Rename the module, mv pkg lib

24 files changed, 1163 insertions, 0 deletions

diff --git a/lib/btrfs/btrfsitem/item_blockgroup.go b/lib/btrfs/btrfsitem/item_blockgroup.go
new file mode 100644
index 0000000..71d960d
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_blockgroup.go
@@ -0,0 +1,16 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+// key.objectid = logical_addr
+// key.offset = size of chunk
+type BlockGroup struct { // BLOCK_GROUP_ITEM=192
+	Used          int64                    `bin:"off=0, siz=8"`
+	ChunkObjectID internal.ObjID           `bin:"off=8, siz=8"` // always BTRFS_FIRST_CHUNK_TREE_OBJECTID
+	Flags         btrfsvol.BlockGroupFlags `bin:"off=16, siz=8"`
+	binstruct.End `bin:"off=24"`
+}
diff --git a/lib/btrfs/btrfsitem/item_chunk.go b/lib/btrfs/btrfsitem/item_chunk.go
new file mode 100644
index 0000000..9256651
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_chunk.go
@@ -0,0 +1,90 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+// Maps logical address to physical.
+//
+// key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID
+// key.offset = logical_addr
+type Chunk struct { // CHUNK_ITEM=228
+	Head    ChunkHeader
+	Stripes []ChunkStripe
+}
+
+type ChunkHeader struct {
+	Size           btrfsvol.AddrDelta       `bin:"off=0x0,  siz=0x8"`
+	Owner          internal.ObjID           `bin:"off=0x8,  siz=0x8"` // root referencing this chunk (always EXTENT_TREE_OBJECTID=2)
+	StripeLen      uint64                   `bin:"off=0x10, siz=0x8"` // ???
+	Type           btrfsvol.BlockGroupFlags `bin:"off=0x18, siz=0x8"`
+	IOOptimalAlign uint32                   `bin:"off=0x20, siz=0x4"`
+	IOOptimalWidth uint32                   `bin:"off=0x24, siz=0x4"`
+	IOMinSize      uint32                   `bin:"off=0x28, siz=0x4"` // sector size
+	NumStripes     uint16                   `bin:"off=0x2c, siz=0x2"` // [ignored-when-writing]
+	SubStripes     uint16                   `bin:"off=0x2e, siz=0x2"` // ???
+	binstruct.End  `bin:"off=0x30"`
+}
+
+type ChunkStripe struct {
+	DeviceID      btrfsvol.DeviceID     `bin:"off=0x0,  siz=0x8"`
+	Offset        btrfsvol.PhysicalAddr `bin:"off=0x8,  siz=0x8"`
+	DeviceUUID    util.UUID             `bin:"off=0x10, siz=0x10"`
+	binstruct.End `bin:"off=0x20"`
+}
+
+func (chunk Chunk) Mappings(key internal.Key) []btrfsvol.Mapping {
+	ret := make([]btrfsvol.Mapping, 0, len(chunk.Stripes))
+	for _, stripe := range chunk.Stripes {
+		ret = append(ret, btrfsvol.Mapping{
+			LAddr: btrfsvol.LogicalAddr(key.Offset),
+			PAddr: btrfsvol.QualifiedPhysicalAddr{
+				Dev:  stripe.DeviceID,
+				Addr: stripe.Offset,
+			},
+			Size:       chunk.Head.Size,
+			SizeLocked: true,
+			Flags:      &chunk.Head.Type,
+		})
+	}
+	return ret
+}
+
+func (chunk *Chunk) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.Unmarshal(dat, &chunk.Head)
+	if err != nil {
+		return n, err
+	}
+	chunk.Stripes = nil
+	for i := 0; i < int(chunk.Head.NumStripes); i++ {
+		var stripe ChunkStripe
+		_n, err := binstruct.Unmarshal(dat[n:], &stripe)
+		n += _n
+		if err != nil {
+			return n, fmt.Errorf("%T.UnmarshalBinary: %w", *chunk, err)
+		}
+		chunk.Stripes = append(chunk.Stripes, stripe)
+	}
+	return n, nil
+}
+
+func (chunk Chunk) MarshalBinary() ([]byte, error) {
+	chunk.Head.NumStripes = uint16(len(chunk.Stripes))
+	ret, err := binstruct.Marshal(chunk.Head)
+	if err != nil {
+		return ret, err
+	}
+	for _, stripe := range chunk.Stripes {
+		_ret, err := binstruct.Marshal(stripe)
+		ret = append(ret, _ret...)
