Get the next UTF-8 gchar at ptr, and return it, advancing ptr to the next character.
If end is reached before a full UTF-8 character can be read, then the invalid Unicode gchar 0xffff is returned as a
sentinel (Unicode 3.1, section 2.7), and ptr is not advanced.
| ptr |
a pointer to read the character from |
| end |
upper limit for the read, must not be null |
|
The next UTF-8 char, or 0xffff. |