient: null,
      noServer: false,
      backlog: null, // use default (511 as implemented in net.js)
      server: null,
      host: null,
      path: null,
      port: null,
      WebSocket,
      ...options
    };

    if (
      (options.port == null && !options.server && !options.noServer) ||
      (options.port != null && (options.server || options.noServer)) ||
      (options.server && options.noServer)
    ) {
      throw new TypeError(
        'One and only one of the "port", "server", or "noServer" options ' +
          'must be specified'
      );
    }

    if (options.port != null) {
      this._server = http.createServer((req, res) => {
        const body = http.STATUS_CODES[426];

        res.writeHead(426, {
          'Content-Length': body.length,
          'Content-Type': 'text/plain'
        });
        res.end(body);
      });
      this._server.listen(
        options.port,
        options.host,
        options.backlog,
        callback
      );
    } else if (options.server) {
      this._server = options.server;
    }

    if (this._server) {
      const emitConnection = this.emit.bind(this, 'connection');

      this._removeListeners = addListeners(this._server, {
        listening: this.emit.bind(this, 'listening'),
        error: this.emit.bind(this, 'error'),
        upgrade: (req, socket, head) => {
          this.handleUpgrade(req, socket, head, emitConnection);
        }
      });
    }

    if (options.perMessageDeflate === true) options.perMessageDeflate = {};
    if (options.clientTracking) {
      this.clients = new Set();
      this._shouldEmitClose = false;
    }

    this.options = options;
    this._state = RUNNING;
  }

  /**
   * Returns the bound address, the address family name, and port of the server
   * as reported by the operating system if listening on an IP socket.
   * If the server is listening on a pipe or UNIX domain socket, the name is
   * returned as a string.
   *
   * @return {(Object|String|null)} The address of the server
   * @public
   */
  address() {
    if (this.options.noServer) {
      throw new Error('The server is operating in "noServer" mode');
    }

    if (!this._server) return null;
    return this._server.address();
  }

  /**
   * Stop the server from accepting new connections and emit the `'close'` event
   * when all existing connections are closed.
   *
   * @param {Function} [cb] A one-time listener for the `'close'` event
   * @public
   */
  close(cb) {
    if (this._state === CLOSED) {
      if (cb) {
        this.once('close', () => {
          cb(new Error('The server is not running'));
        });
      }

      process.nextTick(emitClose, this);
      return;
    }

    if (cb) this.once('close', cb);

    if (this._state === CLOSING) return;
    this._state = CLOSING;

    if (this.options.noServer || this.options.server) {
      if (this._server) {
        this._removeListeners();
        this._removeListeners = this._server = null;
      }

      if (this.clients) {
        if (!this.clients.size) {
          process.nextTick(emitClose, this);
        } else {
          this._shouldEmitClose = true;
        }
      } else {
        process.nextTick(emitClose, this);
      }
    } else {
      const server = this._server;

      this._removeListeners();
      this._removeListeners = this._server = null;

      //
      // The HTTP/S server was created internally. Close it, and rely on its
      // `'close'` event.
      //
      server.close(() => {
        emitClose(this);
      });
    }
  }

  /**
   * See if a given request should be handled by this server instance.
   *
   * @param {http.IncomingMessage} req Request object to inspect
   * @return {Boolean} `true` if the request is valid, else `false`
   * @public
   */
  shouldHandle(req) {
    if (this.options.path) {
      const index = req.url.indexOf('?');
      const pathname = index !== -1 ? req.url.slice(0, index) : req.url;

      if (pathname !== this.options.path) return false;
    }

    return true;
  }

  /**
   * Handle a HTTP Upgrade request.
   *
   * @param {http.IncomingMessage} req The request object
   * @param {Duplex} socket The network socket between the server and client
   * @param {Buffer} head The first packet of the upgraded stream
   * @param {Function} cb Callback
   * @public
   */
  handleUpgrade(req, socket, head, cb) {
    socket.on('error', socketOnError);

    const key = req.headers['sec-websocket-key'];
    const upgrade = req.headers.upgrade;
    const version = +req.headers['sec-websocket-version'];

    if (req.method !== 'GET') {
      const message = 'Invalid HTTP method';
      abortHandshakeOrEmitwsClientError(this, req, socket, 405, message);
      return;
    }

