swarm: codebase split from go-ethereum (#1405)

storage/localstore/schema.go

@@ -0,0 +1,52 @@
+package localstore
+
+import (
+	"github.com/ethersphere/swarm/log"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+)
+
+// The DB schema we want to use. The actual/current DB schema might differ
+// until migrations are run.
+const CurrentDbSchema = DbSchemaSanctuary
+
+// There was a time when we had no schema at all.
+const DbSchemaNone = ""
+
+// "purity" is the first formal schema of LevelDB we release together with Swarm 0.3.5
+const DbSchemaPurity = "purity"
+
+// "halloween" is here because we had a screw in the garbage collector index.
+// Because of that we had to rebuild the GC index to get rid of erroneous
+// entries and that takes a long time. This schema is used for bookkeeping,
+// so rebuild index will run just once.
+const DbSchemaHalloween = "halloween"
+
+const DbSchemaSanctuary = "sanctuary"
+
+// returns true if legacy database is in the datadir
+func IsLegacyDatabase(datadir string) bool {
+
+	var (
+		legacyDbSchemaKey = []byte{8}
+	)
+
+	db, err := leveldb.OpenFile(datadir, &opt.Options{OpenFilesCacheCapacity: 128})
+	if err != nil {
+		log.Error("got an error while trying to open leveldb path", "path", datadir, "err", err)
+		return false
+	}
+	defer db.Close()
+
+	data, err := db.Get(legacyDbSchemaKey, nil)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			// if we haven't found anything under the legacy db schema key- we are not on legacy
+			return false
+		}
+
+		log.Error("got an unexpected error fetching legacy name from the database", "err", err)
+	}
+	log.Trace("checking if database scheme is legacy", "schema name", string(data))
+	return string(data) == DbSchemaHalloween || string(data) == DbSchemaPurity
+}