+		if err != nil {
+			return ret, fmt.Errorf("%T.MarshalBinary: %w", chunk, err)
+		}
+	}
+	return ret, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_dev.go b/lib/btrfs/btrfsitem/item_dev.go
new file mode 100644
index 0000000..d3fe582
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_dev.go
@@ -0,0 +1,33 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+// key.objectid = BTRFS_DEV_ITEMS_OBJECTID
+// key.offset = device_id (starting at 1)
+type Dev struct { // DEV_ITEM=216
+	DevID btrfsvol.DeviceID `bin:"off=0x0,    siz=0x8"`
+
+	NumBytes     uint64 `bin:"off=0x8,    siz=0x8"`
+	NumBytesUsed uint64 `bin:"off=0x10,   siz=0x8"`
+
+	IOOptimalAlign uint32 `bin:"off=0x18,   siz=0x4"`
+	IOOptimalWidth uint32 `bin:"off=0x1c,   siz=0x4"`
+	IOMinSize      uint32 `bin:"off=0x20,   siz=0x4"` // sector size
+
+	Type        uint64              `bin:"off=0x24,   siz=0x8"`
+	Generation  internal.Generation `bin:"off=0x2c,   siz=0x8"`
+	StartOffset uint64              `bin:"off=0x34,   siz=0x8"`
+	DevGroup    uint32              `bin:"off=0x3c,   siz=0x4"`
+	SeekSpeed   uint8               `bin:"off=0x40,   siz=0x1"`
+	Bandwidth   uint8               `bin:"off=0x41,   siz=0x1"`
+
+	DevUUID util.UUID `bin:"off=0x42,   siz=0x10"`
+	FSUUID  util.UUID `bin:"off=0x52,   siz=0x10"`
+
+	binstruct.End `bin:"off=0x62"`
+}
diff --git a/lib/btrfs/btrfsitem/item_devextent.go b/lib/btrfs/btrfsitem/item_devextent.go
new file mode 100644
index 0000000..c346d85
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_devextent.go
@@ -0,0 +1,32 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+// key.objectid = device_id
+// key.offset = physical_addr
+type DevExtent struct { // DEV_EXTENT=204
+	ChunkTree     int64                `bin:"off=0, siz=8"`
+	ChunkObjectID internal.ObjID       `bin:"off=8, siz=8"`
+	ChunkOffset   btrfsvol.LogicalAddr `bin:"off=16, siz=8"`
+	Length        btrfsvol.AddrDelta   `bin:"off=24, siz=8"`
+	ChunkTreeUUID util.UUID            `bin:"off=32, siz=16"`
+	binstruct.End `bin:"off=48"`
+}
+
+func (devext DevExtent) Mapping(key internal.Key) btrfsvol.Mapping {
+	return btrfsvol.Mapping{
+		LAddr: devext.ChunkOffset,
+		PAddr: btrfsvol.QualifiedPhysicalAddr{
+			Dev:  btrfsvol.DeviceID(key.ObjectID),
+			Addr: btrfsvol.PhysicalAddr(key.Offset),
+		},
+		Size:       devext.Length,
+		SizeLocked: true,
+		Flags:      nil,
+	}
+}
diff --git a/lib/btrfs/btrfsitem/item_dir.go b/lib/btrfs/btrfsitem/item_dir.go
new file mode 100644
index 0000000..57f6d6d
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_dir.go
@@ -0,0 +1,115 @@
+package btrfsitem
+
+import (
+	"fmt"
+	"hash/crc32"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+// key.objectid = inode of directory containing this entry
+// key.offset =
+//    for DIR_ITEM and XATTR_ITEM = NameHash(name)
+//    for DIR_INDEX               = index id in the directory (starting at 2, because "." and "..")
+type DirEntries []DirEntry // DIR_ITEM=84 DIR_INDEX=96 XATTR_ITEM=24
+
+func NameHash(dat []byte) uint64 {
+	return uint64(^crc32.Update(1, crc32.MakeTable(crc32.Castagnoli), dat))
+}
+
+func (o *DirEntries) UnmarshalBinary(dat []byte) (int, error) {
+	*o = nil
+	n := 0
+	for n < len(dat) {
+		var ref DirEntry
+		_n, err := binstruct.Unmarshal(dat, &ref)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+		*o = append(*o, ref)
+	}
+	return n, nil
+}
+
+func (o DirEntries) MarshalBinary() ([]byte, error) {
+	var ret []byte
+	for _, ref := range o {
+		bs, err := binstruct.Marshal(ref)
+		ret = append(ret, bs...)
+		if err != nil {
+			return ret, err
+		}
+	}
+	return ret, nil
+}
+
+type DirEntry struct {
+	Location      internal.Key `bin:"off=0x0, siz=0x11"`
+	TransID       int64        `bin:"off=0x11, siz=8"`
+	DataLen       uint16       `bin:"off=0x19, siz=2"` // [ignored-when-writing]
+	NameLen       uint16       `bin:"off=0x1b, siz=2"` // [ignored-when-writing]
+	Type          FileType     `bin:"off=0x1d, siz=1"`
+	binstruct.End `bin:"off=0x1e"`
+	Data          []byte `bin:"-"`
+	Name          []byte `bin:"-"`
+}
+
+func (o *DirEntry) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
+	if err != nil {
+		return n, err
+	}
+	o.Data = dat[n : n+int(o.DataLen)]
+	n += int(o.DataLen)
+	o.Name = dat[n : n+int(o.NameLen)]
+	n += int(o.NameLen)
+	return n, nil
+}
+
+func (o DirEntry) MarshalBinary() ([]byte, error) {
+	o.DataLen = uint16(len(o.Data))
+	o.NameLen = uint16(len(o.Name))
+	dat, err := binstruct.MarshalWithoutInterface(o)
+	if err != nil {
+		return dat, err
+	}
+	dat = append(dat, o.Data...)
+	dat = append(dat, o.Name...)
