code: public static byte[] copy(byte[] src, int offset, int length) {
  		byte[] copy = new byte[length];
  		System.arraycopy(src, offset, copy, 0, length);
  		return copy;
  	}
docs: Create a new byte array with contents initialized to values from the
  argument byte array.
  @param src source byte array of initial values
  @param offset start offset to copy bytes
  @param length number of bytes to copy
  @return a new byte array of size length, containing values from src
  starting from offset in the src array.