    if (upgrade === undefined || upgrade.toLowerCase() !== 'websocket') {
      const message = 'Invalid Upgrade header';
      abortHandshakeOrEmitwsClientError(this, req, socket, 400, message);
      return;
    }

    if (key === undefined || !keyRegex.test(key)) {
      const message = 'Missing or invalid Sec-WebSocket-Key header';
      abortHandshakeOrEmitwsClientError(this, req, socket, 400, message);
      return;
    }

    if (version !== 8 && version !== 13) {
      const message = 'Missing or invalid Sec-WebSocket-Version header';
      abortHandshakeOrEmitwsClientError(this, req, socket, 400, message);
      return;
    }

    if (!this.shouldHandle(req)) {
      abortHandshake(socket, 400);
      return;
    }

    const secWebSocketProtocol = req.headers['sec-websocket-protocol'];
    let protocols = new Set();

    if (secWebSocketProtocol !== undefined) {
      try {
        protocols = subprotocol.parse(secWebSocketProtocol);
      } catch (err) {
        const message = 'Invalid Sec-WebSocket-Protocol header';
        abortHandshakeOrEmitwsClientError(this, req, socket, 400, message);
        return;
      }
    }

    const secWebSocketExtensions = req.headers['sec-websocket-extensions'];
    const extensions = {};

    if (
      this.options.perMessageDeflate &&
      secWebSocketExtensions !== undefined
    ) {
      const perMessageDeflate = new PerMessageDeflate(
        this.options.perMessageDeflate,
        true,
        this.options.maxPayload
      );

      try {
        const offers = extension.parse(secWebSocketExtensions);

        if (offers[PerMessageDeflate.extensionName]) {
          perMessageDeflate.accept(offers[PerMessageDeflate.extensionName]);
          extensions[PerMessageDeflate.extensionName] = perMessageDeflate;
        }
      } catch (err) {
        const message =
          'Invalid or unacceptable Sec-WebSocket-Extensions header';
        abortHandshakeOrEmitwsClientError(this, req, socket, 400, message);
        return;
      }
    }

    //
    // Optionally call external client verification handler.
    //
    if (this.options.verifyClient) {
      const info = {
        origin:
          req.headers[`${version === 8 ? 'sec-websocket-origin' : 'origin'}`],
        secure: !!(req.socket.authorized || req.socket.encrypted),
        req
      };

      if (this.options.verifyClient.length === 2) {
        this.options.verifyClient(info, (verified, code, message, headers) => {
          if (!verified) {
            return abortHandshake(socket, code || 401, message, headers);
          }

          this.completeUpgrade(
            extensions,
            key,
            protocols,
            req,
            socket,
            head,
            cb
          );
        });
        return;
      }

      if (!this.options.verifyClient(info)) return abortHandshake(socket, 401);
    }

    this.completeUpgrade(extensions, key, protocols, req, socket, head, cb);
  }

  /**
   * Upgrade the connection to WebSocket.
   *
   * @param {Object} extensions The accepted extensions
   * @param {String} key The value of the `Sec-WebSocket-Key` header
   * @param {Set} protocols The subprotocols
   * @param {http.IncomingMessage} req The request object
   * @param {Duplex} socket The network socket between the server and client
   * @param {Buffer} head The first packet of the upgraded stream
   * @param {Function} cb Callback
   * @throws {Error} If called more than once with the same socket
   * @private
   */
  completeUpgrade(extensions, key, protocols, req, socket, head, cb) {
    //
    // Destroy the socket if the client has already sent a FIN packet.
    //
    if (!socket.readable || !socket.writable) return socket.destroy();

    if (socket[kWebSocket]) {
      throw new Error(
        'server.handleUpgrade() was called more than once with the same ' +
          'socket, possibly due to a misconfiguration'
      );
    }

    if (this._state > RUNNING) return abortHandshake(socket, 503);

    const digest = createHash('sha1')
      .update(key + GUID)
      .digest('base64');

    const headers = [
      'HTTP/1.1 101 Switching Protocols',
      'Upgrade: websocket',
      'Connection: Upgrade',
      `Sec-WebSocket-Accept: ${digest}`
    ];

    const ws = new this.options.WebSocket(null, undefined, this.options);

    if (protocols.size) {
      //
      // Optionally call external protocol selection handler.
      //
      const protocol = this.options.handleProtocols
        ? this.options.handleProtocols(protocols, req)
        : protocols.values().next().value;

      if (protocol) {
        headers.push(`Sec-WebSocket-Protocol: ${protocol}`);
        ws._protocol = protocol;
      }
    }

    if (extensions[PerMessageDeflate.extensionName]) {
      const params = extensions[PerMessageDeflate.extensionName].params;
      const value = extension.format({
        [PerMessageDeflate.extensionName]: [params]
      });
      headers.push(`Sec-WebSocket-Extensions: ${value}`);
      ws._extensions = extensions;
    }