+	return dat, nil
+}
+
+type FileType uint8
+
+const (
+	FT_UNKNOWN  = FileType(0)
+	FT_REG_FILE = FileType(1)
+	FT_DIR      = FileType(2)
+	FT_CHRDEV   = FileType(3)
+	FT_BLKDEV   = FileType(4)
+	FT_FIFO     = FileType(5)
+	FT_SOCK     = FileType(6)
+	FT_SYMLINK  = FileType(7)
+	FT_XATTR    = FileType(8)
+
+	FT_MAX = FileType(9)
+)
+
+func (ft FileType) String() string {
+	names := map[FileType]string{
+		FT_UNKNOWN:  "UNKNOWN",
+		FT_REG_FILE: "FILE", // XXX
+		FT_DIR:      "DIR",
+		FT_CHRDEV:   "CHRDEV",
+		FT_BLKDEV:   "BLKDEV",
+		FT_FIFO:     "FIFO",
+		FT_SOCK:     "SOCK",
+		FT_SYMLINK:  "SYMLINK",
+		FT_XATTR:    "XATTR",
+	}
+	if name, ok := names[ft]; ok {
+		return name
+	}
+	return fmt.Sprintf("DIR_ITEM.%d", uint8(ft))
+}
diff --git a/lib/btrfs/btrfsitem/item_empty.go b/lib/btrfs/btrfsitem/item_empty.go
new file mode 100644
index 0000000..209b2fc
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_empty.go
@@ -0,0 +1,9 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+type Empty struct { // ORPHAN_ITEM=48 TREE_BLOCK_REF=176 SHARED_BLOCK_REF=182 FREE_SPACE_EXTENT=199 QGROUP_RELATION=246
+	binstruct.End `bin:"off=0"`
+}
diff --git a/lib/btrfs/btrfsitem/item_extent.go b/lib/btrfs/btrfsitem/item_extent.go
new file mode 100644
index 0000000..9a9ea55
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_extent.go
@@ -0,0 +1,165 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+type Extent struct { // EXTENT_ITEM=168
+	Head ExtentHeader
+	Info TreeBlockInfo // only if .Head.Flags.Has(EXTENT_FLAG_TREE_BLOCK)
+	Refs []ExtentInlineRef
+}
+
+func (o *Extent) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.Unmarshal(dat, &o.Head)
+	if err != nil {
+		return n, err
+	}
+	if o.Head.Flags.Has(EXTENT_FLAG_TREE_BLOCK) {
+		_n, err := binstruct.Unmarshal(dat[n:], &o.Info)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+	}
+	o.Refs = nil
+	for n < len(dat) {
+		var ref ExtentInlineRef
+		_n, err := binstruct.Unmarshal(dat[n:], &ref)
+		n += _n
+		o.Refs = append(o.Refs, ref)
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, nil
+}
+
+func (o Extent) MarshalBinary() ([]byte, error) {
+	dat, err := binstruct.Marshal(o.Head)
+	if err != nil {
+		return dat, err
+	}
+	if o.Head.Flags.Has(EXTENT_FLAG_TREE_BLOCK) {
+		bs, err := binstruct.Marshal(o.Info)
+		dat = append(dat, bs...)
+		if err != nil {
+			return dat, err
+		}
+	}
+	for _, ref := range o.Refs {
+		bs, err := binstruct.Marshal(ref)
+		dat = append(dat, bs...)
+		if err != nil {
+			return dat, err
+		}
+	}
+	return dat, nil
+}
+
+type ExtentHeader struct {
+	Refs          int64               `bin:"off=0, siz=8"`
+	Generation    internal.Generation `bin:"off=8, siz=8"`
+	Flags         ExtentFlags         `bin:"off=16, siz=8"`
+	binstruct.End `bin:"off=24"`
+}
+
+type TreeBlockInfo struct {
+	Key           internal.Key `bin:"off=0, siz=0x11"`
+	Level         uint8        `bin:"off=0x11, siz=0x8"`
+	binstruct.End `bin:"off=0x19"`
+}
+
+type ExtentFlags uint64
+
+const (
+	EXTENT_FLAG_DATA = ExtentFlags(1 << iota)
+	EXTENT_FLAG_TREE_BLOCK
+)
+
+var extentFlagNames = []string{
+	"DATA",
+	"TREE_BLOCK",
+}
+
+func (f ExtentFlags) Has(req ExtentFlags) bool { return f&req == req }
+func (f ExtentFlags) String() string           { return util.BitfieldString(f, extentFlagNames, util.HexNone) }
+
+type ExtentInlineRef struct {
+	Type   Type   // only 4 valid values: {TREE,SHARED}_BLOCK_REF_KEY, {EXTENT,SHARED}_DATA_REF_KEY
+	Offset uint64 // only when Type != EXTENT_DATA_REF_KEY
+	Body   Item   // only when Type == *_DATA_REF_KEY
+}
+
+func (o *ExtentInlineRef) UnmarshalBinary(dat []byte) (int, error) {
+	o.Type = Type(dat[0])
+	n := 1
+	switch o.Type {
+	case TREE_BLOCK_REF_KEY, SHARED_BLOCK_REF_KEY:
+		_n, err := binstruct.Unmarshal(dat[n:], &o.Offset)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+	case EXTENT_DATA_REF_KEY:
+		var dref ExtentDataRef
+		_n, err := binstruct.Unmarshal(dat[n:], &dref)
+		n += _n
+		o.Body = dref
+		if err != nil {
+			return n, err
+		}
+	case SHARED_DATA_REF_KEY:
+		_n, err := binstruct.Unmarshal(dat[n:], &o.Offset)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+		var sref SharedDataRef
+		_n, err = binstruct.Unmarshal(dat[n:], &sref)
+		n += _n
+		o.Body = sref
+		if err != nil {
+			return n, err
+		}
+	default:
+		return n, fmt.Errorf("btrfsitem.ExtentInlineRef.UnmarshalBinary: unexpected item type %v", o.Type)
+	}
+	return n, nil
+}
+
+func (o ExtentInlineRef) MarshalBinary() ([]byte, error) {
+	dat := []byte{byte(o.Type)}
+	switch o.Type {
+	case TREE_BLOCK_REF_KEY, SHARED_BLOCK_REF_KEY:
+		_dat, err := binstruct.Marshal(o.Offset)
+		dat = append(dat, _dat...)
+		if err != nil {
+			return dat, err
+		}
+	case EXTENT_DATA_REF_KEY:
+		_dat, err := binstruct.Marshal(o.Body)
+		dat = append(dat, _dat...)
+		if err != nil {
+			return dat, err
+		}
+	case SHARED_DATA_REF_KEY:
+		_dat, err := binstruct.Marshal(o.Offset)
+		dat = append(dat, _dat...)
+		if err != nil {
+			return dat, err
+		}
+		_dat, err = binstruct.Marshal(o.Body)
+		dat = append(dat, _dat...)
