containers: Add OptionalValue and OptionalNil

6 files changed, 30 insertions, 20 deletions

diff --git a/lib/btrfs/btrfsitem/item_chunk.go b/lib/btrfs/btrfsitem/item_chunk.go
index 607df75..9bdef1f 100644
--- a/lib/btrfs/btrfsitem/item_chunk.go
+++ b/lib/btrfs/btrfsitem/item_chunk.go
@@ -61,10 +61,7 @@ func (chunk Chunk) Mappings(key btrfsprim.Key) []btrfsvol.Mapping {
 			},
 			Size:       chunk.Head.Size,
 			SizeLocked: true,
-			Flags: containers.Optional[btrfsvol.BlockGroupFlags]{
-				OK:  true,
-				Val: chunk.Head.Type,
-			},
+			Flags:      containers.OptionalValue(chunk.Head.Type),
 		})
 	}
 	return ret
diff --git a/lib/btrfs/btrfstree/readnode.go b/lib/btrfs/btrfstree/readnode.go
index c5d9145..c2e3b0f 100644
--- a/lib/btrfs/btrfstree/readnode.go
+++ b/lib/btrfs/btrfstree/readnode.go
@@ -63,11 +63,11 @@ func FSReadNode(
 	}
 
 	return ReadNode[btrfsvol.LogicalAddr](fs, *sb, path.Node(-1).ToNodeAddr, NodeExpectations{
-		LAddr:      containers.Optional[btrfsvol.LogicalAddr]{OK: true, Val: path.Node(-1).ToNodeAddr},
-		Level:      containers.Optional[uint8]{OK: true, Val: path.Node(-1).ToNodeLevel},
-		Generation: containers.Optional[btrfsprim.Generation]{OK: true, Val: path.Node(-1).ToNodeGeneration},
+		LAddr:      containers.OptionalValue(path.Node(-1).ToNodeAddr),
+		Level:      containers.OptionalValue(path.Node(-1).ToNodeLevel),
+		Generation: containers.OptionalValue(path.Node(-1).ToNodeGeneration),
 		Owner:      checkOwner,
-		MinItem:    containers.Optional[btrfsprim.Key]{OK: true, Val: path.Node(-1).ToKey},
-		MaxItem:    containers.Optional[btrfsprim.Key]{OK: true, Val: path.Node(-1).ToMaxKey},
+		MinItem:    containers.OptionalValue(path.Node(-1).ToKey),
+		MaxItem:    containers.OptionalValue(path.Node(-1).ToMaxKey),
 	})
 }
diff --git a/lib/btrfsutil/graph.go b/lib/btrfsutil/graph.go
index 45e9878..35848de 100644
--- a/lib/btrfsutil/graph.go
+++ b/lib/btrfsutil/graph.go
@@ -209,7 +209,7 @@ func (g Graph) FinalCheck(ctx context.Context, fs diskio.File[btrfsvol.LogicalAd
 	for laddr := range g.EdgesTo {
 		if _, ok := g.Nodes[laddr]; !ok {
 			_, err := btrfstree.ReadNode[btrfsvol.LogicalAddr](fs, sb, laddr, btrfstree.NodeExpectations{
-				LAddr: containers.Optional[btrfsvol.LogicalAddr]{OK: true, Val: laddr},
+				LAddr: containers.OptionalValue(laddr),
 			})
 			if err == nil {
 				progressWriter.Done()
diff --git a/lib/btrfsutil/old_rebuilt_forrest.go b/lib/btrfsutil/old_rebuilt_forrest.go
index c146935..abe3329 100644
--- a/lib/btrfsutil/old_rebuilt_forrest.go
+++ b/lib/btrfsutil/old_rebuilt_forrest.go
@@ -247,9 +247,9 @@ func (bt *OldRebuiltForrest) readNode(nodeInfo nodeInfo) *btrfstree.Node {
 	}
 
