How can we parse HTTP response header fields using Qt/C++?

c++, http-headers, kde-plasma, parsing, qt

Solution

The HTTP header should initially be in a `QByteArray` (because it is in ASCII, not UTF-16), but the method would be the same with a `QString`:

- split the header line by line,

- split each line at the colon character,

- trim any white spaces (regular spaces and `'\r'` characters) around the 2 resulting strings before storing them.

QByteArray httpHeaders = ...;
QMap<QByteArray, QByteArray> headers;

// Discard the first line
httpHeaders = httpHeaders.mid(httpHeaders.indexOf('\n') + 1).trimmed();

foreach(QByteArray line, httpHeaders.split('\n')) {
    int colon = line.indexOf(':');
    QByteArray headerName = line.left(colon).trimmed();
    QByteArray headerValue = line.mid(colon + 1).trimmed();

    headers.insertMulti(headerName, headerValue);
}

Problem

I am writing a piece of software that uses Qt/KDE libs. The objective is to parse the HTTP header response fields into different fields of a struct. So far the HTTP header response is contained in a QString. It looks something like this: ``` "HTTP/1.1 302 Found date: Tue, 05 Jun 2012 07:40:16 GMT server: Apache/2.2.22 (Linux/SUSE) x-prefix: 49.244.80.0/21 x-as: 23752 x-mirrorbrain-mirror: mirror.averse.net x-mirrorbrain-realm: region link: <http://download.services.openoffice.org/files/du.list.meta4>; rel=describedby; type="application/metalink4+xml" link: <http://download.services.openoffice.org/files/du.list.torrent>; rel=describedby; type="application/x-bittorrent" link: <http://mirror.averse.net/openoffice/du.list>; rel=duplicate; pri=1; geo=sg link: <http://ftp.isu.edu.tw/pub/OpenOffice/du.list>; rel=duplicate; pri=2; geo=tw link: <http://ftp.twaren.net/OpenOffice/du.list>; rel=duplicate; pri=3; geo=tw link: <http://mirror.yongbok.net/openoffice/du.list>; rel=duplicate; pri=4; geo=kr link: <http://ftp.kaist.ac.kr/openoffice/du.list>; rel=duplicate; pri=5; geo=kr digest: MD5=b+zfBEizuD8eXZUTWJ47xg== digest: SHA=A5zw6PkywlhiPlFfjca+gqIGLHA= digest: SHA-256=HOrd0MMBzS8Ctljpe4PauwStijsnBKaa3gXO4L30eiA= location: http://mirror.averse.net/openoffice/du.list content-length: 329 connection: close content-type: text/html; charset=iso-8859-1" ``` In addition to the custom fields there might be few more fields in the header response. The only possible way that I came up was to manually search for the fields like "link", "digest" and others and create a QMap with the fields as keys.However, I guess there must be a better way to do this. I would be thankful to you if you could help me.

Original source