Hi, after the announcement of my ideas for a Storage Redesign in YaST I present now the first draft of the API that libstorage will provide. Remember that this API should be used by all YaST modules using functions from yast2-storage so far since the infamous target map will vanish.
Device Graph ------------ The basic data structure is a directed graph of device objects as already explained (https://github.com/aschnell/libstorage-bgl-eval/wiki). Compared to the target map there are a few new objects, e.g. PartitionTable, Encryption and Filesystem. How to get a Device Graph ------------------------- Libstorage works with several device graphs, mainly the "probed" and the "current". Somehow you will have access to the main storage objects and can use that to get a device graph: DeviceGraph* device_graph = storage->getCurrent(); Manipulating the Device Graph ----------------------------- There are "constructors" for all concrete objects (e.g. Ext4 and Swap are concrete while Filesystem is abstract). Disk* sda = Disk::create(device_graph, "/dev/sda"); The device_graph is the owner of the objects. Creating disks will of course only be allowed in the image/KIWI mode. Most objects will be created by calling member functions of the parent: PartitionTable* gpt = sda->createPartitionTable(GPT); Partition* sda1 = gpt->createPartition("/dev/sda1"); // parameter will change Manipulating is done with member functions, e.g.: filesystem->addMountPoint("/boot"); There is also a low level interface where the vertices and edges of the graph are manipulated directly, e.g.: PartitionTable* gpt = Gpt::create(device_graph); // creates vertex Using::create(device_graph, sda, gpt); // creates edge Partition* sda1 = Partition::create("/dev/sda1"); // creates vertex Subdevice::create(device_graph, gpt, sda1); // creates edge But this low level interface should be reserved for the expert partitioner if needed at all. Querying the Device Graph ------------------------- Generic functions to query relatives of a device: vector<Device*> children = device->getChildren(); Here getChildren, getParents, getSiblings, getDescendants, getAncestors, getLeafs and getRoots is available. Special functions to query relatives of a device, e.g. the partitions of a partition table: vector<Partition*> partitions = gpt->getPartitions(); Functions to find specific devices, e.g. filesystems by mount point: Filesystem::findByMountPoint(device_graph, "/boot"); Combining query functions in a complex example: Suppose the bootloader has to know whether the device mounted at "/" uses a LVM logical volume: for (const Filesystem* filesystem : Filesystem::findByMountPoint(device_graph, "/")) { for (const Device* device : filesystem->getAncestors(false)) { if (dynamic_cast<const LvmLv*>(device)) cout << "mount point \"/\" somehow uses a logical volume" << endl; } } https://github.com/aschnell/libstorage-bgl-eval/blob/master/examples/find1.cc Bindings -------- I have swig generated bindings for Ruby, Python and Perl5. The repository contains a few examples for each of them: https://github.com/aschnell/libstorage-bgl-eval/tree/master/bindings Help ---- The Makefile.am for Perl bindings needs improvement and the bindings should get a tiny testsuite. RFC --- If you see problems with this API for your module, generally miss something or have ideas for improvement please comment now. ciao Arvin -- Arvin Schnell, <[email protected]> Senior Software Engineer, Research & Development SUSE LINUX GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 21284 (AG Nürnberg) Maxfeldstraße 5 90409 Nürnberg Germany -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
