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package main
import (
"encoding/binary"
"encoding/hex"
"hash/crc32"
"strings"
"time"
"lukeshu.com/btrfs-tools/pkg/binstruct"
)
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."`
Offset uint64 `bin:"off=9, siz=8, desc=Offset. The meaning depends on the item type."`
binstruct.End `bin:"off=11"`
}
type Time struct {
Sec int64 `bin:"off=0, siz=8, desc=Number of seconds since 1970-01-01T00:00:00Z."`
NSec uint64 `bin:"off=8, siz=4, desc=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, desc=Checksum of everything past this field (from 20 to 1000)"`
FSUUID UUID `bin:"off=20, siz=10, desc=FS UUID"`
Self PhysicalAddr `bin:"off=30, siz=8, desc=physical address of this block (different for mirrors)"`
Flags uint64 `bin:"off=38, siz=8, desc=flags"`
Magic [8]byte `bin:"off=40, siz=8, desc=magic ('_BHRfS_M')"`
Generation uint64 `bin:"off=48, siz=8, desc=generation"`
RootTree LogicalAddr `bin:"off=50, siz=8, desc=logical address of the root tree root"`
ChunkTree LogicalAddr `bin:"off=58, siz=8, desc=logical address of the chunk tree root"`
LogTree LogicalAddr `bin:"off=60, siz=8, desc=logical address of the log tree root"`
LogRootTransID uint64 `bin:"off=68, siz=8, desc=log_root_transid"`
TotalBytes uint64 `bin:"off=70, siz=8, desc=total_bytes"`
BytesUsed uint64 `bin:"off=78, siz=8, desc=bytes_used"`
RootDirObjectID uint64 `bin:"off=80, siz=8, desc=root_dir_objectid (usually 6)"`
NumDevices uint64 `bin:"off=88, siz=8, desc=num_devices"`
SectorSize uint32 `bin:"off=90, siz=4, desc=sectorsize"`
NodeSize uint32 `bin:"off=94, siz=4, desc=nodesize"`
LeafSize uint32 `bin:"off=98, siz=4, desc=leafsize"`
StripeSize uint32 `bin:"off=9c, siz=4, desc=stripesize"`
SysChunkArraySize uint32 `bin:"off=a0, siz=4, desc=sys_chunk_array_size"`
ChunkRootGeneration uint64 `bin:"off=a4, siz=8, desc=chunk_root_generation"`
CompatFlags uint64 `bin:"off=ac, siz=8, desc=compat_flags"`
CompatROFlags uint64 `bin:"off=b4, siz=8, desc=compat_ro_flags - only implementations that support the flags can write to the filesystem"`
IncompatFlags uint64 `bin:"off=bc, siz=8, desc=incompat_flags - only implementations that support the flags can use the filesystem"`
ChecksumType uint16 `bin:"off=c4, siz=2, desc=csum_type - Btrfs currently uses the CRC32c little-endian hash function with seed -1."`
RootLevel uint8 `bin:"off=c6, siz=1, desc=root_level"`
ChunkLevel uint8 `bin:"off=c7, siz=1, desc=chunk_root_level"`
LogLevel uint8 `bin:"off=c8, siz=1, desc=log_root_level"`
DevItem DevItem `bin:"off=c9, siz=62, desc=DEV_ITEM data for this device"`
Label [0x100]byte `bin:"off=12b, siz=100, desc=label (may not contain '/' or '\\')"`
CacheGeneration uint64 `bin:"off=22b, siz=8, desc=cache_generation"`
UUIDTreeGeneration uint64 `bin:"off=233, siz=8, desc=uuid_tree_generation"`
Reserved [0xf0]byte `bin:"off=23b, siz=f0, desc=reserved /* future expansion */"`
TODOSysChunkArray [0x800]byte `bin:"off=32b, siz=800, desc=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, desc=Contain super_roots (4 btrfs_root_backup)"`
Unused [0x235]byte `bin:"off=dcb, siz=235, desc=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 DevItem struct {
DeviceID uint64 `bin:"off=0, siz=8, desc=device id"`
NumBytes uint64 `bin:"off=8, siz=8, desc=number of bytes"`
NumBytesUsed uint64 `bin:"off=10, siz=8, desc=number of bytes used"`
IOOptimalAlign uint32 `bin:"off=18, siz=4, desc=optimal I/O align"`
IOOptimalWidth uint32 `bin:"off=1c, siz=4, desc=optimal I/O width"`
IOMinSize uint32 `bin:"off=20, siz=4, desc=minimal I/O size (sector size)"`
Type uint64 `bin:"off=24, siz=8, desc=type"`
Generation uint64 `bin:"off=2c, siz=8, desc=generation"`
StartOffset uint64 `bin:"off=34, siz=8, desc=start offset"`
DevGroup uint32 `bin:"off=3c, siz=4, desc=dev group"`
SeekSpeed uint8 `bin:"off=40, siz=1, desc=seek speed"`
Bandwidth uint8 `bin:"off=41, siz=1, desc=bandwidth"`
DevUUID UUID `bin:"off=42, siz=10, desc=device UUID"`
FSUUID UUID `bin:"off=52, siz=10, desc=FS UUID"`
binstruct.End `bin:"off=62"`
}
type ChunkItem struct {
// Maps logical address to physical.
Size uint64 `bin:"off=0, siz=8, desc=size of chunk (bytes)"`
Root ObjID `bin:"off=8, siz=8, desc=root referencing this chunk (2)"`
StripeLen uint64 `bin:"off=10, siz=8, desc=stripe length"`
Type uint64 `bin:"off=18, siz=8, desc=type (same as flags for block group?)"`
IOOptimalAlign uint32 `bin:"off=20, siz=4, desc=optimal io alignment"`
IOOptimalWidth uint32 `bin:"off=24, siz=4, desc=optimal io width"`
IoMinSize uint32 `bin:"off=28, siz=4, desc=minimal io size (sector size)"`
NumStripes uint16 `bin:"off=2c, siz=2, desc=number of stripes"`
SubStripes uint16 `bin:"off=2e, siz=2, desc=sub stripes"`
binstruct.End `bin:"off=30"`
}
type ChunkItemStripe struct {
// Stripes follow (for each number of stripes):
DeviceID ObjID `bin:"off=0, siz=8, desc=device id"`
Offset uint64 `bin:"off=8, siz=8, desc=offset"`
DeviceUUID UUID `bin:"off=10, siz=10, desc=device UUID"`
binstruct.End `bin:"off=20"`
}
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