1 files changed, 77 insertions, 0 deletions
diff --git a/lib/btrfs/btrfsitem/items.go b/lib/btrfs/btrfsitem/items.go
new file mode 100644
index 0000000..33ff390
--- /dev/null
+++ b/lib/btrfs/btrfsitem/items.go
@@ -0,0 +1,77 @@
+package btrfsitem
+
+import (
+	"fmt"
+	"reflect"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfssum"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+type Type = internal.ItemType
+
+type Item interface {
+	isItem()
+}
+
+type Error struct {
+	Dat []byte
+	Err error
+}
+
+func (Error) isItem() {}
+
+func (o Error) MarshalBinary() ([]byte, error) {
+	return o.Dat, nil
+}
+
+func (o *Error) UnmarshalBinary(dat []byte) (int, error) {
+	o.Dat = dat
+	return len(dat), nil
+}
+
+// Rather than returning a separate error  value, return an Error item.
+func UnmarshalItem(key internal.Key, csumType btrfssum.CSumType, dat []byte) Item {
+	var gotyp reflect.Type
+	if key.ItemType == UNTYPED_KEY {
+		var ok bool
+		gotyp, ok = untypedObjID2gotype[key.ObjectID]
+		if !ok {
+			return Error{
+				Dat: dat,
+				Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v, ObjectID:%v}, dat): unknown object ID for untyped item",
+					key.ItemType, key.ObjectID),
+			}
+		}
+	} else {
+		var ok bool
+		gotyp, ok = keytype2gotype[key.ItemType]
+		if !ok {
+			return Error{
+				Dat: dat,
+				Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v}, dat): unknown item type", key.ItemType),
+			}
+		}
+	}
+	retPtr := reflect.New(gotyp)
+	if csums, ok := retPtr.Interface().(*ExtentCSum); ok {
+		csums.ChecksumSize = csumType.Size()
+	}
+	n, err := binstruct.Unmarshal(dat, retPtr.Interface())
+	if err != nil {
+		return Error{
+			Dat: dat,
+			Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v}, dat): %w", key.ItemType, err),
+		}
+
+	}
+	if n < len(dat) {
+		return Error{
+			Dat: dat,
+			Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v}, dat): left over data: got %v bytes but only consumed %v",
+				key.ItemType, len(dat), n),
+		}
+	}
+	return retPtr.Elem().Interface().(Item)
+}