Method Compare

plugins/diff/windows/windows.go:174–310

Compare creates a diff between the given mounts and uploads the result to the content store.

(ctx context.Context, lower, upper []mount.Mount, opts ...diff.Opt)

// Compare creates a diff between the given mounts and uploads the result
// to the content store.
func (s windowsDiff) Compare(ctx context.Context, lower, upper []mount.Mount, opts ...diff.Opt) (d ocispec.Descriptor, err error) {
	t1 := time.Now()

	var config diff.Config
	for _, opt := range opts {
		if err := opt(&config); err != nil {
			return emptyDesc, err
		}
	}
	if tm := epoch.FromContext(ctx); tm != nil && config.SourceDateEpoch == nil {
		config.SourceDateEpoch = tm
	}

	layers, err := mountPairToLayerStack(lower, upper)
	if err != nil {
		return emptyDesc, err
	}

	if config.MediaType == "" {
		config.MediaType = ocispec.MediaTypeImageLayerGzip
	}

	compressionType := compression.Uncompressed
	switch config.MediaType {
	case ocispec.MediaTypeImageLayer:
	case ocispec.MediaTypeImageLayerGzip:
		compressionType = compression.Gzip
	case ocispec.MediaTypeImageLayerZstd:
		compressionType = compression.Zstd
	default:
		return emptyDesc, fmt.Errorf("unsupported diff media type: %v: %w", config.MediaType, errdefs.ErrNotImplemented)
	}

	newReference := false
	if config.Reference == "" {
		newReference = true
		config.Reference = uniqueRef()
	}

	cw, err := s.store.Writer(ctx, content.WithRef(config.Reference), content.WithDescriptor(ocispec.Descriptor{
		MediaType: config.MediaType,
	}))

	if err != nil {
		return emptyDesc, fmt.Errorf("failed to open writer: %w", err)
	}

	defer func() {
		if err != nil {
			cw.Close()
			if newReference {
				if abortErr := s.store.Abort(ctx, config.Reference); abortErr != nil {
					log.G(ctx).WithError(abortErr).WithField("ref", config.Reference).Warnf("failed to delete diff upload")
				}
			}
		}
	}()