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package btrfs
import (
"fmt"
"os"
"lukeshu.com/btrfs-tools/pkg/binstruct"
"lukeshu.com/btrfs-tools/pkg/util"
)
type Device struct {
*os.File
cacheSuperblocks []*util.Ref[PhysicalAddr, Superblock]
cacheSuperblock *util.Ref[PhysicalAddr, Superblock]
}
func (dev Device) Size() (PhysicalAddr, error) {
fi, err := dev.Stat()
if err != nil {
return 0, err
}
return PhysicalAddr(fi.Size()), nil
}
var SuperblockAddrs = []PhysicalAddr{
0x00_0001_0000, // 64KiB
0x00_0400_0000, // 64MiB
0x40_0000_0000, // 256GiB
}
func (dev *Device) ReadAt(dat []byte, paddr PhysicalAddr) (int, error) {
return dev.File.ReadAt(dat, int64(paddr))
}
func (dev *Device) WriteAt(dat []byte, paddr PhysicalAddr) (int, error) {
return dev.File.WriteAt(dat, int64(paddr))
}
func (dev *Device) Superblocks() ([]*util.Ref[PhysicalAddr, Superblock], error) {
if dev.cacheSuperblocks != nil {
return dev.cacheSuperblocks, nil
}
superblockSize := PhysicalAddr(binstruct.StaticSize(Superblock{}))
sz, err := dev.Size()
if err != nil {
return nil, err
}
var ret []*util.Ref[PhysicalAddr, Superblock]
for i, addr := range SuperblockAddrs {
if addr+superblockSize <= sz {
superblock := &util.Ref[PhysicalAddr, Superblock]{
File: dev,
Addr: addr,
}
if err := superblock.Read(); err != nil {
return nil, fmt.Errorf("superblock %v: %w", i, err)
}
ret = append(ret, superblock)
}
}
if len(ret) == 0 {
return nil, fmt.Errorf("no superblocks")
}
dev.cacheSuperblocks = ret
return ret, nil
}
func (dev *Device) Superblock() (*util.Ref[PhysicalAddr, Superblock], error) {
if dev.cacheSuperblock != nil {
return dev.cacheSuperblock, nil
}
sbs, err := dev.Superblocks()
if err != nil {
return nil, err
}
for i, sb := range sbs {
if err := sb.Data.ValidateChecksum(); err != nil {
return nil, fmt.Errorf("superblock %v: %w", i, err)
}
if i > 0 {
if !sb.Data.Equal(sbs[0].Data) {
return nil, fmt.Errorf("superblock %v and superblock %v disagree", 0, i)
}
}
}
dev.cacheSuperblock = sbs[0]
return sbs[0], nil
}
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