btrfsitem: Have all Item implementations be pointers to structs

12 files changed, 88 insertions, 82 deletions

diff --git a/lib/btrfs/Makefile b/lib/btrfs/Makefile
index cbcaf9e..00c22e7 100644
--- a/lib/btrfs/Makefile
+++ b/lib/btrfs/Makefile
@@ -35,7 +35,7 @@ btrfsitem/items_gen.go: btrfsitem/items.txt $(MAKEFILE_LIST)
 	  echo 'var untypedObjID2gotype = map[btrfsprim.ObjID]reflect.Type{'; \
 	  sed -En 's|UNTYPED=0:(.*) (.*)|btrfsprim.\1: reflect.TypeOf(\2{}),|p' $<; \
 	  echo '}'; \
-	  sed -En 's,(.*)=(.*) (.+),\3,p' $< | LC_COLLATE=C sort -u | sed 's,.*,func (&) isItem() {},'; \
+	  sed -En 's,(.*)=(.*) (.+),\3,p' $< | LC_COLLATE=C sort -u | sed 's,.*,func (*&) isItem() {},'; \
 	} | gofmt >$@
 files += btrfsitem/items_gen.go
 
diff --git a/lib/btrfs/btrfsitem/item_extent.go b/lib/btrfs/btrfsitem/item_extent.go
index 66aae1d..72371a9 100644
--- a/lib/btrfs/btrfsitem/item_extent.go
+++ b/lib/btrfs/btrfsitem/item_extent.go
@@ -1,4 +1,4 @@
-// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -114,8 +114,8 @@ func (o *ExtentInlineRef) UnmarshalBinary(dat []byte) (int, error) {
 			return n, err
 		}
 	case EXTENT_DATA_REF_KEY:
-		var dref ExtentDataRef
-		_n, err := binstruct.Unmarshal(dat[n:], &dref)
+		dref := new(ExtentDataRef)
+		_n, err := binstruct.Unmarshal(dat[n:], dref)
 		n += _n
 		o.Body = dref
 		if err != nil {
@@ -127,8 +127,8 @@ func (o *ExtentInlineRef) UnmarshalBinary(dat []byte) (int, error) {
 		if err != nil {
 			return n, err
 		}
-		var sref SharedDataRef
-		_n, err = binstruct.Unmarshal(dat[n:], &sref)
+		sref := new(SharedDataRef)
+		_n, err = binstruct.Unmarshal(dat[n:], sref)
 		n += _n
 		o.Body = sref
 		if err != nil {
diff --git a/lib/btrfs/btrfsitem/item_freespacebitmap.go b/lib/btrfs/btrfsitem/item_freespacebitmap.go
index ad46204..742d126 100644
--- a/lib/btrfs/btrfsitem/item_freespacebitmap.go
+++ b/lib/btrfs/btrfsitem/item_freespacebitmap.go
@@ -1,4 +1,4 @@
-// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -6,13 +6,15 @@ package btrfsitem
 
 // key.objectid = object ID of the FreeSpaceInfo (logical_addr)
 // key.offset = offset of the FreeSpaceInfo (size)
-type FreeSpaceBitmap []byte // FREE_SPACE_BITMAP=200
+type FreeSpaceBitmap struct { // FREE_SPACE_BITMAP=200
+	Bitmap []byte
+}
 
 func (o *FreeSpaceBitmap) UnmarshalBinary(dat []byte) (int, error) {
-	*o = dat
+	o.Bitmap = dat
 	return len(dat), nil
 }
 
 func (o FreeSpaceBitmap) MarshalBinary() ([]byte, error) {
-	return []byte(o), nil
+	return o.Bitmap, nil
 }
diff --git a/lib/btrfs/btrfsitem/item_inoderef.go b/lib/btrfs/btrfsitem/item_inoderef.go
index 083f19e..c90fe44 100644
--- a/lib/btrfs/btrfsitem/item_inoderef.go
+++ b/lib/btrfs/btrfsitem/item_inoderef.go
@@ -1,4 +1,4 @@
-// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -16,10 +16,12 @@ import (
 //
 // Might have multiple entries if the same file has multiple hardlinks
 // in the same directory.
-type InodeRefs []InodeRef // INODE_REF=12
+type InodeRefs struct { // INODE_REF=12
+	Refs []InodeRef
+}
 
