Function buildLayerInfosForCopy

storage/storage_src.go:361–383

buildLayerInfosForCopy builds a LayerInfosForCopy return value based on manifestInfos from the original manifest, but using layer data which we can actually produce — physicalInfos for non-empty layers, and image.GzippedEmptyLayer for empty ones. (This is split basically only to allow easily unit-te

(manifestInfos []manifest.LayerInfo, physicalInfos []types.BlobInfo)

// and image.GzippedEmptyLayer for empty ones.
// (This is split basically only to allow easily unit-testing the part that has no dependencies on the external environment.)
func buildLayerInfosForCopy(manifestInfos []manifest.LayerInfo, physicalInfos []types.BlobInfo) ([]types.BlobInfo, error) {
	nextPhysical := 0
	res := make([]types.BlobInfo, len(manifestInfos))
	for i, mi := range manifestInfos {
		if mi.EmptyLayer {
			res[i] = types.BlobInfo{
				Digest:    image.GzippedEmptyLayerDigest,
				Size:      int64(len(image.GzippedEmptyLayer)),
				MediaType: mi.MediaType,
			}
		} else {
			if nextPhysical >= len(physicalInfos) {
				return nil, fmt.Errorf("expected more than %d physical layers to exist", len(physicalInfos))
			}
			res[i] = physicalInfos[nextPhysical] // FIXME? Should we preserve more data in manifestInfos? Notably the current approach correctly removes zstd:chunked metadata annotations.
			nextPhysical++
		}
	}
	if nextPhysical != len(physicalInfos) {
		return nil, fmt.Errorf("used only %d out of %d physical layers", nextPhysical, len(physicalInfos))
	}
	return res, nil
}

// GetSignaturesWithFormat returns the image's signatures.  It may use a remote (= slow) service.
// If instanceDigest is not nil, it contains a digest of the specific manifest instance to retrieve signatures for