@Override
  public long readI64() throws TException {
    if (readIsNull()) {
      return 0;
    }
    readRawAll(i64rd, 0, 8);
    return ((long) ((i64rd[0] ^ 0x80) & 0xff) << 56)
        | ((long) (i64rd[1] & 0xff) << 48) | ((long) (i64rd[2] & 0xff) << 40)
        | ((long) (i64rd[3] & 0xff) << 32) | ((long) (i64rd[4] & 0xff) << 24)
        | ((long) (i64rd[5] & 0xff) << 16) | ((long) (i64rd[6] & 0xff) << 8)
        | ((i64rd[7] & 0xff));
  }
This method always return the same instance of TSet to avoid creating new
instances. It is the responsibility of the caller to read the value before
calling this method again.
serde/src/java/org/apache/hadoop/hive/serde2/thrift/TBinarySortableProtocol.java