+		if err != nil {
+			return dat, err
+		}
+	default:
+		return dat, fmt.Errorf("btrfsitem.ExtentInlineRef.MarshalBinary: unexpected item type %v", o.Type)
+	}
+	return dat, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_extentcsum.go b/lib/btrfs/btrfsitem/item_extentcsum.go
new file mode 100644
index 0000000..b27dbde
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_extentcsum.go
@@ -0,0 +1,39 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfssum"
+)
+
+// key.objectid = BTRFS_EXTENT_CSUM_OBJECTID
+// key.offset = laddr of checksummed region
+type ExtentCSum struct { // EXTENT_CSUM=128
+	ChecksumSize int
+	// Checksum of each sector starting at key.offset
+	Sums []btrfssum.CSum
+}
+
+func (o *ExtentCSum) UnmarshalBinary(dat []byte) (int, error) {
+	if o.ChecksumSize == 0 {
+		return 0, fmt.Errorf("btrfs.ExtentCSum.UnmarshalBinary: .ChecksumSize must be set")
+	}
+	for len(dat) >= o.ChecksumSize {
+		var csum btrfssum.CSum
+		copy(csum[:], dat[:o.ChecksumSize])
+		dat = dat[o.ChecksumSize:]
+		o.Sums = append(o.Sums, csum)
+	}
+	return len(o.Sums) * o.ChecksumSize, nil
+}
+
+func (o ExtentCSum) MarshalBinary() ([]byte, error) {
+	if o.ChecksumSize == 0 {
+		return nil, fmt.Errorf("btrfs.ExtentCSum.MarshalBinary: .ChecksumSize must be set")
+	}
+	var dat []byte
+	for _, csum := range o.Sums {
+		dat = append(dat, csum[:o.ChecksumSize]...)
+	}
+	return dat, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_extentdataref.go b/lib/btrfs/btrfsitem/item_extentdataref.go
new file mode 100644
index 0000000..aab5426
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_extentdataref.go
@@ -0,0 +1,14 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+type ExtentDataRef struct { // EXTENT_DATA_REF=178
+	Root          internal.ObjID `bin:"off=0, siz=8"`
+	ObjectID      internal.ObjID `bin:"off=8, siz=8"`
+	Offset        int64          `bin:"off=16, siz=8"`
+	Count         int32          `bin:"off=24, siz=4"`
+	binstruct.End `bin:"off=28"`
+}
diff --git a/lib/btrfs/btrfsitem/item_fileextent.go b/lib/btrfs/btrfsitem/item_fileextent.go
new file mode 100644
index 0000000..2f3ac2b
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_fileextent.go
@@ -0,0 +1,137 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+// key.objectid = inode
+// key.offset = offset within file
+type FileExtent struct { // EXTENT_DATA=108
+	Generation internal.Generation `bin:"off=0x0, siz=0x8"` // transaction ID that created this extent
+	RAMBytes   int64               `bin:"off=0x8, siz=0x8"` // upper bound of what compressed data will decompress to
+
+	// 32 bits describing the data encoding
+	Compression   CompressionType `bin:"off=0x10, siz=0x1"`
+	Encryption    uint8           `bin:"off=0x11, siz=0x1"`
+	OtherEncoding uint16          `bin:"off=0x12, siz=0x2"` // reserved for later use
+
+	Type FileExtentType `bin:"off=0x14, siz=0x1"` // inline data or real extent
+
+	binstruct.End `bin:"off=0x15"`
+
+	// only one of these, depending on .Type
+	BodyInline []byte   `bin:"-"` // .Type == FILE_EXTENT_INLINE
+	BodyExtent struct { // .Type == FILE_EXTENT_REG or FILE_EXTENT_PREALLOC
+		// Position and size of extent within the device
+		DiskByteNr   btrfsvol.LogicalAddr `bin:"off=0x0, siz=0x8"`
+		DiskNumBytes btrfsvol.AddrDelta   `bin:"off=0x8, siz=0x8"`
+
+		// Position of data within the extent
+		Offset btrfsvol.AddrDelta `bin:"off=0x10, siz=0x8"`
+
+		// Decompressed/unencrypted size
+		NumBytes int64 `bin:"off=0x18, siz=0x8"`
+
+		binstruct.End `bin:"off=0x20"`
+	} `bin:"-"`
+}
+
+func (o *FileExtent) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
+	if err != nil {
+		return n, err
+	}
+	switch o.Type {
+	case FILE_EXTENT_INLINE:
+		o.BodyInline = dat[n:]
+		n += len(o.BodyInline)
+	case FILE_EXTENT_REG, FILE_EXTENT_PREALLOC:
+		_n, err := binstruct.Unmarshal(dat[n:], &o.BodyExtent)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+	default:
+		return n, fmt.Errorf("unknown file extent type %v", o.Type)
+	}
+	return n, nil
+}
+
+func (o FileExtent) MarshalBinary() ([]byte, error) {
+	dat, err := binstruct.MarshalWithoutInterface(o)
+	if err != nil {
+		return dat, err
+	}
+	switch o.Type {
+	case FILE_EXTENT_INLINE:
+		dat = append(dat, o.BodyInline...)
+	case FILE_EXTENT_REG, FILE_EXTENT_PREALLOC:
+		bs, err := binstruct.Marshal(o.BodyExtent)
+		dat = append(dat, bs...)
