1 files changed, 90 insertions, 0 deletions
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
+}