code: static public byte[] expandByteArray(byte[] src, byte[] dst) {
          int srcLength = (null != src) ? src.length : 0;
          int dstLength = (null != dst) ? dst.length : 0;
          return expandByteArray(src, dst, 0, srcLength, 0, dstLength);
      }
docs: Generic method to copy the entire length of each buffer.
  
  @param src
  @param dst
  @return byte[]