[#421] Try using badger for the write-cache

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/local_object_storage/writecache/writecachebadger/iterate.go

@@ -0,0 +1,32 @@
+package writecachebadger
+
+import (
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/dgraph-io/badger/v4"
+)
+
+// IterateDB iterates over all objects stored in badger.DB instance and passes them to f until error return.
+// It is assumed that db is an underlying database of some WriteCache instance.
+//
+// DB must not be nil and should be opened.
+func IterateDB(db *badger.DB, f func(oid.Address) error) error {
+	return metaerr.Wrap(db.View(func(tx *badger.Txn) error {
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := tx.NewIterator(opts)
+		for it.Rewind(); it.Valid(); it.Next() {
+			var key internalKey
+			if got, want := len(it.Item().Key()), len(key); got != want {
+				return fmt.Errorf("invalid db key len: got %d, want %d", got, want)
+			}
+			copy(key[:], it.Item().Key())
+			if err := f(key.address()); err != nil {
+				return err
+			}
+		}
+		return nil
+	}))
+}