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moby--moby/archive/diff.go

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package archive
import (
"archive/tar"
"io"
"os"
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"path/filepath"
"strings"
"syscall"
"time"
)
// Linux device nodes are a bit weird due to backwards compat with 16 bit device nodes.
// They are, from low to high: the lower 8 bits of the minor, then 12 bits of the major,
// then the top 12 bits of the minor
func mkdev(major int64, minor int64) uint32 {
return uint32(((minor & 0xfff00) << 12) | ((major & 0xfff) << 8) | (minor & 0xff))
}
func timeToTimespec(time time.Time) (ts syscall.Timespec) {
if time.IsZero() {
// Return UTIME_OMIT special value
ts.Sec = 0
ts.Nsec = ((1 << 30) - 2)
return
}
return syscall.NsecToTimespec(time.UnixNano())
}
// ApplyLayer parses a diff in the standard layer format from `layer`, and
// applies it to the directory `dest`.
func ApplyLayer(dest string, layer ArchiveReader) error {
// We need to be able to set any perms
oldmask := syscall.Umask(0)
defer syscall.Umask(oldmask)
layer, err := DecompressStream(layer)
if err != nil {
return err
}
tr := tar.NewReader(layer)
var dirs []*tar.Header
// Iterate through the files in the archive.
for {
hdr, err := tr.Next()
if err == io.EOF {
// end of tar archive
break
}
if err != nil {
return err
}
// Normalize name, for safety and for a simple is-root check
hdr.Name = filepath.Clean(hdr.Name)
if !strings.HasSuffix(hdr.Name, "/") {
// Not the root directory, ensure that the parent directory exists.
// This happened in some tests where an image had a tarfile without any
// parent directories.
parent := filepath.Dir(hdr.Name)
parentPath := filepath.Join(dest, parent)
if _, err := os.Lstat(parentPath); err != nil && os.IsNotExist(err) {
err = os.MkdirAll(parentPath, 600)
if err != nil {
return err
}
}
}
// Skip AUFS metadata dirs
if strings.HasPrefix(hdr.Name, ".wh..wh.") {
continue
}
path := filepath.Join(dest, hdr.Name)
base := filepath.Base(path)
if strings.HasPrefix(base, ".wh.") {
originalBase := base[len(".wh."):]
originalPath := filepath.Join(filepath.Dir(path), originalBase)
if err := os.RemoveAll(originalPath); err != nil {
return err
}
} else {
// If path exits we almost always just want to remove and replace it.
// The only exception is when it is a directory *and* the file from
// the layer is also a directory. Then we want to merge them (i.e.
// just apply the metadata from the layer).
if fi, err := os.Lstat(path); err == nil {
if !(fi.IsDir() && hdr.Typeflag == tar.TypeDir) {
if err := os.RemoveAll(path); err != nil {
return err
}
}
}
if err := createTarFile(path, dest, hdr, tr); err != nil {
return err
}
// Directory mtimes must be handled at the end to avoid further
// file creation in them to modify the directory mtime
if hdr.Typeflag == tar.TypeDir {
dirs = append(dirs, hdr)
}
}
}
for _, hdr := range dirs {
path := filepath.Join(dest, hdr.Name)
ts := []syscall.Timespec{timeToTimespec(hdr.AccessTime), timeToTimespec(hdr.ModTime)}
if err := syscall.UtimesNano(path, ts); err != nil {
return err
}
}
return nil
}