func renderSumForHeader(v Version, h *tar.Header, data []byte) (string, error) {
buf := bytes.NewBuffer(nil)
// first build our test tar
tw := tar.NewWriter(buf)
if err := tw.WriteHeader(h); err != nil {
return "", err
}
if _, err := tw.Write(data); err != nil {
return "", err
}
tw.Close()
ts, err := newTarSum(buf, true, v)
if err != nil {
return "", err
}
tr := tar.NewReader(ts)
for {
hdr, err := tr.Next()
if hdr == nil || err == io.EOF {
break
}
if err != nil {
return "", err
}
if _, err = io.Copy(ioutil.Discard, tr); err != nil {
return "", err
}
}
return ts.Sum(nil), nil
}
func (ts *tarSum) initTarSum() error {
ts.bufTar = bytes.NewBuffer([]byte{})
ts.bufWriter = bytes.NewBuffer([]byte{})
ts.tarR = tar.NewReader(ts.Reader)
ts.tarW = tar.NewWriter(ts.bufTar)
if !ts.DisableCompression {
ts.writer = gzip.NewWriter(ts.bufWriter)
} else {
ts.writer = &nopCloseFlusher{Writer: ts.bufWriter}
}
if ts.th == nil {
ts.th = defaultTHash
}
ts.h = ts.th.Hash()
ts.h.Reset()
ts.first = true
ts.sums = fileInfoSums{}
return nil
}