struct fastbuf *fb_wrap_charconv_in(struct fastbuf *f, int cs_from, int cs_to);
struct fastbuf *fb_wrap_charconv_out(struct fastbuf *f, int cs_from, int cs_to);
struct fastbuf *fb_wrap_charconv_in(struct fastbuf *f, int cs_from, int cs_to);
struct fastbuf *fb_wrap_charconv_out(struct fastbuf *f, int cs_from, int cs_to);