repository: expose ZeroChunk via chunker factory

internal/repository/chunker.go

@@ -19,11 +19,15 @@ func (c *baseChunker) NextSplitPoint(buf []byte) int {
 }
 
 type chunkerFactory struct {
-	pol chunker.Pol
+	pol       chunker.Pol
+	zeroChunk func() restic.ID
 }
 
-func newChunkerFactory(pol chunker.Pol) *chunkerFactory {
-	return &chunkerFactory{pol: pol}
+func newChunkerFactory(r *Repository) *chunkerFactory {
+	return &chunkerFactory{
+		pol:       r.Config().ChunkerPolynomial,
+		zeroChunk: r.zeroChunk,
+	}
 }
 
 func (f *chunkerFactory) NewChunker() restic.Chunker {
@@ -34,6 +38,10 @@ func (f *chunkerFactory) MaxChunkSize() int {
 	return chunker.MaxSize
 }
 
-func (r *Repository) ChunkerFactory() restic.ChunkerFactory {
-	return newChunkerFactory(r.Config().ChunkerPolynomial)
+func (f *chunkerFactory) ZeroChunk() restic.ID {
+	return f.zeroChunk()
+}
+
+func (r *Repository) ChunkerFactory() restic.ChunkerFactory {
+	return newChunkerFactory(r)
 }

internal/repository/repository.go

@@ -51,6 +51,9 @@ type Repository struct {
 	allocDec sync.Once
 	enc      *zstd.Encoder
 	dec      *zstd.Decoder
+
+	zeroChunkOnce sync.Once
+	zeroChunkID   restic.ID
 }
 
 // internalRepository allows using SaveUnpacked and RemoveUnpacked with all FileTypes
@@ -1023,7 +1026,7 @@ func (r *Repository) saveBlob(ctx context.Context, t restic.BlobType, buf []byte
 		// useful for sparse files containing large all zero regions. For these we can
 		// process chunks as fast as we can read the from disk.
 		if len(buf) == chunker.MinSize && restic.ZeroPrefixLen(buf) == chunker.MinSize {
-			newID = ZeroChunk()
+			newID = r.zeroChunk()
 		} else {
 			newID = restic.Hash(buf)
 		}
@@ -1340,13 +1343,9 @@ func (b *packBlobIterator) Next() (packBlobValue, error) {
 	return packBlobValue{entry.BlobHandle, plaintext, err}, nil
 }
 
-var zeroChunkOnce sync.Once
-var zeroChunkID restic.ID
-
-// ZeroChunk computes and returns (cached) the ID of an all-zero chunk with size chunker.MinSize
-func ZeroChunk() restic.ID {
-	zeroChunkOnce.Do(func() {
-		zeroChunkID = restic.Hash(make([]byte, chunker.MinSize))
+func (r *Repository) zeroChunk() restic.ID {
+	r.zeroChunkOnce.Do(func() {
+		r.zeroChunkID = restic.Hash(make([]byte, chunker.MinSize))
 	})
-	return zeroChunkID
+	return r.zeroChunkID
 }

internal/restic/chunker.go

@@ -17,4 +17,6 @@ type ChunkerFactory interface {
 	NewChunker() Chunker
 	// MaxChunkSize is the maximum size of a single chunk (used for output buffer pools).
 	MaxChunkSize() int
+	// ZeroChunk returns the ID of an all-zero chunk with minimum chunk size.
+	ZeroChunk() ID
 }

internal/restorer/filerestorer.go

@@ -11,7 +11,6 @@ import (
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/feature"
-	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
 )
 
@@ -72,7 +71,8 @@ func newFileRestorer(dst string,
 	sparse bool,
 	allowRecursiveDelete bool,
 	startWarmup startWarmupFn,
-	progress ProgressReporter) *fileRestorer {
+	progress ProgressReporter,
+	zeroChunk restic.ID) *fileRestorer {
 
 	// as packs are streamed the concurrency is limited by IO
 	workerCount := int(connections)
@@ -82,7 +82,7 @@ func newFileRestorer(dst string,
 		blobsLoader:          blobsLoader,
 		startWarmup:          startWarmup,
 		filesWriter:          newFilesWriter(workerCount, allowRecursiveDelete),
-		zeroChunk:            repository.ZeroChunk(),
+		zeroChunk:            zeroChunk,
 		sparse:               sparse,
 		progress:             progressOrNoop(progress),
 		allowRecursiveDelete: allowRecursiveDelete,

internal/restorer/filerestorer_test.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/feature"
+	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
 	rtest "github.com/restic/restic/internal/test"
 )
@@ -208,7 +209,8 @@ func restoreAndVerify(t *testing.T, tempdir string, content []TestFile, files ma
 	t.Helper()
 	repo := newTestRepo(content)
 
-	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, sparse, false, repo.StartWarmup, nil)
+	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, sparse, false, repo.StartWarmup, nil,
+		repository.TestRepository(t).ChunkerFactory().ZeroChunk())
 
 	if files == nil {
 		r.files = repo.files
@@ -358,7 +360,8 @@ func TestErrorRestoreFiles(t *testing.T) {
 		return loadError
 	}
 
-	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, false, false, repo.StartWarmup, nil)
+	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, false, false, repo.StartWarmup, nil,
+		repository.TestRepository(t).ChunkerFactory().ZeroChunk())
 	r.files = repo.files
 
 	err := r.restoreFiles(context.TODO())
@@ -399,7 +402,8 @@ func TestFatalDownloadError(t *testing.T) {
 		})
 	}
 
-	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, false, false, repo.StartWarmup, nil)
+	r := newFileRestorer(tempdir, repo.loader, repo.Lookup, 2, false, false, repo.StartWarmup, nil,
+		repository.TestRepository(t).ChunkerFactory().ZeroChunk())
 	r.files = repo.files
 
 	var errors []string

internal/restorer/restorer.go

@@ -362,7 +362,8 @@ func (res *Restorer) RestoreTo(ctx context.Context, dst string) (uint64, error)
 
 	idx := data.NewHardlinkIndex[string]()
 	filerestorer := newFileRestorer(dst, res.repo.LoadBlobsFromPack, res.repo.LookupBlob,
-		res.repo.Connections(), res.opts.Sparse, res.opts.Delete, res.repo.StartWarmup, res.opts.Progress)
+		res.repo.Connections(), res.opts.Sparse, res.opts.Delete, res.repo.StartWarmup, res.opts.Progress,
+		res.repo.ChunkerFactory().ZeroChunk())
 	filerestorer.Error = res.Error
 	filerestorer.Info = res.Info