1 files changed, 141 insertions, 0 deletions
diff --git a/pkg/btrfs/btrfsitem/item_fileextent.go b/pkg/btrfs/btrfsitem/item_fileextent.go
new file mode 100644
index 0000000..0f7fab4
--- /dev/null
+++ b/pkg/btrfs/btrfsitem/item_fileextent.go
@@ -0,0 +1,141 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"lukeshu.com/btrfs-tools/pkg/binstruct"
+)
+
+type FileExtent struct { // EXTENT_DATA=108
+	Generation int64 `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:"-"`
+	BodyReg    struct {
+		// Position within the device
+		DiskByteNr   int64 `bin:"off=0x0, siz=0x8"`
+		DiskNumBytes int64 `bin:"off=0x8, siz=0x8"`
+
+		// Position within the file
+		Offset        int64 `bin:"off=0x10, siz=0x8"`
+		NumBytes      int64 `bin:"off=0x18, siz=0x8"`
+		binstruct.End `bin:"off=0x20"`
+	} `bin:"-"`
+	BodyPrealloc struct {
+		// Position within the device
+		DiskByteNr   int64 `bin:"off=0x0, siz=0x8"`
+		DiskNumBytes int64 `bin:"off=0x8, siz=0x8"`
+
+		// Position within the file
+		Offset        int64 `bin:"off=0x10, siz=0x8"`
+		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:
+		_n, err := binstruct.Unmarshal(dat[n:], &o.BodyReg)
+		n += _n
+		if err != nil {
+			return n, err
+		}
+	case FILE_EXTENT_PREALLOC:
+		_n, err := binstruct.Unmarshal(dat[n:], &o.BodyPrealloc)
+		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:
+		bs, err := binstruct.Marshal(o.BodyReg)
+		dat = append(dat, bs...)
+		if err != nil {
+			return dat, err
+		}
+	case FILE_EXTENT_PREALLOC:
+		bs, err := binstruct.Marshal(o.BodyPrealloc)
+		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 (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)
+}