// copyContent attempts to load and serve the provided blob. If req != nil and writer is an instance of http.ResponseWriter, // response headers will be set and range requests honored. func (pbs *pullthroughBlobStore) copyContent(store distribution.BlobStore, ctx context.Context, dgst digest.Digest, writer io.Writer, req *http.Request) (distribution.Descriptor, error) { desc, err := store.Stat(ctx, dgst) if err != nil { return distribution.Descriptor{}, err } remoteReader, err := store.Open(ctx, dgst) if err != nil { return distribution.Descriptor{}, err } rw, ok := writer.(http.ResponseWriter) if ok { setResponseHeaders(rw, desc.Size, desc.MediaType, dgst) // serve range requests if req != nil { http.ServeContent(rw, req, desc.Digest.String(), time.Time{}, remoteReader) return desc, nil } } if _, err = io.CopyN(writer, remoteReader, desc.Size); err != nil { return distribution.Descriptor{}, err } return desc, nil }