static byte[] toByteArray(final int[] input) {
    ByteBuffer byteBuffer = ByteBuffer.allocate(input.length * 4).order(ByteOrder.LITTLE_ENDIAN);
    byteBuffer.asIntBuffer().put(input);
    return byteBuffer.array();
  }
Converts {@code input} byte array to an int array
java_src/src/main/java/com/google/crypto/tink/aead/internal/ChaCha20Util.java