Merge pull request #22126 from dmcgowan/overlay-native-diff

Overlay multiple lower directory support

archive/archive.go

@@ -33,6 +33,8 @@ type (
 	Reader io.Reader
 	// Compression is the state represents if compressed or not.
 	Compression int
+	// WhiteoutFormat is the format of whiteouts unpacked
+	WhiteoutFormat int
 	// TarChownOptions wraps the chown options UID and GID.
 	TarChownOptions struct {
 		UID, GID int
@@ -47,6 +49,10 @@ type (
 		GIDMaps          []idtools.IDMap
 		ChownOpts        *TarChownOptions
 		IncludeSourceDir bool
+		// WhiteoutFormat is the expected on disk format for whiteout files.
+		// This format will be converted to the standard format on pack
+		// and from the standard format on unpack.
+		WhiteoutFormat WhiteoutFormat
 		// When unpacking, specifies whether overwriting a directory with a
 		// non-directory is allowed and vice versa.
 		NoOverwriteDirNonDir bool
@@ -93,6 +99,14 @@ const (
 	Xz
 )
 
+const (
+	// AUFSWhiteoutFormat is the default format for whitesouts
+	AUFSWhiteoutFormat WhiteoutFormat = iota
+	// OverlayWhiteoutFormat formats whiteout according to the overlay
+	// standard.
+	OverlayWhiteoutFormat
+)
+
 // IsArchive checks for the magic bytes of a tar or any supported compression
 // algorithm.
 func IsArchive(header []byte) bool {
@@ -228,6 +242,11 @@ func (compression *Compression) Extension() string {
 	return ""
 }
 
+type tarWhiteoutConverter interface {
+	ConvertWrite(*tar.Header, string, os.FileInfo) error
+	ConvertRead(*tar.Header, string) (bool, error)
+}
+
 type tarAppender struct {
 	TarWriter *tar.Writer
 	Buffer    *bufio.Writer
@@ -236,6 +255,12 @@ type tarAppender struct {
 	SeenFiles map[uint64]string
 	UIDMaps   []idtools.IDMap
 	GIDMaps   []idtools.IDMap
+
+	// For packing and unpacking whiteout files in the
+	// non standard format. The whiteout files defined
+	// by the AUFS standard are used as the tar whiteout
+	// standard.
+	WhiteoutConverter tarWhiteoutConverter
 }
 
 // canonicalTarName provides a platform-independent and consistent posix-style
@@ -253,6 +278,7 @@ func canonicalTarName(name string, isDir bool) (string, error) {
 	return name, nil
 }
 
+// addTarFile adds to the tar archive a file from `path` as `name`
 func (ta *tarAppender) addTarFile(path, name string) error {
 	fi, err := os.Lstat(path)
 	if err != nil {
@@ -323,6 +349,12 @@ func (ta *tarAppender) addTarFile(path, name string) error {
 		hdr.Gid = xGID
 	}
 
+	if ta.WhiteoutConverter != nil {
+		if err := ta.WhiteoutConverter.ConvertWrite(hdr, path, fi); err != nil {
+			return err
+		}
+	}
+
 	if err := ta.TarWriter.WriteHeader(hdr); err != nil {
 		return err
 	}
@@ -508,11 +540,12 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
 
 	go func() {
 		ta := &tarAppender{
-			TarWriter: tar.NewWriter(compressWriter),
-			Buffer:    pools.BufioWriter32KPool.Get(nil),
-			SeenFiles: make(map[uint64]string),
-			UIDMaps:   options.UIDMaps,
-			GIDMaps:   options.GIDMaps,
+			TarWriter:         tar.NewWriter(compressWriter),
+			Buffer:            pools.BufioWriter32KPool.Get(nil),
+			SeenFiles:         make(map[uint64]string),
+			UIDMaps:           options.UIDMaps,
+			GIDMaps:           options.GIDMaps,
+			WhiteoutConverter: getWhiteoutConverter(options.WhiteoutFormat),
 		}
 
 		defer func() {
@@ -674,6 +707,7 @@ func Unpack(decompressedArchive io.Reader, dest string, options *TarOptions) err
 	if err != nil {
 		return err
 	}
+	whiteoutConverter := getWhiteoutConverter(options.WhiteoutFormat)
 
 	// Iterate through the files in the archive.
 loop:
@@ -773,6 +807,16 @@ loop:
 			hdr.Gid = xGID
 		}
 
+		if whiteoutConverter != nil {
+			writeFile, err := whiteoutConverter.ConvertRead(hdr, path)
+			if err != nil {
+				return err
+			}
+			if !writeFile {
+				continue
+			}
+		}
+
 		if err := createTarFile(path, dest, hdr, trBuf, !options.NoLchown, options.ChownOpts); err != nil {
 			return err
 		}