// 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
}
