private Text evaluateInternal(short n) {
    if (n > 255) {
      n = (short) (n % 256);
    }
    if (n == 0) {
      result.set(nulString);
      return result;
    }
    if (n < 0) {
      result.set("");
      return result;
    }

    result.set(String.valueOf((char) n));

    return result;
  }
UDFChr converts an integer into its ASCII equivalent.
ql/src/java/org/apache/hadoop/hive/ql/udf/UDFChr.java