const file_signature = char_to_string(result) result = await this.readSlice(2) const file_source_id = (new DataView(result)).getUint16() result = await this.readSlice(2) const global_encording = (new DataView(result)).getUint16(0, true) result = await this.readSlice(4) const guid_data1 = (new DataView(result)).getUint32(0, true) … const z = new DataView(result) const max_z = z.getFloat64(0, true) const min_z = z.getFloat64(8, true) this.reader.abort() callback(max_x, min_x, max_y, min_y) } await this.readSlice で何バイト読 むか指定 読まれたバイナリの処理の責務が すべてread関数になる 最後はthis.reader.abort()を実行 してcallbackを呼ぶ