+		if err != nil {
+			return dat, err
+		}
+	default:
+		return dat, fmt.Errorf("unknown file extent type %v", o.Type)
+	}
+	return dat, nil
+}
+
+type FileExtentType uint8
+
+const (
+	FILE_EXTENT_INLINE = FileExtentType(iota)
+	FILE_EXTENT_REG
+	FILE_EXTENT_PREALLOC
+)
+
+func (o FileExtent) Size() (int64, error) {
+	switch o.Type {
+	case FILE_EXTENT_INLINE:
+		return int64(len(o.BodyInline)), nil
+	case FILE_EXTENT_REG, FILE_EXTENT_PREALLOC:
+		return o.BodyExtent.NumBytes, nil
+	default:
+		return 0, fmt.Errorf("unknown file extent type %v", o.Type)
+	}
+}
+
+func (fet FileExtentType) String() string {
+	names := map[FileExtentType]string{
+		FILE_EXTENT_INLINE:   "inline",
+		FILE_EXTENT_REG:      "regular",
+		FILE_EXTENT_PREALLOC: "prealloc",
+	}
+	name, ok := names[fet]
+	if !ok {
+		name = "unknown"
+	}
+	return fmt.Sprintf("%d (%s)", fet, name)
+}
+
+type CompressionType uint8
+
+const (
+	COMPRESS_NONE = CompressionType(iota)
+	COMPRESS_ZLIB
+	COMPRESS_LZO
+	COMPRESS_ZSTD
+)
+
+func (ct CompressionType) String() string {
+	names := map[CompressionType]string{
+		COMPRESS_NONE: "none",
+		COMPRESS_ZLIB: "zlib",
+		COMPRESS_LZO:  "lzo",
+		COMPRESS_ZSTD: "zstd",
+	}
+	name, ok := names[ct]
+	if !ok {
+		name = "unknown"
+	}
+	return fmt.Sprintf("%d (%s)", ct, name)
+}
diff --git a/lib/btrfs/btrfsitem/item_freespacebitmap.go b/lib/btrfs/btrfsitem/item_freespacebitmap.go
new file mode 100644
index 0000000..6158eb0
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_freespacebitmap.go
@@ -0,0 +1,12 @@
+package btrfsitem
+
+type FreeSpaceBitmap []byte // FREE_SPACE_BITMAP=200
+
+func (o *FreeSpaceBitmap) UnmarshalBinary(dat []byte) (int, error) {
+	*o = dat
+	return len(dat), nil
+}
+
+func (o FreeSpaceBitmap) MarshalBinary() ([]byte, error) {
+	return []byte(o), nil
+}
diff --git a/lib/btrfs/btrfsitem/item_freespaceinfo.go b/lib/btrfs/btrfsitem/item_freespaceinfo.go
new file mode 100644
index 0000000..89f555e
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_freespaceinfo.go
@@ -0,0 +1,11 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+type FreeSpaceInfo struct { // FREE_SPACE_INFO=198
+	ExtentCount   int32  `bin:"off=0, siz=4"`
+	Flags         uint32 `bin:"off=4, siz=4"`
+	binstruct.End `bin:"off=8"`
+}
diff --git a/lib/btrfs/btrfsitem/item_inode.go b/lib/btrfs/btrfsitem/item_inode.go
new file mode 100644
index 0000000..9b1b91b
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_inode.go
@@ -0,0 +1,64 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/linux"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+type Inode struct { // INODE_ITEM=1
+	Generation    internal.Generation `bin:"off=0x00, siz=0x08"`
+	TransID       int64               `bin:"off=0x08, siz=0x08"`
+	Size          int64               `bin:"off=0x10, siz=0x08"` // stat
+	NumBytes      int64               `bin:"off=0x18, siz=0x08"`
+	BlockGroup    int64               `bin:"off=0x20, siz=0x08"`
+	NLink         int32               `bin:"off=0x28, siz=0x04"` // stat
+	UID           int32               `bin:"off=0x2C, siz=0x04"` // stat
+	GID           int32               `bin:"off=0x30, siz=0x04"` // stat
+	Mode          linux.StatMode      `bin:"off=0x34, siz=0x04"` // stat
+	RDev          int64               `bin:"off=0x38, siz=0x08"` // stat
+	Flags         InodeFlags          `bin:"off=0x40, siz=0x08"` // statx.stx_attributes, sorta
+	Sequence      int64               `bin:"off=0x48, siz=0x08"` // NFS
+	Reserved      [4]int64            `bin:"off=0x50, siz=0x20"`
+	ATime         internal.Time       `bin:"off=0x70, siz=0x0c"` // stat
+	CTime         internal.Time       `bin:"off=0x7c, siz=0x0c"` // stat
+	MTime         internal.Time       `bin:"off=0x88, siz=0x0c"` // stat
+	OTime         internal.Time       `bin:"off=0x94, siz=0x0c"` // statx.stx_btime (why is this called "otime" instead of "btime"?)
+	binstruct.End `bin:"off=0xa0"`
+}
+
+type InodeFlags uint64
+
+const (
+	INODE_NODATASUM = InodeFlags(1 << iota)
+	INODE_NODATACOW
+	INODE_READONLY
+	INODE_NOCOMPRESS
+	INODE_PREALLOC
+	INODE_SYNC
+	INODE_IMMUTABLE
+	INODE_APPEND
+	INODE_NODUMP
+	INODE_NOATIME
+	INODE_DIRSYNC
+	INODE_COMPRESS
+)
+
+var inodeFlagNames = []string{
+	"NODATASUM",
+	"NODATACOW",
+	"READONLY",
+	"NOCOMPRESS",
+	"PREALLOC",
+	"SYNC",
+	"IMMUTABLE",
+	"APPEND",
+	"NODUMP",
+	"NOATIME",
+	"DIRSYNC",
+	"COMPRESS",
+}
+
+func (f InodeFlags) Has(req InodeFlags) bool { return f&req == req }
+func (f InodeFlags) String() string          { return util.BitfieldString(f, inodeFlagNames, util.HexLower) }
diff --git a/lib/btrfs/btrfsitem/item_inoderef.go b/lib/btrfs/btrfsitem/item_inoderef.go
new file mode 100644
index 0000000..80d70e1
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_inoderef.go
@@ -0,0 +1,35 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+// key.objectid = inode number of the file
+// key.offset = inode number of the parent file
+type InodeRef struct { // INODE_REF=12
+	Index         int64  `bin:"off=0x0, siz=0x8"`
+	NameLen       uint16 `bin:"off=0x8, siz=0x2"` // [ignored-when-writing]
+	binstruct.End `bin:"off=0xa"`
+	Name          []byte `bin:"-"`
+}
+
+func (o *InodeRef) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
+	if err != nil {
+		return n, err
+	}
+	dat = dat[n:]
+	o.Name = dat[:o.NameLen]
+	n += int(o.NameLen)
+	return n, nil
+}
+
+func (o InodeRef) MarshalBinary() ([]byte, error) {
+	o.NameLen = uint16(len(o.Name))
+	dat, err := binstruct.MarshalWithoutInterface(o)
+	if err != nil {
+		return dat, err
+	}
+	dat = append(dat, o.Name...)
