MobileRead Forums - View Single Post - MM / CM13: on sync "library is read only" always after CM update

chaley · 11-07-2016, 11:06 AM

I can't say with any certainty what is happening, but I can make a guess.

CC uses the Android Storage Access Framework (SAF) to get access to the SD card, and in some cases to main memory. The SAF provides a special URL to CC to get access to folders. This URL encapsulates the SAF security. It also masks the "real" path to the folder, something that CC needs to hand books to reader apps. CC recomputes this real path by asking Android for real paths to some special files on both main memory and the SD card, then searches for the folder containing the books. It records the resulting folder path in "Formats and folders".

My guess is that the update does two things:

It changes the path to the special folders, invalidating the path stored in Formats and folders.
It removes write privilege from the special URL.

The effect would be what you see. The books appear to be missing and CC can't write the folders, but CC would be able to read the books to be able to move them. However, CC probably would complain that it can't delete the books, unless you are moving them to the same place in which case CC would be happy to simply use them as is.

You could test this hypothesis somewhat with a file manager by going to the SD card using whatever path the SD card wants, then navigating to where you think the books should be. My guess is that they will be there. I also suspect that when you "create" the new folder the path changes subtly. For example, the 0101-0014/ would change.

I don't see anything that CC can do. It certainly cannot recover from Android changing the path.

11-07-2016, 11:06 AM	#2
chaley Grand Sorcerer Posts: 12,482 Karma: 8025704 Join Date: Jan 2010 Location: Notts, England Device: Kobo Libra 2	I can't say with any certainty what is happening, but I can make a guess. CC uses the Android Storage Access Framework (SAF) to get access to the SD card, and in some cases to main memory. The SAF provides a special URL to CC to get access to folders. This URL encapsulates the SAF security. It also masks the "real" path to the folder, something that CC needs to hand books to reader apps. CC recomputes this real path by asking Android for real paths to some special files on both main memory and the SD card, then searches for the folder containing the books. It records the resulting folder path in "Formats and folders". My guess is that the update does two things: It changes the path to the special folders, invalidating the path stored in Formats and folders. It removes write privilege from the special URL. The effect would be what you see. The books appear to be missing and CC can't write the folders, but CC would be able to read the books to be able to move them. However, CC probably would complain that it can't delete the books, unless you are moving them to the same place in which case CC would be happy to simply use them as is. You could test this hypothesis somewhat with a file manager by going to the SD card using whatever path the SD card wants, then navigating to where you think the books should be. My guess is that they will be there. I also suspect that when you "create" the new folder the path changes subtly. For example, the 0101-0014/ would change. I don't see anything that CC can do. It certainly cannot recover from Android changing the path.