code: public static byte[] readBytes(byte b[], int offset, int length) {
      byte[] retValue = new byte[length];
      System.arraycopy(b, offset, retValue, 0, length);
      return retValue;
    }
docs: Unserializes a byte[] from a byte array at a specific offset
  
  @param b byte array from which to read a byte[].
  @param offset offset within byte array to start reading.
  @param length length of byte[] to read
  @return byte[] read from byte array.