+	return dat, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_metadata.go b/lib/btrfs/btrfsitem/item_metadata.go
new file mode 100644
index 0000000..d51a340
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_metadata.go
@@ -0,0 +1,44 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+// Metadata is like Extent, but doesn't have .Info.
+type Metadata struct { // METADATA_ITEM=169
+	Head ExtentHeader
+	Refs []ExtentInlineRef
+}
+
+func (o *Metadata) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.Unmarshal(dat, &o.Head)
+	if err != nil {
+		return n, err
+	}
+	o.Refs = nil
+	for n < len(dat) {
+		var ref ExtentInlineRef
+		_n, err := binstruct.Unmarshal(dat[n:], &ref)
+		n += _n
+		o.Refs = append(o.Refs, ref)
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, nil
+}
+
+func (o Metadata) MarshalBinary() ([]byte, error) {
+	dat, err := binstruct.Marshal(o.Head)
+	if err != nil {
+		return dat, err
+	}
+	for _, ref := range o.Refs {
+		bs, err := binstruct.Marshal(ref)
+		dat = append(dat, bs...)
+		if err != nil {
+			return dat, err
+		}
+	}
+	return dat, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_persistent.go b/lib/btrfs/btrfsitem/item_persistent.go
new file mode 100644
index 0000000..cbbae76
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_persistent.go
@@ -0,0 +1,19 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+const (
+	DEV_STAT_WRITE_ERRS = iota
+	DEV_STAT_READ_ERRS
+	DEV_STAT_FLUSH_ERRS
+	DEV_STAT_CORRUPTION_ERRS
+	DEV_STAT_GENERATION_ERRS
+	DEV_STAT_VALUES_MAX
+)
+
+type DevStats struct { // PERSISTENT_ITEM=249
+	Values        [DEV_STAT_VALUES_MAX]int64 `bin:"off=0, siz=40"`
+	binstruct.End `bin:"off=40"`
+}
diff --git a/lib/btrfs/btrfsitem/item_root.go b/lib/btrfs/btrfsitem/item_root.go
new file mode 100644
index 0000000..ff9311f
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_root.go
@@ -0,0 +1,51 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+type Root struct { // ROOT_ITEM=132
+	Inode         Inode                `bin:"off=0x000, siz=0xa0"`
+	Generation    internal.Generation  `bin:"off=0x0a0, siz=0x08"`
+	RootDirID     internal.ObjID       `bin:"off=0x0a8, siz=0x08"`
+	ByteNr        btrfsvol.LogicalAddr `bin:"off=0x0b0, siz=0x08"`
+	ByteLimit     int64                `bin:"off=0x0b8, siz=0x08"`
+	BytesUsed     int64                `bin:"off=0x0c0, siz=0x08"`
+	LastSnapshot  int64                `bin:"off=0x0c8, siz=0x08"`
+	Flags         RootFlags            `bin:"off=0x0d0, siz=0x08"`
+	Refs          int32                `bin:"off=0x0d8, siz=0x04"`
+	DropProgress  internal.Key         `bin:"off=0x0dc, siz=0x11"`
+	DropLevel     uint8                `bin:"off=0x0ed, siz=0x01"`
+	Level         uint8                `bin:"off=0x0ee, siz=0x01"`
+	GenerationV2  internal.Generation  `bin:"off=0x0ef, siz=0x08"`
+	UUID          util.UUID            `bin:"off=0x0f7, siz=0x10"`
+	ParentUUID    util.UUID            `bin:"off=0x107, siz=0x10"`
+	ReceivedUUID  util.UUID            `bin:"off=0x117, siz=0x10"`
+	CTransID      int64                `bin:"off=0x127, siz=0x08"`
+	OTransID      int64                `bin:"off=0x12f, siz=0x08"`
+	STransID      int64                `bin:"off=0x137, siz=0x08"`
+	RTransID      int64                `bin:"off=0x13f, siz=0x08"`
+	CTime         internal.Time        `bin:"off=0x147, siz=0x0c"`
+	OTime         internal.Time        `bin:"off=0x153, siz=0x0c"`
+	STime         internal.Time        `bin:"off=0x15f, siz=0x0c"`
+	RTime         internal.Time        `bin:"off=0x16b, siz=0x0c"`
+	GlobalTreeID  internal.ObjID       `bin:"off=0x177, siz=0x08"`
+	Reserved      [7]int64             `bin:"off=0x17f, siz=0x38"`
+	binstruct.End `bin:"off=0x1b7"`
+}
+
+type RootFlags uint64
+
+const (
+	ROOT_SUBVOL_RDONLY = RootFlags(1 << iota)
+)
+
+var rootFlagNames = []string{
+	"SUBVOL_RDONLY",
+}
+
+func (f RootFlags) Has(req RootFlags) bool { return f&req == req }
+func (f RootFlags) String() string         { return util.BitfieldString(f, rootFlagNames, util.HexLower) }
diff --git a/lib/btrfs/btrfsitem/item_rootref.go b/lib/btrfs/btrfsitem/item_rootref.go
new file mode 100644
index 0000000..c851474
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_rootref.go
@@ -0,0 +1,34 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+type RootRef struct { // ROOT_REF=156 ROOT_BACKREF=144
+	DirID         internal.ObjID `bin:"off=0x00, siz=0x8"`
+	Sequence      int64          `bin:"off=0x08, siz=0x8"`
+	NameLen       uint16         `bin:"off=0x10, siz=0x2"` // [ignored-when-writing]
+	binstruct.End `bin:"off=0x12"`
+	Name          []byte `bin:"-"`
+}
+
+func (o *RootRef) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
+	if err != nil {
+		return n, err
+	}
+	o.Name = dat[n : n+int(o.NameLen)]
+	n += int(o.NameLen)
+	return n, nil
+}
+
+func (o RootRef) MarshalBinary() ([]byte, error) {
+	o.NameLen = uint16(len(o.Name))
+	dat, err := binstruct.MarshalWithoutInterface(o)
+	if err != nil {
+		return dat, err
+	}
+	dat = append(dat, o.Name...)
