static int addPads(byte[] b, int start, int count) {
    int i = start;
    int end = start + count;
    for ( ; i < end; i++) {
      b[i] = (byte) 0x20; // blank " " (1 byte)
    }
    return i;
  }
Test vectorized expression and filter evaluation for strings.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/expressions/TestVectorStringExpressions.java