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archive.go
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archive.go
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package docker
import (
"archive/tar"
"bufio"
"bytes"
"errors"
"fmt"
"github.com/dotcloud/docker/utils"
"io"
"io/ioutil"
"os"
"os/exec"
"path"
"path/filepath"
)
type Archive io.Reader
type Compression uint32
const (
Uncompressed Compression = iota
Bzip2
Gzip
Xz
)
func DetectCompression(source []byte) Compression {
for _, c := range source[:10] {
utils.Debugf("%x", c)
}
sourceLen := len(source)
for compression, m := range map[Compression][]byte{
Bzip2: {0x42, 0x5A, 0x68},
Gzip: {0x1F, 0x8B, 0x08},
Xz: {0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00},
} {
fail := false
if len(m) > sourceLen {
utils.Debugf("Len too short")
continue
}
i := 0
for _, b := range m {
if b != source[i] {
fail = true
break
}
i++
}
if !fail {
return compression
}
}
return Uncompressed
}
func (compression *Compression) Flag() string {
switch *compression {
case Bzip2:
return "j"
case Gzip:
return "z"
case Xz:
return "J"
}
return ""
}
func (compression *Compression) Extension() string {
switch *compression {
case Uncompressed:
return "tar"
case Bzip2:
return "tar.bz2"
case Gzip:
return "tar.gz"
case Xz:
return "tar.xz"
}
return ""
}
// Tar creates an archive from the directory at `path`, and returns it as a
// stream of bytes.
func Tar(path string, compression Compression) (io.Reader, error) {
return TarFilter(path, compression, nil)
}
// Tar creates an archive from the directory at `path`, only including files whose relative
// paths are included in `filter`. If `filter` is nil, then all files are included.
func TarFilter(path string, compression Compression, filter []string) (io.Reader, error) {
args := []string{"tar", "--numeric-owner", "-f", "-", "-C", path}
if filter == nil {
filter = []string{"."}
}
for _, f := range filter {
args = append(args, "-c"+compression.Flag(), f)
}
return CmdStream(exec.Command(args[0], args[1:]...))
}
// Untar reads a stream of bytes from `archive`, parses it as a tar archive,
// and unpacks it into the directory at `path`.
// The archive may be compressed with one of the following algorithgms:
// identity (uncompressed), gzip, bzip2, xz.
// FIXME: specify behavior when target path exists vs. doesn't exist.
func Untar(archive io.Reader, path string) error {
if archive == nil {
return fmt.Errorf("Empty archive")
}
bufferedArchive := bufio.NewReaderSize(archive, 10)
buf, err := bufferedArchive.Peek(10)
if err != nil {
return err
}
compression := DetectCompression(buf)
utils.Debugf("Archive compression detected: %s", compression.Extension())
cmd := exec.Command("tar", "--numeric-owner", "-f", "-", "-C", path, "-x"+compression.Flag())
cmd.Stdin = bufferedArchive
// Hardcode locale environment for predictable outcome regardless of host configuration.
// (see https://github.com/dotcloud/docker/issues/355)
cmd.Env = []string{"LANG=en_US.utf-8", "LC_ALL=en_US.utf-8"}
output, err := cmd.CombinedOutput()
if err != nil {
return fmt.Errorf("%s: %s", err, output)
}
return nil
}
// TarUntar is a convenience function which calls Tar and Untar, with
// the output of one piped into the other. If either Tar or Untar fails,
// TarUntar aborts and returns the error.
func TarUntar(src string, filter []string, dst string) error {
utils.Debugf("TarUntar(%s %s %s)", src, filter, dst)
archive, err := TarFilter(src, Uncompressed, filter)
if err != nil {
return err
}
return Untar(archive, dst)
}
// UntarPath is a convenience function which looks for an archive
// at filesystem path `src`, and unpacks it at `dst`.
func UntarPath(src, dst string) error {
if archive, err := os.Open(src); err != nil {
return err
} else if err := Untar(archive, dst); err != nil {
return err
}
return nil
}
// CopyWithTar creates a tar archive of filesystem path `src`, and
// unpacks it at filesystem path `dst`.