 func (o *InodeRefs) UnmarshalBinary(dat []byte) (int, error) {
-	*o = nil
+	o.Refs = nil
 	n := 0
 	for n < len(dat) {
 		var ref InodeRef
@@ -28,14 +30,14 @@ func (o *InodeRefs) UnmarshalBinary(dat []byte) (int, error) {
 		if err != nil {
 			return n, err
 		}
-		*o = append(*o, ref)
+		o.Refs = append(o.Refs, ref)
 	}
 	return n, nil
 }
 
 func (o InodeRefs) MarshalBinary() ([]byte, error) {
 	var dat []byte
-	for _, ref := range o {
+	for _, ref := range o.Refs {
 		_dat, err := binstruct.Marshal(ref)
 		dat = append(dat, _dat...)
 		if err != nil {
diff --git a/lib/btrfs/btrfsitem/items.go b/lib/btrfs/btrfsitem/items.go
index 67f96fa..9964e2d 100644
--- a/lib/btrfs/btrfsitem/items.go
+++ b/lib/btrfs/btrfsitem/items.go
@@ -25,7 +25,7 @@ type Error struct {
 	Err error
 }
 
-func (Error) isItem() {}
+func (*Error) isItem() {}
 
 func (o Error) MarshalBinary() ([]byte, error) {
 	return o.Dat, nil
@@ -43,7 +43,7 @@ func UnmarshalItem(key btrfsprim.Key, csumType btrfssum.CSumType, dat []byte) It
 		var ok bool
 		gotyp, ok = untypedObjID2gotype[key.ObjectID]
 		if !ok {
-			return Error{
+			return &Error{
 				Dat: dat,
 				Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v, ObjectID:%v}, dat): unknown object ID for untyped item",
 					key.ItemType, key.ObjectID),
@@ -53,31 +53,31 @@ func UnmarshalItem(key btrfsprim.Key, csumType btrfssum.CSumType, dat []byte) It
 		var ok bool
 		gotyp, ok = keytype2gotype[key.ItemType]
 		if !ok {
-			return Error{
+			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 {
+	ptr := reflect.New(gotyp)
+	if csums, ok := ptr.Interface().(*ExtentCSum); ok {
 		csums.ChecksumSize = csumType.Size()
 		csums.Addr = btrfsvol.LogicalAddr(key.Offset)
 	}
-	n, err := binstruct.Unmarshal(dat, retPtr.Interface())
+	n, err := binstruct.Unmarshal(dat, ptr.Interface())
 	if err != nil {
-		return Error{
+		return &Error{
 			Dat: dat,
 			Err: fmt.Errorf("btrfsitem.UnmarshalItem({ItemType:%v}, dat): %w", key.ItemType, err),
 		}
 	}
 	if n < len(dat) {
-		return Error{
+		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),
 		}
 	}
 	//nolint:forcetypeassert // items_gen.go has all types in keytype2gotype implement the Item interface.
-	return retPtr.Elem().Interface().(Item)
+	return ptr.Interface().(Item)
 }
diff --git a/lib/btrfs/btrfsitem/items_gen.go b/lib/btrfs/btrfsitem/items_gen.go
index 9daef81..21c6795 100644
--- a/lib/btrfs/btrfsitem/items_gen.go
+++ b/lib/btrfs/btrfsitem/items_gen.go
@@ -80,27 +80,27 @@ var untypedObjID2gotype = map[btrfsprim.ObjID]reflect.Type{
 	btrfsprim.FREE_SPACE_OBJECTID: reflect.TypeOf(FreeSpaceHeader{}),
 }
 
