package btrfs import ( "time" "lukeshu.com/btrfs-tools/pkg/binstruct" ) type ( PhysicalAddr int64 LogicalAddr int64 ObjID int64 ) type Key struct { ObjectID ObjID `bin:"off=0, siz=8"` // Object ID. Each tree has its own set of Object IDs. ItemType uint8 `bin:"off=8, siz=1"` // Item type. Offset uint64 `bin:"off=9, siz=8"` // Offset. The meaning depends on the item type. binstruct.End `bin:"off=11"` } type Time struct { Sec int64 `bin:"off=0, siz=8"` // Number of seconds since 1970-01-01T00:00:00Z. NSec uint64 `bin:"off=8, siz=4"` // Number of nanoseconds since the beginning of the second. binstruct.End `bin:"off=c"` } func (t Time) ToStd() time.Time { return time.Unix(t.Sec, int64(t.NSec)) } type Superblock struct { Checksum CSum `bin:"off=0, siz=20"` // Checksum of everything past this field (from 20 to 1000) FSUUID UUID `bin:"off=20, siz=10"` // FS UUID Self PhysicalAddr `bin:"off=30, siz=8"` // physical address of this block (different for mirrors) Flags uint64 `bin:"off=38, siz=8"` // flags Magic [8]byte `bin:"off=40, siz=8"` // magic ('_BHRfS_M') Generation uint64 `bin:"off=48, siz=8"` // generation RootTree LogicalAddr `bin:"off=50, siz=8"` // logical address of the root tree root ChunkTree LogicalAddr `bin:"off=58, siz=8"` // logical address of the chunk tree root LogTree LogicalAddr `bin:"off=60, siz=8"` // logical address of the log tree root LogRootTransID uint64 `bin:"off=68, siz=8"` // log_root_transid TotalBytes uint64 `bin:"off=70, siz=8"` // total_bytes BytesUsed uint64 `bin:"off=78, siz=8"` // bytes_used RootDirObjectID uint64 `bin:"off=80, siz=8"` // root_dir_objectid (usually 6) NumDevices uint64 `bin:"off=88, siz=8"` // num_devices SectorSize uint32 `bin:"off=90, siz=4"` // sectorsize NodeSize uint32 `bin:"off=94, siz=4"` // nodesize LeafSize uint32 `bin:"off=98, siz=4"` // leafsize StripeSize uint32 `bin:"off=9c, siz=4"` // stripesize SysChunkArraySize uint32 `bin:"off=a0, siz=4"` // sys_chunk_array_size ChunkRootGeneration uint64 `bin:"off=a4, siz=8"` // chunk_root_generation CompatFlags uint64 `bin:"off=ac, siz=8"` // compat_flags CompatROFlags uint64 `bin:"off=b4, siz=8"` // compat_ro_flags - only implementations that support the flags can write to the filesystem IncompatFlags uint64 `bin:"off=bc, siz=8"` // incompat_flags - only implementations that support the flags can use the filesystem ChecksumType uint16 `bin:"off=c4, siz=2"` // csum_type - Btrfs currently uses the CRC32c little-endian hash function with seed -1. RootLevel uint8 `bin:"off=c6, siz=1"` // root_level ChunkLevel uint8 `bin:"off=c7, siz=1"` // chunk_root_level LogLevel uint8 `bin:"off=c8, siz=1"` // log_root_level DevItem DevItem `bin:"off=c9, siz=62"` // DEV_ITEM data for this device Label [0x100]byte `bin:"off=12b, siz=100"` // label (may not contain '/' or '\\') CacheGeneration uint64 `bin:"off=22b, siz=8"` // cache_generation UUIDTreeGeneration uint64 `bin:"off=233, siz=8"` // uuid_tree_generation Reserved [0xf0]byte `bin:"off=23b, siz=f0"` // reserved /* future expansion */ SysChunkArray [0x800]byte `bin:"off=32b, siz=800"` // sys_chunk_array:(n bytes valid) Contains (KEY . CHUNK_ITEM) pairs for all SYSTEM chunks. This is needed to bootstrap the mapping from logical addresses to physical. TODOSuperRoots [0x2a0]byte `bin:"off=b2b, siz=2a0"` // Contain super_roots (4 btrfs_root_backup) Unused [0x235]byte `bin:"off=dcb, siz=235"` // current unused binstruct.End `bin:"off=1000"` } func (sb Superblock) CalculateChecksum() (CSum, error) { data, err := binstruct.Marshal(sb) if err != nil { return CSum{}, err } return CRC32c(data[0x20:]), nil } type SysChunk struct { Key `bin:"off=0, siz=11"` ChunkItem `bin:"off=11, siz=30"` binstruct.End `bin:"off=41"` } func (sb Superblock) ParseSysChunkArray() ([]SysChunk, error) { dat := sb.SysChunkArray[:sb.SysChunkArraySize] var ret []SysChunk for len(dat) > 0 { var pair SysChunk if err := binstruct.Unmarshal(dat, &pair); err != nil { return nil, err } dat = dat[0x41:] for i := 0; i < int(pair.ChunkItem.NumStripes); i++ { var stripe ChunkItemStripe if err := binstruct.Unmarshal(dat, &stripe); err != nil { return nil, err } pair.ChunkItem.Stripes = append(pair.ChunkItem.Stripes, stripe) dat = dat[0x20:] } ret = append(ret, pair) } return ret, nil } type DevItem struct { DeviceID uint64 `bin:"off=0, siz=8"` // device id NumBytes uint64 `bin:"off=8, siz=8"` // number of bytes NumBytesUsed uint64 `bin:"off=10, siz=8"` // number of bytes used IOOptimalAlign uint32 `bin:"off=18, siz=4"` // optimal I/O align IOOptimalWidth uint32 `bin:"off=1c, siz=4"` // optimal I/O width IOMinSize uint32 `bin:"off=20, siz=4"` // minimal I/O size (sector size) Type uint64 `bin:"off=24, siz=8"` // type Generation uint64 `bin:"off=2c, siz=8"` // generation StartOffset uint64 `bin:"off=34, siz=8"` // start offset DevGroup uint32 `bin:"off=3c, siz=4"` // dev group SeekSpeed uint8 `bin:"off=40, siz=1"` // seek speed Bandwidth uint8 `bin:"off=41, siz=1"` // bandwidth DevUUID UUID `bin:"off=42, siz=10"` // device UUID FSUUID UUID `bin:"off=52, siz=10"` // FS UUID binstruct.End `bin:"off=62"` } type ChunkItem struct { // Maps logical address to physical. Size uint64 `bin:"off=0, siz=8"` // size of chunk (bytes) Root ObjID `bin:"off=8, siz=8"` // root referencing this chunk (2) StripeLen uint64 `bin:"off=10, siz=8"` // stripe length Type uint64 `bin:"off=18, siz=8"` // type (same as flags for block group?) IOOptimalAlign uint32 `bin:"off=20, siz=4"` // optimal io alignment IOOptimalWidth uint32 `bin:"off=24, siz=4"` // optimal io width IoMinSize uint32 `bin:"off=28, siz=4"` // minimal io size (sector size) NumStripes uint16 `bin:"off=2c, siz=2"` // number of stripes SubStripes uint16 `bin:"off=2e, siz=2"` // sub stripes binstruct.End `bin:"off=30"` Stripes []ChunkItemStripe `bin:"-"` } type ChunkItemStripe struct { // Stripes follow (for each number of stripes): DeviceID ObjID `bin:"off=0, siz=8"` // device id Offset uint64 `bin:"off=8, siz=8"` // offset DeviceUUID UUID `bin:"off=10, siz=10"` // device UUID binstruct.End `bin:"off=20"` }