QHttp file upload doesn't stream?

[haughki]

Hi All,

Using QT 4.5.2 on Windows XP. Code example at bottom of post.

I have a some file upload code which uses QHttp to send a PUT request to a WebDav server. It works fine except for one major problem: it loads the entire file into memory before it uploads the file. This is a problem with large files, a show stopper if the client runs out of memory.

int QHttp::request ( const QHttpRequestHeader & header, QIODevice * data = 0, QIODevice * to = 0 )

int QHttp::request ( const QHttpRequestHeader & header, QIODevice * data = 0, QIODevice * to = 0 )

To copy to clipboard, switch view to plain text mode 

I'm using QHttp::request to start the request. I can't seem to come up with a device or combination of devices which will stream or otherwise buffer the file from the disk.

My working code (which doesn't stream) just passes in the QFile:

_httpId = _qHttp->request(header, sourceFile);

I tried passing a QDataStream (or TextStream), which is not a QIODevice. Tried to come up with a combination of QBuffer, QFile, just to see if something would work. No luck.

I took a look at the QT source. Interestingly, it _is_ buffering the file read in qhttp.cpp, QHttpPrivate::_q_slotBytesWritten(). The memory load looks to me like it's happening in qsslsocket.cpp, QSslSocket::writeData() when the method memcpy's the buffer.

- Can I use QHttp to do what I want? It doesn't seem like it, but maybe I'm missing something.
- Is this a bug (I don't think so, yet)?
- Is it worth trying QNetworkAccessManager, or am I going to run into the same problem?
- If I need to write custom code to support this, could someone outline a basic approach? Will I need to creat multiple requests for this kind of "chunked" transfer?

Code snippet (builds, haven't tried to run. My actual code has a bunch of classes abstracting/wrapping a lot of this.)

QUrl destUrl(QString("http://www.someDAVserver.com/someFolder/someBigFile.dat"));
    QFile* sourceFile = new QFile("D:\\someLocalDir\\someBigFile.dat");
 
    if (!sourceFile->open(QIODevice::ReadOnly)) {
        //throw
    }
 
    QHttp::ConnectionMode mode = destUrl.scheme().toLower() == "https" ? QHttp::ConnectionModeHttps : QHttp::ConnectionModeHttp;
 
    QHttp http;
    http.setHost(destUrl.host(), mode, destUrl.port() == -1 ? 0 : destUrl.port());
 
    QHttpRequestHeader header("PUT", destUrl.toEncoded(QUrl::RemoveScheme|QUrl::RemoveAuthority));
    header.setValue("Host", destUrl.host());
    header.setValue("Accept-Language", QLocale::system().name());
    header.setValue("Content-Length", QString::number(sourceFile->size()));
 
 
    http.request(header, sourceFile);

QUrl destUrl(QString("http://www.someDAVserver.com/someFolder/someBigFile.dat"));
    QFile* sourceFile = new QFile("D:\\someLocalDir\\someBigFile.dat");

    if (!sourceFile->open(QIODevice::ReadOnly)) {
        //throw
    }

    QHttp::ConnectionMode mode = destUrl.scheme().toLower() == "https" ? QHttp::ConnectionModeHttps : QHttp::ConnectionModeHttp;

    QHttp http;
    http.setHost(destUrl.host(), mode, destUrl.port() == -1 ? 0 : destUrl.port());

    QHttpRequestHeader header("PUT", destUrl.toEncoded(QUrl::RemoveScheme|QUrl::RemoveAuthority));
    header.setValue("Host", destUrl.host());
    header.setValue("Accept-Language", QLocale::system().name());
    header.setValue("Content-Length", QString::number(sourceFile->size()));


    http.request(header, sourceFile);

To copy to clipboard, switch view to plain text mode 

Thanks in advance,

Hawkeye Parker