NKF.guess

static VALUE
rb_nkf_guess(VALUE obj, VALUE src)
{
    reinit();

    input_ctr = 0;
    input = (unsigned char *)StringValuePtr(src);
    i_len = RSTRING_LENINT(src);

    guess_f = TRUE;
    kanji_convert( NULL );
    guess_f = FALSE;

    return rb_enc_from_encoding(rb_nkf_enc_get(get_guessed_code()));
}