    //
    // Allow external modification/inspection of handshake headers.
    //
    this.emit('headers', headers, req);

    socket.write(headers.concat('\r\n').join('\r\n'));
    socket.removeListener('error', socketOnError);

    ws.setSocket(socket, head, {
      allowSynchronousEvents: this.options.allowSynchronousEvents,
      maxPayload: this.options.maxPayload,
      skipUTF8Validation: this.options.skipUTF8Validation
    });

    if (this.clients) {
      this.clients.add(ws);
      ws.on('close', () => {
        this.clients.delete(ws);

        if (this._shouldEmitClose && !this.clients.size) {
          process.nextTick(emitClose, this);
        }
      });
    }

    cb(ws, req);
  }
}

module.exports = WebSocketServer;

/**
 * Add event listeners on an `EventEmitter` using a map of <event, listener>
 * pairs.
 *
 * @param {EventEmitter} server The event emitter
 * @param {Object.<String, Function>} map The listeners to add
 * @return {Function} A function that will remove the added listeners when
 *     called
 * @private
 */
function addListeners(server, map) {
  for (const event of Object.keys(map)) server.on(event, map[event]);

  return function removeListeners() {
    for (const event of Object.keys(map)) {
      server.removeListener(event, map[event]);
    }
  };
}

/**
 * Emit a `'close'` event on an `EventEmitter`.
 *
 * @param {EventEmitter} server The event emitter
 * @private
 */
function emitClose(server) {
  server._state = CLOSED;
  server.emit('close');
}

/**
 * Handle socket errors.
 *
 * @private
 */
function socketOnError() {
  this.destroy();
}

/**
 * Close the connection when preconditions are not fulfilled.
 *
 * @param {Duplex} socket The socket of the upgrade request
 * @param {Number} code The HTTP response status code
 * @param {String} [message] The HTTP response body
 * @param {Object} [headers] Additional HTTP response headers
 * @private
 */
function abortHandshake(socket, code, message, headers) {
  //
  // The socket is writable unless the user destroyed or ended it before calling
  // `server.handleUpgrade()` or in the `verifyClient` function, which is a user
  // error. Handling this does not make much sense as the worst that can happen
  // is that some of the data written by the user might be discarded due to the
  // call to `socket.end()` below, which triggers an `'error'` event that in
  // turn causes the socket to be destroyed.
  //
  message = message || http.STATUS_CODES[code];
  headers = {
    Connection: 'close',
    'Content-Type': 'text/html',
    'Content-Length': Buffer.byteLength(message),
    ...headers
  };

  socket.once('finish', socket.destroy);

  socket.end(
    `HTTP/1.1 ${code} ${http.STATUS_CODES[code]}\r\n` +
      Object.keys(headers)
        .map((h) => `${h}: ${headers[h]}`)
        .join('\r\n') +
      '\r\n\r\n' +
      message
  );
}

/**
 * Emit a `'wsClientError'` event on a `WebSocketServer` if there is at least
 * one listener for it, otherwise call `abortHandshake()`.
 *
 * @param {WebSocketServer} server The WebSocket server
 * @param {http.IncomingMessage} req The request object
 * @param {Duplex} socket The socket of the upgrade request
 * @param {Number} code The HTTP response status code
 * @param {String} message The HTTP response body
 * @private
 */
function abortHandshakeOrEmitwsClientError(server, req, socket, code, message) {
  if (server.listenerCount('wsClientError')) {
    const err = new Error(message);
    Error.captureStackTrace(err, abortHandshakeOrEmitwsClientError);

    server.emit('wsClientError', err, socket, req);
  } else {
    abortHandshake(socket, code, message);
  }
}