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);
    });
  }
Decompresses data.

@param {Buffer} data Compressed data
@param {Function} cb Callback
@private