restic/internal/walker/walker.go

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package walker
import (
"context"
"path"
"sort"
"github.com/pkg/errors"
"github.com/restic/restic/internal/restic"
)
// ErrSkipNode is returned by WalkFunc when a dir node should not be walked.
var ErrSkipNode = errors.New("skip this node")
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// WalkFunc is the type of the function called for each node visited by Walk.
// Path is the slash-separated path from the root node. If there was a problem
// loading a node, err is set to a non-nil error. WalkFunc can chose to ignore
// it by returning nil.
//
// When the special value ErrSkipNode is returned and node is a dir node, it is
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// not walked. When the node is not a dir node, the remaining items in this
// tree are skipped.
type WalkFunc func(parentTreeID restic.ID, path string, node *restic.Node, nodeErr error) (err error)
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type WalkVisitor struct {
// If the node is a `dir`, it will be entered afterwards unless `ErrSkipNode`
// was returned. This function is mandatory
ProcessNode WalkFunc
// Optional callback
LeaveDir func(path string)
}
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// Walk calls walkFn recursively for each node in root. If walkFn returns an
// error, it is passed up the call stack. The trees in ignoreTrees are not
// walked. If walkFn ignores trees, these are added to the set.
func Walk(ctx context.Context, repo restic.BlobLoader, root restic.ID, visitor WalkVisitor) error {
tree, err := restic.LoadTree(ctx, repo, root)
err = visitor.ProcessNode(root, "/", nil, err)
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if err != nil {
if err == ErrSkipNode {
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err = nil
}
return err
}
return walk(ctx, repo, "/", root, tree, visitor)
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}
// walk recursively traverses the tree, ignoring subtrees when the ID of the
// subtree is in ignoreTrees. If err is nil and ignore is true, the subtree ID
// will be added to ignoreTrees by walk.
func walk(ctx context.Context, repo restic.BlobLoader, prefix string, parentTreeID restic.ID, tree *restic.Tree, visitor WalkVisitor) (err error) {
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sort.Slice(tree.Nodes, func(i, j int) bool {
return tree.Nodes[i].Name < tree.Nodes[j].Name
})
for _, node := range tree.Nodes {
p := path.Join(prefix, node.Name)
if node.Type == "" {
return errors.Errorf("node type is empty for node %q", node.Name)
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}
if node.Type != "dir" {
err := visitor.ProcessNode(parentTreeID, p, node, nil)
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if err != nil {
if err == ErrSkipNode {
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// skip the remaining entries in this tree
break
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}
return err
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}
continue
}
if node.Subtree == nil {
return errors.Errorf("subtree for node %v in tree %v is nil", node.Name, p)
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}
subtree, err := restic.LoadTree(ctx, repo, *node.Subtree)
err = visitor.ProcessNode(parentTreeID, p, node, err)
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if err != nil {
if err == ErrSkipNode {
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continue
}
}
err = walk(ctx, repo, p, *node.Subtree, subtree, visitor)
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if err != nil {
return err
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}
}
if visitor.LeaveDir != nil {
visitor.LeaveDir(prefix)
}
return nil
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}