public void testReadWrite() throws IOException{
//write
SequenceFile.Writer w = SequenceFile.createWriter(FileSystem.getLocal(new Configuration()), new Configuration(),
new Path(TMP_FILENAME1), IntWritable.class, PairOfIntNBitSignature.class);
PairOfIntNBitSignature p1 = new PairOfIntNBitSignature(1, null);
PairOfIntNBitSignature p2 = new PairOfIntNBitSignature(2, new NBitSignature(100));
PairOfIntNBitSignature p3 = new PairOfIntNBitSignature(3, null);
w.append(new IntWritable(1), p1);
w.append(new IntWritable(2), p2);
w.append(new IntWritable(3), p3);
w.close();