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moby--moby/archive/changes.go

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package archive
import (
"bytes"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"syscall"
"time"
"github.com/dotcloud/docker/pkg/system"
"github.com/dotcloud/docker/utils"
"github.com/dotcloud/docker/vendor/src/code.google.com/p/go/src/pkg/archive/tar"
)
type ChangeType int
const (
ChangeModify = iota
ChangeAdd
ChangeDelete
)
type Change struct {
Path string
Kind ChangeType
}
func (change *Change) String() string {
var kind string
switch change.Kind {
case ChangeModify:
kind = "C"
case ChangeAdd:
kind = "A"
case ChangeDelete:
kind = "D"
}
return fmt.Sprintf("%s %s", kind, change.Path)
}
// Gnu tar and the go tar writer don't have sub-second mtime
// precision, which is problematic when we apply changes via tar
// files, we handle this by comparing for exact times, *or* same
// second count and either a or b having exactly 0 nanoseconds
func sameFsTime(a, b time.Time) bool {
return a == b ||
(a.Unix() == b.Unix() &&
(a.Nanosecond() == 0 || b.Nanosecond() == 0))
}
func sameFsTimeSpec(a, b syscall.Timespec) bool {
return a.Sec == b.Sec &&
(a.Nsec == b.Nsec || a.Nsec == 0 || b.Nsec == 0)
}
func Changes(layers []string, rw string) ([]Change, error) {
var changes []Change
err := filepath.Walk(rw, func(path string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Rebase path
path, err = filepath.Rel(rw, path)
if err != nil {
return err
}
path = filepath.Join("/", path)
// Skip root
if path == "/" {
return nil
}
// Skip AUFS metadata
if matched, err := filepath.Match("/.wh..wh.*", path); err != nil || matched {
return err
}
change := Change{
Path: path,
}
// Find out what kind of modification happened
file := filepath.Base(path)
// If there is a whiteout, then the file was removed
if strings.HasPrefix(file, ".wh.") {
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originalFile := file[len(".wh."):]
change.Path = filepath.Join(filepath.Dir(path), originalFile)
change.Kind = ChangeDelete
} else {
// Otherwise, the file was added
change.Kind = ChangeAdd
// ...Unless it already existed in a top layer, in which case, it's a modification
for _, layer := range layers {
stat, err := os.Stat(filepath.Join(layer, path))
if err != nil && !os.IsNotExist(err) {
return err
}
if err == nil {
// The file existed in the top layer, so that's a modification
// However, if it's a directory, maybe it wasn't actually modified.
// If you modify /foo/bar/baz, then /foo will be part of the changed files only because it's the parent of bar
if stat.IsDir() && f.IsDir() {
if f.Size() == stat.Size() && f.Mode() == stat.Mode() && sameFsTime(f.ModTime(), stat.ModTime()) {
// Both directories are the same, don't record the change
return nil
}
}
change.Kind = ChangeModify
break
}
}
}
// Record change
changes = append(changes, change)
return nil
})
if err != nil && !os.IsNotExist(err) {
return nil, err
}
return changes, nil
}
type FileInfo struct {
parent *FileInfo
name string
stat syscall.Stat_t
children map[string]*FileInfo
capability []byte
}
func (root *FileInfo) LookUp(path string) *FileInfo {
parent := root
if path == "/" {
return root
}
pathElements := strings.Split(path, "/")
for _, elem := range pathElements {
if elem != "" {
child := parent.children[elem]
if child == nil {
return nil
}
parent = child
}
}
return parent
}
func (info *FileInfo) path() string {
if info.parent == nil {
return "/"
}
return filepath.Join(info.parent.path(), info.name)
}
func (info *FileInfo) isDir() bool {
return info.parent == nil || info.stat.Mode&syscall.S_IFDIR == syscall.S_IFDIR
}
func (info *FileInfo) addChanges(oldInfo *FileInfo, changes *[]Change) {
if oldInfo == nil {
// add
change := Change{
Path: info.path(),
Kind: ChangeAdd,
}
*changes = append(*changes, change)
}
// We make a copy so we can modify it to detect additions
// also, we only recurse on the old dir if the new info is a directory
// otherwise any previous delete/change is considered recursive
oldChildren := make(map[string]*FileInfo)
if oldInfo != nil && info.isDir() {
for k, v := range oldInfo.children {
oldChildren[k] = v
}
}
for name, newChild := range info.children {
oldChild, _ := oldChildren[name]
if oldChild != nil {
// change?