-func (BlockGroup) isItem()      {}
-func (Chunk) isItem()           {}
-func (Dev) isItem()             {}
-func (DevExtent) isItem()       {}
-func (DevStats) isItem()        {}
-func (DirEntry) isItem()        {}
-func (Empty) isItem()           {}
-func (Extent) isItem()          {}
-func (ExtentCSum) isItem()      {}
-func (ExtentDataRef) isItem()   {}
-func (FileExtent) isItem()      {}
-func (FreeSpaceBitmap) isItem() {}
-func (FreeSpaceHeader) isItem() {}
-func (FreeSpaceInfo) isItem()   {}
-func (Inode) isItem()           {}
-func (InodeRefs) isItem()       {}
-func (Metadata) isItem()        {}
-func (QGroupInfo) isItem()      {}
-func (QGroupLimit) isItem()     {}
-func (QGroupStatus) isItem()    {}
-func (Root) isItem()            {}
-func (RootRef) isItem()         {}
-func (SharedDataRef) isItem()   {}
-func (UUIDMap) isItem()         {}
+func (*BlockGroup) isItem()      {}
+func (*Chunk) isItem()           {}
+func (*Dev) isItem()             {}
+func (*DevExtent) isItem()       {}
+func (*DevStats) isItem()        {}
+func (*DirEntry) isItem()        {}
+func (*Empty) isItem()           {}
+func (*Extent) isItem()          {}
+func (*ExtentCSum) isItem()      {}
+func (*ExtentDataRef) isItem()   {}
+func (*FileExtent) isItem()      {}
+func (*FreeSpaceBitmap) isItem() {}
+func (*FreeSpaceHeader) isItem() {}
+func (*FreeSpaceInfo) isItem()   {}
+func (*Inode) isItem()           {}
+func (*InodeRefs) isItem()       {}
+func (*Metadata) isItem()        {}
+func (*QGroupInfo) isItem()      {}
+func (*QGroupLimit) isItem()     {}
+func (*QGroupStatus) isItem()    {}
+func (*Root) isItem()            {}
+func (*RootRef) isItem()         {}
+func (*SharedDataRef) isItem()   {}
+func (*UUIDMap) isItem()         {}
diff --git a/lib/btrfs/btrfstree/ops.go b/lib/btrfs/btrfstree/ops.go
index cdacef9..bda4ac8 100644
--- a/lib/btrfs/btrfstree/ops.go
+++ b/lib/btrfs/btrfstree/ops.go
@@ -207,7 +207,7 @@ func (fs TreeOperatorImpl) treeWalk(ctx context.Context, path TreePath, errHandl
 				ToKey:       item.Key,
 				ToMaxKey:    item.Key,
 			})
-			if errBody, isErr := item.Body.(btrfsitem.Error); isErr {
+			if errBody, isErr := item.Body.(*btrfsitem.Error); isErr {
 				if cbs.BadItem == nil {
 					errHandle(&TreeError{Path: itemPath, Err: errBody.Err})
 				} else {
diff --git a/lib/btrfs/btrfstree/root.go b/lib/btrfs/btrfstree/root.go
index 319904b..ace2b49 100644
--- a/lib/btrfs/btrfstree/root.go
+++ b/lib/btrfs/btrfstree/root.go
@@ -72,14 +72,14 @@ func LookupTreeRoot(fs TreeOperator, sb Superblock, treeID btrfsprim.ObjID) (*Tr
 			return nil, err
 		}
 		switch rootItemBody := rootItem.Body.(type) {
-		case btrfsitem.Root:
+		case *btrfsitem.Root:
 			return &TreeRoot{
 				TreeID:     treeID,
 				RootNode:   rootItemBody.ByteNr,
 				Level:      rootItemBody.Level,
 				Generation: rootItemBody.Generation,
 			}, nil
