Add getDataView() method to QTextureFileData

This method will return a QByteArrayView of the data range corresponding
to the level. This avoids a leaky abstraction by moving the needed data
pointer arithmetic from the caller to the method. It will also make it
easier adding cubemap support in the future.

Change-Id: I2415bd88365d8d69ba14aefc77f5f1117f9e0033
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

src/gui/util/qtexturefiledata.cpp

@@ -167,6 +167,17 @@ int QTextureFileData::dataLength(int level) const
     return (d && d->lengths.size() > level) ? d->lengths.at(level) : 0;
 }
 
+QByteArrayView QTextureFileData::getDataView(int level) const
+{
+    const int dataLength = this->dataLength(level);
+    const int dataOffset = this->dataOffset(level);
+
+    if (d == nullptr || dataLength == 0)
+        return QByteArrayView();
+
+    return QByteArrayView(d->data.constData() + dataOffset, dataLength);
+}
+
 void QTextureFileData::setDataLength(int length, int level)
 {
     if (d.constData() && level >= 0) {

src/gui/util/qtexturefiledata_p.h

@@ -84,6 +84,8 @@ public:
     int dataLength(int level = 0) const;
     void setDataLength(int length, int level = 0);
 
+    QByteArrayView getDataView(int level = 0) const;
+
     int numLevels() const;
     void setNumLevels(int num);