repo_description: Simple to use, blazing fast and thoroughly tested WebSocket client and server for Node.js
repo_topics: javascript node nodejs real-time rfc-6455 websocket websocket-client websocket-compression websocket-server
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;
  