Function compressAndWriteLayer

pkg/cmd/image/import.go:199–241

(ctx context.Context, w content.Writer, r io.Reader)

}

func compressAndWriteLayer(ctx context.Context, w content.Writer, r io.Reader) (digest.Digest, digest.Digest, int64, error) {
	digester := digest.Canonical.Digester()
	tee := io.TeeReader(r, digester.Hash())
	pr, pw := io.Pipe()
	gz := gzip.NewWriter(pw)

	doneCh := make(chan error, 1)
	go func() {
		defer func() {
			_ = gz.Close()
		}()

		if _, err := io.Copy(gz, tee); err != nil {
			doneCh <- err
			_ = pw.CloseWithError(err)
			return
		}
		if err := gz.Close(); err != nil {
			doneCh <- err
			_ = pw.CloseWithError(err)
			return
		}
		doneCh <- pw.Close()
	}()

	n, err := io.Copy(w, pr)
	if err != nil {
		return "", "", 0, err
	}
	if err := <-doneCh; err != nil {
		return "", "", 0, err
	}

	diffID := digester.Digest()
	labels := map[string]string{
		"containerd.io/uncompressed": diffID.String(),
	}
	if err := w.Commit(ctx, n, "", content.WithLabels(labels)); err != nil && !errdefs.IsAlreadyExists(err) {
		return "", "", 0, err
	}

	return w.Digest(), diffID, n, nil
}

func buildImageConfig(diffID digest.Digest, options types.ImageImportOptions) ([]byte, digest.Digest, error) {
	ociplat := platforms.DefaultSpec()