archive: use Mkdev, Major and Minor functions from golang.org/x/sys/unix

Now that golang.org/x/sys/unix provides the Mkdev, Major and Minor
functions for every OS, use them instead of the locally defined version
which uses the Linux specific device major/minor encoding.

This also means that the device number should now be properly encoded on
e.g. Darwin, FreeBSD or Solaris.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

archive/tar_unix.go

@@ -31,25 +31,13 @@ func setHeaderForSpecialDevice(hdr *tar.Header, name string, fi os.FileInfo) err
 	// 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)))
+		hdr.Devmajor = int64(unix.Major(uint64(s.Rdev)))
+		hdr.Devminor = int64(unix.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)
 }
@@ -103,7 +91,7 @@ func handleTarTypeBlockCharFifo(hdr *tar.Header, path string) error {
 		mode |= unix.S_IFIFO
 	}
 
-	return unix.Mknod(path, mode, int(mkdev(hdr.Devmajor, hdr.Devminor)))
+	return unix.Mknod(path, mode, int(unix.Mkdev(uint32(hdr.Devmajor), uint32(hdr.Devminor))))
 }
 
 func handleLChmod(hdr *tar.Header, path string, hdrInfo os.FileInfo) error {