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package btrfs
import (
"errors"
"fmt"
"io"
iofs "io/fs"
"math"
"strings"
"lukeshu.com/btrfs-tools/pkg/util"
)
// A TreeWalkPathElem essentially represents a KeyPointer.
type TreeWalkPathElem struct {
// ItemIdx is the index of this KeyPointer in the parent Node;
// or -1 if this is the root and there is no KeyPointer.
ItemIdx int
// NodeAddr is the address of the node that the KeyPointer
// points at, or 0 if this is a leaf item and nothing is
// being pointed at.
NodeAddr LogicalAddr
// NodeLevel is the expected or actual level of the node at
// NodeAddr, or 255 if there is no knowledge of the level.
NodeLevel uint8
}
func (elem TreeWalkPathElem) writeNodeTo(w io.Writer) {
if elem.NodeLevel != math.MaxUint8 {
fmt.Fprintf(w, "node:%d@%v", elem.NodeLevel, elem.NodeAddr)
} else {
fmt.Fprintf(w, "node@%v", elem.NodeAddr)
}
}
// - The first element will always have an ItemIdx of -1.
//
// - For .Item() callbacks, the last element will always have a
// NodeAddr of 0.
type TreeWalkPath []TreeWalkPathElem
func (path TreeWalkPath) String() string {
if len(path) == 0 {
return "(empty-path)"
}
var ret strings.Builder
path[0].writeNodeTo(&ret)
for _, elem := range path[1:] {
fmt.Fprintf(&ret, "[%v]", elem.ItemIdx)
if elem.NodeAddr != 0 {
ret.WriteString("->")
elem.writeNodeTo(&ret)
}
}
return ret.String()
}
type TreeWalkHandler struct {
// Callbacks for entire nodes
PreNode func(TreeWalkPath) error
Node func(TreeWalkPath, *util.Ref[LogicalAddr, Node], error) error
PostNode func(TreeWalkPath, *util.Ref[LogicalAddr, Node]) error
// Callbacks for items on internal nodes
PreKeyPointer func(TreeWalkPath, KeyPointer) error
PostKeyPointer func(TreeWalkPath, KeyPointer) error
// Callbacks for items on leaf nodes
Item func(TreeWalkPath, Item) error
}
// The lifecycle of callbacks is:
//
// 001 .PreNode()
// 002 (read node)
// 003 .Node()
// for item in node.items:
// if internal:
// 004 .PreKeyPointer()
// 005 (recurse)
// 006 .PostKeyPointer()
// else:
// 004 .Item()
// 007 .PostNode()
func (fs *FS) TreeWalk(treeRoot LogicalAddr, cbs TreeWalkHandler) error {
path := TreeWalkPath{
TreeWalkPathElem{
ItemIdx: -1,
NodeAddr: treeRoot,
NodeLevel: math.MaxUint8,
},
}
return fs.treeWalk(path, cbs)
}
func (fs *FS) treeWalk(path TreeWalkPath, cbs TreeWalkHandler) error {
if path[len(path)-1].NodeAddr == 0 {
return nil
}
if cbs.PreNode != nil {
if err := cbs.PreNode(path); err != nil {
if errors.Is(err, iofs.SkipDir) {
return nil
}
return err
}
}
node, err := fs.ReadNode(path[len(path)-1].NodeAddr)
if node != nil {
if exp := path[len(path)-1].NodeLevel; exp != math.MaxUint8 && node.Data.Head.Level != exp && err == nil {
err = fmt.Errorf("btrfs.FS.TreeWalk: node@%v: expected level %v but has level %v",
node.Addr, exp, node.Data.Head.Level)
}
path[len(path)-1].NodeLevel = node.Data.Head.Level
}
if cbs.Node != nil {
err = cbs.Node(path, node, err)
}
if err != nil {
if errors.Is(err, iofs.SkipDir) {
return nil
}
return fmt.Errorf("btrfs.FS.TreeWalk: %w", err)
}
if node != nil {
for i, item := range node.Data.BodyInternal {
itemPath := append(path, TreeWalkPathElem{
ItemIdx: i,
NodeAddr: item.BlockPtr,
NodeLevel: node.Data.Head.Level - 1,
})
if cbs.PreKeyPointer != nil {
if err := cbs.PreKeyPointer(itemPath, item); err != nil {
if errors.Is(err, iofs.SkipDir) {
continue
}
return err
}
}
if err := fs.treeWalk(itemPath, cbs); err != nil {
return err
}
if cbs.PostKeyPointer != nil {
if err := cbs.PostKeyPointer(itemPath, item); err != nil {
if errors.Is(err, iofs.SkipDir) {
continue
}
return err
}
}
}
for i, item := range node.Data.BodyLeaf {
if cbs.Item != nil {
itemPath := append(path, TreeWalkPathElem{
ItemIdx: i,
})
if err := cbs.Item(itemPath, item); err != nil {
if errors.Is(err, iofs.SkipDir) {
continue
}
return fmt.Errorf("btrfs.FS.TreeWalk: callback: %w", err)
}
}
}
}
if cbs.PostNode != nil {
if err := cbs.PostNode(path, node); err != nil {
if errors.Is(err, iofs.SkipDir) {
return nil
}
return err
}
}
return nil
}
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