Explicitly differentiate between empty and missing tar-split

Empty tar-split shouldn't ever happen, but being precise here doesn't hurt. Signed-off-by: Miloslav Trmač <[email protected]>
containers · Oct 11, 2024 · de3e71f · de3e71f
1 parent d10a922
commit de3e71f
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Showing 3 changed files with 4 additions and 4 deletions.
diff --git a/drivers/driver.go b/drivers/driver.go
@@ -196,7 +196,7 @@ type DriverWithDifferOutput struct {
 	CompressedDigest   digest.Digest
 	Metadata           string
 	BigData            map[string][]byte
-	TarSplit           []byte
+	TarSplit           []byte // nil if not available
 	TOCDigest          digest.Digest
 	// RootDirMode is the mode of the root directory of the layer, if specified.
 	RootDirMode *os.FileMode

diff --git a/layers.go b/layers.go
@@ -2513,7 +2513,7 @@ func (r *layerStore) applyDiffFromStagingDirectory(id string, diffOutput *driver
 		return err
 	}
 
-	if len(diffOutput.TarSplit) != 0 {
+	if diffOutput.TarSplit != nil {
 		tsdata := bytes.Buffer{}
 		compressor, err := pgzip.NewWriterLevel(&tsdata, pgzip.BestSpeed)
 		if err != nil {

diff --git a/pkg/chunked/compression_linux.go b/pkg/chunked/compression_linux.go
@@ -139,7 +139,7 @@ func readEstargzChunkedManifest(blobStream ImageSourceSeekable, blobSize int64,
 }
 
 // readZstdChunkedManifest reads the zstd:chunked manifest from the seekable stream blobStream.
-// Returns (manifest blob, parsed manifest, tar-split blob, manifest offset).
+// Returns (manifest blob, parsed manifest, tar-split blob or nil, manifest offset).
 func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Digest, annotations map[string]string) ([]byte, *internal.TOC, []byte, int64, error) {
 	offsetMetadata := annotations[internal.ManifestInfoKey]
 	if offsetMetadata == "" {
@@ -214,7 +214,7 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 		return nil, nil, nil, 0, fmt.Errorf("unmarshaling TOC: %w", err)
 	}
 
-	decodedTarSplit := []byte{}
+	var decodedTarSplit []byte = nil
 	if toc.TarSplitDigest != "" {
 		if tarSplitChunk.Offset <= 0 {
 			return nil, nil, nil, 0, fmt.Errorf("TOC requires a tar-split, but the %s annotation does not describe a position", internal.TarSplitInfoKey)