Updating embedded files
Updating embedded files - by invalidating
Here are some of my self-imposed requirements An actual implementation will have to handle the details of getting the new rootfs tarball onto the device and checking for corruption and validity.
Full-system upgrades are nice because they are atomic and easy to rollback to a known good state assuming the previous system was not modified.The benefit is to be able to write the logic/synchronization part of the database layer and test its algorithms using Dart VM and not Dartium // Idb factory based on sembast var idb Factory = Idb Sembast Factory(database Factory Io); String store = "my_store"; // Here the indexed db API can be used void _initialize Database(Version Change Event e) Database db = await idb Factory.open(db Path, version: 1, on Upgrade Needed: _initialize Database); Transaction transaction = db.transaction(store, IDB_MODE_READ_WRITE); Object Store object Store = transaction.object Store(store); // put and read on object await object Store.put("value", "test"); expect(await object Object("test"), "value"); await transaction.completed; Each data written is appended lazily to the file for best performance.Compact might happen at any moment to prevent record duplication. To prevent deadlock, never use an existing Database or Store object.// Use the animals store using Map records with int keys var store = int Map Store Factory.store('animals'); // Store some objects await db.transaction((txn) async ); // Look for any animal "greater than" (alphabetically) 'cat' // ordered by name var finder = Finder( filter: Filter.greater Than('name', 'cat'), sort Orders: [Sort Order('name')]); var records = await store.find(db, finder: finder); expect(records.length, 2); expect(records['name'], 'dog'); expect(records['name'], 'fish'); Sembast supports using a user-defined codec to encode/decode data when read/written to disk. Encryption itself is not part of sembast but an example of a simple encryption codec is provided in the test folder.Distribution of the new system can be over a network (ethernet or wifi) or through a USB removable drive.
Transferring files less then 100 MB is fairly trivial today even over wifi.
The drawback to full-system upgrades is traditionally the size when distributing (bandwidth) and the system resources when installing (not enough space for two systems, takes too long to run the upgrade).
With the embedded Linux systems I work on these are typically non-issues.
The implementation described assumes storage of at least 4GB, with the two rootfs partitions being 1GB each.
This amount of storage is not a hard requirement, but as a practical matter less available storage is unlikely to be encountered.
// Initialize the encryption codec with a user password var codec = get Encrypt Sembast Codec(password: '[your_user_password]'); // Open the database with the codec Database db = await Database(db Path, codec: codec); // ..database is ready to use More information here.