1 files changed, 132 insertions, 0 deletions
diff --git a/pkg/btrfs/btrfsitem/item_extent.go b/pkg/btrfs/btrfsitem/item_extent.go
new file mode 100644
index 0000000..7d3eb05
--- /dev/null
+++ b/pkg/btrfs/btrfsitem/item_extent.go
@@ -0,0 +1,132 @@
+package btrfsitem
+
+import (
+	"fmt"
+
+	"lukeshu.com/btrfs-tools/pkg/binstruct"
+	"lukeshu.com/btrfs-tools/pkg/btrfs/internal"
+	"lukeshu.com/btrfs-tools/pkg/util"
+)
+
+type Extent struct { // EXTENT_ITEM=168
+	Head ExtentHeader
+	Info TreeBlockInfo // only if .Head.Flags.Has(BTRFS_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(BTRFS_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(BTRFS_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    int64       `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 (
+	BTRFS_EXTENT_FLAG_DATA = ExtentFlags(1 << iota)
+	BTRFS_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) }
+
+type ExtentInlineRef struct {
+	Type          Type   `bin:"off=0, siz=1"`
+	Offset        uint64 `bin:"off=1, siz=8"`
+	binstruct.End `bin:"off=9"`
+	Body          Item `bin:"-"`
+}
+
+func (o *ExtentInlineRef) UnmarshalBinary(dat []byte) (int, error) {
+	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
+	if err != nil {
+		return n, err
+	}
+	switch o.Type {
+	case TREE_BLOCK_REF_KEY, SHARED_BLOCK_REF_KEY:
+		o.Body = Empty{}
+	case EXTENT_DATA_REF_KEY:
+		return n, fmt.Errorf("the C code to do this doesn't make any sense")
+	case SHARED_DATA_REF_KEY:
+		var sref SharedDataRef
+		_n, err := binstruct.Unmarshal(dat[n:], &sref)
+		n += _n
+		o.Body = sref
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, nil
+}
+
+func (o ExtentInlineRef) MarshalBinary() ([]byte, error) {
+	dat, err := binstruct.MarshalWithoutInterface(o)
+	if err != nil {
+		return dat, err
+	}
+	bs, err := binstruct.Marshal(o.Body)
+	dat = append(dat, bs...)
+	if err != nil {
+		return dat, err
+	}
+	return dat, nil
+}