motiejus/undocker
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This commit is contained in:
Motiejus Jakštys 2021-05-24 00:11:58 +03:00
parent fd244bfc23
commit d61e0a58f1
1 changed files with 14 additions and 15 deletions
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29
rootfs/rootfs.go
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@ -113,7 +113,7 @@ func (r *RootFS) WriteTo(w io.Writer) (n int64, err error) {
if _, err := r.rd.Seek(no.offset, io.SeekStart); err != nil {
return n, err
}
tr, closer = readTar(r.rd)
tr, closer = openTargz(r.rd)
for {
hdr, err := tr.Next()
if err == io.EOF {
@ -156,7 +156,7 @@ func (r *RootFS) WriteTo(w io.Writer) (n int64, err error) {
if _, err := r.rd.Seek(no.offset, io.SeekStart); err != nil {
return n, err
}
tr, closer = readTar(r.rd)
tr, closer = openTargz(r.rd)
for {
hdr, err := tr.Next()
if err == io.EOF {
@ -232,29 +232,28 @@ func whiteoutDirs(whreaddir map[string]int, nlayers int) []*tree {
return ret
}
// readTar creates a tar reader from a targzip or tar
func readTar(r io.Reader) (*tar.Reader, func() error) {
var buf bytes.Buffer
w := &discarder{w: &buf}
r2 := io.TeeReader(r, w)
gz, err := gzip.NewReader(r2)
// openTargz creates a tar reader from a targzip or tar
func openTargz(r io.Reader) (*tar.Reader, func() error) {
var hdrbuf bytes.Buffer
hdrw := &discarder{w: &hdrbuf}
gz, err := gzip.NewReader(io.TeeReader(r, hdrw))
if err == nil {
w.discard = true
buf.Reset()
hdrw.w = nil
hdrbuf.Reset()
return tar.NewReader(gz), gz.Close
}
return tar.NewReader(io.MultiReader(&buf, r)), func() error { return nil }
return tar.NewReader(io.MultiReader(&hdrbuf, r)), func() error { return nil }
}
// discarder is a pass-through writer until asked to 'discard' its writes.
// useful for proxying writes from a TeeReader until a certain point.
// discarder is a pass-through writer until instructed to 'discard' its writes
// by setting its writer to nil. Useful for proxying writes from a TeeReader
// until it's known to be unnecessary.
type discarder struct {
w io.Writer
discard bool
}
func (d *discarder) Write(p []byte) (int, error) {
if d.discard {
if d.w == nil {
return len(p), nil
}
return d.w.Write(p)