Question

i have simple app the gets all the links from web page , im using libexml2 to parse the html
and extract the html links that are inside the
and Qt QNetworkAccessManager for the http requests .
now the problem is how to detecte automatcly the host name of the links if i have for example :

<a href="thelink.html" >
or 
<a href="../../../thelink.html" >  
or
<a href="../foo/boo/thelink.html" > 
i need to convert it to full host path like :
( just example .. ) 
<a href="http://www.myhost.com/thelink.html" >
or 
<a href="http://www.myhost.com/foo/boo/thelink.html" >  
or
<a href="http://www.myhost.com/m/thelink.html" > 

is there any way to do it programmatically ? without manually doing string manipulation

if you know perl its called : Return a relative URL if possible
from the : http://search.cpan.org/~rse/lcwa-1.0.0/lib/lwp/lib/URI/URL.pm

$url->rel([$base])

code example that dosnt work ( Qt )
http://qt.digia.com/support/

QString s("/About-us/");
QString base("http://qt.digia.com");
QString urlForReq;

     if(!s.startsWith("http:"))
     {       
         QString uu = QUrl(s).toString();
         QString   rurl = baseUrl.resolved(QUrl(s)).toString();
         urlForReq = rurl;
     }

the urlForReq value is “/About-us/”

Answer 1

I have not verified if the algorithm mentioned by @sftrabbit is completely followed by this approach, but you can use QUrl::resolved to convert your relative URLs to absolute URLs:

QUrl base("http://www.myhost.com/m/");
qDebug() << base.resolved(QUrl("thelink.html")).toString();
qDebug() << base.resolved(QUrl("../../../thelink.html")).toString();
qDebug() << base.resolved(QUrl("../foo/boo/thelink.html")).toString();

prints

"http://www.myhost.com/m/thelink.html"
"http://www.myhost.com/thelink.html"
"http://www.myhost.com/foo/boo/thelink.html"

---

I can not reproduce the code example from the question which does not work for the OP. The only issue is that the baseUrl object is missing in the code. The following SSCCE

#include <QApplication>
#include <QUrl>
#include <QDebug>

int main(int argc, char ** argv) {

    QApplication app( argc, argv );

    QString s("/About-us/");
    QString base("http://qt.digia.com");
    QString urlForReq;
    QUrl baseUrl(base);          // this was missing in the code from the question
    if(!s.startsWith("http:")) {       
        QString uu = QUrl(s).toString();
        QString rurl = baseUrl.resolved(QUrl(s)).toString();
        urlForReq = rurl;
    }
    qDebug() << "urlForReq:" << urlForReq;

    return 0;
}

prints

urlForReq: "http://qt.digia.com/About-us/"