char *inner_data = pending_data.data() + sizeof(metacube_block_header);
if (flags & METACUBE_FLAGS_HEADER) {
string header(inner_data, inner_data + size);
char *inner_data = pending_data.data() + sizeof(metacube_block_header);
if (flags & METACUBE_FLAGS_HEADER) {
string header(inner_data, inner_data + size);