Move archive to pkg/archive

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/archive/tar_opts_linux.go

@@ -0,0 +1,52 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package archive
+
+import (
+	"archive/tar"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+// OverlayConvertWhiteout converts whiteout files for overlay.
+func OverlayConvertWhiteout(hdr *tar.Header, path string) (bool, error) {
+	base := filepath.Base(path)
+	dir := filepath.Dir(path)
+
+	// if a directory is marked as opaque, we need to translate that to overlay
+	if base == whiteoutOpaqueDir {
+		// don't write the file itself
+		return false, unix.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0)
+	}
+
+	// if a file was deleted and we are using overlay, we need to create a character device
+	if strings.HasPrefix(base, whiteoutPrefix) {
+		originalBase := base[len(whiteoutPrefix):]
+		originalPath := filepath.Join(dir, originalBase)
+
+		if err := unix.Mknod(originalPath, unix.S_IFCHR, 0); err != nil {
+			return false, err
+		}
+		// don't write the file itself
+		return false, os.Chown(originalPath, hdr.Uid, hdr.Gid)
+	}
+
+	return true, nil
+}