 	node, err := btrfstree.ReadNode[btrfsvol.LogicalAddr](bt.inner, *sb, nodeInfo.LAddr, btrfstree.NodeExpectations{
-		LAddr:      containers.Optional[btrfsvol.LogicalAddr]{OK: true, Val: nodeInfo.LAddr},
-		Level:      containers.Optional[uint8]{OK: true, Val: nodeInfo.Level},
-		Generation: containers.Optional[btrfsprim.Generation]{OK: true, Val: nodeInfo.Generation},
+		LAddr:      containers.OptionalValue(nodeInfo.LAddr),
+		Level:      containers.OptionalValue(nodeInfo.Level),
+		Generation: containers.OptionalValue(nodeInfo.Generation),
 		Owner: func(treeID btrfsprim.ObjID) error {
 			if treeID != nodeInfo.Owner {
 				return fmt.Errorf("expected owner=%v but claims to have owner=%v",
@@ -257,8 +257,8 @@ func (bt *OldRebuiltForrest) readNode(nodeInfo nodeInfo) *btrfstree.Node {
 			}
 			return nil
 		},
-		MinItem: containers.Optional[btrfsprim.Key]{OK: true, Val: nodeInfo.MinItem},
-		MaxItem: containers.Optional[btrfsprim.Key]{OK: true, Val: nodeInfo.MaxItem},
+		MinItem: containers.OptionalValue(nodeInfo.MinItem),
+		MaxItem: containers.OptionalValue(nodeInfo.MaxItem),
 	})
 	if err != nil {
 		panic(fmt.Errorf("should not happen: i/o error: %w", err))
diff --git a/lib/btrfsutil/rebuilt_readitem.go b/lib/btrfsutil/rebuilt_readitem.go
index 68aabdd..ff919f0 100644
--- a/lib/btrfsutil/rebuilt_readitem.go
+++ b/lib/btrfsutil/rebuilt_readitem.go
@@ -39,9 +39,9 @@ func (ts *RebuiltForrest) readNode(ctx context.Context, laddr btrfsvol.LogicalAd
 
 	dlog.Debugf(ctx, "cache-miss node@%v, reading...", laddr)
 	node, err := btrfstree.ReadNode[btrfsvol.LogicalAddr](ts.file, ts.sb, laddr, btrfstree.NodeExpectations{
-		LAddr:      containers.Optional[btrfsvol.LogicalAddr]{OK: true, Val: laddr},
-		Level:      containers.Optional[uint8]{OK: true, Val: graphInfo.Level},
-		Generation: containers.Optional[btrfsprim.Generation]{OK: true, Val: graphInfo.Generation},
+		LAddr:      containers.OptionalValue(laddr),
+		Level:      containers.OptionalValue(graphInfo.Level),
+		Generation: containers.OptionalValue(graphInfo.Generation),
 		Owner: func(treeID btrfsprim.ObjID) error {
 			if treeID != graphInfo.Owner {
 				return fmt.Errorf("expected owner=%v but claims to have owner=%v",
@@ -49,8 +49,8 @@ func (ts *RebuiltForrest) readNode(ctx context.Context, laddr btrfsvol.LogicalAd
 			}
 			return nil
 		},
-		MinItem: containers.Optional[btrfsprim.Key]{OK: true, Val: graphInfo.MinItem()},
-		MaxItem: containers.Optional[btrfsprim.Key]{OK: true, Val: graphInfo.MaxItem()},
+		MinItem: containers.OptionalValue(graphInfo.MinItem()),
+		MaxItem: containers.OptionalValue(graphInfo.MaxItem()),
 	})
 	if err != nil {
 		panic(fmt.Errorf("should not happen: i/o error: %w", err))
diff --git a/lib/containers/optional.go b/lib/containers/optional.go
index 5bb7bb6..26ec494 100644
--- a/lib/containers/optional.go
+++ b/lib/containers/optional.go
@@ -13,6 +13,19 @@ type Optional[T any] struct {
 	Val T
 }
 
+func OptionalValue[T any](val T) Optional[T] {
+	return Optional[T]{
+		OK:  true,
+		Val: val,
+	}
+}
+
+func OptionalNil[T any]() Optional[T] {
+	return Optional[T]{
+		OK: false,
+	}
+}
+
 var (
 	_ json.Marshaler   = Optional[bool]{}
 	_ json.Unmarshaler = (*Optional[bool])(nil)