Method unpack

core/unpack/unpacker.go:303–655

(
	h images.Handler,
	config ocispec.Descriptor,
	layers []ocispec.Descriptor,
)

}

func (u *Unpacker) unpack(
	h images.Handler,
	config ocispec.Descriptor,
	layers []ocispec.Descriptor,
) error {
	ctx := u.ctx
	ctx, layerSpan := tracing.StartSpan(ctx, tracing.Name(unpackSpanPrefix, "unpack"))
	defer layerSpan.End()
	unpackStart := time.Now()
	p, err := content.ReadBlob(ctx, u.content, config)
	if err != nil {
		return err
	}

	var i unpackConfig
	if err := json.Unmarshal(p, &i); err != nil {
		return fmt.Errorf("unmarshal image config: %w", err)
	}

	diffIDs := i.RootFS.DiffIDs
	if len(layers) != len(diffIDs) {
		return fmt.Errorf("number of layers and diffIDs don't match: %d != %d", len(layers), len(diffIDs))
	}

	// TODO: Support multiple unpacks rather than just first match
	var unpack *Platform

	imgPlatform := platforms.Normalize(i.Platform)
	for _, up := range u.platforms {
		if up.ConfigType != "" && up.ConfigType != config.MediaType {
			continue
		}
		// "layers" is only supported rootfs value for OCI images
		if (up.ConfigType == "" || images.IsConfigType(up.ConfigType)) && i.RootFS.Type != "" && i.RootFS.Type != "layers" {
			continue
		}
		if up.Platform.Match(imgPlatform) {
			unpack = up
			break
		}
	}

	if unpack == nil {
		log.G(ctx).WithField("image", config.Digest).WithField("platform", platforms.Format(imgPlatform)).Debugf("unpacker does not support platform, only fetching layers")
		return u.fetch(ctx, h, layers, nil)
	}

	u.unpacks.Add(1)

	var (
		sn = unpack.Snapshotter
		a  = unpack.Applier
		cs = u.content

		fetchOffset int
		fetchC      []chan struct{}
		fetchErr    []chan error