// imageFSMetadata creates a container and reads the filesystem metadata out of the archive.
func imageFSMetadata(c *docker.Client, name string) (map[string]*tar.Header, error) {
container, err := c.CreateContainer(docker.CreateContainerOptions{Name: name + "-export", Config: &docker.Config{Image: name}})
if err != nil {
return nil, err
}
defer c.RemoveContainer(docker.RemoveContainerOptions{ID: container.ID, RemoveVolumes: true, Force: true})
ch := make(chan struct{})
result := make(map[string]*tar.Header)
r, w := io.Pipe()
go func() {
defer close(ch)
out := tar.NewReader(r)
for {
h, err := out.Next()
if err != nil {
if err == io.EOF {
w.Close()
} else {
w.CloseWithError(err)
}
break
}
result[h.Name] = h
}
}()
if err := c.ExportContainer(docker.ExportContainerOptions{ID: container.ID, OutputStream: w}); err != nil {
return nil, err
}
<-ch
return result, nil
}