Function utf8_validate

crawl-ref/source/unicode.cc:200–216

}

static string utf8_validate(const char *s)
{
    string d;
    char32_t c;
    int l;

    while ((l = utf8towc(&c, s)))
    {
        s += l;

        char buf[4];
        int r = wctoutf8(buf, c);
        for (int i = 0; i < r; i++)
            d.push_back(buf[i]);
    }
    return d;
}

string mb_to_utf8(const char *s)
{