// The archive is streamed directly with fixed buffering and no
// intermediary disk IO.
//
func CopyWithTar(src, dst string) error {
srcSt, err := os.Stat(src)
if err != nil {
return err
}
if !srcSt.IsDir() {
return CopyFileWithTar(src, dst)
}
// Create dst, copy src's content into it
utils.Debugf("Creating dest directory: %s", dst)
if err := os.MkdirAll(dst, 0700); err != nil && !os.IsExist(err) {
return err
}
utils.Debugf("Calling TarUntar(%s, %s)", src, dst)
return TarUntar(src, nil, dst)
}
// CopyFileWithTar emulates the behavior of the 'cp' command-line
// for a single file. It copies a regular file from path `src` to
// path `dst`, and preserves all its metadata.
//
// If `dst` ends with a trailing slash '/', the final destination path
// will be `dst/base(src)`.
func CopyFileWithTar(src, dst string) error {
utils.Debugf("CopyFileWithTar(%s, %s)", src, dst)
srcSt, err := os.Stat(src)
if err != nil {
return err
}
if srcSt.IsDir() {
return fmt.Errorf("Can't copy a directory")
}
// Clean up the trailing /
if dst[len(dst)-1] == '/' {
dst = path.Join(dst, filepath.Base(src))
}
// Create the holding directory if necessary
if err := os.MkdirAll(filepath.Dir(dst), 0700); err != nil && !os.IsExist(err) {
return err
}
buf := new(bytes.Buffer)
tw := tar.NewWriter(buf)
hdr, err := tar.FileInfoHeader(srcSt, "")
if err != nil {
return err
}
hdr.Name = filepath.Base(dst)
if err := tw.WriteHeader(hdr); err != nil {
return err
}
srcF, err := os.Open(src)
if err != nil {
return err
}
if _, err := io.Copy(tw, srcF); err != nil {
return err
}
tw.Close()
return Untar(buf, filepath.Dir(dst))
}
// CmdStream executes a command, and returns its stdout as a stream.
// If the command fails to run or doesn't complete successfully, an error
// will be returned, including anything written on stderr.
func CmdStream(cmd *exec.Cmd) (io.Reader, error) {
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, err
}
stderr, err := cmd.StderrPipe()
if err != nil {
return nil, err
}
pipeR, pipeW := io.Pipe()
errChan := make(chan []byte)
// Collect stderr, we will use it in case of an error
go func() {
errText, e := ioutil.ReadAll(stderr)
if e != nil {
errText = []byte("(...couldn't fetch stderr: " + e.Error() + ")")
}
errChan <- errText
}()
// Copy stdout to the returned pipe
go func() {
_, err := io.Copy(pipeW, stdout)
if err != nil {
pipeW.CloseWithError(err)
}
errText := <-errChan
if err := cmd.Wait(); err != nil {
pipeW.CloseWithError(errors.New(err.Error() + ": " + string(errText)))
} else {
pipeW.Close()
}
}()
// Run the command and return the pipe
if err := cmd.Start(); err != nil {
return nil, err
}
return pipeR, nil
}
// NewTempArchive reads the content of src into a temporary file, and returns the contents
// of that file as an archive. The archive can only be read once - as soon as reading completes,
// the file will be deleted.
func NewTempArchive(src Archive, dir string) (*TempArchive, error) {
f, err := ioutil.TempFile(dir, "")
if err != nil {
return nil, err
}
if _, err := io.Copy(f, src); err != nil {
return nil, err
}
if _, err := f.Seek(0, 0); err != nil {
return nil, err
}
st, err := f.Stat()
if err != nil {
return nil, err
}
size := st.Size()
return &TempArchive{f, size}, nil
}
type TempArchive struct {
*os.File
Size int64 // Pre-computed from Stat().Size() as a convenience
}
func (archive *TempArchive) Read(data []byte) (int, error) {
n, err := archive.File.Read(data)
if err != nil {
os.Remove(archive.File.Name())
}
return n, err
}