KICONV_IS_VALID_EUC_BYTE
((v) == KICONV_TC_EUCTW_MBYTE || KICONV_IS_VALID_EUC_BYTE(v))
((isplane1 && (KICONV_IS_VALID_EUC_BYTE(*((ib) + 1)))) || \
KICONV_IS_VALID_EUC_BYTE(*((ib) + 2)) && \
KICONV_IS_VALID_EUC_BYTE(*((ib) + 3))))