These classes (UnifiedSavePointManager and the contained SavePoint) isolate the save point handing. Its effect spans both the input stream and the underlying buffer - so the manager keeps it's own reference to these. By doing so this should make save points easier to use. It grabs the buffer from the stream since it need a reference to the UnifiedInputBuffer on most calls and doesn't need an extra de-ref (mostly for code clarity) The general life time of a save point is: . allocate a save point . . start the save point, which sets the start idx and pos - and pins the buffer pages with a use count . . mark_end the save point, which sets the end idx and pos . . . activate the save point, which sets the input streams pos to the start . . . deactivate the save point, which pops the save point stack and restores the stream to its previous position . . clear the save point. this clears its internal values and releases its use counter on the buffer. As the buffers in use count goes to zero it may release any unnecessary pages. . free the save point this order of operation, as nested above, is enforced by checking the state of the save points and member values like the end position. if the end position is not set it is treated as "to end of file"