rootfs runs
This commit is contained in:
parent
4d6476cca9
commit
ce445b19b7
89
rootfs.go
89
rootfs.go
|
@ -58,48 +58,109 @@ type dockerManifestJSON []struct {
|
|||
// 4. go through
|
||||
func (r *cmdRootFS) rootfs(in io.ReadSeeker, out io.Writer) error {
|
||||
tr := tar.NewReader(in)
|
||||
tw := tar.NewWriter(out)
|
||||
// layerOffsets maps a layer name (a9b123c0daa/layer.tar) to it's offset
|
||||
layerOffsets := map[string]int64{}
|
||||
|
||||
// manifest is the docker manifest in the image
|
||||
var manifest dockerManifestJSON
|
||||
|
||||
// phase 1: get layer offsets and manifest.json
|
||||
for {
|
||||
hdrIn, err := tr.Next()
|
||||
hdr, err := tr.Next()
|
||||
if err == io.EOF {
|
||||
break
|
||||
}
|
||||
|
||||
if hdrIn.Typeflag != tar.TypeReg {
|
||||
if hdr.Typeflag != tar.TypeReg {
|
||||
continue
|
||||
}
|
||||
|
||||
switch {
|
||||
case hdrIn.Name == _manifestJSON:
|
||||
case hdr.Name == _manifestJSON:
|
||||
dec := json.NewDecoder(tr)
|
||||
if err := dec.Decode(&manifest); err != nil {
|
||||
return fmt.Errorf("decode manifest.json: %w", err)
|
||||
}
|
||||
case strings.HasSuffix(hdrIn.Name, "/layer.tar"):
|
||||
case strings.HasSuffix(hdr.Name, "/layer.tar"):
|
||||
here, err := in.Seek(0, io.SeekCurrent)
|
||||
if err != nil {
|
||||
return fmt.Errorf("seek: %w", err)
|
||||
}
|
||||
layers[hdrIn.Name] = here
|
||||
layerOffsets[hdr.Name] = here
|
||||
//fmt.Printf("%s\t%x\n", hdr.Name, here)
|
||||
}
|
||||
}
|
||||
|
||||
// phase 1.5: enumerate layers
|
||||
layers := make([]int64, len(layers))
|
||||
for i, name := range manifest.Layers {
|
||||
layers := make([]int64, len(layerOffsets))
|
||||
for i, name := range manifest[0].Layers {
|
||||
layers[i] = layerOffsets[name]
|
||||
}
|
||||
|
||||
// phase 2: iterate through all layers and extract filenames
|
||||
// to files and ordered
|
||||
files := map[string]struct{
|
||||
layer string
|
||||
// file2layer maps a filename to layer number (index in "layers")
|
||||
file2layer := map[string]int{}
|
||||
|
||||
fmt.Printf("layers: %+v\n", layers)
|
||||
// phase 2: iterate through all layers and save filenames
|
||||
// for all kinds of files.
|
||||
for i, offset := range layers {
|
||||
if _, err := in.Seek(offset, io.SeekStart); err != nil {
|
||||
fmt.Errorf("seek: %w", err)
|
||||
}
|
||||
tr = tar.NewReader(in)
|
||||
|
||||
return nil
|
||||
//return tw.Close()
|
||||
for {
|
||||
hdr, err := tr.Next()
|
||||
if err == io.EOF {
|
||||
break
|
||||
}
|
||||
file2layer[hdr.Name] = i
|
||||
}
|
||||
}
|
||||
|
||||
// phase 3: iterate through all layers and write files.
|
||||
for i, offset := range layers {
|
||||
if _, err := in.Seek(offset, io.SeekStart); err != nil {
|
||||
fmt.Errorf("seek: %w", err)
|
||||
}
|
||||
tr = tar.NewReader(in)
|
||||
|
||||
for {
|
||||
hdr, err := tr.Next()
|
||||
if err == io.EOF {
|
||||
break
|
||||
}
|
||||
if file2layer[hdr.Name] != i {
|
||||
continue
|
||||
}
|
||||
|
||||
hdrOut := &tar.Header{
|
||||
Typeflag: hdr.Typeflag,
|
||||
Name: hdr.Name,
|
||||
Linkname: hdr.Linkname,
|
||||
Size: hdr.Size,
|
||||
Mode: int64(hdr.Mode & 0777),
|
||||
Uid: hdr.Uid,
|
||||
Gid: hdr.Gid,
|
||||
Uname: hdr.Uname,
|
||||
Gname: hdr.Gname,
|
||||
ModTime: hdr.ModTime,
|
||||
Devmajor: hdr.Devmajor,
|
||||
Devminor: hdr.Devminor,
|
||||
Format: tar.FormatGNU,
|
||||
}
|
||||
|
||||
if err := tw.WriteHeader(hdrOut); err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
if hdr.Typeflag == tar.TypeReg {
|
||||
if _, err := io.Copy(tw, tr); err != nil {
|
||||
return err
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
return tw.Close()
|
||||
}
|
||||
|
|
Loading…
Reference in New Issue