On 12/29/2015 9:32 AM, Jason Kretzer wrote:
Hello all,
I have an application that must download files in the background. I
separate this process off into a separate thread so that it does not
interfere with the UI. Unfortunately, when it starts downloading, it uses
the full pipe that it has access to and adversely affects the rest of the
network – causing other internet connections to slow to a crawl. The
application is installed on networks which I do not control and cannot
throttle it that way. What I would like to do is have the application not
eat so much bandwidth during the download.
The code I am using to download is pretty run of the mill (error checks
removed for brevity):
void ContentDownloader::downloadFile(QUrl url, QString filename)
{
QNetworkRequest request(url);
QNetworkAccessManager* _manager = new QNetworkAccessManager(this);
QNetworkReply* reply = _manager->get(request);
QEventLoop loop;
connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
loop.exec();
QFile file(filename);
file./open/(QIODevice::/WriteOnly/);
file.write(reply->readAll());
file./close/();
}
Thoughts on how to make it “slow down”? I have been toying with the
setReadBufferSize in the reply but does not really seem to change anything.
Thanks!
Set a timer to read chunks of the file each time it expires, and send that
chunk down the pipe with your call to file.write(). By adjusting the timer's
timeout value and the amount of data you read/send, you can effectively
throttle it yourself to a comfortable bytes-per-second setting.
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