__codecvt_partial
result = __codecvt_partial;
result = __codecvt_partial;
result = __codecvt_partial;
result = __codecvt_partial;
result = __codecvt_partial;
result = __codecvt_partial;
result = __codecvt_partial;
&& (result != __codecvt_partial || new_data - data == 0))
assert (status == __codecvt_partial);
while (__builtin_expect (status == __codecvt_partial, 0));