The iconv_open function allocates a conversion descriptor suitable for
converting byte sequences from character encoding fromcode to character
The values permitted for fromcode and tocode and the supported
combinations are system dependent. For the GNU C library, the permitted values
are listed by the iconv --list command, and all combinations of the
listed values are supported.
The resulting conversion descriptor can be used with iconv any number of
times. It remains valid until deallocated using iconv_close.
A conversion descriptor contains a conversion state. After creation using
iconv_open, the state is in the initial state. Using iconv
modifies the descriptor's conversion state. (This implies that a conversion
descriptor can not be used in multiple threads simultaneously.) To bring the
state back to the initial state, use iconv with NULL as inbuf