+	return dat, nil
+}
diff --git a/lib/btrfs/btrfsitem/item_shareddataref.go b/lib/btrfs/btrfsitem/item_shareddataref.go
new file mode 100644
index 0000000..63897aa
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_shareddataref.go
@@ -0,0 +1,10 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+)
+
+type SharedDataRef struct { // SHARED_DATA_REF=184
+	Count         int32 `bin:"off=0, siz=4"`
+	binstruct.End `bin:"off=4"`
+}
diff --git a/lib/btrfs/btrfsitem/item_untyped.go b/lib/btrfs/btrfsitem/item_untyped.go
new file mode 100644
index 0000000..71a9af4
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_untyped.go
@@ -0,0 +1,14 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+type FreeSpaceHeader struct { // UNTYPED=0:FREE_SPACE_OBJECTID
+	Location      internal.Key        `bin:"off=0x00, siz=0x11"`
+	Generation    internal.Generation `bin:"off=0x11, siz=0x8"`
+	NumEntries    int64               `bin:"off=0x19, siz=0x8"`
+	NumBitmaps    int64               `bin:"off=0x21, siz=0x8"`
+	binstruct.End `bin:"off=0x29"`
+}
diff --git a/lib/btrfs/btrfsitem/item_uuid.go b/lib/btrfs/btrfsitem/item_uuid.go
new file mode 100644
index 0000000..6c7d4f0
--- /dev/null
+++ b/lib/btrfs/btrfsitem/item_uuid.go
@@ -0,0 +1,16 @@
+package btrfsitem
+
+import (
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+// The Key for this item is a UUID, and the item is a subvolume IDs
+// that that UUID maps to.
+//
+// key.objectid = first half of UUID
+// key.offset = second half of UUID
+type UUIDMap struct { // UUID_SUBVOL=251 UUID_RECEIVED_SUBVOL=252
+	ObjID         internal.ObjID `bin:"off=0, siz=8"`
+	binstruct.End `bin:"off=8"`
+}
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)
+}
diff --git a/lib/btrfs/btrfsitem/items.txt b/lib/btrfs/btrfsitem/items.txt
new file mode 100644
index 0000000..7898775
--- /dev/null
+++ b/lib/btrfs/btrfsitem/items.txt
@@ -0,0 +1,29 @@
+BLOCK_GROUP_ITEM=192 BlockGroup
+CHUNK_ITEM=228 Chunk
+DEV_EXTENT=204 DevExtent
+DEV_ITEM=216 Dev
+DIR_INDEX=96 DirEntries
+DIR_ITEM=84 DirEntries
+EXTENT_CSUM=128 ExtentCSum
+EXTENT_DATA=108 FileExtent
+EXTENT_DATA_REF=178 ExtentDataRef
+EXTENT_ITEM=168 Extent
+FREE_SPACE_BITMAP=200 FreeSpaceBitmap
+FREE_SPACE_EXTENT=199 Empty
+FREE_SPACE_INFO=198 FreeSpaceInfo
+INODE_ITEM=1 Inode
+INODE_REF=12 InodeRef
+METADATA_ITEM=169 Metadata
+ORPHAN_ITEM=48 Empty
+PERSISTENT_ITEM=249 DevStats
+QGROUP_RELATION=246 Empty
+ROOT_BACKREF=144 RootRef
+ROOT_ITEM=132 Root
+ROOT_REF=156 RootRef
+SHARED_BLOCK_REF=182 Empty
+SHARED_DATA_REF=184 SharedDataRef
+TREE_BLOCK_REF=176 Empty
+UNTYPED=0:FREE_SPACE_OBJECTID FreeSpaceHeader
+UUID_RECEIVED_SUBVOL=252 UUIDMap
+UUID_SUBVOL=251 UUIDMap
+XATTR_ITEM=24 DirEntries
diff --git a/lib/btrfs/btrfsitem/items_gen.go b/lib/btrfs/btrfsitem/items_gen.go
new file mode 100644
index 0000000..3b84d60
--- /dev/null
+++ b/lib/btrfs/btrfsitem/items_gen.go
@@ -0,0 +1,97 @@
+// Code generated by Make.  DO NOT EDIT.
