/**
     * Validates whether decoding the final trailing character is possible in the context
     * of the set of possible base 64 values.
     *
     * <p>The character is valid if the lower bits within the provided mask are zero. This
     * is used to test the final trailing base-64 digit is zero in the bits that will be discarded.
     *
     * @param emptyBitsMask The mask of the lower bits that should be empty
     * @param context the context to be used
     *
     * @throws IllegalArgumentException if the bits being checked contain any non-zero value
     */
    private static void validateCharacter(final int emptyBitsMask, final Context context) {
        if ((context.ibitWorkArea & emptyBitsMask) != 0) {
            throw new IllegalArgumentException(
                "Last encoded character (before the paddings if any) is a valid base 64 alphabet but not a possible value. " +
                "Expected the discarded bits to be zero.");
        }
    }