How to parse QString

jenya7

I have a function

uint32_t IsIP (char *str)
{
    int segs = 0;   /* Segment count. */
    int chcnt = 0;  /* Character count within segment. */
    int accum = 0;  /* Accumulator for segment. */

    size_t len = strlen(str);
    if (len < 7 || len > 15)
      return 0;

    /* Catch NULL pointer. */
    if (str == nullptr)
        return 0;

    /* Process every character in string. */
    while (*str != '\0')
    {
        /* Segment changeover. */
        if (*str == '.')
        {
            /* Must have some digits in segment. */
            if (chcnt == 0)
                return 0;

            /* Limit number of segments. */

            if (++segs == 4)
                return 0;

            /* Reset segment values and restart loop. */

            chcnt = accum = 0;
            str++;
            continue;
        }
        /* Check numeric. */

        if ((*str < '0') || (*str > '9'))
            return 0;

        //prevent leading zeros
        if ((chcnt > 0) && (accum == 0)) return 0;

        /* Accumulate and check segment. */
        if ((accum = accum * 10 + *str - '0') > 255)
            return 0;

        /* Advance other segment specific stuff and continue loop. */

        chcnt++;
        str++;
    }

    /* Check enough segments and enough characters in last segment. */

    if (segs != 3)
        return 0;

    if (chcnt == 0)
        return 0;

    /* Address okay. */

    return 1;
}

but my system variable is a QString type - QString local_ip;
On cast

 IsIP (static_cast<char *>(local_ip))

I get an error. How can I work with a QString argument? Otherwise I have to rewrite a lot of functions.
Some of it present like QString(str).toLower() or QString(str).startWith() but still some specific functions unavailable.

Christian Ehrlicher

Either directly use a const char* or QByteArray or convert it with e.g. QString::toLatin1() or any other maybe more suitable conversion function you can find in the documentation.

KroMignon

@jenya7 said in How to parse QString:

IsIP (static_cast<char *>(local_ip))

As you should know, QString stored internally as UTF-8.
If you want an ASCII string you have to convert it:

QByteArray b = local_ip.toLatin1();
IsIP(b.constData());

But perhaps you should take a look at QHostAddress to check your IP validity:

QHostAddress ip(local_ip):

if (QAbstractSocket::IPv4Protocol == ip.protocol())
{
    qDebug() << "Is valid IPV4 address";
}

SGaist

Hi,

Beside the good point of @Christian-Ehrlicher, do you realize that:

@jenya7 said in How to parse QString:

IsIP (static_cast<char *>(local_ip))

is just wrong.

static_cast does no transformation at all. You are telling your compiler to access a QString object on the stack as if it were a pointer to a char on the heap. So it's a bit like telling someone to drive a bike on the ground while in fact it's a plane over the clouds.

jenya7

Thank you.