static int[] toIntArray(final byte[] input) {
    if (input.length % 4 != 0) {
      throw new IllegalArgumentException("invalid input length");
    }
    IntBuffer intBuffer = ByteBuffer.wrap(input).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer();
    int[] ret = new int[intBuffer.remaining()];
    intBuffer.get(ret);
    return ret;
  }
Converts {@code input} byte array to an int array
java_src/src/main/java/com/google/crypto/tink/aead/internal/ChaCha20Util.java