-		case btrfsitem.Error:
+		case *btrfsitem.Error:
 			return nil, fmt.Errorf("malformed ROOT_ITEM for tree %v: %w", treeID, rootItemBody.Err)
 		default:
 			panic(fmt.Errorf("should not happen: ROOT_ITEM has unexpected item type: %T", rootItemBody))
diff --git a/lib/btrfs/csums.go b/lib/btrfs/csums.go
index a32f090..2bfa588 100644
--- a/lib/btrfs/csums.go
+++ b/lib/btrfs/csums.go
@@ -60,9 +60,9 @@ func LookupCSum(fs btrfstree.TreeOperator, alg btrfssum.CSumType, laddr btrfsvol
 		return btrfssum.SumRun[btrfsvol.LogicalAddr]{}, fmt.Errorf("item type is %v, not EXTENT_CSUM", item.Key.ItemType)
 	}
 	switch body := item.Body.(type) {
-	case btrfsitem.ExtentCSum:
+	case *btrfsitem.ExtentCSum:
 		return body.SumRun, nil
-	case btrfsitem.Error:
+	case *btrfsitem.Error:
 		return btrfssum.SumRun[btrfsvol.LogicalAddr]{}, body.Err
 	default:
 		panic(fmt.Errorf("should not happen: EXTENT_CSUM has unexpected item type: %T", body))
diff --git a/lib/btrfs/io2_lv.go b/lib/btrfs/io2_lv.go
index ac7ea70..856ac20 100644
--- a/lib/btrfs/io2_lv.go
+++ b/lib/btrfs/io2_lv.go
@@ -173,13 +173,13 @@ func (fs *FS) initDev(ctx context.Context, sb btrfstree.Superblock) error {
 					return nil
 				}
 				switch itemBody := item.Body.(type) {
-				case btrfsitem.Chunk:
+				case *btrfsitem.Chunk:
 					for _, mapping := range itemBody.Mappings(item.Key) {
 						if err := fs.LV.AddMapping(mapping); err != nil {
 							return err
 						}
 					}
-				case btrfsitem.Error:
+				case *btrfsitem.Error:
 					// do nothing
 				default:
 					// This is a panic because the item decoder should not emit CHUNK_ITEM items as
diff --git a/lib/btrfs/io3_btree.go b/lib/btrfs/io3_btree.go
index 8ec4b41..18df98e 100644
--- a/lib/btrfs/io3_btree.go
+++ b/lib/btrfs/io3_btree.go
@@ -1,4 +1,4 @@
-// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -43,7 +43,7 @@ func (fs *FS) populateTreeUUIDs(ctx context.Context) {
 			},
 			btrfstree.TreeWalkHandler{
 				Item: func(_ btrfstree.TreePath, item btrfstree.Item) error {
-					itemBody, ok := item.Body.(btrfsitem.Root)
+					itemBody, ok := item.Body.(*btrfsitem.Root)
 					if !ok {
 						return nil
 					}
diff --git a/lib/btrfs/io4_fs.go b/lib/btrfs/io4_fs.go
index adc0928..c21cafc 100644
--- a/lib/btrfs/io4_fs.go
+++ b/lib/btrfs/io4_fs.go
@@ -88,9 +88,9 @@ func (sv *Subvolume) init() {
 			sv.rootErr = err
 		} else {
 			switch rootBody := root.Body.(type) {
-			case btrfsitem.Root:
-				sv.rootVal = rootBody
-			case btrfsitem.Error:
+			case *btrfsitem.Root:
+				sv.rootVal = *rootBody
+			case *btrfsitem.Error:
 				sv.rootErr = fmt.Errorf("FS_TREE ROOT_ITEM has malformed body: %w", rootBody.Err)
 			default:
 				panic(fmt.Errorf("should not happen: ROOT_ITEM has unexpected item type: %T", rootBody))
@@ -126,9 +126,10 @@ func (sv *Subvolume) LoadBareInode(inode btrfsprim.ObjID) (*BareInode, error) {
 		}
 
