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|
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
}
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