A QDataSource is an asynchronous producer of data. ... List of all member functions. virtual int  readyToSend  ()  . ... A data source is an object which provides data from some source in an asynchronous manner. ... If this function is called with on set to TRUE, and rewindable () is TRUE, then the data source must take measures to allow the rewind () function to subsequently operate as described. ... This function is called to extract data from the source, by sending it to the given data sink. ...