1 files changed, 49 insertions, 0 deletions
diff --git a/cmd/btrfs-rec/inspect/rebuildmappings/file_phony.go b/cmd/btrfs-rec/inspect/rebuildmappings/file_phony.go
new file mode 100644
index 0000000..a41a16b
--- /dev/null
+++ b/cmd/btrfs-rec/inspect/rebuildmappings/file_phony.go
@@ -0,0 +1,49 @@
+// Copyright (C) 2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package rebuildmappings
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfstree"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
+	"git.lukeshu.com/btrfs-progs-ng/lib/slices"
+)
+
+type phonyFile struct {
+	size btrfsvol.PhysicalAddr
+	sb   btrfstree.Superblock
+}
+
+var _ diskio.File[btrfsvol.PhysicalAddr] = (*phonyFile)(nil)
+
+func NewPhonyFile(size btrfsvol.PhysicalAddr, sb btrfstree.Superblock) *phonyFile {
+	return &phonyFile{
+		size: size,
+		sb:   sb,
+	}
+}
+
+func (f *phonyFile) Name() string                { return fmt.Sprintf("phony_file:device_id=%v", f.sb.DevItem.DevID) }
+func (f *phonyFile) Size() btrfsvol.PhysicalAddr { return f.size }
+func (*phonyFile) Close() error                  { return nil }
+
+func (f *phonyFile) ReadAt(p []byte, off btrfsvol.PhysicalAddr) (int, error) {
+	if len(p) == int(btrfs.SuperblockSize) && slices.Contains(off, btrfs.SuperblockAddrs) {
+		bs, err := binstruct.Marshal(f.sb)
+		if err != nil {
+			return 0, err
+		}
+		return copy(p, bs), nil
+	}
+	panic(fmt.Errorf("%T: should not happen: ReadAt should not be called for a phony file", f))
+}
+
+func (f *phonyFile) WriteAt([]byte, btrfsvol.PhysicalAddr) (int, error) {
+	panic(fmt.Errorf("%T: should not happen: WriteAt should not be called for a phony file", f))
+}