![]() Start a QThread to handle incoming data while still keeping our userīool webfile::open(qint64 offset /* = 0*/) Please download the complete code and the Required, gradually filling up memory at the receiving end. Will almost certainly be pulled at a slower speed from the server as the Is a Qt flaw: Our threads are QThreads and the timers actually doĬome up when playing a compressed file from the web, e.g., a 128Kbit MP4 If the data processing thread is not fast enough, the memory can still run full.Īpplication complains that “ QTimers must be created from QThread”. Unfortunately, a few small glitches remain: Using different approaches for thread synchonisation depending on whether running in GUI or non GUI mode.įor GUI threads, using QEventLoop ensures that we are maintaining a snappy user interface. Using a QThread to handle the incoming data. Getting this to work is a combination of several little tricks: When using this code in non GUI threads the QEventLoop can, and will, cause deadlocks. Streams cannot be handled this way, as finish() would never be called – the app will lock up, eventually run out of memory and crash. There is no way to display a progress to the user whilst downloading. Using a different signal that fires earlier like readyRead() by the QNetworkRequest reply object will leave you with the first portion of a large file, but you are unable to get the rest. For large files, this can take quite a while and even fill up all memory (causing your application to crash). The file will be downloaded completely into memory before finished() fires. Alas, there areĭrawbacks which prove to be quite nasty showstoppers: Internet sources that already describe the steps above. QString strData( " bytes=" + QString::number(m_nPos) + " -") If we want to be able to start reading at an arbitrary offset, we could throw in these lines just before the get(request) call: Went well subsequently call reply->readAll() or similar to get our Reply->error() to see if there was a problem and report it, or if all When it arrives, the request has completed -Įither successfully or it has failed. ![]() Get(), we enter an event loop and wait for the finished() signal from tRawHeader( " User-Agent", " Qt NetworkAccess 1.3") SLOT(slotAuthenticationRequired(QNetworkReply *, QAuthenticator *))) SLOT(slotProxyAuthenticationRequired( const QNetworkProxy &, QAuthenticator *))) Ĭonnect(manager, SIGNAL(authenticationRequired(QNetworkReply *, QAuthenticator *)), QNetworkAccessManager *manager = new QNetworkAccessManager( this) Ĭonnect(manager, SIGNAL(proxyAuthenticationRequired( const QNetworkProxy &, QAuthenticator *)), Happened – did we get a connect, have we been able to access the file weĪsked for? There is a whole bunch of things that could go wrong at that Up front, after sending out the request, the code So: Why write a new class? Reinvent the wheel just because it seems that the Qt approach cannot handle synchronous downloads? In other words: everything you need when talking to web servers. Parameters or data, and can manipulate the http headers as well as Servers, implements the http put/get methods including passing of Supports Microsoft NTLM), can send sign on credentials to remote Server support, can authenticate against proxies if required (it even Qt offers the QNetworkManager class which has proxy To a virtual single large image and handle them as such. And finally I want to playĭVDs directly via http, which involves concatenating the 1GB file parts Immediately without having to complete the download in the first place.Īlso, I want to play Shoutcast streams which are simply impossible toĭownload first, as they have no end-of-file. Or sound file via http from a web server and start playing it The reason in my case is, I want to stream a video Reason why we want to download synchronously. Of course I know how to do that, as probably does Sounds to me like "Don't you know how to use it asynchronously, ![]() ![]() Tends to make me angry, not only because the reply is useless. Several times, the first hint is "Use it in asynchronous mode." This Many places: "How can I use QNetworkManager for synchronous downloads?". Using Google on the topic, the question can be found in Sometimes help forums frankly turn out to not being ![]()
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