Add archive package

Archive package handles generating and applying diff tar streams
based on the OCI diff tar specification.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

archive/tar_linux.go

@@ -0,0 +1,134 @@
+package archive
+
+import (
+	"archive/tar"
+	"os"
+	"sync"
+	"syscall"
+
+	"github.com/opencontainers/runc/libcontainer/system"
+	"github.com/pkg/errors"
+	"github.com/stevvooe/continuity/sysx"
+)
+
+func tarName(p string) (string, error) {
+	return p, nil
+}
+
+func chmodTarEntry(perm os.FileMode) os.FileMode {
+	return perm
+}
+
+func setHeaderForSpecialDevice(hdr *tar.Header, name string, fi os.FileInfo) error {
+	s, ok := fi.Sys().(*syscall.Stat_t)
+	if !ok {
+		return errors.New("unsupported stat type")
+	}
+
+	// Currently go does not fill in the major/minors
+	if s.Mode&syscall.S_IFBLK != 0 ||
+		s.Mode&syscall.S_IFCHR != 0 {
+		hdr.Devmajor = int64(major(uint64(s.Rdev)))
+		hdr.Devminor = int64(minor(uint64(s.Rdev)))
+	}
+
+	return nil
+}
+
+func major(device uint64) uint64 {
+	return (device >> 8) & 0xfff
+}
+
+func minor(device uint64) uint64 {
+	return (device & 0xff) | ((device >> 12) & 0xfff00)
+}
+
+func mkdev(major int64, minor int64) uint32 {
+	return uint32(((minor & 0xfff00) << 12) | ((major & 0xfff) << 8) | (minor & 0xff))
+}
+
+func open(p string) (*os.File, error) {
+	return os.Open(p)
+}
+
+func openFile(name string, flag int, perm os.FileMode) (*os.File, error) {
+	return os.OpenFile(name, flag, perm)
+}
+
+func mkdirAll(path string, perm os.FileMode) error {
+	return os.MkdirAll(path, perm)
+}
+
+func prepareApply() func() {
+	// Unset unmask before doing an apply operation,
+	// restore unmask when complete
+	oldmask := syscall.Umask(0)
+	return func() {
+		syscall.Umask(oldmask)
+	}
+}
+
+func skipFile(*tar.Header) bool {
+	return false
+}
+
+var (
+	inUserNS bool
+	nsOnce   sync.Once
+)
+
+func setInUserNS() {
+	inUserNS = system.RunningInUserNS()
+}
+
+// handleTarTypeBlockCharFifo is an OS-specific helper function used by
+// createTarFile to handle the following types of header: Block; Char; Fifo
+func handleTarTypeBlockCharFifo(hdr *tar.Header, path string) error {
+	nsOnce.Do(setInUserNS)
+	if inUserNS {
+		// cannot create a device if running in user namespace
+		return nil
+	}
+
+	mode := uint32(hdr.Mode & 07777)
+	switch hdr.Typeflag {
+	case tar.TypeBlock:
+		mode |= syscall.S_IFBLK
+	case tar.TypeChar:
+		mode |= syscall.S_IFCHR
+	case tar.TypeFifo:
+		mode |= syscall.S_IFIFO
+	}
+
+	if err := syscall.Mknod(path, mode, int(mkdev(hdr.Devmajor, hdr.Devminor))); err != nil {
+		return err
+	}
+	return nil
+}
+
+func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo) error {
+	if hdr.Typeflag == tar.TypeLink {
+		if fi, err := os.Lstat(hdr.Linkname); err == nil && (fi.Mode()&os.ModeSymlink == 0) {
+			if err := os.Chmod(path, hdrInfo.Mode()); err != nil {
+				return err
+			}
+		}
+	} else if hdr.Typeflag != tar.TypeSymlink {
+		if err := os.Chmod(path, hdrInfo.Mode()); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func getxattr(path, attr string) ([]byte, error) {
+	b, err := sysx.LGetxattr(path, attr)
+	if err == syscall.ENOTSUP || err == syscall.ENODATA {
+		return nil, nil
+	}
+	return b, err
+}
+
+func setxattr(path, key, value string) error {
+	return sysx.LSetxattr(path, key, []byte(value), 0)
+}