static ByteBuffer resetBuffer(ByteBuffer buffer, int len) {
    int pos = buffer.position();
    buffer.put(getEmptyChunk(len), 0, len);
    buffer.position(pos);

    return buffer;
  }
@Test
  public void testResetBuffer() {
    ByteBuffer buf = ByteBuffer.allocate(chunkSize * 2).putInt(1234);
    buf.position(0);
    ByteBuffer ret = CoderUtil.resetBuffer(buf, chunkSize);
    for (int i = 0; i < chunkSize; i++) {
      assertEquals(0, ret.getInt(i));
    }

    byte[] inputs = ByteBuffer.allocate(numInputs)
        .putInt(1234).array();
    CoderUtil.resetBuffer(inputs, 0, numInputs);
    for (int i = 0; i < numInputs; i++) {
      assertEquals(0, inputs[i]);
    }
  }