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package btrfs
import (
"encoding/binary"
"fmt"
"lukeshu.com/btrfs-tools/pkg/binstruct"
"lukeshu.com/btrfs-tools/pkg/util"
)
type Node struct {
// Some context from the parent filesystem
Size uint32 // superblock.NodeSize
// The node's header (always present)
Head NodeHeader
// The node's body (which one of these is present depends on
// the node's type, as specified in the header)
BodyInternal []KeyPointer // for internal nodes
BodyLeaf []Item // for leave nodes
}
type NodeHeader struct {
Checksum CSum `bin:"off=0x0, siz=0x20"` // Checksum of everything after this field (from 20 to the end of the node)
MetadataUUID UUID `bin:"off=0x20, siz=0x10"` // FS UUID
Addr LogicalAddr `bin:"off=0x30, siz=0x8"` // Logical address of this node
Flags NodeFlags `bin:"off=0x38, siz=0x7"`
BackrefRev uint8 `bin:"off=0x3f, siz=0x1"`
ChunkTreeUUID UUID `bin:"off=0x40, siz=0x10"` // Chunk tree UUID
Generation Generation `bin:"off=0x50, siz=0x8"` // Generation
Owner ObjID `bin:"off=0x58, siz=0x8"` // The ID of the tree that contains this node
NumItems uint32 `bin:"off=0x60, siz=0x4"` // Number of items
Level uint8 `bin:"off=0x64, siz=0x1"` // Level (0 for leaf nodes)
binstruct.End `bin:"off=0x65"`
}
type NodeFlags uint64
func (NodeFlags) BinaryStaticSize() int {
return 7
}
func (f NodeFlags) MarshalBinary() ([]byte, error) {
var bs [8]byte
binary.LittleEndian.PutUint64(bs[:], uint64(f))
return bs[:7], nil
}
func (f *NodeFlags) UnmarshalBinary(dat []byte) (int, error) {
var bs [8]byte
copy(bs[:7], dat[:7])
*f = NodeFlags(binary.LittleEndian.Uint64(bs[:]))
return 7, nil
}
var (
_ binstruct.StaticSizer = NodeFlags(0)
_ binstruct.Marshaler = NodeFlags(0)
_ binstruct.Unmarshaler = (*NodeFlags)(nil)
)
const (
NodeWritten = NodeFlags(1 << iota)
NodeReloc
)
var nodeFlagNames = []string{
"WRITTEN",
"RELOC",
}
func (f NodeFlags) Has(req NodeFlags) bool { return f&req == req }
func (f NodeFlags) String() string { return util.BitfieldString(f, nodeFlagNames) }
type KeyPointer struct {
Key Key `bin:"off=0, siz=11"`
BlockPtr LogicalAddr `bin:"off=11, siz=8"`
Generation Generation `bin:"off=19, siz=8"`
binstruct.End `bin:"off=21"`
}
type ItemHeader struct {
Key Key `bin:"off=0, siz=11"`
DataOffset uint32 `bin:"off=11, siz=4"` // relative to the end of the header (0x65)
DataSize uint32 `bin:"off=15, siz=4"`
binstruct.End `bin:"off=19"`
}
type Item struct {
Head ItemHeader
Body []byte
}
// MaxItems returns the maximum possible valid value of
// .Haad.NumItems.
func (node Node) MaxItems() uint32 {
bodyBytes := node.Size - uint32(binstruct.StaticSize(NodeHeader{}))
if node.Head.Level > 0 {
return bodyBytes / uint32(binstruct.StaticSize(KeyPointer{}))
} else {
return bodyBytes / uint32(binstruct.StaticSize(ItemHeader{}))
}
}
func (node *Node) UnmarshalBinary(nodeBuf []byte) (int, error) {
n, err := binstruct.Unmarshal(nodeBuf, &node.Head)
if err != nil {
return n, err
}
if node.Head.Level > 0 {
// internal node
for i := uint32(0); i < node.Head.NumItems; i++ {
var item KeyPointer
_n, err := binstruct.Unmarshal(nodeBuf[n:], &item)
n += _n
if err != nil {
return n, fmt.Errorf("(internal): item %d: %w", i, err)
}
node.BodyInternal = append(node.BodyInternal, item)
}
return n, nil
} else {
// leaf node
lastRead := 0
for i := uint32(0); i < node.Head.NumItems; i++ {
var item Item
_n, err := binstruct.Unmarshal(nodeBuf[n:], &item.Head)
n += _n
if err != nil {
return n, fmt.Errorf("(leaf): item %d: %w", i, err)
}
dataOff := binstruct.StaticSize(NodeHeader{}) + int(item.Head.DataOffset)
dataSize := int(item.Head.DataSize)
if dataOff+dataSize > len(nodeBuf) {
return max(n, lastRead), fmt.Errorf("(leaf): item references byte %d, but node only has %d bytes",
dataOff+dataSize, len(nodeBuf))
}
lastRead = max(lastRead, dataOff+dataSize)
item.Body = nodeBuf[dataOff : dataOff+dataSize]
node.BodyLeaf = append(node.BodyLeaf, item)
}
return max(n, lastRead), nil
}
}
func (node Node) MarshalBinary() ([]byte, error) {
panic("TODO")
}
func (node *Node) LeafFreeSpace() uint32 {
if node.Head.Level > 0 {
panic(fmt.Errorf("Node.LeafFreeSpace: not a leaf node"))
}
freeSpace := node.Size
freeSpace -= uint32(binstruct.StaticSize(NodeHeader{}))
for _, item := range node.BodyLeaf {
freeSpace -= uint32(binstruct.StaticSize(ItemHeader{}))
freeSpace -= item.Head.DataSize
}
return freeSpace
}
func (fs *FS) ReadNode(addr LogicalAddr) (util.Ref[LogicalAddr, Node], error) {
var ret util.Ref[LogicalAddr, Node]
sb, err := fs.Superblock()
if err != nil {
return ret, err
}
// read
nodeBuf := make([]byte, sb.Data.NodeSize)
if _, err := fs.ReadAt(nodeBuf, addr); err != nil {
return ret, err
}
var node Node
node.Size = sb.Data.NodeSize
if _, err := node.UnmarshalBinary(nodeBuf); err != nil {
return ret, fmt.Errorf("node@%d: %w", addr, err)
}
// sanity checking
if !node.Head.MetadataUUID.Equal(sb.Data.EffectiveMetadataUUID()) {
return ret, fmt.Errorf("node@%d: does not look like a node", addr)
}
if node.Head.Addr != addr {
return ret, fmt.Errorf("node@%d: read from laddr=%d but claims to be at laddr=%d",
addr, addr, node.Head.Addr)
}
stored := node.Head.Checksum
calced := CRC32c(nodeBuf[binstruct.StaticSize(CSum{}):])
if !calced.Equal(stored) {
return ret, fmt.Errorf("node@%d: checksum mismatch: stored=%s calculated=%s",
addr, stored, calced)
}
// return
return util.Ref[LogicalAddr, Node]{
File: fs,
Addr: addr,
Data: node,
}, nil
}
func (fs *FS) WalkTree(nodeAddr LogicalAddr, fn func(Key, []byte) error) error {
if nodeAddr == 0 {
return nil
}
node, err := fs.ReadNode(nodeAddr)
if err != nil {
return err
}
for _, item := range node.Data.BodyInternal {
// fn(item.Data.Key, TODO)
if err := fs.WalkTree(item.BlockPtr, fn); err != nil {
return err
}
}
for _, item := range node.Data.BodyLeaf {
if err := fn(item.Head.Key, item.Body); err != nil {
return err
}
}
return nil
}
|
