restic/internal/walker/rewriter.go

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package walker
import (
"context"
"fmt"
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"path"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/restic"
)
type NodeRewriteFunc func(node *restic.Node, path string) *restic.Node
type FailedTreeRewriteFunc func(nodeID restic.ID, path string, err error) (restic.ID, error)
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type RewriteOpts struct {
// return nil to remove the node
RewriteNode NodeRewriteFunc
// decide what to do with a tree that could not be loaded. Return nil to remove the node. By default the load error is returned which causes the operation to fail.
RewriteFailedTree FailedTreeRewriteFunc
AllowUnstableSerialization bool
DisableNodeCache bool
}
type idMap map[restic.ID]restic.ID
type TreeRewriter struct {
opts RewriteOpts
replaces idMap
}
func NewTreeRewriter(opts RewriteOpts) *TreeRewriter {
rw := &TreeRewriter{
opts: opts,
}
if !opts.DisableNodeCache {
rw.replaces = make(idMap)
}
// setup default implementations
if rw.opts.RewriteNode == nil {
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rw.opts.RewriteNode = func(node *restic.Node, _ string) *restic.Node {
return node
}
}
if rw.opts.RewriteFailedTree == nil {
// fail with error by default
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rw.opts.RewriteFailedTree = func(_ restic.ID, _ string, err error) (restic.ID, error) {
return restic.ID{}, err
}
}
return rw
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}
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type BlobLoadSaver interface {
restic.BlobSaver
restic.BlobLoader
}
func (t *TreeRewriter) RewriteTree(ctx context.Context, repo BlobLoadSaver, nodepath string, nodeID restic.ID) (newNodeID restic.ID, err error) {
// check if tree was already changed
newID, ok := t.replaces[nodeID]
if ok {
return newID, nil
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}
// a nil nodeID will lead to a load error
curTree, err := restic.LoadTree(ctx, repo, nodeID)
if err != nil {
return t.opts.RewriteFailedTree(nodeID, nodepath, err)
}
if !t.opts.AllowUnstableSerialization {
// check that we can properly encode this tree without losing information
// The alternative of using json/Decoder.DisallowUnknownFields() doesn't work as we use
// a custom UnmarshalJSON to decode trees, see also https://github.com/golang/go/issues/41144
testID, err := restic.SaveTree(ctx, repo, curTree)
if err != nil {
return restic.ID{}, err
}
if nodeID != testID {
return restic.ID{}, fmt.Errorf("cannot encode tree at %q without losing information", nodepath)
}
}
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debug.Log("filterTree: %s, nodeId: %s\n", nodepath, nodeID.Str())
tb := restic.NewTreeJSONBuilder()
for _, node := range curTree.Nodes {
path := path.Join(nodepath, node.Name)
node = t.opts.RewriteNode(node, path)
if node == nil {
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continue
}
if node.Type != "dir" {
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err = tb.AddNode(node)
if err != nil {
return restic.ID{}, err
}
continue
}
// treat nil as null id
var subtree restic.ID
if node.Subtree != nil {
subtree = *node.Subtree
}
newID, err := t.RewriteTree(ctx, repo, path, subtree)
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if err != nil {
return restic.ID{}, err
}
node.Subtree = &newID
err = tb.AddNode(node)
if err != nil {
return restic.ID{}, err
}
}
tree, err := tb.Finalize()
if err != nil {
return restic.ID{}, err
}
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// Save new tree
newTreeID, _, _, err := repo.SaveBlob(ctx, restic.TreeBlob, tree, restic.ID{}, false)
if t.replaces != nil {
t.replaces[nodeID] = newTreeID
}
if !newTreeID.Equal(nodeID) {
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debug.Log("filterTree: save new tree for %s as %v\n", nodepath, newTreeID)
}
return newTreeID, err
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}