5 files changed, 112 insertions, 93 deletions

diff --git a/cmd/btrfs-dbg/main.go b/cmd/btrfs-dbg/main.go
index 0990378..3d2103a 100644
--- a/cmd/btrfs-dbg/main.go
+++ b/cmd/btrfs-dbg/main.go
@@ -6,7 +6,7 @@ import (
 
 	"github.com/davecgh/go-spew/spew"
 
-	"lukeshu.com/btrfs-tools/pkg/binstruct"
+	"lukeshu.com/btrfs-tools/pkg/btrfs"
 )
 
 func main() {
@@ -27,7 +27,7 @@ func Main(imgfilename string) (err error) {
 	if err != nil {
 		return err
 	}
-	img := &Img{
+	img := &btrfs.Img{
 		File: fh,
 	}
 	defer func() {
@@ -42,8 +42,8 @@ func Main(imgfilename string) (err error) {
 	spew := spew.NewDefaultConfig()
 	spew.DisablePointerAddresses = true
 
-	spew.Dump(superblocks[0].data)
-	sum, err := superblocks[0].data.CalculateChecksum()
+	spew.Dump(superblocks[0].Data)
+	sum, err := superblocks[0].Data.CalculateChecksum()
 	if err != nil {
 		return err
 	}
@@ -51,66 +51,3 @@ func Main(imgfilename string) (err error) {
 
 	return nil
 }
-
-type Img struct {
-	*os.File
-}
-
-func (img *Img) Size() (int64, error) {
-	fi, err := img.Stat()
-	if err != nil {
-		return 0, err
-	}
-	return fi.Size(), nil
-}
-
-type Ref[T any] struct {
-	img  *Img
-	addr int64
-	data T
-}
-
-func (r *Ref[T]) Read() error {
-	size, err := binstruct.Size(r.data)
-	if err != nil {
-		return err
-	}
-	buf := make([]byte, size)
-	if _, err := r.img.ReadAt(buf, r.addr); err != nil {
-		return err
-	}
-	return binstruct.Unmarshal(buf, &r.data)
-}
-
-func (img *Img) Superblocks() ([]Ref[Superblock], error) {
-	const superblockSize = 0x1000
-
-	var superblockAddrs = []int64{
-		0x00_0001_0000, // 64KiB
-		0x00_0400_0000, // 64MiB
-		0x40_0000_0000, // 256GiB
-	}
-
-	sz, err := img.Size()
-	if err != nil {
-		return nil, err
-	}
-
-	var ret []Ref[Superblock]
-	for i, addr := range superblockAddrs {
-		if addr+superblockSize <= sz {
-			superblock := Ref[Superblock]{
-				img:  img,
-				addr: addr,
-			}
-			if err := superblock.Read(); err != nil {
-				return nil, fmt.Errorf("superblock %d: %w", i, err)
-			}
-			ret = append(ret, superblock)
-		}
-	}
-	if len(ret) == 0 {
-		return nil, fmt.Errorf("no superblocks")
-	}
-	return ret, nil
-}
diff --git a/pkg/btrfs/crc32c.go b/pkg/btrfs/crc32c.go
new file mode 100644
index 0000000..4ea4169
--- /dev/null
+++ b/pkg/btrfs/crc32c.go
@@ -0,0 +1,16 @@
+package btrfs
+
+import (
+	"encoding/binary"
+	"hash/crc32"
+)
+
+type CSum [0x20]byte
+
+func CRC32c(data []byte) CSum {
+	crc := crc32.Update(0, crc32.MakeTable(crc32.Castagnoli), data)
+
+	var ret CSum
+	binary.LittleEndian.PutUint32(ret[:], crc)
+	return ret
+}
diff --git a/pkg/btrfs/image.go b/pkg/btrfs/image.go
new file mode 100644
index 0000000..6037c4d
--- /dev/null
+++ b/pkg/btrfs/image.go
@@ -0,0 +1,71 @@
+package btrfs
+
+import (
+	"fmt"
+	"os"
+
+	"lukeshu.com/btrfs-tools/pkg/binstruct"
+)
+
+type Img struct {
+	*os.File
+}
+
+func (img *Img) Size() (int64, error) {
+	fi, err := img.Stat()
+	if err != nil {
+		return 0, err
+	}
+	return fi.Size(), nil
+}
+
+type Ref[T any] struct {
+	img  *Img
+	addr int64
+	Data T
+}
+
+func (r *Ref[T]) Read() error {
+	size, err := binstruct.Size(r.Data)
+	if err != nil {
+		return err
+	}
+	buf := make([]byte, size)
+	if _, err := r.img.ReadAt(buf, r.addr); err != nil {
+		return err
+	}
+	return binstruct.Unmarshal(buf, &r.Data)
+}
+
+func (img *Img) Superblocks() ([]Ref[Superblock], error) {
+	const superblockSize = 0x1000
+
+	var superblockAddrs = []int64{
+		0x00_0001_0000, // 64KiB
+		0x00_0400_0000, // 64MiB
+		0x40_0000_0000, // 256GiB
+	}
+
+	sz, err := img.Size()
+	if err != nil {
+		return nil, err
+	}
+
+	var ret []Ref[Superblock]
+	for i, addr := range superblockAddrs {
+		if addr+superblockSize <= sz {
+			superblock := Ref[Superblock]{
+				img:  img,
+				addr: addr,
+			}
+			if err := superblock.Read(); err != nil {
+				return nil, fmt.Errorf("superblock %d: %w", i, err)
+			}
+			ret = append(ret, superblock)
+		}
+	}
+	if len(ret) == 0 {
+		return nil, fmt.Errorf("no superblocks")
+	}
+	return ret, nil
+}
diff --git a/cmd/btrfs-dbg/types.go b/pkg/btrfs/types.go
index 3cd348d..2949a8b 100644
--- a/cmd/btrfs-dbg/types.go
+++ b/pkg/btrfs/types.go
@@ -1,10 +1,6 @@
-package main
+package btrfs
 
