motiejus/undocker
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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 { if _, err := r.rd.Seek(no.offset, io.SeekStart); err != nil {
return n, err return n, err
} }
tr, closer = readTar(r.rd) tr, closer = openTargz(r.rd)
for { for {
hdr, err := tr.Next() hdr, err := tr.Next()
if err == io.EOF { 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 { if _, err := r.rd.Seek(no.offset, io.SeekStart); err != nil {
return n, err return n, err
} }
tr, closer = readTar(r.rd) tr, closer = openTargz(r.rd)
for { for {
hdr, err := tr.Next() hdr, err := tr.Next()
if err == io.EOF { if err == io.EOF {
@ -232,29 +232,28 @@ func whiteoutDirs(whreaddir map[string]int, nlayers int) []*tree {
return ret return ret
} }
// readTar creates a tar reader from a targzip or tar // openTargz creates a tar reader from a targzip or tar
func readTar(r io.Reader) (*tar.Reader, func() error) { func openTargz(r io.Reader) (*tar.Reader, func() error) {
var buf bytes.Buffer var hdrbuf bytes.Buffer
w := &discarder{w: &buf} hdrw := &discarder{w: &hdrbuf}
r2 := io.TeeReader(r, w) gz, err := gzip.NewReader(io.TeeReader(r, hdrw))
gz, err := gzip.NewReader(r2)
if err == nil { if err == nil {
w.discard = true hdrw.w = nil
buf.Reset() hdrbuf.Reset()
return tar.NewReader(gz), gz.Close 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. // discarder is a pass-through writer until instructed to 'discard' its writes
// useful for proxying writes from a TeeReader until a certain point. // by setting its writer to nil. Useful for proxying writes from a TeeReader
// until it's known to be unnecessary.
type discarder struct { type discarder struct {
w io.Writer w io.Writer
discard bool
} }
func (d *discarder) Write(p []byte) (int, error) { func (d *discarder) Write(p []byte) (int, error) {
if d.discard { if d.w == nil {
return len(p), nil return len(p), nil
} }
return d.w.Write(p) return d.w.Write(p)