Socket.getnameinfo

static VALUE
sock_s_getnameinfo(int argc, VALUE *argv, VALUE _)
{
    VALUE sa, af = Qnil, host = Qnil, port = Qnil, flags, tmp;
    char hbuf[1024], pbuf[1024];
    int fl;
    struct rb_addrinfo *res = NULL;
    struct addrinfo hints, *r;
    int error, saved_errno;
    union_sockaddr ss;
    struct sockaddr *sap;
    socklen_t salen;

    sa = flags = Qnil;
    rb_scan_args(argc, argv, "11", &sa, &flags);

    fl = 0;
    if (!NIL_P(flags)) {
        fl = NUM2INT(flags);
    }
    tmp = rb_check_sockaddr_string_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        if (sizeof(ss) < (size_t)RSTRING_LEN(sa)) {
            rb_raise(rb_eTypeError, "sockaddr length too big");
        }
        memcpy(&ss, RSTRING_PTR(sa), RSTRING_LEN(sa));
        if (!VALIDATE_SOCKLEN(&ss.addr, RSTRING_LEN(sa))) {
            rb_raise(rb_eTypeError, "sockaddr size differs - should not happen");
        }
        sap = &ss.addr;
        salen = RSTRING_SOCKLEN(sa);
        goto call_nameinfo;
    }
    tmp = rb_check_array_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        MEMZERO(&hints, struct addrinfo, 1);
        if (RARRAY_LEN(sa) == 3) {
            af = RARRAY_AREF(sa, 0);
            port = RARRAY_AREF(sa, 1);
            host = RARRAY_AREF(sa, 2);
        }
        else if (RARRAY_LEN(sa) >= 4) {
            af = RARRAY_AREF(sa, 0);
            port = RARRAY_AREF(sa, 1);
            host = RARRAY_AREF(sa, 3);
            if (NIL_P(host)) {
                host = RARRAY_AREF(sa, 2);
            }
            else {
                /*
                 * 4th element holds numeric form, don't resolve.
                 * see rsock_ipaddr().
                 */
#ifdef AI_NUMERICHOST /* AIX 4.3.3 doesn't have AI_NUMERICHOST. */
                hints.ai_flags |= AI_NUMERICHOST;
#endif
            }
        }
        else {
            rb_raise(rb_eArgError, "array size should be 3 or 4, %ld given",
                     RARRAY_LEN(sa));
        }
        hints.ai_socktype = (fl & NI_DGRAM) ? SOCK_DGRAM : SOCK_STREAM;
        /* af */
        hints.ai_family = NIL_P(af) ? PF_UNSPEC : rsock_family_arg(af);
        res = rsock_getaddrinfo(host, port, &hints, 0, Qnil);
        sap = res->ai->ai_addr;
        salen = res->ai->ai_addrlen;
    }
    else {
        rb_raise(rb_eTypeError, "expecting String or Array");
    }

  call_nameinfo:
    error = rb_getnameinfo(sap, salen, hbuf, sizeof(hbuf),
                           pbuf, sizeof(pbuf), fl);
    if (error) goto error_exit_name;
    if (res) {
        for (r = res->ai->ai_next; r; r = r->ai_next) {
            char hbuf2[1024], pbuf2[1024];

            sap = r->ai_addr;
            salen = r->ai_addrlen;
            error = rb_getnameinfo(sap, salen, hbuf2, sizeof(hbuf2),
                                   pbuf2, sizeof(pbuf2), fl);
            if (error) goto error_exit_name;
            if (strcmp(hbuf, hbuf2) != 0|| strcmp(pbuf, pbuf2) != 0) {
                rb_freeaddrinfo(res);
                rb_raise(rb_eSocket, "sockaddr resolved to multiple nodename");
            }
        }
        rb_freeaddrinfo(res);
    }
    return rb_assoc_new(rb_str_new2(hbuf), rb_str_new2(pbuf));

  error_exit_name:
    saved_errno = errno;
    if (res) rb_freeaddrinfo(res);
    errno = saved_errno;
    rsock_raise_resolution_error("getnameinfo", error);

    UNREACHABLE_RETURN(Qnil);
}