QNAM: Fix previous HTTP upload CPU fix

My previous fix for CPU load issues between HTTP thread
and user thread  was fragile if the upload QIODevice
emitted readyRead() multiple times.

[ChangeLog][QtNetwork][QNetworkAccessManager] Fix behavior of upload QIODevice
that generate data on readyRead() for HTTP PUT/POST

Change-Id: Idb1c2d5a382a704d8cc08fe03c55c883bfc95aa7
Reviewed-by: Christian Kamm <kamm@incasoftware.de>
Reviewed-by: Richard J. Moore <rich@kde.org>

src/network/access/qnetworkreplyhttpimpl.cpp

@@ -428,6 +428,7 @@ QNetworkReplyHttpImplPrivate::QNetworkReplyHttpImplPrivate()
     , synchronous(false)
     , state(Idle)
     , statusCode(0)
+    , uploadDeviceChoking(false)
     , outgoingData(0)
     , bytesUploaded(-1)
     , cacheLoadDevice(0)
@@ -1291,9 +1292,12 @@ void QNetworkReplyHttpImplPrivate::wantUploadDataSlot(qint64 maxSize)
     char *data = const_cast<char*>(uploadByteDevice->readPointer(maxSize, currentUploadDataLength));
 
     if (currentUploadDataLength == 0) {
+        uploadDeviceChoking = true;
         // No bytes from upload byte device. There will be bytes later, it will emit readyRead()
         // and our uploadByteDeviceReadyReadSlot() is called.
         return;
+    } else {
+        uploadDeviceChoking = false;
     }
 
     // Let's make a copy of this data
@@ -1306,7 +1310,12 @@ void QNetworkReplyHttpImplPrivate::wantUploadDataSlot(qint64 maxSize)
 void QNetworkReplyHttpImplPrivate::uploadByteDeviceReadyReadSlot()
 {
     // Start the flow between this thread and the HTTP thread again by triggering a upload.
-    wantUploadDataSlot(1024);
+    // However only do this when we were choking before, else the state in
+    // QNonContiguousByteDeviceThreadForwardImpl gets messed up.
+    if (uploadDeviceChoking) {
+        uploadDeviceChoking = false;
+        wantUploadDataSlot(1024);
+    }
 }
 
 

src/network/access/qnetworkreplyhttpimpl_p.h

@@ -212,6 +212,7 @@ public:
     // upload
     QNonContiguousByteDevice* createUploadByteDevice();
     QSharedPointer<QNonContiguousByteDevice> uploadByteDevice;
+    bool uploadDeviceChoking; // if we couldn't readPointer() any data at the moment
     QIODevice *outgoingData;
     QSharedPointer<QRingBuffer> outgoingDataBuffer;
     void emitReplyUploadProgress(qint64 bytesSent, qint64 bytesTotal); // dup?

tests/auto/network/access/qnetworkreply/tst_qnetworkreply.cpp

@@ -7883,6 +7883,8 @@ protected slots:
         //qDebug() << Q_FUNC_INFO;
         bandwidthQuota = 8*1024; // fill quota
         emit readyRead();
+        // Emitting readyRead() several times triggers a bug ("QIODevice::read: Called with maxSize < 0") we fix with this commit
+        emit readyRead();
     }
 };