feat(fsrepo/component.datastore) basic shell

repo/fsrepo/component/datastore.go

+package component
+
+import (
+	datastore "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	levelds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/leveldb"
+	ldbopts "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt"
+	config "github.com/jbenet/go-ipfs/repo/config"
+	dir "github.com/jbenet/go-ipfs/repo/fsrepo/dir"
+	util "github.com/jbenet/go-ipfs/util"
+	ds2 "github.com/jbenet/go-ipfs/util/datastore2"
+	debugerror "github.com/jbenet/go-ipfs/util/debugerror"
+)
+
+var _ Component = &DatastoreComponent{}
+var _ Initializer = InitDatastoreComponent
+var _ InitializationChecker = DatastoreComponentIsInitialized
+
+func InitDatastoreComponent(path string, conf *config.Config) error {
+	// The actual datastore contents are initialized lazily when Opened.
+	// During Init, we merely check that the directory is writeable.
+	dspath, err := config.DataStorePath(path)
+	if err != nil {
+		return err
+	}
+	if err := dir.Writable(dspath); err != nil {
+		return debugerror.Errorf("datastore: %s", err)
+	}
+	return nil
+}
+
+// DatastoreComponentIsInitialized returns true if the datastore dir exists.
+func DatastoreComponentIsInitialized(path string) bool {
+	dspath, err := config.DataStorePath(path)
+	if err != nil {
+		return false
+	}
+	if !util.FileExists(dspath) {
+		return false
+	}
+	return true
+}
+
+// DatastoreComponent abstracts the datastore component of the FSRepo.
+// NB: create with makeDatastoreComponent function.
+type DatastoreComponent struct {
+	path string
+	ds   ds2.ThreadSafeDatastoreCloser
+}
+
+// Open returns an error if the config file is not present.
+func (dsc *DatastoreComponent) Open() error {
+	ds, err := levelds.NewDatastore(dsc.path, &levelds.Options{
+		Compression: ldbopts.NoCompression,
+	})
+	if err != nil {
+		return err
+	}
+	dsc.ds = ds
+	return nil
+}
+
+func (dsc *DatastoreComponent) Close() error                             { return dsc.ds.Close() }
+func (dsc *DatastoreComponent) SetPath(p string)                         { dsc.path = p }
+func (dsc *DatastoreComponent) Datastore() datastore.ThreadSafeDatastore { return dsc.ds }