code: function RarLocalFile(bstream) {
      this.header = new RarVolumeHeader(bstream);
      this.filename = this.header.filename;
  
      if (this.header.headType != RarUtils.VOLUME_TYPES.FILE_HEAD && this.header.headType != RarUtils.VOLUME_TYPES.ENDARC_HEAD) {
          this.isValid = false;
          RarEventMgr.error("Error! RAR Volume did not include a FILE_HEAD header ");
      } else {
          // read in the compressed data
          this.fileData = null;
          if (this.header.packSize > 0) {
              this.fileData = bstream.readBytes(this.header.packSize);
              this.isValid = true;
          }
      }
  }
docs: bstream is a bit stream