+
+package btrfsitem
+
+import (
+	"reflect"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
+)
+
+const (
+	BLOCK_GROUP_ITEM_KEY     = internal.BLOCK_GROUP_ITEM_KEY
+	CHUNK_ITEM_KEY           = internal.CHUNK_ITEM_KEY
+	DEV_EXTENT_KEY           = internal.DEV_EXTENT_KEY
+	DEV_ITEM_KEY             = internal.DEV_ITEM_KEY
+	DIR_INDEX_KEY            = internal.DIR_INDEX_KEY
+	DIR_ITEM_KEY             = internal.DIR_ITEM_KEY
+	EXTENT_CSUM_KEY          = internal.EXTENT_CSUM_KEY
+	EXTENT_DATA_KEY          = internal.EXTENT_DATA_KEY
+	EXTENT_DATA_REF_KEY      = internal.EXTENT_DATA_REF_KEY
+	EXTENT_ITEM_KEY          = internal.EXTENT_ITEM_KEY
+	FREE_SPACE_BITMAP_KEY    = internal.FREE_SPACE_BITMAP_KEY
+	FREE_SPACE_EXTENT_KEY    = internal.FREE_SPACE_EXTENT_KEY
+	FREE_SPACE_INFO_KEY      = internal.FREE_SPACE_INFO_KEY
+	INODE_ITEM_KEY           = internal.INODE_ITEM_KEY
+	INODE_REF_KEY            = internal.INODE_REF_KEY
+	METADATA_ITEM_KEY        = internal.METADATA_ITEM_KEY
+	ORPHAN_ITEM_KEY          = internal.ORPHAN_ITEM_KEY
+	PERSISTENT_ITEM_KEY      = internal.PERSISTENT_ITEM_KEY
+	QGROUP_RELATION_KEY      = internal.QGROUP_RELATION_KEY
+	ROOT_BACKREF_KEY         = internal.ROOT_BACKREF_KEY
+	ROOT_ITEM_KEY            = internal.ROOT_ITEM_KEY
+	ROOT_REF_KEY             = internal.ROOT_REF_KEY
+	SHARED_BLOCK_REF_KEY     = internal.SHARED_BLOCK_REF_KEY
+	SHARED_DATA_REF_KEY      = internal.SHARED_DATA_REF_KEY
+	TREE_BLOCK_REF_KEY       = internal.TREE_BLOCK_REF_KEY
+	UNTYPED_KEY              = internal.UNTYPED_KEY
+	UUID_RECEIVED_SUBVOL_KEY = internal.UUID_RECEIVED_SUBVOL_KEY
+	UUID_SUBVOL_KEY          = internal.UUID_SUBVOL_KEY
+	XATTR_ITEM_KEY           = internal.XATTR_ITEM_KEY
+)
+
+var keytype2gotype = map[Type]reflect.Type{
+	BLOCK_GROUP_ITEM_KEY:     reflect.TypeOf(BlockGroup{}),
+	CHUNK_ITEM_KEY:           reflect.TypeOf(Chunk{}),
+	DEV_EXTENT_KEY:           reflect.TypeOf(DevExtent{}),
+	DEV_ITEM_KEY:             reflect.TypeOf(Dev{}),
+	DIR_INDEX_KEY:            reflect.TypeOf(DirEntries{}),
+	DIR_ITEM_KEY:             reflect.TypeOf(DirEntries{}),
+	EXTENT_CSUM_KEY:          reflect.TypeOf(ExtentCSum{}),
+	EXTENT_DATA_KEY:          reflect.TypeOf(FileExtent{}),
+	EXTENT_DATA_REF_KEY:      reflect.TypeOf(ExtentDataRef{}),
+	EXTENT_ITEM_KEY:          reflect.TypeOf(Extent{}),
+	FREE_SPACE_BITMAP_KEY:    reflect.TypeOf(FreeSpaceBitmap{}),
+	FREE_SPACE_EXTENT_KEY:    reflect.TypeOf(Empty{}),
+	FREE_SPACE_INFO_KEY:      reflect.TypeOf(FreeSpaceInfo{}),
+	INODE_ITEM_KEY:           reflect.TypeOf(Inode{}),
+	INODE_REF_KEY:            reflect.TypeOf(InodeRef{}),
+	METADATA_ITEM_KEY:        reflect.TypeOf(Metadata{}),
+	ORPHAN_ITEM_KEY:          reflect.TypeOf(Empty{}),
+	PERSISTENT_ITEM_KEY:      reflect.TypeOf(DevStats{}),
+	QGROUP_RELATION_KEY:      reflect.TypeOf(Empty{}),
+	ROOT_BACKREF_KEY:         reflect.TypeOf(RootRef{}),
+	ROOT_ITEM_KEY:            reflect.TypeOf(Root{}),
+	ROOT_REF_KEY:             reflect.TypeOf(RootRef{}),
+	SHARED_BLOCK_REF_KEY:     reflect.TypeOf(Empty{}),
+	SHARED_DATA_REF_KEY:      reflect.TypeOf(SharedDataRef{}),
+	TREE_BLOCK_REF_KEY:       reflect.TypeOf(Empty{}),
+	UUID_RECEIVED_SUBVOL_KEY: reflect.TypeOf(UUIDMap{}),
+	UUID_SUBVOL_KEY:          reflect.TypeOf(UUIDMap{}),
+	XATTR_ITEM_KEY:           reflect.TypeOf(DirEntries{}),
+}
+var untypedObjID2gotype = map[internal.ObjID]reflect.Type{
+	internal.FREE_SPACE_OBJECTID: reflect.TypeOf(FreeSpaceHeader{}),
+}
+
+func (BlockGroup) isItem()      {}
+func (Chunk) isItem()           {}
+func (Dev) isItem()             {}
+func (DevExtent) isItem()       {}
+func (DevStats) isItem()        {}
+func (DirEntries) 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 (InodeRef) isItem()        {}
+func (Metadata) isItem()        {}
+func (Root) isItem()            {}
+func (RootRef) isItem()         {}
+func (SharedDataRef) isItem()   {}
+func (UUIDMap) isItem()         {}