+ base64Value = -3; /* initialize as illegal */
+ if(b>=126 || (base64Value=fromBase64[b])==-3 || base64Value==-1) {
+ /* either
+ * base64Value==-1 for any legal character except base64 and minus sign, or
+ * base64Value==-3 for illegal characters:
+ * 1. In either case, leave Unicode mode.
+ * 2.1. If we ended with an incomplete UChar or none after the +, then
+ * generate an error for the preceding erroneous sequence and deal with
+ * the current (possibly illegal) character next time through.
+ * 2.2. Else the current char comes after a complete UChar, which was already
+ * pushed to the output buf, so:
+ * 2.2.1. If the current char is legal, just save it for processing next time.
+ * It may be for example, a plus which we need to deal with in direct mode.
+ * 2.2.2. Else if the current char is illegal, we might as well deal with it here.
+ */