Possible raise condition while moving data windows

pushBackDataFinished which is used for window movement is called by the same thread which pushes data.

Though reading the data from a window is done in a different thread. In order to prevent concurrent access, the following measure needs to be done. Two possible solutions:

Solution 1:

• Use a std::mutex for window movement and readout
  • Whenever the window is moved or modified ... required to expose mutex lock/unlock in order dont toggle it to frequently during movement / update of metadata
  • Whenever the windoe is read out

Solution 2:

• Create a copy of the window after each movement
• Pass that copy to the DataReadyQueue, though keep a reference in BufferManager in order to invalidate it on each subsequent move operation of the write iterator. (mutex protected valid_ flag)
• Once a window is invalidated, there is no need to further track it in the BufferManager.

I think Solution 2 would be more elegant. An unfinished attempt (meanwhile conflicting) can be seen here: https://gitlab.com/al.schwinn/cabad/-/tree/%2331_pass_copied_window_to_client