 		switch itemBody := item.Body.(type) {
-		case btrfsitem.Inode:
-			val.InodeItem = &itemBody
-		case btrfsitem.Error:
+		case *btrfsitem.Inode:
+			bodyCopy := *itemBody
+			val.InodeItem = &bodyCopy
+		case *btrfsitem.Error:
 			val.Errs = append(val.Errs, fmt.Errorf("malformed inode: %w", itemBody.Err))
 		default:
 			panic(fmt.Errorf("should not happen: INODE_ITEM has unexpected item type: %T", itemBody))
@@ -164,24 +165,25 @@ func (sv *Subvolume) LoadFullInode(inode btrfsprim.ObjID) (*FullInode, error) {
 			switch item.Key.ItemType {
 			case btrfsitem.INODE_ITEM_KEY:
 				switch itemBody := item.Body.(type) {
-				case btrfsitem.Inode:
+				case *btrfsitem.Inode:
 					if val.InodeItem != nil {
 						if !reflect.DeepEqual(itemBody, *val.InodeItem) {
 							val.Errs = append(val.Errs, fmt.Errorf("multiple inodes"))
 						}
 						continue
 					}
-					val.InodeItem = &itemBody
-				case btrfsitem.Error:
+					bodyCopy := *itemBody
+					val.InodeItem = &bodyCopy
+				case *btrfsitem.Error:
 					val.Errs = append(val.Errs, fmt.Errorf("malformed INODE_ITEM: %w", itemBody.Err))
 				default:
 					panic(fmt.Errorf("should not happen: INODE_ITEM has unexpected item type: %T", itemBody))
 				}
 			case btrfsitem.XATTR_ITEM_KEY:
 				switch itemBody := item.Body.(type) {
-				case btrfsitem.DirEntry:
+				case *btrfsitem.DirEntry:
 					val.XAttrs[string(itemBody.Name)] = string(itemBody.Data)
-				case btrfsitem.Error:
+				case *btrfsitem.Error:
 					val.Errs = append(val.Errs, fmt.Errorf("malformed XATTR_ITEM: %w", itemBody.Err))
 				default:
 					panic(fmt.Errorf("should not happen: XATTR_ITEM has unexpected item type: %T", itemBody))
@@ -225,15 +227,15 @@ func (dir *Dir) populate() {
 		switch item.Key.ItemType {
 		case btrfsitem.INODE_REF_KEY:
 			switch body := item.Body.(type) {
-			case btrfsitem.InodeRefs:
-				if len(body) != 1 {
+			case *btrfsitem.InodeRefs:
+				if len(body.Refs) != 1 {
 					dir.Errs = append(dir.Errs, fmt.Errorf("INODE_REF item with %d entries on a directory",
-						len(body)))
+						len(body.Refs)))
 					continue
 				}
 				ref := InodeRef{
 					Inode:    btrfsprim.ObjID(item.Key.Offset),
-					InodeRef: body[0],
+					InodeRef: body.Refs[0],
 				}
 				if dir.DotDot != nil {
 					if !reflect.DeepEqual(ref, *dir.DotDot) {
@@ -242,14 +244,14 @@ func (dir *Dir) populate() {
 					continue
 				}
 				dir.DotDot = &ref
-			case btrfsitem.Error:
+			case *btrfsitem.Error:
 				dir.Errs = append(dir.Errs, fmt.Errorf("malformed INODE_REF: %w", body.Err))
 			default:
 				panic(fmt.Errorf("should not happen: INODE_REF has unexpected item type: %T", body))
 			}
 		case btrfsitem.DIR_ITEM_KEY:
 			switch entry := item.Body.(type) {
-			case btrfsitem.DirEntry:
+			case *btrfsitem.DirEntry:
 				namehash := btrfsitem.NameHash(entry.Name)
 				if namehash != item.Key.Offset {
 					dir.Errs = append(dir.Errs, fmt.Errorf("direntry crc32c mismatch: key=%#x crc32c(%q)=%#x",
@@ -262,8 +264,8 @@ func (dir *Dir) populate() {
 					}
 					continue
 				}
-				dir.ChildrenByName[string(entry.Name)] = entry
-			case btrfsitem.Error:
+				dir.ChildrenByName[string(entry.Name)] = *entry
+			case *btrfsitem.Error:
 				dir.Errs = append(dir.Errs, fmt.Errorf("malformed DIR_ITEM: %w", entry.Err))
 			default:
 				panic(fmt.Errorf("should not happen: DIR_ITEM has unexpected item type: %T", entry))
@@ -271,15 +273,15 @@ func (dir *Dir) populate() {
 		case btrfsitem.DIR_INDEX_KEY:
 			index := item.Key.Offset
 			switch entry := item.Body.(type) {
-			case btrfsitem.DirEntry:
+			case *btrfsitem.DirEntry:
 				if other, exists := dir.ChildrenByIndex[index]; exists {
 					if !reflect.DeepEqual(entry, other) {
 						dir.Errs = append(dir.Errs, fmt.Errorf("multiple instances of direntry index %v", index))
 					}
 					continue
 				}
-				dir.ChildrenByIndex[index] = entry
-			case btrfsitem.Error:
+				dir.ChildrenByIndex[index] = *entry
+			case *btrfsitem.Error:
 				dir.Errs = append(dir.Errs, fmt.Errorf("malformed DIR_INDEX: %w", entry.Err))
 			default:
 				panic(fmt.Errorf("should not happen: DIR_INDEX has unexpected item type: %T", entry))
@@ -361,12 +363,12 @@ func (file *File) populate() {
 			// TODO
 		case btrfsitem.EXTENT_DATA_KEY:
 			switch itemBody := item.Body.(type) {
-			case btrfsitem.FileExtent:
+			case *btrfsitem.FileExtent:
 				file.Extents = append(file.Extents, FileExtent{
 					OffsetWithinFile: int64(item.Key.Offset),
-					FileExtent:       itemBody,
+					FileExtent:       *itemBody,
 				})
-			case btrfsitem.Error:
+			case *btrfsitem.Error:
 				file.Errs = append(file.Errs, fmt.Errorf("malformed EXTENT_DATA: %w", itemBody.Err))
 			default:
 				panic(fmt.Errorf("should not happen: EXTENT_DATA has unexpected item type: %T", itemBody))