@Override
  public final byte readByte() throws IOException {
    int temp = in.read();
    if (temp < 0) {
      throw new EOFException();
    }
    return (byte) temp;
  }
Reads an 8-bit byte value from this stream.

@return the next byte value from the source stream.

@throws IOException
          If a problem occurs reading from this DataInputStream.
ql/src/java/org/apache/hadoop/hive/ql/io/NonSyncDataInputBuffer.java