 import (
-	"encoding/binary"
-	"encoding/hex"
-	"hash/crc32"
-	"strings"
 	"time"
 
 	"lukeshu.com/btrfs-tools/pkg/binstruct"
@@ -14,28 +10,8 @@ type (
 	PhysicalAddr int64
 	LogicalAddr  int64
 	ObjID        int64
-	CSum         [0x20]byte
-	UUID         [16]byte
 )
 
-func (uuid UUID) String() string {
-	str := hex.EncodeToString(uuid[:])
-	return strings.Join([]string{
-		str[:8],
-		str[8:12],
-		str[12:16],
-		str[16:20],
-		str[20:32],
-	}, "-")
-}
-
-func crc32c(data []byte) CSum {
-	sum := crc32.Update(0xFFFFFFFF, crc32.MakeTable(0x1EDC6F41), data)
-	var buf CSum
-	binary.LittleEndian.PutUint32(buf[:], sum)
-	return buf
-}
-
 type Key struct {
 	ObjectID      ObjID  `bin:"off=0, siz=8, desc=Object ID. Each tree has its own set of Object IDs."`
 	ItemType      uint8  `bin:"off=8, siz=1, desc=Item type."`
@@ -107,7 +83,7 @@ func (sb Superblock) CalculateChecksum() (CSum, error) {
 	if err != nil {
 		return CSum{}, err
 	}
-	return crc32c(data[0x20:]), nil
+	return CRC32c(data[0x20:]), nil
 }
 
 type DevItem struct {
diff --git a/pkg/btrfs/uuid.go b/pkg/btrfs/uuid.go
new file mode 100644
index 0000000..5218a3f
--- /dev/null
+++ b/pkg/btrfs/uuid.go
@@ -0,0 +1,19 @@
+package btrfs
+
+import (
+	"encoding/hex"
+	"strings"
+)
+
+type UUID [16]byte
+
+func (uuid UUID) String() string {
+	str := hex.EncodeToString(uuid[:])
+	return strings.Join([]string{
+		str[:8],
+		str[8:12],
+		str[12:16],
+		str[16:20],
+		str[20:32],
+	}, "-")
+}