oldStat := &oldChild.stat
newStat := &newChild.stat
// Note: We can't compare inode or ctime or blocksize here, because these change
// when copying a file into a container. However, that is not generally a problem
// because any content change will change mtime, and any status change should
// be visible when actually comparing the stat fields. The only time this
// breaks down is if some code intentionally hides a change by setting
// back mtime
if oldStat.Mode != newStat.Mode ||
oldStat.Uid != newStat.Uid ||
oldStat.Gid != newStat.Gid ||
oldStat.Rdev != newStat.Rdev ||
// Don't look at size for dirs, its not a good measure of change
(oldStat.Size != newStat.Size && oldStat.Mode&syscall.S_IFDIR != syscall.S_IFDIR) ||
!sameFsTimeSpec(system.GetLastModification(oldStat), system.GetLastModification(newStat)) ||
bytes.Compare(oldChild.capability, newChild.capability) != 0 {
change := Change{
Path: newChild.path(),
Kind: ChangeModify,
}
*changes = append(*changes, change)
}
// Remove from copy so we can detect deletions
delete(oldChildren, name)
}
newChild.addChanges(oldChild, changes)
}
for _, oldChild := range oldChildren {
// delete
change := Change{
Path: oldChild.path(),
Kind: ChangeDelete,
}
*changes = append(*changes, change)
}
}
func (info *FileInfo) Changes(oldInfo *FileInfo) []Change {
var changes []Change
info.addChanges(oldInfo, &changes)
return changes
}
func newRootFileInfo() *FileInfo {
root := &FileInfo{
name: "/",
children: make(map[string]*FileInfo),
}
return root
}
func collectFileInfo(sourceDir string) (*FileInfo, error) {
root := newRootFileInfo()
err := filepath.Walk(sourceDir, func(path string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Rebase path
relPath, err := filepath.Rel(sourceDir, path)
if err != nil {
return err
}
relPath = filepath.Join("/", relPath)
if relPath == "/" {
return nil
}
parent := root.LookUp(filepath.Dir(relPath))
if parent == nil {
return fmt.Errorf("collectFileInfo: Unexpectedly no parent for %s", relPath)
}
info := &FileInfo{
name: filepath.Base(relPath),
children: make(map[string]*FileInfo),
parent: parent,
}
if err := syscall.Lstat(path, &info.stat); err != nil {
return err
}
info.capability, _ = system.Lgetxattr(path, "security.capability")
parent.children[info.name] = info
return nil
})
if err != nil {
return nil, err
}
return root, nil
}
// Compare two directories and generate an array of Change objects describing the changes
func ChangesDirs(newDir, oldDir string) ([]Change, error) {
var (
oldRoot, newRoot *FileInfo
err1, err2 error
errs = make(chan error, 2)
)
go func() {
oldRoot, err1 = collectFileInfo(oldDir)
errs <- err1
}()
go func() {
newRoot, err2 = collectFileInfo(newDir)
errs <- err2
}()
for i := 0; i < 2; i++ {
if err := <-errs; err != nil {
return nil, err
}
}
return newRoot.Changes(oldRoot), nil
}
func ChangesSize(newDir string, changes []Change) int64 {
var size int64
for _, change := range changes {
if change.Kind == ChangeModify || change.Kind == ChangeAdd {
file := filepath.Join(newDir, change.Path)
fileInfo, _ := os.Lstat(file)
if fileInfo != nil && !fileInfo.IsDir() {
size += fileInfo.Size()
}
}
}
return size
}
func major(device uint64) uint64 {
return (device >> 8) & 0xfff
}
func minor(device uint64) uint64 {
return (device & 0xff) | ((device >> 12) & 0xfff00)
}
func ExportChanges(dir string, changes []Change) (Archive, error) {
reader, writer := io.Pipe()
tw := tar.NewWriter(writer)
go func() {
// In general we log errors here but ignore them because
// during e.g. a diff operation the container can continue
// mutating the filesystem and we can see transient errors
// from this
for _, change := range changes {
if change.Kind == ChangeDelete {
whiteOutDir := filepath.Dir(change.Path)
whiteOutBase := filepath.Base(change.Path)
whiteOut := filepath.Join(whiteOutDir, ".wh."+whiteOutBase)
timestamp := time.Now()
hdr := &tar.Header{
Name: whiteOut[1:],
Size: 0,
ModTime: timestamp,
AccessTime: timestamp,
ChangeTime: timestamp,
}
if err := tw.WriteHeader(hdr); err != nil {
utils.Debugf("Can't write whiteout header: %s\n", err)
}
} else {
path := filepath.Join(dir, change.Path)
if err := addTarFile(path, change.Path[1:], tw); err != nil {
utils.Debugf("Can't add file %s to tar: %s\n", path, err)
}
}
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}
// Make sure to check the error on Close.
if err := tw.Close(); err != nil {
utils.Debugf("Can't close layer: %s\n", err)
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}
writer.Close()
}()
return reader, nil
}